4.0l internals

[yamaha7928]

does any one know of good sources for lower compression pistons, new rods and better head gaskets for the 4.0l SOCH
i am working on a turbo set up and haven't really found all that much

 

[pcollins]

I'm no expert on turbos but...wouldn't you want Higher compression pistons to better handle the turbo? I'm just applying baseline engine knowledge here....maybe its different in this situation.

 

[Gotta_gofast]

No. The SOHC engine is already a higher compression motor with somewhere around 9.7:1 ratio. A real good tune and cool air charge will accept single digit boost pressures, but any more and you'll be barking up the detonation tree. Drop down to 8.8-9.0:1 and you'll be able to run a lot more pressure (this isn't an N/A motor). Also, the cylinder head deck design sucks for high cylinder pressure. Each cylinder has 8 coolant passages and 4 stud holes. That is 12 holes around each cylinder! Even the best gaskets are going to have a hard time not separating.

I would check out the 05-10 mustang V6 guys who have work done to their engines. The rotating assembly from the factory is balanced and is actually a decent system. The crankshaft is stout and the connecting rods have been pushed safely by guys running 400hp at the flywheel. Any big name piston manufacturer should have low comp forged pistons for you. The question is, will the rest of the drivetrain and truck handle it? The 5R55E and M5OD-R1HD both will not hold the power of a 350-400hp torque happy turbo motor. The 28 spline 8.8 axles have been known to throw their guts out the back at 400hp with enough tire (unless you stuff your rear end with aftermarket parts). When I did my V8 swap I was right around 400 at the flywheel and the frame did NOT like that. If it wasn't for an unfortunate accident, I would have ended up boxing the frame and running a roll cage along with bracing (had big plans for drivetrain lol).

Moral of the story, a conservative tune on 6-7 intercooled psi will be about the limits of drivetrain and rotating assembly. Need more? If you have a 2wd then i encourage you to look toward the 4.0L mustang guys.

 

[yamaha7928]

No. The SOHC engine is already a higher compression motor with somewhere around 9.7:1 ratio. A real good tune and cool air charge will accept single digit boost pressures, but any more and you'll be barking up the detonation tree. Drop down to 8.8-9.0:1 and you'll be able to run a lot more pressure (this isn't an N/A motor). Also, the cylinder head deck design sucks for high cylinder pressure. Each cylinder has 8 coolant passages and 4 stud holes. That is 12 holes around each cylinder! Even the best gaskets are going to have a hard time not separating.

I would check out the 05-10 mustang V6 guys who have work done to their engines. The rotating assembly from the factory is balanced and is actually a decent system. The crankshaft is stout and the connecting rods have been pushed safely by guys running 400hp at the flywheel. Any big name piston manufacturer should have low comp forged pistons for you. The question is, will the rest of the drivetrain and truck handle it? The 5R55E and M5OD-R1HD both will not hold the power of a 350-400hp torque happy turbo motor. The 28 spline 8.8 axles have been known to throw their guts out the back at 400hp with enough tire (unless you stuff your rear end with aftermarket parts). When I did my V8 swap I was right around 400 at the flywheel and the frame did NOT like that. If it wasn't for an unfortunate accident, I would have ended up boxing the frame and running a roll cage along with bracing (had big plans for drivetrain lol).

Moral of the story, a conservative tune on 6-7 intercooled psi will be about the limits of drivetrain and rotating assembly. Need more? If you have a 2wd then i encourage you to look toward the 4.0L mustang guys.

Thanks I think I might sway away from boost just seems like there's too many loose ends to tie up especially considering its my daily and a 09 and I want it to be around for years to come

 

[Gotta_gofast]

Didn't mean to scare ya. I still vote go for it. Just be smart about it and honest/realistic with your goals and expectations. A 4.0L SOHC with 6lbs of boost is going to be a fun daily driver. Spend a little on a reputable SCT dyno tune for a safe program and you'll be set. What transmission do you run? If you have the manual, a tougher clutch and some good synthetic fluid will help you out. I have the 5R55E auto and to prepare it for 6-7psi, I'm in the process of installing a superior shift kit (less the EPC resistor as I can increase line pressure with my SCT tuner), Sonnax increased ratio boost valve, new borg warner EPC, +3 quart pan, filter, gasket, and amsoil atf.

The 8.8 rear has 4.10 gears and a powertrax no-slip. Also installed a diff cover with bearing cap brace. Should be fine with my tire size.

Do it man, just don't overdo it.

 

[wahlstrom1]

You can run older model OHV pistons to lower the CR, the 90-94' will lower it less then 95'+ heads. Even the early heads should drop the CR nearly a full point.