High lift rockers - desirable but incorrectly tested.

[@zAvAvAz]

David i remember that mini, although i was in heaven then, the immediate heavens, the clouds! Luv you! Glad you did it!

[@ljpowersports3675]

Thank you for sharing your wealth of knowledge with everyone, most all would rather die with that vast amount of knowledge. You are a great teacher! I'm trying to absorb as much of it as I can!

[@thatcarguy2778]

This! I always wondered why people are like that. In my opinion people who hold back helpful information just holds whatever industry they are in back. I answer any questions to the best of my ability. Competition breeds innovation!

[@ljpowersports3675]

@@thatcarguy2778 Correct, I too, believe that by being that way, would slow the way, to an extent, the potential for future generations of some innovation and quick gains of experience, to be of continual industrial leadway, whatever it may be.

[@Bbbbad724]

I really used to get so tired of people dragging their feet on sharing ideas and growing new parts for older platforms. There is no excuse for there not being a siamesed bore 4.125 bore Cleveland! The best ever made and no blocks to put original cars together? Few FE blocks, and since COVID good luck. It is wrong.

[@TheJagjr4450]

Chevrolet SB Stamped Steel rockers even the long slot high lift cam design are actually a 1.37 ratio. The BB rockers are a 1.7 nominal 1.57 nominal. Yunkick made a dimpling tool to dimple SB stamped covers in order to run the BB rockers with 7/16 studs on a SB head.

[@DAVEITTERLY]

Hello David, I am not the author of a book on cylinderhead machining, but I was a graphic artist on a book about high speed machining in the automotive industry (GM Ford Daimler Chrysler Saturn etc). I knew the author. But I had an 80 Z28 and he had a 944 turbo: that he blew everyone away in on the street. This is in regards to your Mini. Being it was suitable for this particular race, and you worked your ass off to make it the best car on that day, and that it was an anomaly and with it's racing heritage that make it a contender for being the greatest of all time. And you are the man behind the machine. That's why it will be another 20 years before another can exist.

[@floydsgarage]

My first engine book was How to Build Horsepower - Volume 1. I like to read books you can learn from. Thanks, I learned a lot

[@lewis730]

Thank you for getting me to “think”. Your videos underscore that an engine build philosophy is infinite, and that is what makes this hobby (or profession) so much fun!

[@timsullivan3935]

Dear sir, first I would like to say I admire your confidence, after watching several of your videos I can see why you have such confidence,I like all the videos you guys produce, they are very informative and make me think about the physical aspects of engine dynamics, you do the math that most of us take for granted manufacture’s have done! My favorite video was the one on equal length headers for sbc ! Wow, mind blowing!

[@FizzaMC]

G'day DV, just a quick note to pass on for the video @6:22 is that the story you were going to tell actually had me interested. I've heard you talk about the very massive amount of achievements you've made throughout the 75 years plus of race and engine journalism including the 4 or 5 stories that tend to get mentioned above all else including the title to the videos but when I hear of a tale that I've not yet heard and then go to save it for another time is good work on keeping the audience engaged but please do try and remember to share that story with us soon before you forget and yes I understand about your surgery which is why I'm politely asking for it to be added if it hasn't already, so it can keep viewers like myself and others interested and engaged with some new content and not a recycling of the stories you tend to tell a fair bit. All from a place of respect because a dear late friend of mine who helped me when I was starting out lent me some of your publications and it was very good information for the time and still relevant in most aspects today. Thanks DV and keep that new stuff coming

[@umakemerandy3669]

Yes, where is this story? If its out here somewhere

[@95Sn95]

When I put my budget 355 SBC together I bought roller top rockers not because I thought I would get an increase in power I did it hoping they would help extend the life of my valve guides.

[@gordowg1wg145]

As a side issue, some of the bleeding edge builders are using "negative valve to piston clearance" - by that, they're factoring in the deflection of the valve-train parts for their cam' grinds so that where there is a 'paper' interference it isn't actually interference occuring because the barts are bending and flexing under load to give them the clearance they need.

[@nitro1631]

I completely understood that I was thinking the same thing in a similar situation thanks Mr. David great explanation

[@julianobrod]

In Silverstone, 60 passes! Awesome. Thank's for the technical knowledge David.

