What Cam?

Dennis...
I have the Comp EX284H in my 73. I love it! Runs great and has a great lope to it!
Curt

Aloha Dennis,

I've not run the XE274, but I have recommended it to others, it looks to be a great street cam. I would choose it for myself if I were purchasing a flat tappet hydraulic cam. Lots of lift, short duration, low overlap, especially desireable for a low compression cobra jet motor. It is rated for the right powerband, 2000 to 6000 rpm.

I want to provide the normal warning about the oem Ford valve train. Hydraulic cam clevelands had the multi-groove valve locks that actually but up to one another before they seat tightly in the valve stem grooves. this very small clearance was some engineer's bright idea to promote "valve rotation" and thereby prolong valve and valve seat life. It didn't work. The valves were made of 2 pieces, a valve head induction welded onto the stem.

Running the XE274 cam would require installation of new springs, because the oem valve springs will coil bind with that much lift, and they do not provide enough pressure for the aggressive lobes of the XE274 camshaft.

It is always recommended if you're going to run a Cleveland vigorously, run more valve spring pressure or a higher lift cam, to replace the oem 2 piece multi groove Ford valves with one piece, single groove, stainless steel valves, replace the spring retainers with chrome moly (or better) retainers and to utilize single groove style locks. This is because perhaps the single most common mode of failure for the 351C is dropping the valves, either because a valve head separates from the stem or the spring retainers split, or the keepers let go of the valve stem. When this occurs, the damage to your motor is massive, if not terminal.

Your friend on the DTBB, George

How would you define 'vigorously'?

Would a stock '72 351CJ with Holley 600 that's probably on the original valves be in danger of losing it's valve heads during road use (i.e. rarely above 5000rpm for more than a few seconds).

Yes

I can't put a number on it for you, like 10% or something, but frankly, all Clevelands running oem valves are in danger. Some owners will luck out and never have a problem, but some will. I don't think the issue was solely a design problem, because the valves fail under every degree of use but not consistently, this leads me to believe it is also partially a quality control issue.

I could write you that since the car has gone this far without failure, the chances are it won't. But it is much safer for YOU to assume that it's only time before it does fail.

I have the oem valves in my car too, we both need to pull the heads on our motors and correct this situation in the near future.

your friend on the DTBB, George

Is there a way to identify OEM valves without pulling the head off. The OEM valve retainers will be the multi-groove type - but can you 'see' this without removing them?

You would have to compress one valve spring, remove the locks & retainer to expose the top of one valve stem.

This would be easier than pulling an intake manifold & head.

George

> Is there a way to identify OEM valves without pulling the head off. The OEM
> valve retainers will be the multi-groove type - but can you 'see' this without
> removing them?

Yes. Look at the retainer where the keepers and valve stem stick through.
If the keepers butt together, you have the OEM parts. If there is a gap
between one side of the keepers then you have aftermarket keepers and likely
single groove valves, though there are aftermarket multi-groove keepers.

Dan Jones

Thanks George, as usual a wealth of knowledge gained from your posts. I guess that I'll pull the heads at the same time and swap out the valves and valve train components. My motor is has low mileage (25,000) but I guess I should get the heads completely redone?

My '72 Pantera had 37,000 miles on the odometer when the two-piece valves decided to part company. I wasn't driving vigorously at the time, and the cam and intake limited me to 5500 rpm on that engine anyway. I was cruising at a constant 3000 rpm or so when the motor just shut off. No bang, no explosion, it just stopped working.

They are right - really bad things happen to a 351C when it "processes" valve parts.

Dennis,

one additional suggestion I think I should include along with my original comments about the XE274 cam: I believe usage of that cam & associated springs warrants installation of roller rockers. Not necessarily adjustable valve train, but a good set of roller rockers. Ford Motorsport sells a set that bolt down on the pedestals just like the oem rocker assemblies. And finally add to that list 3/8" push rods of the proper length. It is best to install cam, lifters & rockers after the new valves are installed in the heads, the rocker arm geometry is checked and adjusted, and the heads are bolted down, and then use a "test" push rod to determine what length of push rod is needed for your modified valve train. You may luck out & only need an off the shelf size, but odering custom length push rods is no big deal either.

This should give you an idea of the expense & work involved for the cam swap. More than you initially thought I'll bet. Well worth the effort however.

George

George,

I got the crane cams adjustable stud kit installed with a set of roller rockers. Do you think that I should swap out to the Ford Motorsport version with the original pedestals? Do you have the part numbers/source for these rockers? Thanks

Dennis,

What you have will work just fine.

Aloha, George

Dennis.. I have the cam that you are thinking about getting (XE-274H). I'm pleased with it, it's streetable, yet I've taken it on numerous road trips with no problems. I did have my machinist put aftermarket valves and the matching springs- per his recommendation.As well as roller rockers. I dont know the exact parts he used but I could always get that info.

Topcat, thanks for the input.

George, another question. Since I'll have the heads off the motor to replace the valves, is it of any benefit to have the heads milled down to increase compression? If so how much can be milled off using the aforementioned cam and how much will I gain? My bottom half is all stock 1973 Cleveland. Thanks.

Dennis, don't bother, nothing to be gained. Your motor has a dismal 8.0:1 compression. Closed chamber heads or flat top pistons would bring that up to 8.8:1, which would be good. Milling just won't make a big enough "dent" to make it worth your while.

You'll have to phone Comp's tech line to find out their compression recomendation for the cam, my "guess" is it will be around 9.5:1. That's just a guess, not a recommendation. If they give you a range of compression, for instance 9.0:1 to 10.0:1, my recommendation is to run on the low side. Compression is NOT a big horsepower maker, not on a street motor burning pump gas. It's purpose is to compliment the characteristics of your camshaft, cylinder heads and fuel.

If you're contemplating a head job to install new stainless vales, new springs, etc, you might consider finding a set of closed chamber heads and reworking them instead. There are closed chamber heads on ebay constantly.

Your friend on the DTBB, George

Thanks George, I did call Comp Cams and gave them my motor specs and the XE274 cam is what they recommended. Unless I find a pair of cheap closed chamber heads, I guess that I'll have mine redone with new 1 piece valves.

Dennis,

Your current heads have the smaller 2V size valves, since you're buying new ones, you may want to upgrade to the 4V size valves.

Aloha, George

I thought that all the 4v heads have the 2.190/1.710. What is the other valve sizes? Are they larger than these or do I have smaller sized valves? Are the larger ones found on the early model year heads? Enlighten me oh wise one!

I went back to the open vs. closed cylinder head topic and found the answer to my question. Is it difficult/expensive to convert the heads to the larger valves?