I don't really know much about engine rebuilds so I'm asking for recommendations. I currently have an AP1 (115k miles) with SoS stage 2 recently installed. During the dyno tune we found that the motor really needs to be rebuilt. Did compression and leak down, had losses in both areas.

I picked up a ProFlow head that should work ok (I hope) but I'm not really sure what to do about the bottom end. One thing I'm pretty sure on, I want to keep compression at 11:1. I don't intend to run more boost than I currently have (Approx 12psi) and don't want to kill my daily driving with a low compression build. I thought this might be a good chance to bump up displacement though by maybe doing an AP2 block? This is where I run out of knowledge, I don't even know if thats really possible or a good idea.

So, what do you suggest for rebuilding a motor for a S/C setup, daily driven but also track abused a few times per year.

Thanks,
J

 

even if you dropped the compression your not gonna lose your daily driving ability. you might not even notice the compression difference, it will give more room for your tuner to tune and provide more potential to your set-up

 

i am thinking the same
I was thinking JE 11.5 Pistons or CR 11 CR pistons..
Was thinking Darton MID sleeves but i am leaning to Basic Sleeves and maybe a block guard.
stefce

 

laskey bottom end stock bore, 10:1CR or less.,F22crank. i personally would go 9ish:1. your boosted and bear that in mind. boost is drug.......you give up approx 10whp per full compression point drop, but can crank boost up to more then compensate

/thread

 

90% of the time, I'm commuting to work and seeing zero boost. So I'd be running essentially a stock car with 9:1 compression. Maybe if that was combined with the 2.2 displacement, it might offset and I'd still have enough torque at the bottom for normal driving?

The SoS blower maxes out at like 15psi anyway I think, so I couldnt add all that much more boost.

J

 

I'm in the 9:1 range, and it didn't hurt my daily drivablility. It would actually make it safer when just cruising.

 

Not being argumentative, honest question here, what would make it safer? When just cruising there isnt any boost at all, engine not under any real stress (comparatively).

I dont get detontation at all unless I'm at 8700 rpms or higher. During the tuning we really didnt see any det, just barely got close to it at the peak rpms.

It is very good to hear from someone currently at 9:1 though, that makes me feel much better about it.

J

 

its not that you cruise and see no boost. even if you saw 10 psi only for an instant, thats what you build for. decide on teh max you will ever go, and build around that. personally, again, if i am building a motor, i am gonna sacrafice a small amount of NA power for the ability to rape face down the road. your not building a motor for your current setup, yoru building a motor for any setup you may run down the road.

that being said, yeah 10psi SOS kit is fine on stock CR. hell, 12-14psi can be done too. but for 100% assurance that 14-15 psi will be repeatably fine i would go lower on CR. now, what if you get use to the 400whp your at with 15psi, well, turbola time.

anywho, the highest i would go is 10:1. that gives you forged internals, a lower CR to work with when tuning/boosting, and still some power from slightly higher compression.

think of it this way, how many oem cars out there FI with hi CR? the only i can think of are Direct Injection. otherwise, all factory FI cars that had incredible reliabllity and crazy power potential had CR in the 7.8-9.0:1 range. theres a reason.

 

This motor has great daily driven abilities without boost and lowered compression.

I also have a Darton sleeved AP1 built block, 8.9:1 compression, fully built head with oversized valves 1mm on exhaust side and 1/2mm on the intake, ported SOS TB, 900cc injectors and K-Pro. I

 

Definitely reassuring on the lowered compression side. I don't feel so bad about it now and could probably live with it just fine.

Some things to consider: This is the last build I'm doing on this car so if it ends up not being enough for me some day, then I'm just switching cars. I won't take this one over 15psi guaranteed.

Interestingly, even though my current pulley was sized to give around 11psi (3.4") I was hitting 13 psi with some belt slip at the top. Not sure what was up with that, maybe my head wasn't flowing properly or something. No idea really.

I'm also very interested in the idea of going to a 2.2 motor but keeping the 9k rpms. Whats involved with going to an F22 block/crank? I'm already kpro'd and I think this new head could handle whatever I throw at it.

Appreciate the input so far.

J