What are LSA and overlap? Are they important? Why do camshafts have 4 degrees of advance ground in?

[@davidreed6070]

That was a very good explanation of the valve events

[@goldsgarage8236]

thanks David. AG

[@StuartBlake-iz6rf]

Alan, great explanation, the charts were spot on. Thank you for the tuition. Slowly getting a better understanding. all of us benefit. It finally exposed the compromises we have to consider when changing events. Good job mate.

[@goldsgarage8236]

Thanks you for the nice compliment Stuart. AG

[@toddbrown2236]

Excellent video. Great explanation. Your visual aids really helped me wrap my brain around what you were explaining. Thanks!

[@goldsgarage8236]

Thanks you Todd. AG

[@mrho4speed]

Great video and thanks for showing the hydraulic cam and the roller cam. The visuals really help the explanations. I can see how important it is to be realistic with regard to the car = is it for street only, street and strip, or strip only? And the cubic inch of the engine, the combustion chamber size of the cylinder head, the compression ratio, the valve timing is so critical here!! And the rear gearing and the weight of the car and if the car is an automatic transmission = what is the stall speed of the converter? It all matters and has to work together to give the car the desired result for the driver!!!!

[@goldsgarage8236]

Thanks 4 speed. You are a great student. AG

[@heathvice8365]

Thanks for the breakdown, this will make for an excellent reference guide.

[@goldsgarage8236]

Thanks for watching and commenting. AG

[@goratgo1970]

Good presentation with helpful graphics. Another aspect of cam choice is dual pattern. Also I learned for my application of a Tstorm charger on BBC crate 502 is higher LSA for boost, so chose Crane roller with 112 LSA. JIC you read this it has 288/296 dur, 587/610 lift.

[@goldsgarage8236]

Thanks for your comment Goratgo. AG

[@PCMenten]

Thank you for this detailed explanation. For me, it is timely. I need to decide on fuel grade (octane), compression ratio and cam timing, with my intended use. In my case, middle grade fuel - 89 octane and daily driver use with a view toward efficiency. I have a Ford Cleveland to assemble as well as a Ford Cologne 2.8/3.5. At 18:00 in the video, you talk about the need to get the valve open in time to fill the cylinder, and 4° of advance is a sweet spot. Clevelands have enormous valves and flow well at low lifts. They can be further goosed by using Pontiac valve angles. I’m thinking I can finesse the duration a bit, or widen the LSA and shorten the exhaust duration to get back some efficiency.

[@goldsgarage8236]

Thanks Pc, you have given this a lot of thought. AG

[@joshuagarvey9362]

Very nice video.Going to have to watch it a couple times.Very nicely explained.Thanks.

[@goldsgarage8236]

Thanks for watching and commenting Jo. AG

[@davepilling3134]

Another very informative video Allan. You mentioned a dyno day in the future. For those of us who have never had an engine dyno'd but plan to, could you go through the procedure,cost and what to expect when delivering your motor if possible.

[@goldsgarage8236]

Great suggestion, We are always looking for ideas, thanks Dave. I will do that. First we fire up the engine and break in the cam on my test stand so it is ready to go when we get to the dyno. We will plan to explain the complete process for you. Our next Dyno date is March 30 for Joe's 400 Pontiac. Watch for it. AG

[@DeanStewart-t4v]

Good.. Great, explanation, only proves one size does not fit all.

[@goldsgarage8236]

Thanks for watching and commenting. AG

[@Scubasteve22]

Thanks for sharing! Glad you mentioned DV! Many people are in denial about LSA what it should be. I have had great success with camshaft selection over the years. One thing I would say to the viewers is; If in doubt about which cam to pick, a straight pattern on a 108-110 will generally give more smiles per gallon.

[@goldsgarage8236]

And thank you for your comments Steve. AG

[@robertfontaine3650]

This one helped a lot. I'm going to have to watch this a few times.

[@goldsgarage8236]

Thanks Robert, glad it was helpful.AG

[@GrandPitoVic]

Sir Gold, thank you for the video. A lot of great information. Very good video. I appreciate it very much sir.

