Jeep 4.0 0331 top end swap?

[streetxj]

I've read this:
"In brief, the 0331 head and manifolds, were redesigned by Rick Mudge (who ported Garth Hill's NHRA 4.0 drag racer) to do a better job in the RPM range that Jeep 4.0's are intended to operate. The intake manifold is longer (11.5" long runners compared to about 9"), more equal runners and feeds the slightly higher, and slightly larger intake ports of the 0331 head. The cast iron exhaust manifold has longer primaries (10" on average compared to 6" average on the header style factory exhausts) and matches up to the 0331's exhaust ports much more closely than previous tube headers (which means better scavenging).

IMO you can't talk about the 0331 head without also talking about the manifolds which are both better than previous factory pieces.

The 0331 intake ports flow better than any other HO head in my experience, Both I and Alex22 have flowed the 7120 (or 0630, they are the same) and 0331 and both of us found the 0331 to have higher CFM on the intakes. There's some numbers here if you do a search.

The exhaust ports are MUCH smaller but flow only a little less than older HO heads, this is because the area that was "filled in" so to speak to make them smaller was a "lazy" area (the floor of the port after the short side radius) NOSIGMA's velocity maps show this area on 7120 heads plain as day. And he also talked about how he'd love to be able to fill in the floor of the port raising it and increasing exhaust gas velocity... Looks like Rick Mudge did this, raising the floor makes the port smaller, but it also makes the short side radius much more gradual. He also gave the new exhaust port a trapazoidal crossection where the roof is smaller than the floor which has also been found to be a more ideal shape for the 4.0 heads, even the intakes have a small amount of trapezoidal narrowing towards the roof.

I used EA pro to sim the 99+ intake, the exhaust and the 0331 head as single mods (retrofitted to an older HO) and as a full system (in other words like a 99+(WJ) or 2000+ (XJ and TJ) factory engine without the factory emissions/MPG camshaft, and the emissions tuning (and without the pre-cats)...

I've never posted the numbers up here because I think no one will believe they are realistic... And even if Engine Analyzer Pro is a great engine simulator used by race engine builders, it might be wrong, and I might be wrong to believe it.... I'll just say this... I believe the SYSTEM (not only the head) without the factory emissions tuning and fuel economy cam is good for a LOT of torque over an earlier HO.

A lot of this info can be pieced together by reading the sticky thread on head porting (collected work of NOSIGMA). "

And these flow numbers from http://www.jeep4.0performance.4mg.com/tech_specs.html

"HO head #7120 & #0630 (Courtesy of John Brown)

Valve lift (in)... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow.... 66.0 128.0 179.0 206.0 209.0 209.0
Exhaust flow. 55.0 100.0 120.0 136.0 141.0 141.2

HO head #0331

Valve lift (in)..... 0.1 ... 0.2 ... 0.3 ... 0.4 ... 0.5 ... 0.6
Intake flow..... 59.4 122.6 171.1 201.1 214.3 218.4
Exhaust flow... 47.1 93.4 123.3 140.9 147.0 149.7 "


I was thinking about swapping out my 0630 head, log intake manifold, and small down pipe for a TUPY 0331 head refreshed with 3 angle valve job, mopar performance head gasket to reduce quench height, newer style horseshoe intake manifold, stock 0331 exhaust manifolds with federal emissions y pipe(no pre cats) and 00-01 2.5 inch cherokee down pipe.

Will this be worth the effort or just be a waste of time?

 

[O-Gauge Steamer]

I will agree that raising the floor is the right thing to do. And I will agree that just because an exhaust port is smaller it is not inferior as long as the velocity of the exhaust is improved. Velocity is the thing. Get the exhaust as far away as fast as possible.

It is basic head work ro fill the floor as it reduces the amount of turbulence and so doing provides a smoother delivery of the air charge. This delivery is a critical part of head porting as the fuel will want to get flung out of suspension and deposit on the walls.

If you go this way, get pre and post dyno runs made. And, there are some headers out there for that engine so you may want to look at them.

 

[streetxj]

Yeah, I'm still trying to calculate more or less the cost of doing this. I'm probably going to have to make some trips to different junkyards or just buy an alabama 0331 head and get the intake manifold and exhaust parts from the junk yard. Not sure how much a machine shop will charge to refresh a 2003-up 4.0 head and do a 3 angle valve job. I'm still thinking about it.

 

[gradon]

Things to keep in mind: obd2 jeeps used lower lift cams than obd1/renix and the exhaust lobes had longer duration than the intake lobes. Most aftermarket cams are under .5" lift, so the .6" number is basically useless and the .5" is hardly used.

 

[streetxj]

Things to keep in mind: obd2 jeeps used lower lift cams than obd1/renix and the exhaust lobes had longer duration than the intake lobes. Most aftermarket cams are under .5" lift, so the .6" number is basically useless and the .5" is hardly used.

I was just thinking about that. They were probably talking about swapping the 0331 system onto the 91-95's for a lot of torque. As it is now, my stock 4x2 158,000 mile 96' with K&N panel filter and air silencer deleted, feels 4 times quicker than my moms 55,000 mile 2000 4x4 cherokee with exhaust and ebay intake.