[@johnj2496]

we love listening to your life stories and not just the knowledge you share but the stories of the process you gained your knowledge

[@jr78racer]

Thank you for all your great content.

[@mikesperling8758]

Another great video. That made complete sense that's when you change the rocker ratio how the cam profile will still not match up how you set it

[@ercost60]

Another very informative video. Thank you for sharing your amazing knowledge, Sir David!

[@frankglasgow]

Thank you Mr Vizard. This content is the best.

[@brianalbrecht4423]

Thank u D.V. 4 sharing ALL your years of knolage......!...priceless information....reguards....Brian

[@williamherring5441]

Thanks, DV. I notice in a similar path of analysis that folks testing various LCA camshafts generally compare lobe separations without pulling back the duration on the tighter lobes to keep the overlap consistent; thus arriving at a flawed conclusion (even when the tighter LCA made more power). v/r wh

[@trailerparkcryptoking5213]

Do you actually mean LCA (lobe centerline angle) or LSA (lobe separation angle) ? Two completely different things....

[@danferraro3034]

David, super informative video as always!!!! I love the science behind your thinking. Your wisdom is greatly appreciated!

[@rogerdavenport9618]

You have a great understanding of the "science" of distance and timing, I have a layman's question, is the purpose of the design of the rocker, especially the roller rocker, to prevent the least amount of "binding" which is a big reason for the loss of horsepower, when the cam is at its height or the duration of lift, and in no ones comment, no one mentioned the inventor or modern inventor of the roller rocker/lifter and cam, Chet Herbert.

[@Jeffsa12]

Interesting David! I became aware of complexity of engineering rocker arms when began programming a CNC machine to cut a set of billet shaft rockers for my Cadillac 500, 25 years ago. I learned rocker geometry is a surprisingly complex subject. Set actual ratio at no, mid, or high lift? The height of the pushrod seat in relation to the pivot point has a dramatic effect on dynamic ratio changing lift acceleration rates throughout the lift curve. I ended up using the radius of both contact points in relation to the pivot point at a mid lift to set the ratio geometry. I've always wondered since then if camshaft designers take the dynamic principal of the geometry involved of a specific brand rocker into account when designing camshaft lobes. Or if they don't take dynamic rocker ratio into consideration at all?

[@jmflournoy386]

Fast off the seat valve motion per degree of rocker rotation is greatest when the axis through the fulcrum and rocker roller are perpendicular to the valve- simple geometry With a Crane style this is done by effectively and raising the fulcrum and either angling down the pushrod arm or using a longer pushrods. No free lunch as angling down the pushrod side arm usually decreases the rotation degrees per movement of the pushrod. The sweep across the valve tip tends to start on the outside and moves towards the inside If the tip is coming off the tip on either side you need to move the valve tip or use a different length rocker arm OR move the fulcrum down so the effect is not so great Now we have maxium acceleration (assuming the pushrod is perpendicular to the pushrod arm) AND we have the least load at maximum lift and thus less tendency to float the valves and you can see if you plot the roller tip it is moving more sideways so you do loose a little lift' Now unless you are really in a class build where your changes are limited where you might want to go the complete opposite way with the rocker axis perpendicular to the valve at max lift well think about it real hard Best for general use is to use the mid lift method where the axis is perpendicular to the valve at half lift. Easy to do with stud rockers and you will have fewer wear problems if this makes a difference With MOPAR shaft rockers kits are available to raise and relocate the rocker shafts WELL WORTH EVERY PENNY you will end up with the smallest possible contact patch DO NOT TRY AND CENTER YOUR CONTACT PATCH this can only be done by changing the rocker arm length or relocating the fulcrum/ shaft/ rocker stud not in the exact center is NO BIG DEAL Be sure to work with your camgrinder as they may advise a specific geometry AND Several BIG camgrinders have wrong information in their catalogs and no idea what they are talking about Trying to get some clarity on what David was saying about adjusting lash and centerlines would be very difficult END RANT Ps do not draw you axis line between the fulcrum and valve stem with a roller tip rocker- through the center of the roller tip. You draw to the top of the valve with a flat tip stock type rocker now put in longer valves for those new longer springs and start allover again cheers

