Are there any other differences, besides the fuel pump lobe, between the Mark IV and Gen 6 cams?

Gen VI cams have a stepped nose, to be used with the factory thrust plate. Thus they use a different timing chain sprocket as well.

Thanks, I guess what I was wondering about was the bearing spacing and diameter. I know my mark IV is a flat tappet and my Gen 6 is set up for roller and has the fuel pump boss but wasn't sure if the cams interchanged.

yes you can run the gen VI cam in the mark 4 block if the mk4 has the threaded bolt holes to each side of the cam. those bolt holes are for the cam retainer plate. you then have to run a gen VI timing chain set. you could probably run the mk4 cam in the gen VI block but you would have to use the mk4 timing chain set and a cam button on it to set the cam end play.

OK Thanks, you answered my question, better to get the cam for the specific Gen. motor, does the Gen 6 cam come with the fuel pump lobe or does it have to be special ordered with it?

The Gen6 cams do not come with the retainer plate or screws but you can get them from your local Chevy dealer. I have the part numbers at the shop if you need them. My local dealer has alway gotten them in a day. I have been using these cams on any Big Block lately, they make it so much easier not having to mess with a cam button etc

Bill Koustenis
Advanced Automotive Machine
Waldorf Md

I bought two brand new 502's. One had the fuel pump boss.
I had RMBUILDER grind me new cams. He told me all the custom cams have the lobe. Better cams and I used a mechanical fuel pump from my Mark IV.

Why would you want to run a flat tappet in a Gen VI block? I have two brand new take outs with springs and retainers I will sell CHEAP.

I didn't want to run a flat tappet cam, just curious about what the differences were. Bought two new GM perf 502 blocks and they came with the pump boss, just got me thinking

Most Gen VI cams do not have the fuel pump lobe on them. If you are having a cam specially ground, then you can specify that you need a core with the fuel pump lobe. Be prepared to pay for it. The last one I got was quite a bit more money than a Gen VI core without the pump lobe. It was almost worth just running an electric pump. I'm not sure why it was so much more expensive. Maybe because it is just not in that much of a demand since most 502 blocks do not have the pump boss.
Eddie

Funny thing is there are a few 502 GM auto crate engines available that have fuel pumps on them !!!