Valve spring sanity check
- Thread starter louisb
- Start date
GOSFAST
Well-known member
Hi Louis, Good Luck whichever route you choose.
Let me put a couple numbers here that anyone working in this area should "copy & save" on their computers (or in their Flathead notebook). It explains how you can use the "standard-length" Flathead valves in builds where you believe you MUST use the longer Chevy pieces.
The OEM Flathead valve measures 4.820" (nominally), the OEM Chevy valve measures 4.920" (also nominally).
With the OEM Flathead valve when you simply add a Chevy type lash cap (Comp, Crower, etc) into the equation, the overall length on THAT valve goes to 4.910" (again nominally). If you jot these numbers down you see this is about "spot-on" lengthwise to the OEM Chevy pieces.
BUT, here's the important part, using this method has NO effect on the installed spring height, none! The spring will work with the OEM Flathead valve even on a cam with a "huge" base-circle reduction.
Long story shortened, the Flathead valve WITH the lash cap is almost identical (give or take a few thou') to the Chevy valve "as-is".
Thanks, Gary in N.Y.
P.S. I've been doing this "stuff" for more than 50 years now, I need to keep EVERYTHING in my life at this point as simple and trouble-free as possible. I know have much company here thinking the same!
Ronnie
Well-known member
poo-poo'd shims Really at 10 hp a cylinder it isn't much of a fire breathing dragon on the street. You are living proof it will get you by."LOL" just sayin. One should weigh the lash caps against the vsi and record the difference.
R
Bored&Stroked
Well-known member
I would replace the springs with 185G springs as was suggested by a few (is the only spring I use!). Also, I would aim to achieve 60 lbs (minimum) on the seat with that cam profile. You may get away with less, but 45-50# on the seat is not enough in my mind.
As Gary noted, if you've not yet done a valve job - you can change out the valves to achieve a shorter installed spring height, with lash caps to make up for the smaller cam base circle.
You have options . . . most importantly, you didn't just throw it together without exploring them!
As Gary noted, if you've not yet done a valve job - you can change out the valves to achieve a shorter installed spring height, with lash caps to make up for the smaller cam base circle.
You have options . . . most importantly, you didn't just throw it together without exploring them!
flatheadmurre
Well-known member
Going the sheapskate route as usual...cheapest valve around still the chebby.
.060 offset locks and .060 shim at guide with speedways springs(they have a copy of the iskys) gives you a lot of bang for the buck.
But as said more then one way to skin the cat...and i dont care if the part is meant to be in a itsumishi as long as its good cheap and makes the engine go faster.
.060 offset locks and .060 shim at guide with speedways springs(they have a copy of the iskys) gives you a lot of bang for the buck.
But as said more then one way to skin the cat...and i dont care if the part is meant to be in a itsumishi as long as its good cheap and makes the engine go faster.
Ol' Ron
Well-known member
WE learn by doing. 60 years ago, the flathead had been out of production for 3 years. 63 years later we know everything about it. Just remember, almost everything works in a flathead, at least for awhile.I had never built a flathead for the street untill, maybe 20 years ago. Even then, ypu had to get your foo tin it once in awhile. But we learned by our mistakes. Right now I know of two engines that have L-100 cams in them that have turned 5500 a few times one in Richard 276 and Robs 294. Both have 50lbs on the seat. However, they spend 95% of the time below 3k/ You can spend allot of money on these engines, if you have a good reason.
GOSFAST
Well-known member
Hi Ron, not exactly sure what you mean here?? The lash caps have no direct effect on the spring pressure and on the flip side the shims have none on the valve lengths??
You should be able to pick up a set of OEM (style) Flathead stainless valves for near $110.00, we consider this a fair price? Not sure what an economy-priced Chevy valve is going for, we don't use them! When we make a valve sale here we include new keepers in the package, no charge. If it's a sale for both valves and guides we also include new horseshoe (guide) locks now! Same deal for the bronzed-lined guides alone, new horseshoe locks!
One other item worth mentioning, whether you use the longer valves OR the lash caps (makes no difference in this instance) you end up sinking the lifter adjusting screw deep into the body. This isn't really necessary even when the cam base is smaller. This is why many grind the tops of the lifter bores down, I'm not saying this is a problem but we've not done a SINGLE build with this included.
Thanks, Gary in N.Y.
P.S. If you go back in time some up here you can see a high number of posts with spring/retainers/locks/shim issues for many when using the Chev valves. If you have limited (building) experience with these Flatheads it's best to keep it all as simple as possible? The only time I may consider the longer Chevy valves is when install larger diameters, 1.550", 1.600", 1.625", 1.750", etc.