Do Different Valves Effect Flow Undercut vs Straight Stem, Back Cut Vs No Back Cut

[@Mike62501]

One thing that I learned over 60 years is the under cut stems are three fold reduce weight, air flow and adding flexibility between valve stem and valve head. Flexibility helps allowing better sealing when running. Nice job my friend.

[@markbuskens6070]

Wow that was the very first test I’ve seen on intake valves on a flow bench!!I always thought the smaller stem would make more flow but it didn’t always😮I built a 408 smallblock Chevy with iron vortec heads an Rev valves it flowed like 242 at .400 with 2.02 had about 180 on the exhaust.worked very well in a street camaro 4 speed.Love your videos I’ve been binge watching to catch up.very technical content 😮

[@bobgyetvai9444]

The shape of that tulip is what really matters . The flatter the better !!! Your tests show that too . Big back cuts are a good thing . Thats part of a multi angle valve job to me .

[@vinknepprath4404]

Awesome info man! Keep up the hard work. Can't wait to see some more s10 footage

[@johnmortimer7862]

Eric, Thank you for making this video. I have been wondering about valve grinding for a long time!

[@WeingartnerRacing]

Im glad you watched.

[@engineguyeric682]

Will be sending a 243 LS head t have a flow/review that I ported soon. Love your videos.keep it up

[@andysteele4056]

Great info! Is there any guide on when you would go with 33 degrees over 30 degrees? Does it favor low or high lift flow? Would it be more for use with a seat angle greater than 45 degrees?

[@edsmachine93]

Great comparison Eric. I appreciate your time and analysis on this subject. I use the PBM/Erson valves also. While in some cases, I know there are better valves. The Erson valve are not to bad. I also use SI Valves. I like the Ferrea also, can be expensive for some of the projects. But good quality. I always like the backcut on intakes. I think it is worth the expense and effort. Take care, Ed.

[@Stale_Mahoney]

i got to say working on my volvo head now for better performance and it's crazy seeing how up to 1" is actually used lift numbers and what is low range for them is sport/strack lift for my engine. as i got a 0.472 lift currently and considering 0.492. but it's a nice to see what back cut is doing, got to cut my valves as well it seems :)

[@rickseeman5679]

Informative. Thank you.

[@neilhansen9886]

Very good information 👍

[@yodawunn6700]

Great video, answered a lot of questions. So how about the flat edge on the O.D. of most exhaust valves? Maybe a 60 deg "front cut"? Just enough so the spent gasses aren't hitting a flat edge.

[@donalbershardt9290]

35°

[@Errol.C-nz]

A LOT being left out or missed.. focus has been only on the port side of the valve.. thats half the venturi.. & it affects swirl within the cylinder.. & back flow.. with or without an angled chamber cut.. back flow is affected by dished valve heads & its important to retain a sharp edge on the valve head rim to reduce back flow.. that wide rim on the face perimeter of the no name valve is there to add a level of stiffness to the heads seat & help avoid head distortion & associated seat seal.. a small head size dia increase out past the seat can improve the venturi flow & effect into the cylinder.. dependent on chamber clearances for full lift flow tradeoff.. theres still a LOT of art in porting when valve float & resonances are considered.. not just fluid dynamic resonances but the mechanicals of the valve head at high rpm or critical harmonic rpm factors.. necking the stem is a risky business.. i saw a slomo strobe video decades ago that showed just how much at critical rpm a valve head can wobble.. & exhaust valves are even more critical with heat blow torching effects on head & stem

[@richardprice5978]

something im considering is 5/16" aka 5MM ish vs 3/8" aka 8mm ish vs 10mm ( thinking of using the 10mm stems all the way around but making them hollowed out and packing it with aluminium core or oil/engine oiling hole's or sodium and using inconlel material aka upgrade materials ) stems air flow vs longevity as the 60's iron 426 hemi stroker ( 440's have the same problem or similar problems with valves ) im building is known for eating the 5/16 stock valve's as the intake's are about a 60MM head and are heavy basters and the exhaust is about a 2" or 50mm ish size and roller camshaft's and heavy 300*lb over the nose springs needed don't help the problem add in longer TOB's/100K-mile and or higher rpm's ie 6K-RPM runs and it can pop a head off or spitting rod's out the side of it i think 🤔im right that using larger 10MM stems as fair trade off for my application as i don't think it will kill dyno-flow-bench-numbers to bad but maybe im wrong

