Flathead Valve vs Chevy Valves

[GOSFAST]

Let me start a separate post here about the Ford vs Chevy valve controversy, it will make it a bit easier for me to follow the topic without jumping around. I know the valve combos have been done by many here but we've learned over the past 40+ years most times and on most builds the (longer) Chevy valves are NOT necessary, no matter what anyone believes! Even today if we needed a larger 1.550", 1.600", 1.625", etc, (not longer) we would simply order a set from our friends down at Ferrea Valves. We would order ANY head diameter we need but leave the length OEM, 4.820" (nominal). I have already used some 1.750" (intake) diameters, in my opinion a total waste of time and money!

There's one other dimension that I haven't seen mentioned, actually anywhere in any post (my own included), even past ones, but it would pertain to the valve "margins", the thickness of the face of the valves.

If you think about it for a minute this real dimension MAY play a very large role in the overall spring-height scenario for sure, follow:
most Chev valves are mfd to the original OEM specs (dimensions), with some racing valve exceptions this is true for the most part. The OEM's will normally have about an .085"/.090" (nominal) margin (especially when using Chevy exhaust valves), the Flathead's I have on the shelf here, all new, come in around .050"/.055" (nominal). This fairly large difference comes into play with the topside spring heights/pressures during the final ass'y. Technically speaking, even though the Chevy valves are listed as being approx .100" longer that the OEM Flatheads if you factor in those "margins" it makes the Chevy valves slightly shorter than the .100". You wind up "seeing" only .040"/.050" difference on topside! The final spring heights and pressures will reflect this difference.

Like I've mentioned up here numerous times we do not use the Chevy valves in any builds anymore and it's for this reason I had totally forgotten about the "margin" thicknesses. Like I stated above here, if we needed any type "special/custom" valves mfd, we simply contact the guys down at Ferrea, they will make almost any configuration we desire! We've only used these type valves on Flatheads on very rare occasions due to the cost factor, most builds here do not need these custom valves.

Now, here's the issue, when you choose the Chevy valves (with these thicker margins?) over the OEM Flatheads you WILL most likely end up addressing this difference on the topside (valve-to-head)?? Think about it for a minute, I'll use a nominal measurment between the difference on the Ford and Chevy valve margins, let's say .040" for arguments sake. If the Chevy valves have that added height sticking above the deck surfaces it MAY have an effect on the "piston-to-head" clearances after the fact. If this proves true it's just one more reason to avoid these valves. Once more, if we need some slight add'l valve length (.060"/.080" simply add some lash caps. The lash caps add to the valve length but have no effect whatsoever on the spring heights/pressures.

This possible add'l issue I mention above here is one that Casey (in the other post) may also end up experiencing, we call it "the domino effect", solve a perceived problem (believing longer valves are needed) while simply creating another, and it's no fun when your in the middle of the build with a number of (possibly) useless new parts on the bench.

I would also add this, and it will make life easy for many here, if you are considering purchasing ANY components for a decent build and I'm not talking a "repair" here, but basically a complete new build, I strongly recommend getting ALL the related parts as a single purchase, this would be with respect to a "top-end" package (like all the valve-train parts), AT THE SAME TIME. In other words, when buying individual pieces and trying to get EVERY last piece to "match" in the end is likely going to cause some grief, not sure how much, but it's what we've learned over the years. Most builders of the Flathead's should have this down to a science, all the correct parts on the first shot, it's very easy at this point at least for us.

Let me touch on regrinding previously run cam blanks, I doubt very much anyone involved in that business is going to remove anywhere near .080" from the "base-circle" (the heel of the lobes), it sounds unreasonable to me. I don't grind cams here but that amount sounds like a "stretch"? The total removed for chasing add'l valve-lift would definitely be offset using the lash caps, and again, with absolutely NO effect on the spring heights/pressures. The OEM (Flathead) installed heights would remain a constant? On the non-rotator platform this should be about 2.125" (nominal).

(Add) Casey, the valve head margins is the "lurker" I meant earlier.

Thanks, Gary in N.Y.

P.S. I will add this again, begin your build with the components that aren't going to create headaches, try to get the correct ones from "day-one", life will be much easier at that point! Another very important issue, don't be afraid to ask any shops you're contemplating using for your build ANY questions at all, if they "squawk" or seem "non-compliant", move on. I realize this is difficult in many areas due to the limited shops/builders around but I would not settle for "second-best" on any work at all. For many years we've tried to take advantage of today's technology and reverse-apply it to the Flathead platform. This is the reason we started (very long ago) with the bronze guides, it is a "positive" in the end. Same with respect to torque-plate/finish-honing the blocks, with the extremely light ring-packs used today we felt (also a while back) it was time to use these methods on EVERY build, race or not! Using this scenario the rings are literally "broken-in" on the dyno. Even without the dyno between the finish on the bore and the "new" ring material, the rings seat reasonably fast/easy.