[@johnelliott7375]

I agree with you, just because someone says that if you put these on your engine it will fix the problem. Back before we had all these fancy gadgets, I had to adjust my valves every Friday and night at the local races. I drove the car every day to get to work and wherever I had to go. When I would set the valves for more intake lift and to try and get as much as I could while making runs, would not behave nicely for the stop in go driving around you would do during the week. That said I would have to wait after it cooled down some and readjust my valves before I went home along with a small adjustment to my carburetor. I had no idea how much geometry was involved and what I would have to do to figure it out. This was before the days of the tuners, laptops, and all the fancy gadgets that you are able to utilize today. If I would have had a clue, I would probably not have to have to put in so much adjustment on my solid lifter cam in my 400 SBC and would have not had to do so much for so little, that said that little made a good difference between daily and straight line 1/8 & 1/4 runs. Good morning and thank you again for sharing your knowledge with the geometry of how just a little bit here and there, equals more and probably way better manners if I would have had a clue or some help from someone who knows what the little changes here and there will accomplish. I will wish you all a Happy Holiday Season and a Merry Christmas! Great day and enjoyed the video as always. Never to late to try and learn how to do it and make it work for you and not against you.

[@terryheimerl8674]

thank you David.

[@mikecondoluci53]

THANK YOU DAVID FOR ANOTHER GREAT ONE, I HAVE ALL YOUR BOOKS AND WATCHED ALL OF YOUR VIDEOS AT LEAST TWICE, THANK YOU AGAIN FOR SHARNG YOUR KNOLEDGE WITH ALL OF US, WISH YOU AND YOUR FAMILY A MERRY CHRISTMAS AND MOST OF ALL A SAFE ONE

[@mikkokuorttinen3113]

Great thank you to you DV for all the informative videos you post! I've two pairs of sbc factory 113 heads ready for porting. It's been said they don't flow that well on the intake side, exhaust being a bit better. I'd love to see or hear some tips on improving the choking points of the runners

[@andreichichak5242]

Daphne has a solid rear end and she wiped out all of the boys. You'll never see that kind of action ever again!

[@jamesgeorge4874]

All canted valve engines with different angles, and different lengths, suffer these issuse more than engines with inline valves. The New Hemi pushrod arrangement, with non adjustable shaft mounts, can be fickle with getting quiet lifters, with aftermarket camshafts. Making an adjustable pushrod, and measuring each one for optimal lifter preload was an all day affair.

[@jedgarsquink]

Regarding the degree wheel, I can see that the second scale has increments twice as big, so it would read cam degrees, and I can see that it's readily indexable with respect to the main scale. I don't see it at the Comp Cams website, but the main wheel does come with the holes for it. I suppose you could use it for adjusting the cam for a desired degree change, and then quickly return to the previous setting to test for repeatability of the original readings.

[@bcbloc02]

I believe in another video you mentioned the track banking and turns having been altered since the race record you set so I know the record can't be broken because the conditions can not be duplicated.

[@michelcote]

I would love to see the opening curves/flow of those two rockers. The results are one thing, but how the geometry of the rockers acheive that is more interesting so we know how to replicate and think about the geometry of rockers. Thanks.

[@Comet-hn3gm]

Good information. I had seen this before (I will probably watch it again) good information for me as I am doing a 496 BBC now.

[@joe-hp4nk]

You should have put a 1.8 on the exhaust as well because the exhaust on those particular heads needed help. That's why you have split duration cams with more on the exhaust side as much as 14 degrees in extreme cases.

[@DiscoVette81]

David, always learn so much from your presentations. Regarding rocker material and weight. I have seen a lot of folks state aluminum will rev higher due to lower mass. However typically SS rockers have larger trunnions and only rotating mass should be compared, not total weight. So the rotating mass may actually still be less. My thought is SS may still actually have less rotational mass than an aluminum counterpart with a smaller trunnion, especially with rockers like the Comp Cams Pro Magnum HD, while having less deflection and longer life. Thoughts?

[@AlanRoehrich9651]

Great video. Now, why did it happen? Did opening the intake too soon cause some intake charge to go out the exhaust?

