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AMC 258 cam upgrade

AMC 258 cam upgrade
J

jakeh937

Senior Jeeper
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Location
Petaluma, CA
Vehicle(s)
'79 Cj5, 258 with Howell Fuel injection kit, T18 with dana 20 Tcase, dana 30 front with Detroit locker, AMC 20 rear with LSD and one piece shafts, Warn 8k winch, 1" body lift, 2" suspension lift, 33 tires
Hey guys, new to this forum and looking for some ideas and thoughts. I am rebuilding my 74 CJ5 and currently am working on rebuilding the engine. AMC 258 i6 / 4.2l AMC 258 i6 / 4.2l . I am thinking about doing an upgraded cam but I am not to sure on how it will run. I am looking at Comp cam 260h or an "RV" cam. I plan to use this jeep for hunting trips, light/mod wheeling and cruising. Nothing to extreme. I have also read and heard of upgrading these engines with an HEI ignition, clifford intake and exhaust and an MC2100. Im also not looking for a ton of HP, but more torque on the lower end for trails, but to not loose total fuel mileage either. I know I have read that a 4.0 head swap is a good way to go, but I'd prefer to keep the AMC 258 i6 / 4.2l head. Any experience or knowledge on any of this would be greatly appreciated. Thanks. :)
 
The 2100 and HEI are great upgrades and are pretty easy to do, I've done both, but hands down the best thing is the 4.0 head.

As far as cams go, I used a comp 252 and I have no complaints.
 
Tinman hit it right on the nose. I have the same upgrades and it works great. Stay away from the newer Clifford stuff. It's junk.
 
In a 75 I would check the block number to confirm that it is , in fact a AMC 258 i6 / 4.2l . Does it have a one or 2 Bbl. carb now? I don't think the cam upgrade will give you enough improvement to make it worth the extra money over stock cam. Depending on millage I would question replacing it at all. What distributer do you presently have? I switched to the motorcraft with the cap and rotor upgrades and an MSD6 and it was probably the best bang for the buck I have yet found in a single mod. The Mc2100 is 5x better carb than the Carter 2 Bbl.
 
tinman said:
The 2100 and HEI are great upgrades and are pretty easy to do, I've done both, but hands down the best thing is the 4.0 head.

As far as cams go, I used a comp 252 and I have no complaints.
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How do you like the performance of the 252 cam?
 
IOPort51 said:
In a 75 I would check the block number to confirm that it is , in fact a AMC 258 i6 / 4.2l . Does it have a one or 2 Bbl. carb now? I don't think the cam upgrade will give you enough improvement to make it worth the extra money over stock cam. Depending on millage I would question replacing it at all. What distributer do you presently have? I switched to the motorcraft with the cap and rotor upgrades and an MSD6 and it was probably the best bang for the buck I have yet found in a single mod. The Mc2100 is 5x better carb than the Carter 2 Bbl.
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I will look tonight when I get home and let you know
 
caveman said:
Tinman hit it right on the nose. I have the same upgrades and it works great. Stay away from the newer Clifford stuff. It's junk.
Click to expand...



Did you leave the stock intake/exh manifolds on and just run bigger carb and dist?
 
252 duration is about right. Don't go any higher though without doing some internal mods.
I ran a 262 with a whole bunch of engine work and it was phenomenal but expensive. :cool:
 
CJim7 said:
252 duration is about right. Don't go any higher though without doing some internal mods.

I ran a 262 with a whole bunch of engine work and it was phenomenal but expensive. :cool:
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I'm thinking of either the 252 or 260. I'm just afraid of going to big for what I want to do. I have read with both you can get away with stock valve springs and rockers, but I'm thinking about upgrading if I go to the 260. What mods did you have to do to run the 262?
 
jakeh937 said:
Did you leave the stock intake/exh manifolds on and just run bigger carb and dist?
Click to expand...

My whole setup is an odd duck. I have a stroker engine with a motorcraft 2100 sitting on a Clifford intake, that I wouldn't buy again. The distributor is an HEI. Exhaust is a cheepo tube header that I got off Ebay. I built it for low speed power for crawling and it works the way I wanted it to.
 
So I found out that in fact my motor is an AMC 232 i6 instead of a AMC 258 i6 / 4.2l . Not a huge deal to me. Wondering if anyone knows the difference between comp cam 260 and 252? Thanks everyone for the input!


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caveman said:
My whole setup is an odd duck. I have a stroker engine with a motorcraft 2100 sitting on a Clifford intake, that I wouldn't buy again. The distributor is an HEI. Exhaust is a cheepo tube header that I got off Ebay. I built it for low speed power for crawling and it works the way I wanted it to.
Click to expand...



Why wouldn't you buy Clifford again?
 
jakeh937 said:
Why wouldn't you buy Clifford again?
Click to expand...
Very poor quality' the intake I bought had a bunch of casting voids in it. I should have taken pics. I will The next time I have the carb off. I've seen better stuff from third world countries.
 
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