ApexClone

I've seen recommendations on getting the stock LS7 heads machined by AHP/Katech/Frankenstein/etc when they start getting too much valve guide play. Does this actually fix the underlying issue though or is it a temporary fix that still needs to be monitored? From what I've read one of the theories is that the valve geometry is off which causes the excessive wear. I wouldn't think that putting new valve guides in would change that. Or is there something more that happens when the heads get machined that does fix the geometry?

I'm going to be measuring my valve guide play soon and am making temporary plans based on the outcome. Just don't want to spend the money on having the stock heads machined if it doesn't fix the underlying issue. At that point I'd rather just spend the extra money on new heads that don't have the issue to begin with.

703z06

Fix permanently ? This question is like opening up a can of worms and you will receive plenty of different responses. New GM LS7 heads have been measured and found to have the valve guides not concentric to the valve seats. Aftermarket heads are most likely your best bet

furious427

This is a topic that has been discussed a million times, and to be honest you will read many different opinions on it. From what I have read over the years, it seems the ultimate fix is to get aftermarket heads. I myself went the AHP route, my car runs fine so far with over 10,000 miles on the heads. If I could go back in time and do it over, I myself would go with aftermarket heads. Not saying AHP fixed heads are bad, just the way I look at it now.

dmuellenberg

No, just machining the heads won't fix the issue. GM claimed it was a machining problem for a few years (2008-2011?) and they corrected the issue, but every year still has the problem with excessive guide wear. It is pretty agreed on by major performance shops that the problem is a geometry problem like you mentioned, and just machining the heads won't fix that.

ZRCLONE

I say NO, and plenty will agree. GM also has discontinued all LS7 production/sales, what does that say.

Pb82 Ronin

Agree with everyone else. Go aftermarket.

Apocolipse

It’s not a “geometry” problem. Do people really think that a computer model can’t be verified for proper movement?

ClothSeats

Maybe some of the problem is related to the offset in the intake rocker arms. When everything is new with little clearance in the rocker arm bearings, it is not a problem, but when a little clearance develops with time, forces acting on the rocker arm will allow it to go cockeyed. That will cause undue wear at the valve stem/valve guide, and cause misalignment at the valve face when it closes.

Apocolipse

The problem on properly concentric heads is material incompatibilities. PVD CrN is a picky coating to work with since it has no pores / cracks where oil can hide to help with lubrication like normal chromed valves have.

Turbo6TA

I am no expert, but if I was in this situation, I would opt for a new set of aftermarket heads (such as Trick Flow) that have stainless valves ... no titanium

furious427

So, your saying having a company like AHP with their package 4 heads with their hardened pm guides is the ultimate fix?

AzDave47

GMs supplier NEVER FIXED the problem with the valves not being centered on the valve seats. Brand new 2013 heads were disassembled for Hib Haberson and found to be outside the wear limit GM specified. My personal opinion is that any valves that have been run in out of spec valve guides should not be reused. Many had their Ti intake valves tumble polished to "recondition" them, but if the valve head had seen fatigue in the out of spec guides, they may still fail after more use. The very thin coating on the valve stems was also likely worn.

When I had my power build done, a month before my extended warranty ran out, I chose to keep the valvetrain lightweight and WCCH used CHE bronze guides, new OEM exhaust valves and new Katech Ti Mo intake valves, which were compatible with the bronze guides. After 10K mile on my ~600rwhp build, I had the bottom end forged. At that time the heads were sent back to WCCH to be disassembled and valve guide clearances checked as many on the forum said "they will just wear again, go aftermarket heads". All the valve guides measured .0011" to .0016 " not far off what they had been installed at by WCCH. The wear spec is .0037" 14 of my 16 valves were out of spec when my first build was done at 47K miles, some more than double the spec. I am at 23K miles on the build and all is well, as far as I know. The PSI 1511 springs were just replaced after 22K miles - a routine maintenance item on a power build like mine.

I am not saying you must go to expensive TiMo intake valves. I chose to keep the springs light (PSI 1511), but you could go with stainless steel valves and heavier valve springs to control the valves and maintain the RPM limit. The heavier valve springs will be harder on the rest of the valve train. As mentioned above you need to use valves that are compatible with the new guide material.

I run a 7300 FSO, do road course and 1/2 mile and 1-mile trap speed events so do run the engine hard when I am out to play. I drive easy on the street, most of the time.

A competent shop who does regular work on LS7s will know what valves are compatible with what valve guides. The valve guide install/alignment is not a hard task, just one that Chevy's LS7 head supplier Linimar screwed up. They also did the e-Difs for the C7Z and short-filled the "ready to install" difs with dif fluid, resulting a number of failures and lots of noise complaints. Linimar cuts corners and Chevy keeps rewarding them with contracts as a "premium" supplier. Dumb!

ApexClone

I appreciate all the insight here.

AzDave47

Some of us spent several years following the info as it developed before we did HCI builds that were $10-20K. We all had to evaluate what info we beleived and what we felt comfortable doing for mods. We don't all agree.

For someone looking to deal with the heads issue on a basically stock LS7, with no power build adders, the major well know shops on the forum do great work. I would add though, do not reuse valves that have been run in out of spec guides.

shane p

If the problem with the heads are that the valve seat and the guides are not in line (concentric) with each other then having new guides installed and remachined then, yes, that should fix the problem.

Apocolipse

Right which many have found to solve the problem. The PM guides they use have lubrication channels that help the stock valve finish from wear and tear.

This is why the moly valves ($) don’t have the same problem.

American Heritage

Yes!
We have taken apart several sets of our Package 4 Ls7 heads with over 80,000 miles on them and all the guides were still perfectly in spec and ready for many more miles. Some of these heads even had large camshaft in them for 30,000 plus miles.
We offer upgrade to the heads as well. Things like Ti Moly intake valves and or Moldstar90 valve guides (superior to any other valve guide on the market and the same alloy many Indy car and F1 cars run).
Sirp tuning who has the fastest n/a c6z06 on the plannet ran our package 4 ls7 heads for many seasons with a .700"+ lift super aggressive camshaft shifting at well past 7,500rpms every time checked his heads when he took them off to switch to our Archangel LS7 Heads (for more power and quicker 1/4 mile time) and found that the guides were all exactly where we set them up at... and thats after seasons of 7,500+rpm shifting with a super aggressive cam and pad style (stock style) rocker arms!

If you have any questions feel free to shoot me an email

Hp@americanheritageperformance.com

https://americanheritageperformance.com/

Texasthunder

My 2 cents. Why would spend a bunch of money " fixing" a set of used heads with a problem when you can buy a set of new aftermarket heads for about the same amount of money?

AQWIKZ

my heads we done by AHP by the previous owner and the currently have 90k on them!! I have tracked the car as well.

Package 4 Cylinder Heads

Apocolipse

Which aftermarket heads cost $1600ish?