Had a bent valve today! It was the exhaust valve on cylinder 2. I recently installed a trex v2 cam and pp stage 2 heads with 2.055 and 1.57 valves and 59cc chambers and stock head gaskets. I did no fly cutting, but I checked ptv clearance and it was ok. Was it valve float? I thought it may be since the intake valve did not bend. I am using 7.4 pushrods, comp pro mag lifters (which I dropped in as OEM replacements), stock rockers, and the patriot gold springs and retainers. Any help is appreciated!! My first h/c swap and I am going nuts!!!

 

well darn it...I am installing the same cam and going with the same springs and pushrods as you. Hope we get some input on this.

 

Your first problem is that you used magnum lifters as a stock replacement with stock preload when the preload should be .003 on those lifters. magnums are not a OEn replacement lifter the preload is different.

What size cam are you running and what heads? What was your PTVC when you measured it and did you use a solid lifter whne you took the measurement?

 

My cam is a trex 242/248 608/612 110 lsa. I first installed 7.45 pushrods and when I rotated the assembly it was close so I changed to 7.4s. I installed patriot stg 2 assembled heads with 2.055 intake and 1.57 exhaust valves 59cc chambers and stock gaskets.

 

Car ran fine for 50 miles before the valve bent.

 

ttt. Come on guys, need help.

 

ttt. Need Help!!

 

the rocker is not touching the valve... could it be just a broken valve spring???

 

anyone have any opinions??

 

Also you should not have been running that cam with those big valves and 59cc heads without flycutting.

 

PR size will not effect PTVC at all. if it was too tight you should have changed other things because pushrods have nothing to do with PTVC.

 

Sounds like you jacked up that install pretty good, just tear it all back apart and do it right this time. If PTVC isnt correct then you run a thicker head gasket, change cams, change heads, or flycut.

Once again i will ask you how much PTVC did you have when you measured it?

 

What was your:

Intake = ------
and
Exhaust = ------

PtV Clearance???

Christian

 

I don't remember the measurement. I'll have to pull it apart and check it all out again. I talked to a few people and the told me I might just have a broken valvespring and that is why the rocker is not touching the valve. I'm gonna pump up the cylinder with air and check it out. If it was ptv clearance, why would the exhaust valve bend and not the intake? If it was valve float, wouldn't it have been the intake valve? I hope it is a spring.

 

Becasue the exhaust valve is always more likely to hit the piston due to heat expansion. And it also has to do with valve events from the cam. Thats why the exhaust side needs to have more PTVC than the intake.

 

What kind of springs, or there could have been a weak one too

There are pro stock cars running almost NO clearance, but they change springs every pass, so there is always that possiblility of a weak one that floated..

 

yeah not only do they change the springs that often but they also run tight solid valvetrains, not hydraulic ones. We are talking street cars here not pro stockers.