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Unread 11-04-2013, 06:23 PM   #61
swatson454
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1983 CJ7 
 
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Quote:
Originally Posted by NH2112 View Post
3) How about a cam swap to take advantage of the 4.0l head's better flow characteristics? I'm running stock cast pistons and can't tell you how much was removed from the head & deck, but the machinist said it'll still run on 87 octane. I've been told swapping to a. 4.0l head is a bolt-on 40hp and that with the right cam & jetting I'll see a nice increase in torque off idle as well, I might as well take advantage of it! If I can't get this thing right on the next try it's coming out and I'm swapping a diesel in like I should have done in the first place!
Well, a head's ability to flow air is only relevant if the cam gets the valve off its seat.

My gut tells me that a cam having roughly 260 degrees of advertised duration and cut on a 106 LSA (custom for sure) should pull like a freight truck in a 258.

Aside from that, you've moved beyond what a Weber 32/36 is capable of doing. I'd go to a 38 at a minimum or entertain a manifold swap and stepping up to a Holley 390 or even a 470 T/A.


Shawn

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Unread 11-04-2013, 06:51 PM   #62
NH2112
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1990 YJ Wrangler 
 
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Quote:
Originally Posted by swatson454
Well, a head's ability to flow air is only relevant if the cam gets the valve off its seat. My gut tells me that a cam having roughly 260 degrees of advertised duration and cut on a 106 LSA (custom for sure) should pull like a freight truck in a 258. Aside from that, you've moved beyond what a Weber 32/36 is capable of doing. I'd go to a 38 at a minimum or entertain a manifold swap and stepping up to a Holley 390 or even a 470 T/A. Shawn
Thanks, Shawn. I really know next to nothing about the particulars of these engines. My '83 CJ had the stock BBD and burned so much oil I never bothered with it and my '00 TJ's stock 4.0l did everything I wanted and needed it to do, so I didn't get into performance. I've been told by some that the 32/36 is more than adequate, others say a 38 at a minimum like you do. A 390cfm 4-barrel does sound good, it's not going to overfuel but should supply enough for anything I might want to do short of forced induction. I was looking over my engine earlier and apparently a lot of the preservative oil from the machine shop ran into the pan, so I'm most likely going to pull it out and have the bores, deck, and head freshened up to get rid of the rust. Looks like it's time to really start researching these engines and deciding what exactly I want out of mine. Thanks again.
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