[@goldsgarage8236]

Thanks for watching and commenting Vic. AG

[@joe-hp4nk]

Cams are a black art for most people and we rely on cam companies description application and specs to come up with one that'll suit your purpose. In the end, it ends up being an expensive trial and error.

[@LJK69187]

Yeah you call back the next day and a different guy will give you an entirely different cam suggestion!!!

[@GrandPitoVic]

This is very true!!!

[@mariocooldude9092]

​@@LJK69187hahaha 😂it's all a game and a joke

[@vinceyoung5912]

The longer exhaust is from circle track racers. It bleeds power so they stay on the throttle in the turns.

[@goldsgarage8236]

Thanks Vince, good point, we will be doing some experimenting with that. AG

[@vinceyoung5912]

@@goldsgarage8236 it would be interesting to see if symmetrical cams make more power

[@Nobody-ld7mk]

Possibly in the future, while you're degreeing a cam... you might look at how much increased lobe lift is aquired with the 4° advance @15° ATDC vs. the straight up 110° @15° ATDC or any suitable reference point ATDC. More lift when the intake stroke really starts to drink... equals more early fill in the intake cycle. One small detail often overlooked when advancing. Excellent tutorial...

[@goldsgarage8236]

Thanks for the suggestion and comment. AG

[@sharkskinboy]

Great video Allan! I just had one question though - I like to work things out myself and I actually calculate 2.5 degrees of what you refer to as advance, rather than 4 degrees. If you look at your graphic with the two cam lumps on it (introduced at 14:25), this shows a timing sequence that spans from 0 degrees to 720 degrees on the horizontal axis. The midpoint is 360 degrees which corresponds with TDC. The intake opening occurs 32 degrees before TDC (which is at 328 degrees) and the exhaust closes 27 degrees after TDC (which is at 387 degrees). The difference between these of course is the overlap: 387 - 328 = 59 degrees. The midpoint of this overlap area is at 357.5 degrees, which is 2.5 degrees before TDC, not 4 degrees. I know that this assumes the same ramp on both lobes (symmetrical lobes) which is not exactly true because of the duration difference between intake and exhaust, but that's only a 2% difference - pretty negligible. Am I missing something? The other thing I wanted to mention is that what is being discussed here is not exactly cam advance, but cam asymmetry. If this camshaft is installed such that all the specified opening and closing points are correct relative to the crankshaft position, then it's considered to be installed straight up, regardless of how it's ground. Some people however then actually advance the camshaft on installation (I'm sure you're aware of the offset bushes that are used on Chevys to achieve this) so that all the timing points shown on the cam card actually occur a few degrees sooner than specified. That's what advancing a camshaft technically means. 😀

[@goldsgarage8236]

Thanks for your comments Shark. You have given this a lot of thought. On the first point, have you taken into consideration that the exhaust valve has more duration than the intake? on your second comment, you are correct. Advancing the cam refers to moving it relative to the crank. The factory advance however is ground in and cannot be moved. Hope this helps, AG

[@sharkskinboy]

@@goldsgarage8236 Yes the difference in duration has a very small effect, basically it becomes about 2.55 degrees.

[@andrewslagle1974]

Great explanation !

[@goldsgarage8236]

Thanks Andrew. AG

[@mikediamond1522]

Great Video! David Vizard has an excellent cam formula!!! Mike

[@goldsgarage8236]

Yes he does Mike. I referred to it in the video. AG

[@bigboreracing356]

Comps catalog is a better source for picking the correct cam.

[@leonardfoster6252]

I may not know everything about cams, but I know enough to work for me on the engines I build.

[@100amps]

That's million dollar advice Allan... 👉 DON'T RELY ON VERBAL INSTRUCTIONS! 👈 for any kind of vendor job.

[@goldsgarage8236]

Thanks 100. Glad you enjoyed it. AG

[@johngoddard6644]

I would love to see in the future posible big block budget build.