[@mwall1296]

5/16 is 8mm.....and everything else you said is wrong after that also

[@Anarchy-Is-Liberty]

Thanks Eric, great stuff!! Maybe with the heavier valve you could center drill it or just go with a slightly stiffer spring, no?

[@samstewart4807]

hi, a very interesting video. I am sure you only scratched the surface- of the subject- not any of the valves.

[@jim-er8in]

This was a Great Video !!! Thanks for taking the time to explain it !!!!

[@WeingartnerRacing]

Thanks for taking the time to watch.

[@Archermboi]

As someone who just built a engine with a pair of the pre assembled IK 180 this past summer I hope my heads had the old valves especially because my peak power is much lower than 6500

[@YerkitRacingChannel]

Great information in this one! Appreciate you sharing and looking forward to seeing more s10 track content!

[@nealcardozo2146]

Great information: If port velocity was to change at some point, how much change would there be in flow in these differences?

[@krusher74]

we arnt doing anywetflow here, so in reality the best CFM airflow might not wet flow fuel/air to the combustion chamber the best.

[@HYDESCRAZY]

Nice..You are the man.

[@WeingartnerRacing]

Not all the time.

[@FatBoy7.3Powerstroke]

Humble is good, Nobody’s perfect. You do have fantastic videos loaded with experience and knowledge, great insight too

[@jacquesgold]

Great video! Thank you

[@FatBoy7.3Powerstroke]

Man I’m porting a set of 7.3 powerstroke turbo diesel cylinder heads with helical intake ports. Stock stainless steel valves have a 1.675” diameter. I’m bound and determined to cram as much of an increased diameter valve in there, both intake and exhaust are the same size from factory, and there’s room for more, not much but more. I’m aiming for the 1.755-1.825” and want to reduce VT weight as much as possible. Not looking to win a championship, Looking to improve low end torque, drop EGTs, and pick up efficiency for a heavy tow rig. Intake valve seats are integrated but exhaust can be replaced and inserted with better heat transfer materials. I’m prepared to pay more for titanium Retainers, keepers, valves for weight/inertia mass reduction. Valve guides I believe to be integrated as well but could possibly be inserted with better guides with better heat transferring properties. Is this a scenario you have any insight on? I created Coast to Coast Diesel Enthusiasts to be a channel for the diesel community because there is a tremendous void of knowledge available for our community. I value your opinion and have ultimate respect for your knowledge and proven results. I need some guidance and am open to being corrected. Can you please offer an opinion on this matter, any response will be appreciated. Thank You in Advance Sir! - Jay

[@warby8138]

Do you every radius into the back cut from the angle on the back of the valve, or are you relying on the sharp edge to cause local separation to help turn the flow? Also, would it be possible to do a video on different back cut angles, keeping the Valve seat angle the same?

[@n4thawin]

Good test. But the straight stem doesn't matter at low lifts as there is too little area and flow to matter at that point.

[@lcambilargiu]

Does a rounded back cut (instead of the 30 or 33 deg cut) exist, I imagine it would be shaped a bit like a velocity stack and may enhance flow?

[@Friendsofdonr]

Random question, have you ever compared under cut "stock" size to non-undercut oversized valves? I'd be curious to see the difference between increasing valve size (+1mm) compared to oe sizing.

[@flinch622]

Mystery valve reminds me of the old Manley pro-flow.

[@Kapnez]

yeah this goes right quality information the trade-off is real build your motor to how you’re going to drive it

[@WeingartnerRacing]

Yep.