[@bcbloc02]

The rocker ratio is a combination of two arcs so the actual ratio varies a ton based on where you measure it at. Not sure how far down that optimization road you went but I expect with the better ratio rockers the ideal duration likely also got less since the longer rockers effectively add duration as well.

[@terryheimerl8674]

Thank you David, I have trouble absorbing information on the first pass these days, I am just a youngster at 68. I don't know how many times I have watched this video but I seem to pick up new things every time. Did you ever do more testing on the Offenhauser intake manifold that had individual/split Primary and split secondary runners/ports all the way to the heads. In other words a total of 8 runners for the primaries and 8 runners for the secondaries? You did a test on intakes and commented that it didn't give the highest HP but you wished you had of made part throttle tests for all the manifolds.

[@stickman-1]

Hello David, Thank you for your videos and willingness to share your knowledge here on YT. Can I offer a suggestion? Can you put your episode # in the title of each video? It just makes it so much easier to find them. You can update the title on YT easily. You do have a lot of videos but still it should not take more than 1 to 2 hours. Thank you. PS. As for why your record will not be broken, I'd guess rule changes. That's one of the things that I hate about sanctioned racing: As soon as someone figures something out, they rewrite the rules to take away the advantage. Considering your innovative methods, I'd say that is why.

[@StefanRügamer]

I've got 1,5 Comp Cams Full Roller Rocker, on my stock 283 - now I know on what I have to look after before I go to the next Dyno session

[@kyproset]

What a beautiful channel this is, thank you.

[@larryburns4605]

I have used PRW rockers good parts .

[@exploranator]

I like that pointer. So David Vizard!

[@Bbbbad724]

The engine family I am most interested in is the Ford FE. The rockers stock are 1.73 hyd and 1.76 ratio on a shaft system. I measured mine and they were factory replacements for the shaft system and they were all 1.8 , and did not break any valve springs. That was quite a bit off but they were to my advantage.

[@jmflournoy386]

Pretty good for a motor designed PRE WAR I like the larger balls on the rocker adjusters compared to MOPAR I convert to ball pushrods and cups on the adjusters and oil through the pushrods

[@Bbbbad724]

@@jmflournoy386 Yep, Ray Paquet is still chopping wood with one of those pre-war axes in SuperStock, running Low 8s in the quarter. They still do surprisingly well.

[@Bbbbad724]

@@jmflournoy386 No I don’t believe that the FE was designed Pre-War. Are you thinking of the Lincoln-Y block? It was the same bore spacing but it came out in 1952 in Lincoln Mercury and Trucks at 317ci. It was discontinued in 1957. They never used it in Fords. Mercury and Lincoln are a few in trucks. In 1958 the Edsel came out with the FE and the MEL. The Y block 272-312 soldiered on until 1964 but was overlapped by the 221-351W. The FE was around in cars until 1970 and trucks until 1976. The MEL was in use until 1968, when the 429 came out in the Tbird and Lincoln and 1970 across the entire line. The 4.63 bore spacing was discontinued in 1976. The 335 series had small block bore spacing with the 351M 400 having a taller deck height. The 460 came along in 1970. I hope this helps. But the FE didn’t appear until 1958. It wasn’t used trucks until 1964. And they do have a great valvetrain. I have pushed stock stuff with the right springs and aftermarket pushrods or 427 pushrods on .030 over 390s to 7000 rpm +

[@jmflournoy386]

@@Bbbbad724 some research needed I was referencing a recent podcast where the question was replacement cylinder heads for the FE where the pushrods would not hqve to be through the intake manifold where the 1937 and not into production for 20 years was mentioned

[@Bbbbad724]

@@jmflournoy386 Thank you Jim

[@robertreavley7145]

Never in the field of racing has there ever been a engine that has given the cars name it’s put in a retrospective ironically wrong meaning!! Mini!! In nam size yes but a slayer of giants, Titans, and renown maters of speed and acceleration! This placid unassuming ma built this glorious small package of strength and power. That holds a high ranking in present past and future engine learning and development. David you sir are a true genius. A place in history has been hewn out by your prowess and accomplishments over your time! Something that I can categorically say is rare and awesomely brilliant accomplishment!!

