blaylock6502
New member
I have a 74 cj5 with a 258. It has an edelbrock intake for a 2 barrel . I am wanting to put a cam in it, just big enough for a lopey idle. Any recommendation on the best carb for the money? Also what cam?
Best carb for 258
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PoliceMonkey161
New member
Well.....That is a popular question and really comes down to matter of personal perference. I perfer Weber carbs,with a slightly modified cam and a single plane intake my choice would be the 38 DGES synro . However, if you have the Edelbrock with the dual plane, a synchronous 2 barrel carb would not be ideal. I'm not that familiar with Edelbrock intakes?The smaller 32/36 would work better on a daul plane. But there are Holley and Motocraft carbs that perform similiarly.
As for Cams, a lot of folks seem to like the Competion Cams model. I like the Clifford cam, it offers great low to mid range torque.
As for Cams, a lot of folks seem to like the Competion Cams model. I like the Clifford cam, it offers great low to mid range torque.
blaylock6502
New member
Ok that thoroughly confused me but thanks I think I'm figuring it out. I talked to another guy at work and he said to try to match rpm range of intake and cam and for a good idle I would need around .500 duration cam and according to a formula he used I would need around 350 cfm carb.?? Does that sound right? It blows my mind when people talk about not wanting to work on computerized fuel injected vehicles and at 29 and a technician at a gm dealer that's all I know. I couldn't begin to understand carburetors!
PoliceMonkey161
New member
You're way too scientific for me........But if you go to: http://www.compcams.com/Company/CC/cam-specs/cam-search-results.aspx?sc=1&sm=By%20Engine%20Family , this is the Competition Cams spec list. It will show you the duration/lift of the different "grinds". It's a good reference.
As for the manifolds, generally with the 258 you will find open plenum or a single plane design. The air/fuel mixture flows through a single/open channel into the combustion chamber (stock and Clifford designs). Some manifolds are dual plane (like certain Edelbrock), in short they provide a second channel (plenum) for the higher velocity air/fuel mixture created by the secondary barrel(s) during their activation.
When it comes to carbs, generally the secondary barrels are brought on-line via a vacuum metered system or progressive linkage. With a synchronous design, both (or more on larger domestic models) are synchronized using a mechanical linkage system to operate all the barrels equally.
As a rule of thumb or as I understand it away, you would not need much more than 400 cfm (on the top end) with a modified 258. The Weber 38 DGES is rated for approximately 400 cfm and can be adjusted up or down by changing jets (like most other carbs).
I know some will disagree with me, this is my opinion so the subject.
As for the manifolds, generally with the 258 you will find open plenum or a single plane design. The air/fuel mixture flows through a single/open channel into the combustion chamber (stock and Clifford designs). Some manifolds are dual plane (like certain Edelbrock), in short they provide a second channel (plenum) for the higher velocity air/fuel mixture created by the secondary barrel(s) during their activation.
When it comes to carbs, generally the secondary barrels are brought on-line via a vacuum metered system or progressive linkage. With a synchronous design, both (or more on larger domestic models) are synchronized using a mechanical linkage system to operate all the barrels equally.
As a rule of thumb or as I understand it away, you would not need much more than 400 cfm (on the top end) with a modified 258. The Weber 38 DGES is rated for approximately 400 cfm and can be adjusted up or down by changing jets (like most other carbs).
I know some will disagree with me, this is my opinion so the subject.
blaylock6502
New member
I may be starting over completely! I wanted to bump compression from stock 8:1 to somewhere between 9:1 and 10:1. I talked to the local machine shop and he said all that is offered is factory style pistons so to increase compression the next most reasonable option would be to deck the block which could cause valve piston clearance and the only way to know for sure would be to deck the block and mock up with clay on top of piston roll over by hand and see what happens. This makes me think maybe I should find an 81-86 258 when from what I've seen they raise compression from 8:1 to 9.2:1. If I do decide this is the way to go would it be an easy swap???
PoliceMonkey161
New member
Yes....... Easy swap, same everything on the outside.
superj
Active member
Dude, google jeep stroker or jeep 4.0 stroker and make whatever you want. My wrangler came already stroked and is a blast to drive. Mine is a 4.5 using a 98 block and 87 & 98 internals. I run a foie barrel 450cfm holley on an offenhauser intake. It really rocks.
Check out the stroker option though since you aLready have the 258. You can pick up a 4.0 for the other parts for cheap and probably get most of the parts to do a fuel injection swap too for less then 500 bucks. I have seen 4.0s go for 100 to 400 locally so hit craiglist and build a straight 6 monster that embarrasses your v8 buddies
Check out the stroker option though since you aLready have the 258. You can pick up a 4.0 for the other parts for cheap and probably get most of the parts to do a fuel injection swap too for less then 500 bucks. I have seen 4.0s go for 100 to 400 locally so hit craiglist and build a straight 6 monster that embarrasses your v8 buddies
