[zac]

What cam are you running, kenn? I have noticed some of the GM performance roller cams appear to be billet and others ductile iron.

Here are some pics, in all of them they are IROC with fuel pump lobe, Vortec L31 and standard old cast hydraulic flat tappet, left to right.

I watched the Comp Cams video again regarding picking the correct distributor gear, and as far as I can tell the IROC and Vortec cams are billet steel. You can see the IROC cam has some different machining marks than the Vortec. It also has a little more lift and noticibly more duration. The distributor gear seems to be a somewhat lighter color as well, although that could just be staining.

As far as I can tell, no GM production car came with a carb, mechanical fuel pump and a roller cam. I think these cams with fuel pump lobes came only in Corvettes and 3rd Gen F-bodies. One board I saw was talking about SS Monte Carlos in this era, but I found no evidence of that. One guy claimed his '87 Caprice 4 door came with a factory roller cam. Unlikely.

As has been pointed out, it doesn't seem likely that any production GM car came with a bronze gear. So I assume all OEM roller cams use the melonized gear. My idea to just use the stock original Camaro gear on my HEI won't work. The shaft size on the distributors is apparently smaller on roller cammed vehicles. I guess maybe it could be drilled out (what could possibly go wrong with that plan?).

With GM cams most people seem to get along fine with the standard fuel pump pushrod. But one guy posted that he took a roller cammed 305 from a '92 Camaro and put it in his street rod with a mechanical pump and standard pushrod. Eventually the pump wouldn't move enough fuel to supply the carb. His comment was "the eccentric on the cam wasn't fully machined to drive a fuel pump." I have no idea what to make of that. Sounds like it wore down.

Discussion boards are littered with these issue, particularly the distributor gear part. I'm having a hard to figuring out why there are all these problems this far down the road with these cams. If the Holy Grail article on this is out there on the internet, I haven't seen it yet. Please post the link when you find it. Comp Cams solution is to have you buy their $100 distributor gear.