Cam question

[dkg4244]

OK folks, my stroker build has been coming along slowly but surely over the past few months. My machinist finally told me that all the machine work will be done tomorrow. I have a 93 4.0 block bored .020 over with IC944s, moly rings and factory reconditioned rods. New scat crank with king bearings. Block is zero decked and I'm running a felpro head gasket with a .052 compressed thickness. Head has a valve job and a nice porting job done. I'll be running the OBD1 setup on this.

My goal above all else is reliability and longevity. I don't mind giving up a few ponies to ensure that all the parts will be happy and last a long time.

My question is regarding camshaft choice. I want torque more than power. This is going into an 83 scrambler that I'm using as a daily driver and mild off road rig. It will live below the 4500 rpm range most of the time. I have heard that a stock cam can yield good results but so can a mild cam like a comp 231 or 232. I also saw from Moses Ludel's site that comp has a 252 grind that is good for torque.

I guess my question is this: does an aftermarket cam make a big power difference in an application like this to make up for the reliability issues and short life, or am I better off sticking with a stock cam and being happy with reliability?

I know there are endless threads about this topic buy I seem to not find the info I'm really looking for. Thanks for any help.

Dave

[Retlaw01XJ]

In general, stock cams produce good low rpm torque due to the relatively early closing of the intake valve, which keeps the dynamic pressure high. Performance cams with longer duration will allow better breathing at higher rpm's, but (usually) give up some low rpm torque since the intake closes later.

In your case, zero-decking the block will likely increase the static compression ratio to higher-than stock. Therefore you could use a mild performance cam without losing some of that 'Dynamic compression' that gives you the low rpm grunt. Which head are you using?

Use the sites 'Stroker Compression Ratio Calculator' to determine your CR and try different cams there. That's a good starting point.

[Cheromaniac]

In your case, zero-decking the block will likely increase the static compression ratio to higher-than stock. Therefore you could use a mild performance cam without losing some of that 'Dynamic compression' that gives you the low rpm grunt.

With the block zero decked and a Felpro HG, the SCR will be around 9.6:1 so I think the 231 cam would be a good choice. That's definitely too much compression to run a stock cam.

[dkg4244]

Thanks for the replies. My static compression comes in at 9.5:1. With a comp 231 cam, I get 8.29:1 DCR. With a 232, I get 8.15:1. What should I be shooting for to run on pump gas, whether it be premium or mid-grade?

[SilverXJ]

You might squeak by on midgrade.

[dkg4244]

I'm running the 7120 head that came with the block. Both are '94 vintage. I've been thinking about running the Mopar P4529229AC cam, the P4529228AD or the Comp 68-231-4. I've heard that the Mopar cam has wider lobes and would probably last longer. With that cam I have a DCR of 8.29:1. That should still give me low end torque while being able to use pump fuel. I've also heard that the stock valve springs can be used with this cam. Can anyone confirm this?

Also, is there a definitive answer as to what springs are recommended for the Comp 231?

I guess my point is that my engine is ready to put together with the exception of the camshaft and valvetrain. The machinist is waiting on me to choose a cam so he can install the correct springs and I can begin assembling the engine. Any input as to which cam has proven to be a better choice and has proven to hold up to real driving conditions would be much appreciated.

Thanks,

Dave G

[Cheromaniac]

Also, is there a definitive answer as to what springs are recommended for the Comp 231?

The Mopar 5249464 springs would have been the best choice but apparently they're no longer being made.
I suggest you just go for the Mopar 29 cam so that you have the wider lobes for longevity and you can use the stock springs.

[dkg4244]

I had a brief chat with my machinist today before work. We discussed using the MOPAR cam, but he feels as if the 108 degree lobe separation is going to cause problems with my idle and vacuum, etc. He feels I should use a cam that is more around 110 or greater. I was pretty set on running a MOPAR cam, but I don't want to have drive-ability issues. Has anyone run this cam with a OBD1 setup without issue?

[akadeutsch]

Is your Jeep an automatic or manual? If its an automatic you don't need the super low end power of the comp cams. The mopar cam kicks in around 1100 I think. And its good till 5000. It is going to depend where you want your power. Man Trans guys want their power at 600. Auto Trans don't need it till a little later...1000RPMs