07 GXP - Building engine, Head questions - Pontiac Solstice Forum
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post #1 of 3 (permalink) Old 07-10-2018, 09:07 AM Thread Starter
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07 GXP - Building engine, Head questions

Hello guys, first post here. I’ve got an 07 GXP that cracked a factory piston and I’m taking the opportunity to do a full build on since it’s down anyway. My full plan is as follows:

ZZP Gen 3 stock block
ZZP Neutral balance shaft
Stock K04 replacement turbo
ZZP E85 injectors
ZZP E85 intake cam
ZZP 4340 forged Rods
Wiseco forged pistons

Past that it’s bolt ons and a good tune, those are the main engine parts I’m planning on. I’m planning on reusing my original head, all other parts listed are brand new.

What are some good things to do to the stock head while it’s out? This is my first engine build so forgive me if I’m asking basic questions. Ive heard people talk about ‘valve jobs’ and port and polish, etc.

I’ve got a supposedly reputable machine shop locally that should handle it fine, just wondering what’s best to do. I want to squeeze as much power and airflow out of this head as I can.

My plans for the car are track days/autocross and cruising/street fun. At some point after the break in, I’ll be doing a turbo/IC upgrade and I’d like to be around 400 whp when it’s all said and done. That won’t be until my wallet recovers from the build though.

Sorry again to ask basic questions, also feel free to move or whatever if this isn’t in the right place. Thanks everyone!
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post #2 of 3 (permalink) Old 07-10-2018, 10:12 AM
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If you're autocrossing, be careful of which modifications you make as they can push you into SSM or CAM-S - running against Vipers and C7s.

Have the head soda blasted, checked for flatness and decked if necessary. The machine shop should also do a valve job, replacing any springs, etc. where necessary. My local guys did the whole thing on my 2.4 head for $250 and turned it around in 24 hours, though YMMV.

Port and polish are obviously good for airflow, but I haven't seen much - really, any - mention of what's been done in that area on these engines. For your application, I suspect that would be overkill. (Though, if you can get it done cheaply, why not?) Talk do Dave at DDM Works - he can give you some pointers.

While the engine is out, I'd consider an aluminum flywheel and possibly upgraded clutch. I got mine from Performance Autowerks. DDM also has great units. The flywheel made a huge difference on my 2.4 (turbo). It revs significantly faster than my 07 GXP.

Anything you do that reduces the mass of a rotating assembly - pistons, rods, crank, pulleys, flywheel, driveshaft, axles, wheels - will have a significant performance impact. Compare the weight of the new components you're getting against the stock units. Adding mass to the bottom end is a huge performance killer.

Blue-ish 2006 2.4, Werks stage 1 turbo, Borla cat-back, DDM braces, Spec aluminum flywheel, Spec stage 2 clutch, Werks aluminum radiator, some gauges, RKSport hood, Morimoto FX-Rs, GReddy Profec, Norm's fenders

'07 GXP, RPM Stage 2, Solocatless downpipe, TCE Wilwood 6 piston front brakes, 4-piston rears , Stainless brake lines, slotted/drilled rotors, BC Racing BR coilovers, Performance Autowerks intercooler, DDMWorks CAI, charge pipes and braces

Last edited by raygun; 07-10-2018 at 10:18 AM.
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post #3 of 3 (permalink) Old 07-10-2018, 11:22 AM Thread Starter
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Thanks for the reply! I’m taking it to the local shop today or tomorrow to get the process started. I can only hope it’s that cheap! I’ll report back with progress.

Totally forgot to mention, the car already has a Spec stage 3 clutch with the Spec aluminum flywheel as well. It barely got broken in before the engine blew sadly.

And absolutely on the reduction of the rotating mass. That’s why I’m going with the ZZP neutral balance shaft!

Last edited by 07GXPVille; 07-10-2018 at 11:24 AM.
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