[@goldsgarage8236]

Thanks John. I did some videos on a 427 build about a year ago. Check out the mighty 427 video. It wasn't really a budget build but i would be happy to do one in the future also. AG

[@ronbo422]

I would like to see you KZbin engine builder/guru's start teaching us some stuff about the Gen 3 Hemi's. I included DV in this "challenge". The G3 hemi, especially the later Eagle and Apache variants, offer a lot of power, equipped properly. DV's "128 rule" (I think that's what he calls it) is aimed at SBC's. I've heard that it doesn't apply to the G3 Hemi. Understandable, to a degree. An engine is an engine is an engine... except when it comes to the cylinder head. And that's where DV's formula doesn't work on the Hemi. As an Eagle owner (5.7), my heads flow just over 300CFM (I) and 155-ishCFM (E). With all that said, I'd like to see you guru's pick apart a Hemi and show us what does work, what won't work, and why. Thanks for the video, too.

[@goldsgarage8236]

Thanks Ron, lot's of interest in this, I am not an expert in this area, but i will talk to Bill Little about doing something. AG

[@ws2664]

Great video, I'm just learning the ins and outs of cam specs, this is great. I don't know if you know this or not but your shop is painted in Toyota colors. I don't want your American muscle fans to get the wrong idea. Just say'in.

[@goldsgarage8236]

Thanks for the comment, never thought of that. They are also similar to the GM Goodwrench colors, which was my intention. AG

[@ws2664]

@@goldsgarage8236 My chevy dealer was white and dark blue, Mr. Goodwrench colors, I was there for a year then went to Toyota for 2, so you're going to have to build toyota motors or repaint. LOL.

[@sheerwillsurvival2064]

Great video it’s been a long time for me . Thanks

[@goldsgarage8236]

Thanks for the comment! AG

[@tylermcpheron1966]

Hi Allan, I was watching your videos on rocker arms and was wondering which budget-minded sbc rocker arms you have had good luck with over the years? Thanks!

[@goldsgarage8236]

Thanks for the question Tyler. according to Mike's research, the PRW rocker arms are the most economical and they performed very well. AG

[@patrickwendling6759]

Thank you for your knowledge and video's USA 🇺🇸

[@goldsgarage8236]

Thanks Patrick. AG

[@488ci]

When you are bleeding off your compression, wouldn't you also be sending unburnt fuel out the exhaust making less HP?

[@utahcountypicazospage5412]

Yes but only at low rpm.once rpm goes up that goes away. As the events are happening faster.

[@Freedomishere-im6ug]

Static comp vs dynamic comp Also remember hp= fuel bill

[@erikscotchlas7173]

Great video! Thank you for sharing. Question: I have a Pontiac 350 but do not have any information on the cam that was installed when the motor was rebuilt. What is your recommended process for determining the cam spec without opening-up the motor? If you can please share, then I can move forward with determining proper cam set-up, including setting proper valve lash. Thank you!

[@goldsgarage8236]

Thanks for the question Eric. If the engine is in the car, remove one rocker arm and measure the valve lift. You can do this using a dial indicator directly on the push rod. Compare this lift to the factory specification. Lift and duration go together so it will give you an idea of the cam size. If the engine is out of the car you can use a degree wheel to check the duration. Hope this helps. AG

[@jessesyfie7244]

Hey Allen, u seen very smart and knowledgeable on engines. Id like your ideas and what u think on David Vizards 128 formula for the correct LSA in engines. It's probably more for performance race engines rather not so much for towing and pulling engines. Seems his formula favors the tight LSA numbers. 106/108 etc. For the most low rpm, mid range and top end all across the torque band of the engine they make more power. He uses it to pick the correct LSA of cams then overlap.

[@goldsgarage8236]

Good question Jesse. I have David's book and I have used the formula. Sure, i think it works, especially for max power. I think cam makers often use a wider LSA to improve drivability for street engines. Even Bill Jenkins, years ago published that he thought 109 LSA was ideal for a SBC. AG

[@FreeSwimmer]

It seems that by changing the degrees of timing, it controls the length of time the valves are being open or closed. It appears to have a direct effect on the overlap time. So, is this how timing has such a major part in Hp making ?