[@joe-hp4nk]

I bet it was bone head David Freiburger that said you were wrong.

[@leehedger5056]

If that race at Silverstone was a game of ten pin bowling then you would have scored a STRIKE! 😄

[@Scarlet_1971_cuda]

This was cool. All the parts need to play well together to get max HP/torque.

[@Mewanrahnam575]

You are a legend Sir.

[@keithfilkins2043]

Thank you David!

[@peggyparrow2059]

Excellent explanation !

[@joekalmar8881]

Hello love your videos. Just got finished from a old pro 383 sbc 010 virgin block mickey Thompson cross ram running great 👍. Have a Cadillac 472 high $ heads . Did they stick a valve spring shim to increase the valve opening and closing. Thank you for your great work.

[@g0fvt]

The mini overtook 30 cars before the third corner and was overtaken by then all before the fourth corner. (It spun)

[@Lagrange1186]

Great story sir thanks for sharing

[@pierrecarlsson902]

Hm... If "fast off the seat" is a issue, then more avancerad angle at the pushrod end would be a solution then? The closer to the vertical centerline of the pivot will give a virtually higher ratio that descends as the angle in that radius move upvards increase. I guess this will put higher quality demands on cam, lifter, pushrod and oil. So by choosing a co-operating camprofile that work with the lyfter there would be a great advantage by doing this more than a higher ratio? Or is the downsides a greater concern, and what are they?

[@EricErnst]

I'm running 1.7 scorpion roller rockers on a tbi 350 sbc. Surely that's better than the stock stamped 1.5s

[@DavidVizard]

Yes - have used a lot of those rocker with zero problems

[@jeffrykopis5468]

Did it make any difference in power? I figured the cork in the tbi was the crummy 2 bl throttle body, not the (puny) cam. I woke mine up with a true dual exhaust and no meowers.

[@EricErnst]

@@jeffrykopis5468 it helped some. The thing about the tbi motors is that the components are matched pretty well.. and NONE of it is designed to make horsepower. Lol The stock cam had .385"/.402" lift. If you simply multiply the lobe lift by the advertised rocker ratio lift, you'll get .437"/.456". I haven't mic'd it.. I just slapped them on the stock pressed-in rocker studs. I don't rev the motor past 5k so they're fine for now. I've got a comp xfi252hr roller cam (202⁰/212@.050") (.585"/.581" with 1.7's) and a different set of heads with screw-in rocker studs and comp beehive springs. The rest of the tbi 350's combination is very well matched.. anemic 2bbl throttle body with 2 small injectors to feed 8 cylinders. A 20hz computer. Hz.. like 20 calculations per second... not khz. Not mhz. Not ghz. Not thz. Simply hz. .. Swirl port cylinder heads with a giant ramp in the intake port that are done flowing by 3500rpms. The best thing about them is the exhaust manifolds and exhaust system. They flow just good enough to support the stock horsepower. That's why open headers give almost zero horsepower increase on a bone stock engine. Peak torque was rated at a lugging 2400rpms. Which, with a th400 and 4.10 gears and stock 245/75R16 tires would net cruising speed of 50mph@2400rpms in 1990. Right in the meat of the torque curve. They actually mathed things out back then. To meet lower emissions requirements, just turn the engines slower and tune them for low end torque. I figured a little more valve lift would allow a marginally higher amount of airflow throughput. It can't hurt the rated 190hp, right? I've got the parts together to make approximately 325hp@5000rpms and 430ish lb-ft@3500ish. My biggest hurdle will be tuning the stock tbi unit at over double the stock fuel pressure. My plan is to run a vacuum-referenced fuel pressure regulator before the stock internal fuel pressure regulator fitted with a 29ps spring. The vacuum referenced regulator will deliver around 19-20psi at idle and cruise while bumping fuel pressure (and overall fuel flow) under wide open throttle. With a completely stock engine and computer tune (aside from headers and free-flowing exhaust) my commanded injector duty cycle was 114%@3800rpms. My exhaust setup is a pair of 1⅝" long tube headers into a 2½"collector, a smooth y-pipe to single 3". 3"idx24" glasspack. Immediately opened up to 4" and a 4"idx30" glasspack and a 4" tailpipe out the stock location at the passenger's rear corner of the 8' longbed. It has a mellow tone at idle and cruise but seems to growl at wide open throttle. As much as 190hp can. The tone is deep from the large diameter pipe. The mellow note is due to 4.5 feet worth of muffler. It's a nice setup. It doesn't beat the sound of true duals.. but I was trying to be efficient with it. With cruise control set at 55mph, my instantaneous gas mileage shows as 26-28mpg in a pickup truck with the aerodynamics of a brick. I've figured that the stock fuel system provides 122lbs/hr of gasoline. That's roughly 244hp @100% duty cycle worth of gasoline on old iron. Injectors die at 100%DC, so if you figure 85%duty cycle, that'd be roughly 207hp worth of gasoline in stock form. Very roughly calculated and going off of a lot of assumptions. But the stock fuel injection system is very inadequate. That's why I set my power goal so low on this project. Apparently, the stock throttle body flows about 480cfm. It should be easier than Vizard and Uncle Tony's 318hp through a 2bbl carb that flows 260cfm. I do not have access to a dyno so all of my tuning will be on the street and horsepower estimates will be based on 0-60 time improvements. It should work well. If not, I'll install an aftermarket efi system to feed the beast. This is my final attempt at making decent power with the stock tbi system. If it doesn't work this time, I'll never attempt it again.

