jb78L-82

Ok Gents, I have been reading and researching the best head fix for years now and have been in contact with Kohle at AHP but would like opinions from those that have actually done the head correction with exact details of what you had done and why?...not just what exhaust valve was used but springs, retainers, milling etc. I do NOT intend to mod the car from stock...cam change etc

I have a 2010 C6Z06 bought new in March 2010 with very little mileage on the car today-3,800 miles-but want to address the head issue soon. I do not race the car but just drive it relatively hard (no 7K shifts, mostly 6,500 rpm when spirited). I do intend to track the car on a road course in the future (about 2X per year maybe) and would like to safely rev the car very occasionally to 7K.

I am interested in first and foremost in reliability and secondarily, do NOT want to compromise the ability to rev the engine to 6,500-7,000 occasionally with a heavier valve train.

Here are my options as I know them today:

option #1:

Rebuild heads with stock TI intake and stock Sodium filled exhaust with PM/bronze guides/ with stock springs....Not likely

Option #2:

Port stock heads with PM guides, Ferrea exhaust valves, stock springs and retainers. Stock TI intake valves

Option #3:

Port stock heads, Moldstar 90 guides, Stock TI intake valves, Ferrea exhaust, stock springs and retainers (OR light weight beehive springs and TI retainers?..I believe that changing springs/retainers is necessary to reduce the SS exhaust valve total mass and retain OEM rev capability)...THINKING OF THIS OPTION!

Option #4

Iconel Exhaust valves but need more details of the rest of this setup and why....???

I am very mechanically inclined (completely rebuilt the L-82 in my 78 C3 in 2014 with JE forged racing pistons, AFR aluminum heads, roller cam, etc) so I may tackle this job myself to change the heads...depends more on time than money. I only want to do this job once...50,000+mile life at least?

Thoughts?

AzDave47

It seems you are going with ARH (PM guides). Tell Kohle your goals and he will recommend what is best for you. What gas do you have 91 or 93. If not 93, no need to shave the heads, just cleanup pass.

I would not recommend stock valve springs with the heavier exhaust valves you are favoring; again AHP can recommend. When the engine is tuned, tell the tuner exactly what you will be doing with the engine. With the road racing you look to do and wanting to run to 7K occasionally that will call for improved springs with the valves you are looking to use and going with the Ti retainers makes good sense. For your use, porting is not necessary, but you can decide if the additional $ are worth the additional porting while the heads are in the shop.

I figured that the factory valves that may have been run in worn guides would not be good for me, so I replaced intakes with new Ti/Mo valves and exhaust were new OEM valves. 14 or 16 guides were out of spec on my 46K stock LS7. HCI build with 602/489 rwhp/tq.

JoesC5

Option #5

Go with aftermarket heads. This is what I did. PRC265 heads with solid stem exhaust and Ti intakes and dual springs. They flow about the same as the ported stock heads, as they have larger ports cast in. 25,000 miles on them with no problems. They are not reworked GM castings, but new castings with 6 bolt design(in case you ever want to go with a 6 bolt block, but fit with the stock exhaust manifolds).

If you still want more air flow than they will port their PRC265 heads to PRC285.

Check Texas Speed & Performance website.

Unreal

Option 4 shouldn't even be considered unless you are looking for a power adder. (n2o, blower, turbo)

Would no use stock springs. At least do PSi or PACs.

If you don't plan on a bunch of mods, skip the port work. Just get guides, ferrera hollow valves and matching springs IMO.

As for only doing it once in 50k miles, good luck with that. I would not plan on that, especially if seeing track time.

jb78L-82

Ok Thanks

93 octane is available and what I use now. I would think that my OEM intake are good with 4,000 miles on them, You used OEM Sodium Hollow SS valves, why? Not worried about a failure? What guides did you use? Bronze or PM? How many miles on reworked heads? Moldstar 90 guides with Ferrea SS valves for added longevity? Reuse Stock TI intake valves?

jb78L-82

Makes sense on no iconel valves/porting. Track time would be VERY limited, 99% street.

jb78L-82

Want to retain stock heads. Thanks

Dan_the_C5_Man

This is an easy one..

AHP / #4 package, they will polish and treat the stock Ti valves, for safety go with the HOLLOW Ferrea exhaust valves, PSI 1511 springs with Ti retainers, DONE. For my build, I also had the heads milled .020.

It's by far the most cost-effective, practical solution to this problem. The one change would be to have them swap their PM guides with the MS90 guides - I use my car similar to yours, I did not spend the extra cash on the MS90 guides but put those dollars into a roller rocker instead, which significantly reduces the valve tip scrub, negating the need for harder guides.

And as another cost savings measure, I am using latest version OEM exhaust valves - nothing wrong with them, when run in an in-spec guide. The hollow aftermarket valve is more of an insurance policy IF the guides go out of spec again AND you don't periodically check them. And to be completely transparent, if I had to do it again, I would probably spring for the hollow Ferrea - with the additional spring pressure and mass reduction of the 1511's, it offsets the small mass gain from the aftermarket valve.

