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Race Prep early 4.0L heads?

CheapXJ

NAXJA Forum User
Location
570, 813 or 303
I know that there was a team of race MJs or something like that in the early years of the XJ/MJ, and I've heard of a race prep or race spec or something to that effect head for the 4.0L

does anyone have any concrete information on this, and if it might have been plopped into some random production models?

Reason I ask, my 87 MJ, which has a rebuilt 4.0L in it with 4.10 gears and 33's can NOT beat my 89 XJ w. 3.55s and 36's off the line. both are automatic

both are 4.0L, both are running the later ECU (don't know if that has anything to do with the 173hp vs 177hp differences from 87 and 88-90) and the 89 seriously has got to be the ballsiest 4.0L I've EVER driven (worked at a Jeep shop for a year, and drove a boatload of 4.0Ls)

I just can't for the life of me understand WHY this 4.0L with 340,5xx miles on it runs so damn good. sure, it leaks, and smokes, but it's fast!

I used to use it to tow the drag car to the strip (this was before it was lifted)

with 225/70s that 89 ran a 15.8 sec 1/4 mile with nothing more than a relatively new cheapo air filter and a cherry bomb.

my MJ would never do that. I'd be lucky if it was in the high 17's.

:dunno:
 
My brother had a 5.0L mustang that was like that once. It was completely stock except for the exhaust, and would blow away other 5.0s that had way more mods. I remember riding in one of my friends mustangs that was the same year and engine, and couldn't even come close to keeping up with my brother's. I still don't know why it was so fast.
 
from what I recall...I remember a few guys running off high 15 sec. 1/4 's in xj's. Low 16's seems to be more common though. I know that I could spank most ricer honda preludes when mine had stock tires/lift. Ahh, the good ole days. Anyone want to do my gears?

-Keith
 
Sounds like you have a Wednesday Motor. Built right on Wednesday because everybody is hung over on Monday and they want to leave early on Friday:)

AARON
 
The 87 to 90 had the same head casting - altho there were different casting batches (several years). Some of the early ones were very rough with slag in the ports, etc. MOPAR Performance sold a ported head for $1000 back in the early days (since discontinued). It is possible to port a early head to outflow a stock HO head, but its not going to make any difference in your application. Most likely compression and camshaft timing (t-chain stretch) are the two major differences between the Jeeps.
 
rsalemi said:
The 87 to 90 had the same head casting - altho there were different casting batches (several years). Some of the early ones were very rough with slag in the ports, etc. MOPAR Performance sold a ported head for $1000 back in the early days (since discontinued). It is possible to port a early head to outflow a stock HO head, but its not going to make any difference in your application. Most likely compression and camshaft timing (t-chain stretch) are the two major differences between the Jeeps.
well, I know that the timing chain is stretched (had to cut the tabs off and "re-index" my distributor to get engine speeds above 4000rpm back)
 
HodgePodge said:
I Believe Archer Brothers raced the 4.0l But I can run down the street and ask them on monday maybe. :)

Maybe talk to their tech and try to get some specs out of him for ya.

hodge

Hodge, are you in Duluth? Hermantown?
 
From what I could figure they ran the 2.5L in the SCAA. I wish there was more info on those mj's.

racemj.jpg
 
XJZ said:
Hodge, are you in Duluth? Hermantown?

I live in duluth, and work up by the airport about 3 blocks from archer racing.

And it was 2.5l I was wrong. Borla is using their header design according to my neighbor but I haven't gotten around to running up there yet. I'll see how much info I can get out of them. What kind of specs are you looking for?

Hodge
 
CW said:
From what I could figure they ran the 2.5L in the SCAA. I wish there was more info on those mj's.

racemj.jpg
for some reason thats nicer looking than one on 35's(sorry brettm) but a jeep that can kick ass on the street is always nice
 
There was an article in one of the past JP on a Baja prepped XJ that had some interesting engine info. Not sure if it's what you are looking for however.
 
The boys at Hesco know their way around a Jeep motor pretty well...They helped me get 150+ honest HP out of my 2.5...the only downside is that I have to really put the boot to it to get the power...but it does sound kinda cool at 6,500... :fuse:
 
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