[@jeffrykopis5468]

@@EricErnst Very good info. I knew some but not all of it. Why not try the 454 throttle body and injectors, a spacer, and an adjustable regulator?

[@jeffrykopis5468]

@@EricErnst I've had 3 or 4 TBI SBCs, from an 87 Suburban to my 92 2500. I haul scrap, a lot of it, never been over 5000 rpm, and my 92 has now spun a rod bearing twice. Bone stock, except for dual exhaust, no kitties (but an O2 sensor in the H pipe), and glasspacks. It SOUNDED faster, lol. I'm now driving a 98 Vortec 454 2500.

[@kmbriggs2693]

Would imagine that your power to weight ratio in the mini is so good that record stands still.

[@bobgyetvai9444]

David who makes the quickest accelorating LS replacement rockers ?? Are the PRW steel with a roller tip rockers designed properly ??

[@VGHCX]

Help me understand please. If I have an engine with a rocker arm ratio of 1.5 and a valve spring with an open pressure of 300lbs. Does this mean the pounds of pressure at the cam would be 450lbs since there is NO mechanical advantage when opening the valve?

[@joeinmi8671]

I'll never look at rockers arms the same again.

[@chuckkellogg2404]

I don’t fully agree that a stroker motor requires the valve to open faster relative to a stock stroked motor due to fact that the piston dwell at TDC is longer on a stroked motor thus allowing the valves to open, in essence, faster.

[@jmflournoy386]

With same rod length piston dwell around TDC is shorter plot where the rod is pependicular to the crank throw

[@dondotterer24]

I remember the variable ratio rockers back int he day. What happened to them? I'm thinking they where where made by Crane?

[@theshed8802]

Good stuff David. I still like my Cleveland's, but it's difficult to get any really good books on them. Have you ever considered doing one? Regards Greg

[@davidreed6070]

Check out drag boss garage

[@DavidVizard]

Greg - you must have read my mind.

[@theshed8802]

@@davidreed6070 Tim and I converse regularly.

[@theshed8802]

@David Vizard if I was in the US I would offer you any amount of help that I could give. That said I am in Australia and have some stuff that you might find of interest. One thing being a photo copy of the genuine Ford GTHO phase 3 workshop manual that includes things like the camshaft specs. It appears that Australia got 2 special solid lifter camshafts that were different to the US solid cams

[@davidreed6070]

@@theshed8802 I'm a Chevy man, but I built Cleveland for someone, it had closed chamber rec heads and it was impressive

[@umakemerandy3669]

Please edit your video so the volume is not going up and down with your voice loudness. I love the information in your videos.

[@benjamindover761]

Hi David, this is why I chose your CosCam service and it recommended the Crane Gold 1.8 for my 496. Im laughing because I just keep thinking Freiburger lol

[@kenselleck2414]

Thank you for this!