AzDave47

What year is your engine? 4K miles is low and normally you wouldn't expect to see guide wear that early, but the OEM LS7's with the heads done by Linimar are not usual.. A sort of general trend has been early cars lost exhaust valves and newer cars (? after the exhaust valves were updated in ?) lose intake valves.

My work was done at CPR in Mesa AZ and they usually work with WCCH, who do not do PM guides, so my guides were CHE bronze guides. After extensive reading for years on this forum I was comfortable with the new OEM exhaust valves in the CHE bronze guides where all the work was done by a shop that makes sure the guides are done right and the valves are concentric with the seats. My head build was essentially what Katech has WCCH do on their preped cars, lightweight, stable to 7800 RPM. Only 3K miles on the engine/heads since the May 2016 build. I did new Katech Ti/Mo intake valves and sold my used TI OEm valves on the forum (disclosed all info including guide measurements).

My choice would be if your were going to reuse any valves, make sure they were run on in-spec guides, so you'd have to get the guide measurements before knowing what valves to buy.

OEM Ti valves should be fine in the PM guides, for your use probably the Moldstar guides are overkill, but do it if it gives you added piece of mind.

I do road course and other high speed performance events so my engine will see a lot of 4-7K+ RPM time, Fuel Shut Off is set at 7300 RPM

jb78L-82

2010 LS7 bought brand new...yes 3,800 miles is not much and the reason I think that the OEM intakes might be reused after being treated. I expect the guides are fine right now but I am not waiting for them to be out of spec. Sounds like PM or bronze guides with OEM sodium exhaust valves, reusing my 3,800 mile TI intake valves after being treated, and stock springs or Reusing Stock TI intake valves treated, SS Ferrea exhaust valves, aftermarket Springs/TI retainers, and possibly roller tipped rockers.

A few variables here but you guys are helping me when I talk to AHP or others. Thanks

redbird555

I personally did the Hollow stainless valves with the PSI upgrade and Pm guides. It's a good cost effective option as others have said but there is also no issues with going in that same direction but using stock springs as comes in the base package from Kohle. They have been spintron tested and are fine all the to 8k. So if you want to keep it as original as possible and simple you could easily do that and retain the stock redline no problem

Personally I agree and I think you would be ok in the 50k expectation. A fix isn't a fix if it has to be done again outside what would be normally expected for a modern car. I don't plan on doing this every 50k, that's rediculous, from what I've seen from AHP you won't have to either he understands the issues with the heads and seems to have addressed the . No stock ls needs guides at 50k and I wouldn't expect and ls7 to either once they've been addressed

jswilke

I just completed my head swap earlier this week on my 2008 Z06. After numerous discussions with Kohle at AHP and Rich at Abel Chevrolet I went with this. My Z06 is otherwise bone stock and is not tracked. It does see occasional spirited driving at 6,500 RPM shift points max. For my needs I believe this combination will be fine and cost effective:

jb78L-82

Excellent! How many miles were on your heads?

I am strongly leaning towards this package but with the 1511 springs/TI retainers (although my guess is with my mileage I could reuse my OEM springs/retainers) to reduce valve train weight and possibly the roller tipped rockers to further reduce friction on the valve tip.

jswilke

Only 7,950 miles were on my heads when I took the car in earlier this week. I will not know how far out of speck my original heads actually were until Kohle measures my original heads next week. There was definitely wiggle on the intakes. I did not experience excessive valve train noise as others have reported so I do not expect my wear was off the map. Nevertheless, since my warranty is expired I chose to replace the stock original heads.

jb78L-82

Wow! You and I are on the same thought process with my heads currently at 3,800 miles and no warranty now. I guess the springs need to replaced regardless whether LS7 springs or the aftermarket 1511's with low mileage on the engine. I need to talk with Kohle about the PM guides or the moldstar 90 guides along with the roller tipped rockers. I am looking for bullet proof reliability and longevity. If the MS90 guides will give me much longer wear than I would go for them.

So it looks like:

OEM TI valves treated
SS hollow ferrea valves
PM or Moldstar 90 guides
Stock LS7 springs/retainers or 1511 springs with TI retainers (leaning towards this option to get the SS ferrea valve closer to the stock OEM SS sodium valve mass)
Roller tipped rockers or stock LS7 rockers (leaning towards the roller tipped to reduce friction).

Edit-After reading about Yella Terra rollers, I think I will stick with stock LS7 rockers.....

jswilke

Good luck! Kohle is good people.

Unreal

What roller tip? If you are doing it then have AHP or whoever just do the crower setup. Should only be ~$1800 or so. Otherwise there are not many good options for roller tips, otherwise everyone would be running them.

jb78L-82

I think I will pass on the roller tipped rockers for that price and my intended use....Thanks

AzDave47

I agree, skip those. I think you will be fine with AHP PM guides and the PSI 1511 springs and Ti retainers and the rest you last discussed.

RamAir972003

Well after doing multiple heads its been proven now others may not have heard but the moldstar guides will not have any guide wear, compared to bronze there have been reports where the bronze guides have worn..but then again why is a bronze guide wearing.