cam shaft

[IOPort51]

I am trying to find enough information to make an intelligent choice of a new cam. This is to be suited to a AMC 258 i6 / 4.2l with a 4.0 head and Howell fuel injection with header. I have been lead to believe that for low end torque the duration remains the same and the lift is greater.
Words of wisdom?? anybody??

 

[cerrajero]

im not sure this will help.....its on my list of things to read...

Classic Inlines - How to Select a Cam Profile

i havent read it yet
I am acquiring a block so i am reading all build articles.

 

[cerrajero]

found one more
amc six cylinder performance mods

hope this helps

 

[Old Dog]

Well here's my . If you begain with the average street engine, I would go less duration (less valve overlap) which meens you need a bigger lift to make up for the valve being open less degrees.
But IMO jeep used a cam that makes lots of low end torque to begain with. I'd stay stock for a offroader, DD.

 

[IOPort51]

sound wisdom Dog and will give it serious thought.
cerrajero; I am looking forward to reading this as soon as I make it back to the house.
I am sure I need a different cam as the one I have is for the one barrel carburator. At least I have been told there was a different cam for this carb.
So if one needs to be swaped in it may as well be the best possible choice.

 

[73CJ]

I'm running a Comp Cams fuel inj cam. Also a Holley Projection. My cam was shot anyway.

Not a lot of performance difference, but more a higher RPM. Like running in mud .

What the heck - give her a try.

 

[Cheepjeep85]

the later model AMC 258 i6 / 4.2l had a different cam profile right? for the 2bbl. what about staying with mid 80s stock cam.

 

[IOPort51]

I have never changed a cam without it being part of a totol rebuild. And when I did it was just a mater of having the machine shop do it. How much trouble could I get in by changing the cam and not the bearings??
how hard is it to replace the bearings with out dismanteling the motor??

 

[Old Dog]

How much trouble could I get in by changing the cam and not the bearings??
how hard is it to replace the bearings with out dismanteling the motor??

IMO never change the cam and not the bearings (and the lifters), it just isn't a good idea. (unless you just did a rebuild and the bearings were pertty new anyway.)
Changing the bearings isn't hard but I don't think you could do it without dismanteling the engine. Maybe one of our I6 people can confirm though.

 

[73CJ]

I had the local auto cook the block and put the bearings in. Cheap insurance.

You might be able to stand on your head coming from the bottom,by why not just pull it and put it on a stand.

 

[Cheepjeep85]

IO when you pull the cam out take a look at the inside top of the bearing if it is much darker (such as oil burn) you definately want to replace the bearings, if the wear pattern is fairly even and you still have pretty good oil pressure i'd leave em alone and stick your new cam in, assuming they aren't all groovy then you might have bigger issues.

i just picked up the new issue of JP and read a short letter from a reader in the "your jeep" section in which he asked the exact same question you asked in this post. best cam for 4.0 head swap and howell tbi. christian hazel, (if you read the magazine regular you know he's the engine guy there) recommends the comp cams X250H-13(PN 68-AMC 232 i6 -4) for efi engines. this is what he said: 206/212 duration @0.50 and 0.460/0.476 lift ground on a 113 deg lobe separation angle for the smoother idle that the tbi will look for. recommended for a moderately stock, fuel injected jeep I6 engine. sounds to me exactly what your looking for