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Unread 05-26-2010, 01:48 AM   #1
danheit
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How can I tell if the PO did the 4.0 head swap?

Judging by some other upgrades, I can easily see the PO doing the 4.0 head swap. Is there an easy way to find out? How can I tell?

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Unread 05-26-2010, 03:54 AM   #2
CJ7-Tim
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Look for the head casting number near the 3 & 4 spark plugs.

1987-1990 Jeep 4.0L used head casting 2686

1991-1995 Jeep 4.0L used head casting 7120

1996-1999 Jeep 4.0L used head casting 0630
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Unread 05-26-2010, 04:26 AM   #3
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Quote:
Originally Posted by CJ7-Tim View Post
Look for the head casting number near the 3 & 4 spark plugs.

1987-1990 Jeep 4.0L used head casting 2686

1991-1995 Jeep 4.0L used head casting 7120

1996-1999 Jeep 4.0L used head casting 0630
1975-1986 6-258 would get the #2685 head (if you're wondering,) and the 1999-2006 head was numbered 0331 (also, it had COP/DIS - and therefore bosses to mount the coil rail, which need not have been used - and if you see #0331 you'll want to pull the valve cover and look for "TUPY" cast into the surface on top of the head - those are the ones that are not prone to cracking, and appeared 2001.5-2002. Ish.)

The later 258 heads still had siamesed #3 and #4 exhaust ports as well - if you only see five exhaust primaries, it's the 258 head. If you see six, it's the 242ci. I believe the 258ci manifolds were cast iron log-style jobs, and I know the 242ci manifolds were all tubular steel.)
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Unread 05-26-2010, 05:18 AM   #4
Fatman
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Quote:
Originally Posted by danheit View Post
Is there an easy way to find out? How can I tell?
It will have a 4.0 exhaust.
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Unread 05-26-2010, 11:43 AM   #5
danheit
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Dunno what kind of exhaust and intake it is, as I am running a Clifford Performance Aluminum intake and a header (cracked, of course).
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