Thread: Swapping a 03' GTP SC 3.8 into my 07' Subaru WRX need advise!

Like the title says swapping a 03' GTP SC 3.8 into my 07' Subby. Its going to be rear drive only with a camaro 4L60e trans.

I'm in the process of going through the engine. So far I've had it bored 10 over, new pistons, line honed and decked. The crank has been turned to 10/10 to true it up. Reconditioned the connecting rods, both ends. Rotating assembly has been balanced. Bought a new set of heads (old ones were cracked), installed LS6 springs and had them ported and polished. The S/C has been rebuilt and ported and polished along with the LIM. New Intense racing pushrods, and timing set. Using ARP headstuds and mainstuds.

Questions - What cam should I run? Should I upgrade to a GEN V S/C?

I want to make decent power without compromising durability and driveability.

Thanks in advance.

Normally opening the bottom end is compromising durability and driveability, I hope the machine shop did it right or it'll last a few hundred miles like most rebuilt motors do.

Past that, toss a mild VS or S1X cam in it for extra bump it power. Keep the gen 3 for now as it will work just fine for what you are after it seems. If you bought a camshaft you'd have to buy pushrods again, so is that worth your money??

I think all the cam are made from comp cams blanks.

3800performance is that website is still around and ZZP Performance sells after market camshafts.


Personally I'd just run the stock cam and drop pulley sizes to increase boost and power. Maybe I'm just cheap though.

You'll also likely need some larger fuel injectors depending on power output. If you do indeed add a camshaft you'll want some larger injectors. The factory 33 or 36lbs ( I forget) don't go much past a 3.3 pulley range.

Yes, those are the ones. They the milder cams they have out there. The more agressive cams are the XP cam, the XPZ and NIC cams. Both the last two wouldn't be what you are after.

Figure a stock engine makes 7-8psi depending on where you live, DA etc etc. Add some headers and or a plog/downpipe combo you are at 5-6psi now with better flow. Add a cam with the same stock 3.8 pulley and you'd maybe be around 3-5psi. Drop down to a 3.4 pulley and it'll bring you back to the 7-8psi range. So even going as far down as a 3.2 on a stock cam you should be around 10-12psi and not that much boost. May be less if you ported the heads.

To me with these engines the aftermarket cams are designed make use of higher boost numbers, so only running 7-8psi on a cammed engine wouldn't be putting that cam to good use.

ls7

I've daily-driven a s1x and currently now a s3 cam.
If the engine is open now, do a s1x or s3 / xpz.
You might be able to skip the intercooler for now.
The intercooler can be slapped on later down the road. Especially when you decide if you want to keep the gen3 or go to a gen5.

A mid to low 2000 stall converter would do just fine. You'd be looking at converters for the 4L60e and not just 3800 in general. You would have to make sure it bolts to the flexplate though. If the factory V6 camaro converter is in that range it should be alright to use.

Circle D is a very well known brand in the LS world. Might be worthwhile to broswe a few LS1 tech threads on converter compaines to look into.

Definitely install a more aggressive cam in that thing while your in there. I've been running an xp cam in my 5 speed car since I rebuilt over 20k ago with a 3.4 Gen 5 and my only regret is not going bigger on the cam. Most cams for these things are very street able and don't give you reliability issues. The truth for most is that you will almost always want more power down the road. I'd cam now, then add the intercooler later , which is much easyer to do after the motors in.


...or just save money in the long run and turbo.lol

Loved the s1x. Love the s3 even more. With 130lb springs, s3 heads , it pulls soo damn hard to redline.
https://vimeo.com/183033670