[@goldsgarage8236]

Thanks for the question Free. Overlap is the number of crankshaft degrees that the intake and exhaust valves are open together. The overlap cycle occurs at the end of the exhaust cycle. At this time, the exhaust valve is closing and the intake valve is opening. Overlap is the product of duration and LSA (lobe separation angle) More duration provides more overlap and more (wider) LSA results in less overlap. Typically, more overlap increases high RPM power at the expense of low speed drivability and vacuum. Hope this helps. AG

[@roberthollinshead2325]

Vizard says on the smaller duration cams the flat tappet cam opens the valve a lot faster than a roller.

[@goldsgarage8236]

He is correct. Thanks Robert. AG

[@midnyte_ryder]

So if I understand correctly, the lsa is relative to overlap, is that what gives an engine “chop”? Like loping idle? I bought a chopsticks cam from mmx because I wanted it to sound dope but still drivable. The thing is an absolute beast of a machine now I love it. I have a 392 SRT Jeep.

[@goldsgarage8236]

You have it right Midnight. Less LSA = more overlap. Congrats on getting it right. AG

[@twgarage-terrywatson1672]

Fantastic channel. 👍

[@goldsgarage8236]

Thanks Terry, glad you are enjoying it. AG

[@topgunpressurecleaning8930]

Can you do a video on full float pistons compared to press fit? And maybe roller cams and full roller rockers. Is their horsepower savings with these add on's and how much?

[@goldsgarage8236]

Sure thanks for asking. i will be building a 406 race engine next with both floating pins and roller cam. AG

[@fredblase5608]

At 27:02 to 27:07 the camshafts are rolling back and forth (the heaver area is trying to go to lowest point) "an out of balance condition" > Any ideas on how to correct this condition?

[@MarkVanWey]

Good catch on a small detail. He said one of them was a BB Chevy. The lobes for 4&8 or 5&7 are on the same side of the engine so they are close to each other in the rotation (NOT front to back, but as it turns) When the cam stops rocking, the centers of those pairs will be top & bottom.

[@stevenshepherd1905]

Why does the 455 Pontiac self-destruct at 5500 rpm.

[@tedzehnder961]

I`ve always wondered why when degreeing the cam shaft, only #1 cylinder gets checked by engine builders ? If a cam grinder is worn out, be it the machine or the guy running it,the lobes might not be (in sync) with each other. I know nothing can be done about it after the cam has been ground except to try a different cam.But precisely setting the #1 piston is not proving the whole cam is optimized. Being in the ballpark might just be it.

[@goldsgarage8236]

Thanks Ted. AG

[@musclebone7875]

Camshafts are the brain of the engine.

[@goldsgarage8236]

For sure, thanks for the comment. AG

[@scotthatch4548]

Ok ... A few things Inertia ram happens at the intake closing point not at overlap and is also why you understanding of dynamic compression is not accurate .... At overlap what happens is scavenging caused by exhaust to pull on intake charge but that only happens at high rpm ..... Overlap is not needed at all to make power and i have proven this by grinding a camshaft without it and the hp was still great ... Scavenging is a minor player in power and only works wit open exhaust and long header ... In drawing a camshaft with events a circle with 720 degrees rather than 360 really helps see whats going on the old way you use is confusing ... Its better to look at .050 numbers because not all camshaft advertised numbers are at .006 so hard to compare I have my chalkboard videos on my site that shows more what I am talking about

[@littlevman2997]

Not sure why you watched this video if you already know everything. Those who exhault themselves will be humbled

[@scotthatch4548]

@@littlevman2997 because my health is bad and I'm trying to teach people what I have learned in 40 years of doing this stuff

[@joshkrause2977]

@@littlevman2997 quit virtue signaling, he is sharing his knowledge in a subject he is interested in, which happens to be stuff like in this video. Maybe you should get off your high horse, perhaps look at his info then research to find out? What if he is 100% right and the guy who made the original video is mistaken??? Do you even know who is right or wrong do you even care to research and find out???