[super flat]

Thanks GOSFAST, that is a great explanation! Gary

[outlaw]

Gary, Thank you for explaining this. Never thought about the thickness of the valve face before. Makes sense to me. Bill

[flatheadmurre]

I use the chebby valves cause it is simply the cheapest performance valves around due to the fact they are manufactured and sold in a quantity !
That ugly stock valve you compare the OEM flathead valve with isn´t the choice of anyone looking for flow and performance.
But im the first one in line to buy your custom undercut proflow valves with the correct lenght for the same money i pay for a set of chebby valves !!!
The dish thickness of a performance valve ain´t thicker then the flathead stock ones...

[Russ/40]

Your observations are dead on. Especially when new seats are installed, as valve head intrusion complicates valve to head clearances.

[tubman]

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And all along, I thought the reason I always used original Ford valves was because I was cheap! Seriously Gary, this is a much appreciated write-up; it opened my eyes to a couple of things.

[Ol' Ron]

Fortunately,I understand what Gary is talking about. Unfortunately, I can't afford his method of solving these problems. Now not to complicate this issue, the head of the Chevy or stock valve is not compatible with flow. If you were to look at my or JWL's book you'll see the mods necessary to the valve head to improve flow in the under the head area. I seat my valves very near the edge of the valve, as this is the hottest area of the valve and only cooling the valve gets. When carving the combustion chamber you take into consideration valve lift and the clearance you deem necessary.
Now we approach the valve length. I find that on a reground hi lift cam such as the L-100 or 400 jr the base circle is small enough to allow the use of a stock Ckevy valve stem to use an adjustable lifter. Now some of you don't like to use adjustable lifters. I've been using them all my life with no problems, if I did, I'd have Walt do my valve jobs. For some las caps and special valves do the same thing, it may be a better way. I just can't afford it.
As far as installed spring height is concerned, that's just a few shims. Now for a street engine, this is just5 a cow's opinion. A MOOO Point.

[Admiral]

Great post! Thanks for sharing. One of the big take-aways is doing things right THE FIRST TIME. Apropos buying all the valvetrain components at once, I couldn't agree more. Don't try to save a nickel here because it will often cost you a dime over there.

[JSeery]

Like this.

[GOSFAST]

Originally Posted by JSeery

Like this.

Hi "J", the stepped down neck on that Manley valve will flow approx 3 or 4 CFM over a non-stepped neck. We have tons of experience on the flow benches (I own 2 them) with getting airflow through any unit and that CFM number is accurate for the most part.

Having said that it takes approx 1 CFM to be able to produce 2 HP on a normally aspirated build. There are numerous other variables but this is in the ballpark. On the Flathead platform I would gladly sacrifice 6 or 8 HP to have no issues like so many up here experience due to longer valves, from my standpoint here it's ludicrous to have so many issues related to that single item. If we were building an all-out race Flattie I would begin with a 5/16" (.312") valve stem, possibly even the newer "metric" stems, this type platform will get some air moving! Not needed here for "streeters" in my opinion.

Again, that ride in my signature doesn't have any stepped-down valve necks but still managed to produce over 150 HP. I'll say it again here, the Chevy valves just aren't needed.

I've sent out a high number of "valve-kits", this includes valves, springs, retainers, valve keys, guides, guide locks (horseshoe clips), etc. and haven't gotten a single phone call where any parts sent out didn't "fit" on the first try, not a single one? This really makes the ass'y part of the build a pleasure to do.

(Add ) Following Casey's post up here I really believe tonight if his parts had been an add'l hundred or two extra he would have been VERY comfortable if there were NOT these issues he's having? He can correct me if I'm wrong, but I believe he'll agree! It takes much of the fun out of what should be an enjoyable project!

Thanks, Gary in N.Y.

P.S. I want to avoid pricing up here for a few reasons, one mainly being it isn't fair to vendors on here. The main purpose of my posts is really to help solve problems more than anything and to help others avoid the "pitfalls" many here encounter. I feel a number of members up here would be in a real "pickle" without many of the other (more experienced) members who participate in solving problems. This is good.