[@ericschumacher5189]

Would it make a bigger difference on a head that you couldn’t port the bowl dimensions to the correct % of the throat (example a class where the head can’t be ported and the bowl is roughly the same size as the throat)???

[@Errol.C-nz]

i would think it comes down to the section area of the port.. a fraction of a mm in port wall.. valve head support (stability) at higher rom would return better results in real world running

[@nicholasDaigle-c6m]

Is it possible that brodix change their ik180 again? My intake valve have a longer undersized stem (more like ferrea) and the 30* back cut is wider than the 45*. Seems like they listen to you! Edit. The valve face is not flat. So they have changed the intake valves

[@richardsmith-qy6vl]

I like it good information so I can buy a set of ik215 heads and have you port them for around the same cost of a set of afr 210s or 220. Good to know. Thanks for the video eric. Your friend from Louisiana Rick 427

[@BuzzLOLOL]

Test of radiused valve/seat like I do would also be interesting...

[@Danglebarry62]

My understanding is that they work well on the exhaust side but suffer on the intake due to lack of shear angles. I honestly haven't played with radius seats myself...what have you found?

[@BuzzLOLOL]

@@Danglebarry62 - Just the opposite, work well on intake like backcutting does, even better, smooths flow, but can allow more exhaust heat/heat transfer to get under the head of the exhaust valve... so just radius the exhaust seat...

[@AmirPomen]

Would love to see follow up video on which exhaust valve flow the best.. and then combine best intake valve with best exhaust valve style and see how much its improve flow.. Cheers 🍻🦾

[@WeingartnerRacing]

Maybe in the future.

[@wizardshome9686]

What is the difference between various angles for the back-cut - wedge heads like flatter back angles then a Hemi would - for instance - at one time Manley was making some intake valves that were 10 degrees on the back angle and they flowed more that the same size valve in a SBC than a 14 degree valve?????? Good video though interesting stuff regardless

[@WeingartnerRacing]

Back cut angles are really individual head dependent. What works on one may not work on another. Hemi heads have a very different intake valve as compared to other heads.

[@stevenmitchell6347]

There appears to be a difference in the flute of the Brodix valves. Fluting is known to affect flow.

[@WeingartnerRacing]

It can. They make different angles with the valve head to stem.

[@jjmccloud]

I have a sbc head from PBM (strike force or something) 200cc 64cc chamber with all erson valves, springs, retainers etc. Curious how they hold up and flow. I don't know much about them but hear they're decent for the money

[@brandonroseman1039]

Hey Eric, would you say that there is a series/brand valve that outflows the rest with the back cut being equal amongst the them?

[@WeingartnerRacing]

No good valves come with a back cut 90% of the time. You have to put them on yourself. I like rev and ferrea.

[@brandonroseman1039]

@@WeingartnerRacing thanks

[@Redneckairflow]

Off subject but have you ever tried flowing the head mocked up in the overlap part of the cycle? Like pulling from the exh with a cup over the chamber and sucking thru the intake to see if there is power to gain from that without having to use as aggressive of a cam in the overlap department?

[@jmflournoy386]

Do you od hone your stems to hold a little lube in these no lead days?

[@davidreed6070]

Eric do you round off the top side of the exhaust and clip the top of the intake

[@MrKawa74]

What t does this Tell ? Port to Large for Under cut Stem ?? Nascar runs 6mm or 7mm

[@jimhalbrook9155]

Wheres the best place to buy cartridge rolls

[@brandoncurp5952]

I took some factory LS solid valves, put em in the drill press and used a dremel to turn down the stem just above the head where you'd have an undercut stem on aftermarket valves. But I just made them perfectly straight not undercut. Do you think this would reduce strength enough to worry about? Seems like it would be just as strong or stronger than an undercut valve stem. On the factory valves there's a little bit of a "hump" where the valve stem OD increases just above the head of the valve

[@WeingartnerRacing]

If you removed material at the radius that is were it is weakest.