[@leonardfoster6252]

At some point the intake valve and the exhaust valve are partial open to scavge the exhaust... It has too be balanced...

[@DANTHETUBEMAN]

cam sales has been the most deceptive thing for the newer engine builder for the street, all those 1/4 mile cams look GREAT with peak hp numbers, but low and mid torques is what you need on the street. ppl are smarter about it nowadays. 🤠

[@goldsgarage8236]

Great observation, thanks Dan. AG

[@leonardfoster6252]

Cam companies take the information from a person and put it in a computer and it tells them what cam specs will work, although it may not work perfect for the engine and the car. A lot of variables are involved great nding the right cam AG.

[@mariocooldude9092]

Yeah it's really a task isn't it.. like you'd have to dyno a bunch of cams to make sure you got the most you can out of your combination

[@josecuevas8602]

I think you forgot the fenonon called explain blow down. the moment the exhaust valve is opened. A good demonstration that you can use is get a can of your favorite soda. Shake the can and crack it open as a viedo illustration on how the exhaust gases escape past the exhaust valve, don't forget to mention that the exhaust gases are traveling supersonic.

[@utahcountypicazospage5412]

As long as you have long tube header to use that force to create a vacuum behind for suction of fuel/air your good

[@utahcountypicazospage5412]

I have found that there is never over, converting or over gearing even with the stock cam those two can be added.boost nitrous will help to big of a cam lol

[@mikes.1882]

The talk of the 21st century But, lsa, or lobe split back in the day, has always been argued. Depending on whether or not you followed everybody else, or you wore out Smokey Yunick's SBC book.

[@goldsgarage8236]

Thanks for your comments Mike.AG

[@gregleenyit]

Well done

[@goldsgarage8236]

Thanks Greg, glad you enjoyed it. AG

[@waynechristie1405]

Thank You, from another Saultite. [ Sault, Ont.}

[@goldsgarage8236]

Thanks Wayne, I know that name. I still cheer for the Greyhounds! AG

[@waynechristie1405]

Cool. Been watchin you for a while...Rd 2 for the Hounds [playoffs]. Got 2 projects on the go, 1 pending. 302 got strectched..347...aluminum hemi heads trimmed out by Jon Kaase.. cant wait to hear it on the dyno 351 being built out to 408. LT1 will get refit when the others are done. Following folks I trust makes the 'builds' less tedious. Thanks for that !!@@goldsgarage8236

[@goldsgarage8236]

Thanks agian Wayne, lot's going on. I will be up in the Sault this summer. AG

[@Dwlukinbill]

😎👍

[@goldsgarage8236]

Thanks Dw.AG

[@stevemiller7654]

LSA, what a waste of time when the overlap is the important thing, and it depends on timing events and duration. As soon as you change the duration of any cam design the LSA loses its significance. Years ago no one even mentioned LSA, and we got along just fine.... ...RooDog....

[@goldsgarage8236]

Thanks for the comment. AG

[@sethbarnes7608]

Check out David Visard's formula for determining the perfect LCA. Its great stuff.

[@goldsgarage8236]

Thanks 43. You have given this a lot of thought. On your calculations, have you taken into consideration that the exhaust duration is more than the intake? On the advance, yes you are correct. advancing the cam refers to moving it relative to the crank. The factory advance is ground in and cannot be changed. Hope this helps. AG

[@leonardfoster6252]

One size doesn't fit all AG, well said...

[@goldsgarage8236]

Thanks Leonard. AG

[@topgunpressurecleaning8930]

Too much cam can kill torque and hp. I'm doing my homework on the next engine before buying parts. I through one together when I was twenty years old and man what a low compression dog. Live and learn $$$$

[@utahcountypicazospage5412]

Nitrous would of made that a killer combo with a 3500 converter you would of had a 10 second capable engine

[@leonardfoster6252]

The hot ticket on cams for bbc or sbc os the LS firing order AG.

[@yarrdayarrdayarrda]

Built in cam advance will also offset the never mentioned cam retard once the engine is running, as well as timing chain stretch which happens over time.

[@goldsgarage8236]

Thanks for the comment. AG