I'm currently helping a friend build his 390. Is a Complete stock rebuild except for headers and a 600 holley. The cam he has is from Comp its a 268 Adv. Duration/218 @.050 Duration, .494 lift and 110 lobe seperation. I wanted to know what if this cam will work with the stock rockers and his set-up. Also what does everyone think of this cam? What will the idle be like?

 

I can't say for sure on the idle, but it should be pretty smooth. It also should work fine with stock components, and be a good all around cam for a stock build.

-Scouder

 

It should sound like a stock cam, and pretty much act like one.

On the rockers:

The stock non-adjustable system is kind of pickey when changing things. The way they (ford) "adjusted" things from the factory was with varied length pushrods. Various things can change required pushrod length though. These are a DIFFERENT CAM, different valves, a valve / valve seat regrind job, rocker wear, and pushrod wear. There are two ways to work around this. One is to go buy a length checking pushrod. You then mock-up the motor, and check what length each position needs, record it, and order a set of custom pushrods to give you the proper lifter preload.

The other option, kind of an easy-out, is to get the adjustable system. DSC has 'em. $260 for the adjustable rocker setup, and $40 for the matching pushrods. The advantage to this is they can be reused if you'll be changing out the cam again, or plan on subsequent rebuilds.

 

He just ordered the pushrods and valvesprings for that cam from comp. With this setup using the stock rockerarms do you guys think he will run into any problems with
them. Also whats the open and close spring pressure for stock valvesprings. Thanks guys

 

What year 390 for valve spring specs?

 

Oh and single or dual with damper?

 

I Believe its a 74' but not sure, the springs look to be single with another small spring in the middle, the damper maybe? do you guys think the stock springs would work or is it good that we got the comp springs?

 

Go with Comp's recommended springs for that cam. Your stockers are probably the ones from the last build I am guessing and unless they didn't have much for miles on them, then you definately would want to go with the recomended springs. Prevents a pretty likely valve float issue.

 

Ok guys I need some more help. I took my buddy's word for it that this was a 390, well I was messing around and deceided to check the stroke and it turns out its a 360. Is the compression alot lower then in a 390 or are they fairly close. The guy at Comp recommended the 270H 270 Adv. Dur/ 224 Dur@.050 .519 Lift, 110 Sep. and 106CL. We went with previously stated cam. Do you guys think we made the right choice? Comp said both cams have a noticeable idle? I just wanna make sure this thing isnt gonna turn out to be a dog.

 

If that is a 360, it will definately be a dog with the 270 cam. The 268 might run OK but is probably stretching it pretty far. I'm sure some of the gurus will jump in soon and help you. As far as being comparable in compression (390 and 360) well no. The lower output 390's (later pickups) had at best like 8.4:1 comp ratio (if that) and the highest an earlier 360 might have had was like 8.3:1 (a lot of them have like 7.8:1). There are some things you can do to help this depending on how much your buddy wants to spend. Some of the cheaper things that will help a little (I think anyway) would be to run steel shim head gaskets (360's might have came factory with 'em though, not sure on that one) mill the heads and block (depending on how much you mill it could help a little). If he is going to stay with the 360 and wants to run a bigger cam you guys should maybe look into some higher compression (if they even exist anymore or if they ever did) .050 over 352 pistons and/ or (depending on how much compression you need/ want) the real small chamber hi-po factory heads which came on the hi-po 352 and the super hi-po 390 I believe. Where the real limiting factor with 360's and low-perf 352's is the lack of quench and then the narrow cross-section beam connecting rods. A somewhat educated idea tells me that the most theasible thing to do other than the above mentioned ideas (which may be damn near impossible as far as those small chamber heads go) is a custom set of pistons made for the shorter and stronger 390/427/428 connecting rods. That will get somewhat expensive depending on what you consider expensive anyway. About the only other option is to do what most people do and convert it to a 390 based engine with 390 crank, rods, and pistons and/or convert it to a 410 based engine with 410/428 crank, 390/427/428. There are some other items involves in converting to a 410 like a flywheel or flexplate, counterweight (I think), and most likely having the whole rotating assembly balanced. When you get into 428 CJ and 428 SCJ stuff there are some more variations as far as certain rods, flywheel/flexplates, and counterweights but figure out what you guys want to do and we can probably help you with whatever decision you make.

JC