arkus

Just wondering if any of the "fixed heads" had any exhaust valve failures ?

Or any out of spec valves.

REDZED2

FWIW I am getting my heads done next year, but I have read countless threads on many Corvette Forums the last year and never saw one yet if that means something. I am sure more will throw their hat in to the ring.

08mojo

Chadyellowz, a member that rebuilt heads for living, claimed he ran across several rebuilt heads, from reputable shops with bronze guides, that had valve guides out of spec.

arkus

This is important
Is there a study on the percentage of "fixed heads that failed"

Tech

Unlikely this will exist. You can't even accurately estimate the number of stock heads that had out of spec guides. Corvette Forum represents a small percentage of the actual vette owners.

arkus

If I get my heads fixed for 3k , should I feel secure about my engine not dying ?

Tech

The amount you pay has no direct correlation to the longevity if your engine. GM already proved this with the car itself. Any head rebuilder is going to tell you their process is best. The definition of "best" is somewhat subjective since nobody has irrefutable evidence of the root cause of the failures.

LFZ

There are cases where a SS valve failed and/or a "fixed" head was out of spec after checking.......if you search hard enough, you'll find them....however, they get swept under the rug pretty fast around here.

REDZED2

I have heard a couple SS ex. valve issues after heads were redone.. I was thinking about going with a hollow SS ex. valve for a stock cam since spintron testing has shown no real danger or issues at 7K rpm (stock cam again) but I might insist on new factory ti ex. valves now. I have been there for stuff and done it twice. Do it once right. $$

OnPoint

What about aftermarket heads. Are there any aftermarket heads that have shown to not have the valve guide wear issue?

I'm not asking to derail the thread - just wondering if this might be easier/simpler way to go, IF in fact there is an aftermarket head that has shown to not suffer valve guide issues.

GTJim

I'm very tempted to go aftermarket as I just don't trust the rebuilt factory heads won't give me problems later on down the road.

rio95

There's a guy on here that checked his and they were out of spec. Didn't fail though.... I'm a firm believer that the higher the lift the faster they will wear and I also think they should be checked every 10-20k miles if you have such a cam.

jdm.recon

I came across this thread a while back.
https://www.corvetteforum.com/forums...n-germany.html

REDZED2

That is true I found a thread where it was stated by one of the top shops that the heads are far more reliable and thousands of more miles in spec with the LS7 cam over some aftermarket sticks. Ramp rates and lobe design etc.. accelerate wear.

American Heritage

Bronze guides and Stock LS7 rocker arms do not mix well (longevity). If running a rail mount aftermarket roller rocker then your fine with bronze but with the stock rockers you will start to see guide wear much sooner than expected. Powder Metal is the way to go if you want to run the stock rockers.

We have reworked a number of LS7 heads that came in with bronze guides and SS valves that were out of spec.
Also higher lift camshafts will reduce the longevity of the valve train.

http://www.americanheritageperformance.com/

MarkC

AH, has anyone come out with a high quality pedestal mount roller rocker? I called Comp Cams years ago and their answer was there were not enough LS7's built to justify the R & D. Also, what do you think of the Crower shaft mounted rocker? Thanks

LS3Knight

There are plenty of threads on here speaking of out of spec "fixed heads." I have yet to hear about any that have been reworked by American Heritage that have gone out of spec, and some of their customers have put a lot of miles on their cars. It will be an easy choice when I get mine fixed.

Dan_the_C5_Man

Yes, and I run them -.Yella Terra. Their half-shaft paired design is rather brilliant. If you speak to the lead engineer at YT, he will tell you how GM copied his design to build the LS series rockers, and I believe him.

I am running AH reworked heads with PM guides, PSI beehives appropriately shimmed, STOCK(!) cam, stock intake and exhaust valves, and my valve train is dead-nuts-quite.

I have to use my mechanics stethoscope to hear the valves closing on the seat or any other related VT noises over the injectors firing.

...and now I will prepare for the "YT haters" to rush in, repeating the same one or two issues from years ago with the older style product, with silly setups like excessive sping pressure and cam lifts - hint: the YT's are not appropriate for those setups - stick with the crap stock steel rocker arms if you are pounding your VT components into the ground with heavy springs and high-lift aftermarket cams, and just deal with the resultant negative effects like excessive valve tip scrubbing and higher guide wear rates.

It is refreshing to finally have a reputable vender like AH speak openly on the point I've been repeating for some time now; stock LS7 rockers equate to higher loading of valve tips, which in turn MUST impact guide wear to some degree.

And don't even get me started on how much slop exists in the stock trunions - it is laughable.

Bottom line; any QUALITY roller (of course you must account for additional MOI with a heavier rocker) is better than stock - it's all about how much you want to spend (YT's which are bolt-on, Crower and others require heads to be machined = $$).

Michael_D

YT's suck. LOL - I'm kiddin.... Just had to say that to get Dan spun up. I really have no personal experience with them. My engines don't normally get along well with anything that's not built to take a lot abuse.

I installed the Crower system on my personal car's engine. I think they're engine jewelry. The quality is excellent. The Geo is spot on. The witness marks in the pics below, are after full engine rotation with a solid lifter. 650/670 lift.

Dan_the_C5_Man

LoL..

If I wasn't such a cheap-a$$ (in my defense, I reworked my heads during the Christmas holiday), I'd probably be running those as well; they look bad-a$$.