finding exaust valves

[sbc]

I race oval tracks in the northeast and am having
trouble locating 1 piece steel exaust valves for
a sm.blk. chevy. The rules state 1.5" oem or stock
replacement steel only, no stainless/swirl etc.
The problem is that the only valves I can find are
made from 2 pieces spin welded together. I have
had the valve heads break off and destroy 2 engines.
I only have 110# of seat pressure & less than .500"
lift. I don't want to build another grenade!!!
Any help would be greatly appreciated.

 

[ivymike]

any idea what the kinematic seating velocity is on that cam?

 

[sbc]

ivymike, We have a lift rule of .390I/.410EX
hydraulic only, no Rhodes etc... lifters.
I don't know the seating velocity is but it
can't be very high compared to other cams.
With this lift, a base circle of 1.250, a 2bbl
carb., & r.p.m. of 5500 max. I can only attribute
the failure to the valve. It's a 350 chev. 8.9:1
max per. rules. I run it 2 percent rich & max
water temp. is 195 deg.f. The plugs look great
(nice&tan), & so does the exaust system. I just
need a 1pc. valve that will comply with the rules.

 

[evelrod]

sbc, It sounds like you got some BAD aftermarket valves. New parts fail , too. I have described elswhere how I lost a set of Tilton (high dollar) inlet valves, the same way, on one of the Lotus engines after only a few hours running time. Being a DOHC engine, we cought the broken valves before any great damage was done, fortunately, these heads are REALLY high dollar.
Seating at 110# is vertually stock and @.500 pressure sould be something like 275# or so. You should not have problems with OEM valves, except valve float if you overrev!


Rod

 

[sbc]

I'm still looking for 1pc. valves. Can anyone out
there please help? Thanks in advance.

 

[cycle]

I"m with Rod on this one. It would seem to me you got into a bad batch , which of course does happen. Another possibility is you are not running enough seat pressure?? Could the valve be bouncing off the seat , causing higher than normal shock?? Maybe something to think about. It would definitly pay for you to have any new valves to be magnafluxed,better to pay a little more now than alot later. Your rules make it difficult , but I would think at least one manufacture would have one peice valves. I regret I don"t know of one. Now this may seem really out of line but what of the possibility of using used valves out of a older engine? They already have been "proven". Yeah I know its strange but????? Craig

 

[evelrod]

Not strange at all, Craig. 'Parts is parts!'

I don't have the money, time or, talent to indulge myself with NEW parts when GOOD used stuff is available!!!(When you deal with 'vintage' engines, it is sometimes difficult to find 'new' that are up to standards.)


Rod

PS---I ran the crap out of SB Chevys and never dropped a valve!!! NHRA records way back when.

 

[cycle]

I hear you Rod.. SBC , I think we all have been bitten a few times by new parts. Again it is going to happen on occasion. Go racing and you open yourself up to failures.I have been enjoying the punishment of racing for many years!! Anyway, Hereis something I found that might help you.. They claim one piece valves in a large variety of materials,carbon steel,martensitic steel,austesitic,inconel,nimonic,etc.. They are ISO 9002/QS9000 .... Here is there site

http://www.qualcast.com

... Hope they can help you out..... Craig

 

[sbc]

Craig, I'm sure we don't have any float or
bouncing going on. We've run the same seat
press. at other tracks at higher r.p.m.
with stainless valves & had zero problems.
'Mater of fact I'd like to get to 100#s for
this track. Thanks for the link, it didn't
work but I did a search & found the company.
I'd like to find the parts here in the U.S.
but maybe I'll have to contact them in the
U.K. By the way, 2 different engines & 2
different mfgs. of valves were used.

 

[cycle]

Two valve manufactures would discount a bad batch problem.Now I want to know what is happening!! I can only surmise the only common denominator left is heat or excessive heat. No matter , A two piece valve is probably not the best choice. I am a little suprised that valve bounce did not intrigue you. I would think that towards the end of the race that with only 110 pounds of seat pressure you may experience bounce. Due to high heat and spring fatigue.. Valve bounce is definietly a contributor to breakage, specificly , the valve head seperating from the stem. Now you have me wondering!! Craig

 

[evelrod]

Well, the only thing I can think of now, is the valve is makeing contact with the piston at some point, even lightly, but enough to bend and fatigue the valve. Have you backed off your lifters so the valve seating misses the decel ramps completely? 110# seat is enough for a 1.5 Chevy EX valve under 'normal' circumstances but will definately 'bounce' if the cam profile 'drops' the valve from the nose to the seat unaided (valve float, technically).
Well, so much for the 'experts', eh? I think at this point, I would be taking everything apart and starting from square one. If this was MY engine, at this point, I would be assuming the problem was 'builder generated'.


Rod

 

[sbc]

Well, in hopes of finding something not builder
related I spent a lot of time sifting through
the mangeled parts & found nothing. I ALLWAYS
degree the cam & ck piston to valve clearance.
This is a free spining engine @ up to .520 lift.
If the timing chain broke there wouldn't be any
damage. Still looking for the answers I went
back to the pile of junk and think Iv'e found
something. 3 of the hydraulic lifters don't
leak down very easily. The same set was used
in both engines! They were supplied with the cam.
I didn't notice anything while setting the lash,
so maybe it is my fault. I will however use 1pc
valves from now on. (still looking)

Thanks all for your help.
This is a great site.

 

[sprintcar]

I'd try MANLEY for valves - I've run them without problem - just be sure you get the race (not oem) parts

http://www.manleyperformance.com

talk to the factory and see if they can help

 

[cycle]

I believe the real problem here is that SBC has to run O.E.M. replacement valves. Of Course most are of the 2 piece variety. And there in is part of the problem.. They will not hold up to the rigors of his type of racing. Max r.p.m. for an extended period of time,extreme heat and pressure. No doubt a harsh enviroment. If Manley has a "legal" replacement then this would be the way to go..Craig