[@scottmcmullen7541]

Hello Mr. Vizard, I have a Cam Card of a Solid Roller Cam I'd Like your opinion on. I am thinking about using the cam in a 383 SBC build.

[@darrellsomers5427]

Roller rockers limit the oil pressure a good stamped stell rocker arm is way better for a street engine in my oppion my how to rebuild your big block Chevy book says the same thing ?your thoughts

[@ruxoneto6560]

David have you tried to adjust the valve lash as the engine running on dyno under load ??

[@romychajla880]

you forgot to say: opening faster will slam your valve faster on the seat, no free lunch. jerk/jounce depends on installation height. midlift-square is not the holy grail, its disregarding the pushrod side and wear considerations.

[@slickline4576]

ONCE AGAIN GREAT VIDEO. TY DV

[@donaldgilbreath4200]

I know how making more HP was the problem. In high school we did a test in science class. We put two erasers 40' apart. Each student, had to run and pick up an eraser and drop it 40' away next to another eraser, then pick up the other, and drop it at the spot the other eraser was. Then, based on our time the teacher calculated how much HP we produced. Only the smallest girl in the class could produce one HP. HP is potential power, but the real force that moves the car is torque. If you sacrifice torque, it does not matter how much HP you can produce. Bug rig trucks only produce about 300-400 HP, but they haul 80,000lbs all day every day. Because of torque. Just as the little girl in class had 1 hp, she would lose a tug of war with all of us every time, because she did not have torque. So if you have a Chevy 350 producing 500hp with 350ftlbs of torque that's not good, you want 550-600 ftlbs of Torque. Your torque should always be numerically higher than hp so you can apply the hp to the wheels. You can make an engine spin faster and make more HP but if it can not apply that force through torque, the HP is useless.

[@ljpowersports3675]

I believe you are correct to the situation you are implying as in the pulling or hauling power, the extra load of moving something is where torque over hp comes into factor, but in racing if you have a sbc 350 with 500 hp with 500 lb ft tq against the same engine with 475 hp and 500 ft lb tq, that extra hp with the 500 horse engine with pull away on the track

[@ljpowersports3675]

Now in dirt track situation, considering the condition of the track weather it's dry slick or tacky. In dry slick condition the lower hp engine may pull on the straight over the higher hp because more hp will spin tires farther down the straight wasting energy while the lower hp will not as much and I have witnessed this overcoming over higher hp output many times. Now the more hp will have advantage in the turns with weight transfer into the grove in the banking. But also may not be as much advantage as lower hp engine with momentum around the top Grove against the cushion. Many different factors in all situations, my opinions from my experiences.

[@donaldgilbreath4200]

@@ljpowersports3675 , Thank you for adding to my comment, I could not have articulated any better. That said, I have never raced track, so the whole concept is foreign to me. On the strip it's a different ball game. I have a neighbor that races on a dirt track nearby, Ihe has me thinking doing the same, never to old to learn. I'm not sure how I would do.

[@ljpowersports3675]

Not problem at all, you're very welcome. The same applies to the drag strip and the street. The variables and discrepancies (not limited to) lie within equipment used that transfer the tq and hp to the surface and surface conditions also. The difference in a drag strip and the street strip can almost be compared to dirt track with tacky surface (drag strip) or dry slick surface (street strip). So with some of those variables in mind to how the suspension is built, the tires used, gearing, etc., etc. A higher torqued lower hp engine could have an advantage over lower torque higher hp unless that guy has fell behind in all other areas the make up the car engine is in. So, in conclusion it's all about the components that make up everything else the engine is connected to that also helps determine the potential of finished product, not (limited to) just what the numbers say is at the flywheel.

[@donaldgilbreath4200]

@@ljpowersports3675 , I've found gear ratio to be more important than almost anything else. You can have all the horse power and torque in the world, but if your gears are to high, it's hard to get off the line, to steep, you will get beat towards the end of the race.

[@chrisgreen3100]

hard to break a lap record on a circuit that no longer exists

[@Thumper68]

Hard to prove I didn’t break it either since it doesn’t exist lol 😂

[@johnrisher3007]

How can you get the power and torque right by adjusting the valve lash and timing without a dyno

[@bobgyetvai9444]

Time slips from the drag strip.

