Distributor Gear Play

[Dan Lee]

I was trying to set the timing on my 434 cu. in. Ford 'M' block and noticed the timing jumping.

It's a Ford 400 bored & stroked to 434 with a steel crank, H beam rods, and forged pistons. It's fuel injected using a Ford EEC-IV computer. 42 lb injectors, & 90mm Lightning MAF. It has CHI-3V alloy heads and full roller valve train.

The cam is a Comp Cams Custom Roller retro-fit with small base circle. The cam is a -8, so it has a special gear to drive the distributor.

Since this is an EFI motor, the distributor is an aftermarket TFI type with a 5/16" oil pump shaft drive.

Upon examination, I found that there is at least 10 degrees play in the cam to distributor mesh. The timing chain is tight with only a few degrees play. The motor has only a few thousand miles of moderate use in a '53 Ford F100.

The distributor gear is some type of steel. I tried a Mallory Unilite distributor for fit, and found almost the same amount of play with it.

The gears on the distributors look good, but the gear on the cam shows wear.

Why did my cam gear wear?

[iwannagofaster]

If the distributor you were using came with a "hardened" steel gear, then I have an explanation. "Hardened" steel gears will work with our -8 material, but they must be filed down and meshed perfectly. We recommend using a "melonized" steel gear because it is much more forgiving. A lot of companies heard that a "hardened" steel gear will work with the material we use, so they started using them, but the hardening process can distort the gear a little and they normally leave really sharp edges on them. The sharp edges and harder suface than the cam gear will cause the cam gear to wear. How long have you had this cam in there?

[Dan Lee]

The motor was built several years ago, but the actual mileage is low. It's in a '52 Ford F100 that is only used for Cruises and Shows.

[iwannagofaster]

That sounds like the "hardened" gear scenario to me, sorry for the bad news. Please email me at whood@compcams.com if you would like to discuss your options for a new cam.

[Dan Lee]

That's a '53 Ford F100, not a '52.

I spoke to Chris Mays today and he gave me an RMA #. I explained to him that the Installation directions call for a New Distributor Gear, but nowhere do they specify 'melonized'. I used a new distributor with a steel gear. I thought that I would be OK with the -8 cam gear.

[iwannagofaster]

Good deal, I hope he can help get this resolved.

[Dan Lee]

I returned the old cam with the distributor gear to Comp, and they are issuing a partial credit, since the cam was out of warranty. I had hoped for more, but I am willing to accept a partial credit.

Now, I am faced with selecting a new cam. I liked the old grind. It was something that I worked out on my Dyno-Simulation program.

I am considering dumping the old Spider and Dogbones in favor of a Link Bar lifter setup. Some of the Link Bar lifters require a large Base Circle cam, instead of the small Base Circle.

Are the 32-0000-8 cams available in a large Base Circle?

How much will a large Base Circle add to my Lifter height, or subtract from my pushrod length?

My present lifters are 2.5" x 0.874", and my pushrods are 8.75" x 5/16". I want to avoid changing pushrods, as they are hardened Chromalloy for guideplates.

[iwannagofaster]

With the link bar style lifters, you do not need a different base circle cam. They are designed to be used with any size base circle. If you stay with the smaller base circel, you may be able to use your pushrods, but that would have to be checked once you got the new cam. We can make the base cirlce larger on those cams if you wanted, but it is not necessary. The lifter seats are higher in the link bar style lifters, so it may change pushrod length, but like I said, that will be determined after the new cam installed.