[40cpe]

Originally Posted by GOSFAST

I feel a number of members up here would be in a real "pickle" without many of the other (more experienced) members who participate in solving problems. This is good.

I can't agree with that statement enough! I have wrenched as a hobby for 60 years but never built a flathead from scratch. Even with several books I still didn't feel comfortable in some areas until I batted it around with those of you who have so much experience. I'm still asking advice, I could call out a lot of names but I'm afraid I would miss somebody.

THANKS TO YOU ALL!

[40 Deluxe]

Originally Posted by GOSFAST

Hi "J", the stepped down neck on that Manley valve will flow approx 3 or 4 CFM over a non-stepped neck. We have tons of experience on the flow benches (I own 2 them) with getting airflow through any unit and that CFM number is accurate for the most part.
If we were building an all-out race Flattie I would begin with a 5/16" (.312") valve stem, possibly even the newer "metric" stems, this type platform will get some air moving! Not needed here for "streeters" in my opinion.

Again, that ride in my signature doesn't have any stepped-down valve necks but still managed to produce over 150 HP. I'll say it again here, the Chevy valves just aren't needed.

I have a question: If I remember correctly, the necked down portion of a Manley (or similar) vale stem is 5/16". So what is the difference in airflow between that and a straight 5/16" stem valve?

[JSeery]

The Chevy valve in #9 has a ~0.343 stem diameter and ~0.305 in the necked down area.

"If I remember correctly, the necked down portion of a Manley (or similar) vale stem is 5/16". So what is the difference in airflow between that and a straight 5/16" stem valve?"

If they both had the same diameter none. The air stream would see the same cross-section.

[JWL]

Frankly I do not see any problem with using the (much) less expensive and available Chevy valves. There has been many, MANY, Flatheads built with Chevy valves. There is also no downside to picking and choosing which components to purchase from which supplier. Often that is the only way to get exactly what you want. Of course it is important to actually know what you want.

I wouldn't be manipulated into buying all my stuff from one guy unless he had EXACTLY what I wanted for my engine and the price was right.

[GOSFAST]

Originally Posted by 40 Deluxe

I have a question: If I remember correctly, the necked down portion of a Manley (or similar) vale stem is 5/16". So what is the difference in airflow between that and a straight 5/16" stem valve?

Hi "40", the most popular/least expensive Manley valve that I'm aware of is part #10777-8 (1.500") and #10749 (1.600") and both stepped "necks" measure .335", stems measure .341". All "neck" sizes do vary and depend on the chosen valve.

Originally Posted by JWL

Of course it is important to actually know what you want.

Hi John, herein lies the main problem, most members up here that are building/assembling a single unit maybe every few years or so just aren't familiar enough in the big picture to know exactly what will OR won't work. Point in case up here right now is Casey working on his, he's had numerous issues already up to this point AND may have more later?? In all honesty in the time he's spent just trying to get through his issues we could probably have completely assembled the entire unit? This is NOT meant to be a "knock" on Casey but to make a point about getting the right parts from the getgo! I personally don't trust whoever is guiding him.

Let me go back to the Chevy valves with respect only to pricing for one moment. We do not use "cheap" or inexpensive Chevy valves in any of our Chevy builds. I have no clue what brands/prices you are speaking of with reference to the Chevy valves you are all using on your Flatties, but the ones we do use for our "race" Chevy builds run in the neighborhood of $25.00 per valve. We are OK with this number on our higher-end builds for the Chevy's.


I just recently priced out for a member here 16 stainless valves ($120.00) that we use on 99% of the Flathead's here and they come in very close to Manley's pricing but for the 16 pieces not 8. I believe the Manley #10777-8 (this is 1/2 set on the Flatheads, 8 valves) runs about 120.00?, this would make a set price for 16 in the area of $240.00. If there are "cheaper" Chevy valves out there I don't know anything about them and have NO need to know.[/COLOR]

At this time I'm not overly concerned with "moving" full valve train packages anyway (we do it now, but I'm not concentrating on it at the moment), as I'm waiting on Comp Cams to help with the Flathead spring-locators where I believe all these spring height issues will totally disappear?? I had brought this sole issue up in another post here where this setup would allow as many as (6) .060" shims to fit between the existing register and below ANY spring used. You'd probably never need that many but it would be a real nice option for many up here!

Thanks, Gary in N.Y.

P.S. On a side note, above I mentioned a full-length .310" (5/16") stem (or smaller), this would be on an all-out race deal and be an advantage with the entire valve being much lighter. This makes "keeping control" of the valve easier when racing.