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LS3 top end questions

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Old Dec 28, 2015 | 12:31 AM
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Default LS3 top end questions
I have the opportunity to get a great deal on an LS3 top end. I have searched far and wide and cant find what im looking for.

I know that ls2 injectors are taller than LS3

LS2 fuel rail is the same as the ls3.

Will my LS2 injectors work on an LS3 manifold??

My setup will be

PRC CNC ported LS3 heads milled to 66cc
LS7 Cam
LS3 intake
and Full ls7 exhaust

Any ideas on RWHP?

Right now with Vararam, LS7 Exhaust and Ported LS2 intake I believe im right around 370whp untuned.

I figure that after I sell my 243 heads and LS2 Ill ill have to come out of pocket about 600 bucks. Im buying the heads for 900.

Please dont chime in about the LS7 cam. I know im leaving tons of room on the table but ive done the big cam thing twice on previous cars and im not doing it again.

Thanks in advance!
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Old Dec 28, 2015 | 12:41 AM
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Another question is do I order LS3 head bolts or LS2?

Will my stock MAP sensor work on the LS3 intake?

Can I reuse my exhaust valve rockers?
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Old Dec 28, 2015 | 09:46 AM
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Regarding the injectors they should work. You just add spacers between the rail and manifold. I had to use taller injectors to clear my FAST LSXR manifold with a stock LS3 fuel rail. I just picked some chrome spacers up from Home Depot in the hardware section.
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Old Dec 28, 2015 | 09:49 AM
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Awesome! Thank you for clearing that up for me. Wouldnt suppose you have a part number or picture of the spacer you used?
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Old Dec 28, 2015 | 10:06 AM
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Regarding the injectors they should work. You just add spacers between the rail and manifold.
I'm not sure they would work as the LS2s are longer than the LS3s, so adding a spacer will make it even longer.

I know that I had to use a spacer to use LS3s in my LS2 since they are shorter, but I don't think it works the other way around.
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Old Dec 28, 2015 | 10:27 AM
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I think he was referring to spaces between the fuel rail and the intake manifold where it bolts down
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Old Dec 28, 2015 | 11:29 AM
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Originally Posted by Jarren_b
I think he was referring to spaces between the fuel rail and the intake manifold where it bolts down
Or.....instead of buying spacers and using your old LS2 injectors, you could buy my never used (new) take-off LS3 injectors.

PM me if interested.

KW
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Old Dec 28, 2015 | 11:31 AM
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Old Dec 28, 2015 | 11:32 PM
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what do you think my setup will make power wise? the same top end made 490whp with crappy exhaust on the previous owners trans am but with a bigger cam.
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Old Dec 29, 2015 | 12:59 PM
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Originally Posted by Jarren_b
what do you think my setup will make power wise? the same top end made 490whp with crappy exhaust on the previous owners trans am but with a bigger cam.
HP wise.....I'd say in the neighborhood of 430 to maybe 440 HP at the wheels.

KW
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Old Jan 18, 2016 | 01:09 PM
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Last question-

Since ls3 heads are 69.4cc stock Mine have been milled about .030 to get to 66cc

I know that right now I dont have any piston to valve issues but If the machine shop takes off another .005 to get them flat, am I asking for trouble?

My specs are 211/230 120 LSA .558/.558 lift

The lift is pretty low with my 1.7 ratio rocker.

could I mill even more?

What do you guys think
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Old Jan 18, 2016 | 05:17 PM
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Originally Posted by Jarren_b
Last question-

Since ls3 heads are 69.4cc stock Mine have been milled about .030 to get to 66cc............I know that right now I dont have any piston to valve issues but If the machine shop takes off another .005 to get them flat, am I asking for trouble? My specs are 211/230 120 LSA .558/.558 lift

The lift is pretty low with my 1.7 ratio rocker.

could I mill even more? What do you guys think
Jarren, lift has nothing to do with piston to valve clearance. It's all about WHEN the valves open and close and that is a cam spec issue.

Off the top of my head, I'd say you're fine with milling another .005" of the heads.

KW
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Old Jan 24, 2016 | 03:55 PM
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Default Mill heads
Originally Posted by Jarren_b
Last question-

Since ls3 heads are 69.4cc stock Mine have been milled about .030 to get to 66cc

I know that right now I dont have any piston to valve issues but If the machine shop takes off another .005 to get them flat, am I asking for trouble?

My specs are 211/230 120 LSA .558/.558 lift

The lift is pretty low with my 1.7 ratio rocker.

could I mill even more?

What do you guys think
You should be able to mill.0.050 total with no issues by the way checking piston to valve clearance is so easy....
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Old Jan 24, 2016 | 04:02 PM
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How did you come to .050? do you have any solid instructions on how to measure?
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