[@randywl8925]

So if a person replaced a 1.5 ratio rocker with a 1.6 or 1.7 on the intake, would it always require retarding the cam slightly..... 1 to 3 degrees, or was your example specific to that big block build with the 1.8? I love how you bring up, what should be obvious. ...if you change or modify one part, other parts may need tweaking. Kind of like medicines or vitamins. If you take one pill, it depletes a vitamin. ....so you increase that vitamin and taking an excess of that vitamin depletes you of a specific mineral. Round and round we go. If that didn't make sense, it's because my name isn't David. 😁

[@davidreed6070]

Dv that is simple, it hasn't been beaten yet. It's not likely to

[@autonomous_collective]

David, do you still use your "Oil Extreme" in all your engines?

[@DavidVizard]

Sure do!

[@rolandtamaccio3285]

I think this guy got better marks in geometry than I did ,,, !

[@hankreszka9319]

David, have you ever evaluated the Miller Mid lift rockers?

[@26Petermc]

Thanks great explanation

[@NewEngland462]

Sorry about your daughter man. I have 4 of them Very beautiful looking lady inside and out.

[@steelcitycaprice.899]

Question. Doesn't spring rate tie into this equation at some point.. or is it a none factor..

[@darrellsomers5427]

Can you give us the cam specs on that 572 5 thousands is 5 thousands was that a hot or cold

[@blueyhis.zarsoff1147]

When will we get rockers where theyare spec'd by their geometry of the 3 important points?

[@earlbrown]

Jim Miller holds the patents on correct rocker geometry on the 3 important parts. So his are the only ones that are legally correct right out of the box. And if you're building an engine that he doesn't support, you just have to get close with different parts.

[@darrellsomers5427]

Horse power to weight is hard to beat I've seen a few mini's that could run with just about anything because the competition weighed around 3000 pounds give or take a few pounds

[@dwaynehagle7445]

The class doesn't exist anymore.

[@LoneWrencher]

on the 5 million dollar bet contest here is how i see it. when im sure of myself,what i know,what i can do,or what i just did,here is what i say when questioned about it.i tell them[IM NOT BRAGGING,IM JUST STATING A FACT]

[@cobra7250]

I have never seen any one of those rockers that you show in a pro stock car or a Cup car or a top fuel car. WHY???

[@58sportsuburban]

Would a Pontiac 350, with 2.11/1.77 valves and 1.65 rockers, be undervalved?

[@jmflournoy386]

not as much but still are valves shrouded? When picking cams Pontiac is not SBC so if the cam recommendation is the same RUN

[@johnrisher3007]

On a street engine just for fun would cost a fortune for the dyno

[@Michael_Lorenson]

Excellent, thanks

[@cuda6496]

Hey Dave the answer your record question I believe you passed 30 drivers before the third turn and you were passed by 30 drivers before the 3rd turn ?

[@K_spawn]

Thanks!

[@lewis730]

Thank you!

[@dannoyes4493]

Thank you.

[@hunnybunnysheavymetalmusic6542]

What are the rules for this 5 million dollar bet?

[@james10739]

What do you mean not a valid test I could see as accurate but are you saying that a much bigger cam didn't make more power than a stock cam

[@james10739]

He said that about cams and never mentioned cams again

[@briantayes2418]

Those fast off the seat rockers would really help someone who has a cam with too wide of an LCA.

[@Chris-bn1bn]

Usually you do a good job of demonstrating a principle. This isn't one of them. How do I know I'm getting what I'm paying for using a mic or whatever you use to verify the ratio?

[@andrewf8486]

I subscribed, but you said you were looking for input. I think you need to work on your sound quality. It gets loud and quiet. I would also eliminate the background music when you are explaining something.

[@jedgarsquink]

Agreed. The background music detracts and distracts. It's like being in a class next to another student who's playing music on headphones, so loud that you can't avoid hearing it, while you're trying to listen to the lecture.

[@theshed8802]

This is a re-release of an old episode off David's old channel that he can no longer access. Since this was made he has purchased new camera equipment and new audio equipment. Many of us agree longer time followers agree with you about the background music. It was there to cover up the noise of the air-conditioner running in the background. Personally, I'd rather hear the air-conditioner.