timafey

My Z is an 08, with 20k miles. I am getting the heads reworked, getting 1 3/4 LG catted headers, and a haltech superbee intake. and this is what a very reputable local shop that does in house engine machining recommended:
Shave the bottom of the head, and increase compression by 1 point. Porting was an extra ~$800 and he didn't really recommend it with the stock cam.
Ferrea hollow stem valves, bronze guides, keep stock springs if they check out ok, keep stock rockers if they check out ok. Use ARP bolts and OEM gaskets Keep in mind I am sticking with stock cam. and a 160T stat.

I am shooting for 520 RWHP, think its doable with a tune and the above mods?

Any reason I should think about upgrading the springs? My goal is to keep engine components as light as possible, and I haven't heard a bad thing about the beehive LS7 springs?

Car goes under the knife tomorrow! Trying to figure out if I need to change anything last minute

Edit:
Went with the PSI springs, thanks for the suggestion guy!
Here is the results of the wiggle test, only the visual test was done, but looking at the guides, they had an elliptical shape to them, and a lot of wiggle.


The car dynoed stock with SuperBee Intake 460hp/406tq and 452/416 on the second base run
After the above mod and tune the final number was 525hp/480tq SAE corrected.


Not sure what mod did what since it was all done at the same time.

Scios

looks like a good set up. I would guess those upgrades would get you 40-50 hp over stock. are you getting it dynoed before the work that will be the best way to know what you gained.

RamAir972003

You will be around 515 525 depends on tune and weather... Good luck...

ctsv510

I did close to the same mods but no intake:

- heads were ported and milled 0.020" for about a half a point of compression
- american racing 1 7/8" headers

520 rwhp up from a baseline of 460: https://www.corvetteforum.com/forums...0-milling.html

timafey

I'll try and get a base dyno run, the car just has a super bee intake so not 100% stock but close enough.

Unreal

I would do some PSI springs with the new intake valves just to be safe.

Mark2009

With the stock cam I'd pass on the headers... you'll pick up maybe 15 HP and have a never ending pain in the *** from the heat (plug wires, starters, etc) and extra noise (some people like noise though).

Absolutely would not increase compression. Asking for detonation/cracked piston-block, especially with a tuner in there tweaking the safety margin in order to impress the customer with peak dyno numbers.

I would suggest the PSI 1511 springs w/Ti retainers -- stronger and lighter than stock. Use the header money for those Be sure your shop knows how to set these up (they really should use a different locator and seal, IMHO).

On the guides go with CHE's or the ones that WCCH uses or the new ones that American Heritage is starting to use (actually new ones from AH seem like they would be the absolute best in the bronze category, altho probably the most expensive).

I like the idea of polishing the tips of the exhaust valves and the rocker arm pads (where they interface with the tip of the exhaust valve) to reduce friction/side load, but that is still a rather overlooked concept at this point.

So, only a few last minute changes

psp6158

Other than money, why not throw in a cam? All the work you are having done, I'd come up with a couple bucks and throw one in, I don't think you would regret it. I went with the same components you are and got close to 600 with the heads ported and cam... Just a thought

2StrikeHtr

I wouldn't increase the compression that much either, for reasons Mark states. Probably wouldn't go too much more than a 0.020" mill on the heads.

Either way, you'll probably need new/different length push rods ... right ?

My last 2 cents is to possibly upgrade the trunion in the rocker arms given the year your
engine build falls in (check that) if you are going to be pushing the redline a lot. I've had both Comp and CHE. The CHE's seem to be both smooth and solid.

Good luck with your build !

LS7 BUD

My car has been at 12:1 for over a year with zero issues... I have forged pistons and run a meth kit tho...

Unreal

I disagree with Mark on the compression. I wouldn't go a full point, but .030" mill to bring it to 11.5-11.6 works amazing on these cars. I've tuned 3-4 of them and they all gained 25-30rwhp and tons of low end, and took ~1-1.5 degrees less timing, but made more power everywhere. That is on 91 octane too, not even good gas. I would agree on skipping headers and take the money and do a cam at the same time. Do something mild. You will get better results and power than headers. Hell, even doing a torque 116 will .030 milled heads and stock manifolds should be a solid 530rwhp car with a great power band. I would just have Pat G spec something that drives like stock. Something like a 228/236 .600/.600 116 LSA would be a great cam.

Michael_D

What machinery does this shop use for seat and guide work? I can tell you from personal hands on experience running a Serdi 100, that this is an activity that takes good machinery, and a daft hand. Do they even have the multi angle cutter and stones for these heads?

You are looking to gain about 60 hp, with just a new intake, headers, 1 point of compression and some tuning??? Don't think so...... 30-40, maybe. I'd run the PSI beehives with Ti retainers if I were you. The Ferrea valve is a bit heavier than the OEM valve.

I'd also send the OE intakes to Del West for re-coat and polish. They do a fantastic job at that, and it's not all that expensive.

ctsv510

I did. I gained 60 rwhp without an intake and less than 1 point of compression.

https://www.corvetteforum.com/forums...0-milling.html

Michael_D

Try that on an engine dyno and I might take the gains seriously.

ctsv510

Mark2009

Well, reviewing your link you also had the heads ported which might account for some of that 60 (say, 15-20 maybe).

Air filter/intake is irrelevant if you're having a tune done.

timafey

I gained closer to 35hp from just a tune on my ls2 c6 with vararam and bullets... would think headers, heads, intake and tune on ls7 would be little better then 30hp? I confirmed getting milled .030, he said about 1 point but I guess it's little less on compression.

timafey

Place builds 1000hp race engines, machine most major vendors heads r&d on custom built engines, every machine possible to work on the block, 5axes cnc machines for porting, etc. I'm assuming they know what they are doing.

What is everyone thoughts on the psi springs with the ferrea hollow valves?

timafey

Money is not a problem, the headers already bought, want them for sounds also, just feel that with a mild cam my hp wont be anything more then 30 over where I'll be with stock? And I'm not going to go with an aggressive cam. Is there a concern to have the springs checked regularly and replaced if going with a cam?

BOTTLE FEDvette

Do they work on LS stuff?
This means NOTHING. Not trying to be a dick but just because is not something I can bank on. I had a buddy who let a well know local to him engine build build him a short block...Well needless to say the guy installed the pistons backwards and something else to deal with the piston and crank wheel.

I read that trickflow uses ferrea hollow valves in some of there ls heads so i'm sure its a great valve.