[@2damnkwik]

isn't valves like the ferrea with the indent head of valve make it prone to deform with lean conditions? seen it on blower engines

[@WeingartnerRacing]

I haven't seen that but I'm not saying it hasn't happened.

[@diyhomeandautos1702]

Ok, ok, not interested in exhaust, well the exhaust isn't about the stem side back cut, it's about the cylinder side back cut because the is flowing opposite. Also the sharp edges. Please show intake flow with good # using exhaust back cut on the chamber side. The chamber side exhaust back cut may help intake flow and exhaust flow plus help reversion. Of course at < 0.55 lift. I would say it is complete to at least mention exhaust vs a hand wave.

[@SealofPerfection]

Geez, we need to know exactly what that old Brodix valve was...it beat them all.

[@Rob94hawk]

I picked a really crappy time to build a new engine. Really good heads cost a fortune plus plus now.

[@WeingartnerRacing]

It’s rough right now.

[@jfv65]

Nice info. But putting a backcut on those valves at the expense of seating surface hurts heat transfer and will accelerate valve wear. Not important for a race car engine but it might be important for a street car engine. Something that should also be considered.

[@WeingartnerRacing]

The back cut on the valve does not change the seating surface. You never bring the back cut out far enough to touch the seat cut in the valve. In other words you lap a valve. Then when you do a back cut you grind it until you are close to the lap line not in it.

[@sepg5084]

Maybe Brodix went ahead with their "new" design based on dyno results

[@doubletee4391]

why do the Ferrea valves perform so badly? I know you explain why it's just that they have such a good reputation it's disappointing. Even after you cut them they still didn't do quite as well as the broadix. Are there and redeeming qualities for the Ferrea?

[@WeingartnerRacing]

Ferrea valve are one of the best quality steel valves but they are made for engine builders to put on there own back cuts. If I had tried a few different things I would have gotten the Ferrea to do better.

[@MrTrustafox]

can you do curved back cuts?

[@WeingartnerRacing]

No

[@dougsadler5923]

I'd like to send you my twisted wedge sbf heads for 302 actually....and let you work your magic on them....

[@MJPilote]

One thing I’ve learned over the years is if you dont do nothing else do a back cut and radius seats, it’ll make better power than ported head without the back cut and radius seat. That applies to 4 valve heads, I don’t do any old school pushrod stuff, that has been obsolete for ages. The stock pushrod heads where so bad, no matter what you did they usually ended up better.

[@robh87]

Well isn't it all about flow when it comes to your heads? That's all I would care about. Moflow mopowa baby

[@WeingartnerRacing]

There are other factors as well.

[@DANTHETUBEMAN]

the valve is only half a valve,, the valve seat / the head is the other half of a valve. probable best if they work together in there geometry there doin in the.

[@JC-gw3yo]

A lot of numbers, but I didn't hear many conclusions

[@WeingartnerRacing]

I let people make their own conclusions. Usually when I add my own people complain about me adding my opinion.

[@rightsidelanechoice7702]

Those huge ass intake valves aren’t doing shit because the combustion chambers are shrouded as hell.

[@WeingartnerRacing]

Ok

[@rightsidelanechoice7702]

@@WeingartnerRacing On a stock set of closed chamber camel humps the 194” intake head will out flow a 202” especially with 1.6” exhaust valves then there’s obviously a shrouding problem. A larger valve will restrict air if it’s shrouded, the valve gets in the way of the air flow. Do you not agree with my theory or what?

[@WeingartnerRacing]

@@rightsidelanechoice7702 yes if it’s severely shrouded. The easy solution is to unshroud the chamber. About .170 valve to chamber is unshrouded. Although I have run tighter and still moved more air. The best flowing double hump heads I have seen had 2.055/1.60 valve. Made amazing power too.

[@Danglebarry62]

@@rightsidelanechoice7702 Camel humps haven't been relevant in 3 decades at least, not that you can't make good power with them, and Eric has filled in the blanks above. This chamber isn't a camel hump chamber, thats for sure.