Help picking distributor gear?
 

I've been using Chevythunder.com as a reference for my TPI swap, and he's been great so far (Even supplied my reconditioned TPI harness for me).

Now I know that there has been some controversy over the need to swap distributor gears if you're using a flat-tappet cam or a roller cam.

Maybe this will help?

http://chevythunder.com/fuel%20injec...20applications

(Scroll to the bottom of the page)


Anyways, here's my question:

My motor is the 330 HP crate engine from Chevy with a flat-tappet cam. I'm assuming that the distributor gear on the cam is iron (If I'm wrong, correct me). I'm going to be running a small-cap distributor, which I'm also assuming has a bronze gear, so I'm going to need to swap it out for an iron distributor gear for a longer lifespan?

It looks like I need this part number (Jegs 270-11970-1), but when I look at all the details for the item, this is listed: "With Left-Hand Helix for Opposite Rotation Camshafts"? Should I go with the new hardened bronze gear instead (Jegs 270-11988-1), or just leave it be and hope that the stock gear isn't going to wear down anytime soon?

:confused:

I've dealt with some of this before... Here is what I've learned.. I've got a factory roller motor. For my Comp Cams 268XFI (OE roller style), I called and asked them what distributor gear I should use--they said the stock one (which is an iron gear on the factory roller cams).. The only ones that need the bronze gear are retrofit roller cams (roller cams for use in blocks that were originally flat-tappet)... To be sure though, I would call your cam manufacturer and ask them (that's what I've done the last couple times) which one to use..

Another thing that you NEED TO MAKE SURE OF is that if you have a roller cam and a mechanical fuel pump, get a fuel pump pushrod with a bronze tip.. On my first motor, I used a new standard fuel pump pushrod.. A couple years later, I found my fuel pump eccentric on the cam ground down about a quarter of an inch (no wonder my fuel pressure right before I took the motor apart was only about 3 psi)...

Hope this helps.

Oh, I guess you're doing a TPI swap, so no need for the fuel pump pushrod...

I just dealt with this myself so I will share everything I learned. If you have a factory roller cam you need the steel GM melonised gear. It is available from summit racing under part number NAL-10456413. If you are using a flat tappet cam then you just need to use a regular steel dizzy gear. I am sure you can get this from Summit or your GM dealership. I was told by a Summit tech that a Bronze dizzy gear would only last about 3000 miles!! your best bet is to just use a stock GM gear for a flat tappet cam. it will be of good quality and will last the longest.

Thanks for the info!

Is the gear on a small-cap HEI steel though? I thought it was bronze, which is part of the reason why there is a problem.

The information on that page isnt exactly accurate. The factory gears were never bronze. The newer ones were melonized, its a treatment process and any of those will work fine. The gear on the cams (and many aftermarket ones) are not billet steel but iron pressed onto the core I guess while its formed and they are safe to use with whatever distributor you have. In any case, I'd only use the bronze gear if the cam manufacturer says you HAVE to use one. Those gears wear out over time, a non-bronze gear wont wear out over time unless something is wrong.

As far as distributors, there's an error there too. The large cap with screw on cap as opposed to latches changed in the 1986 model year, anything 85-down is latches, 86-up is screw on. Its a moot point anyway because the computer controlled distributors used the same connectors and none of those items care how the cap attaches to the distributor.