Mark IV cam in Gen VI
 

Has anybody put a mark IV style cam in a gen VI block, want to try this to cure my reverse rotation issues been battling for years

I don't see why it shouldn't work. I am assuming you are talking about the gear drive setup. As far as I know the front of the blocks are the same. Biggest issue I see is trying to match the grind on the other engine. That and maybe clearing the timing cover but I just looked at one and it looks like there should be enough room.

The timing cover is different.

The reverse rotation set up is gear drive and uses a plate similar to the Gen6 engines

Yes, done with this thing eating distributors(even the high $$ special bearing ones) looking to go back to what I had in the mark IV engines I had run trouble free for years. Had I known the deal on how they reversed the gen VI's and all the issues I've delt with for 8 years never would have done those. The old style flat tappet cams are still available(uses a special snout w/center bolt) for the gear to gear set up, but have not found someone who can grind a roller because no cores available unless you get 10. I know all about the timing cover be different and clearance is going to be a issue, may end up machining the gear set down ?? Milodon makes a extra clearance cover to run a std double roller chain setup so I know that will give me a little more. My one concern is the retainer plate for the cam, the gen VI uses one and the cam is cut for that, the gear drive setup also used a plate on the mark IV blocks which one other one did, so sure its needed because of the helical cut gears, just not sure if the mark IV style cam will work with the gen VI retainer plate..

EZ,

My warehouse has a set of the gears. I will try to get them to measure the thickness on them. The bolt pattern for the plate is the same, not sure of the thickness but I can easily find out. I have several Gen6 blocks and timing covers I can look at for you.

By the way, do you do any hand pin striping ?

Bill that would be awesome, called comp yesterday see if there was any shout of them grinding a roller with ft snout to accept the gear to gear setup, they said they could if they had a core, which he thought they had(showed in inventory) but did not, and had no idea on getting another. I slipped a mark IV cam I had here into a gen VI block, seemed fine, it sat flush with block so looked like retainer plate would work as well(all the gear to gear ones used a retainer like a gen VI). again, thanks for the help !!!!

Will do. I will give them a call on Friday.

Thanks Bill, and forgot answer your question, no I do not do hand pin striping but I do have a friend here that does..Rob

you don't need the step on cam nose to use the retainer plate? the 10-bolt cover can be retrofitted to the gen 6. and I always thought your screen name came from the fish, not paint work. and every time I see those 20 foot center consoles going by with STRIPPER written on the side I think they are pretty, but their cocaine habits get EXPENSIVE!

To clarify, I have in the striping, graphics, sign business for almost 32 years now but vinyl only now, did some hand painting way back. On the cam I'm not sure on the retainer, I know about the step on the gen VI and know the early gear to gear used one as well, assuming the helical cut gears required one. When I tried a mark IV cam in gen VI the ft was flush with block.

Rob,

The cam gear is .988" thick. If I have a few minutes I will do some measuring on a block and front cover.

I do have a stupid question. Is the chain drive reverse rotation setup something that Mercruiser or OMC etc actually used from the factory ? If so what did they have for a distributor ? I would almost think it would be easier to machine a distributor for a small roller bearing at the top but then I have to wonder how it would get any oil.

Bill, the timing chain is a std GM one, nothing different, marine power(crusader) did that on the GM EST dist. ran several of them, the bearing they used was plastic and I could only 20-40 hours before they failed as well..no way to lube with out taking apart. can you PM me a contact # would love to talk to you on this if you dont mind..Thanks Rob

here's what I had, I took the gen 5 cam out and put it in the gen 6 block the bolt pattern is different between the 2 on the cam. when I put the cam gear on, the cam was coming out of the block cause the cam didn't have the step on it. I try'd different things and nothing worked so I bit the bullet and bought a Teague stage 4 cam to put in my gen 6 block. well that's just my 2 cents.

This is a reverse rotation engine which changes everything :(

The cam used for the gear to gear reverse rotation setup does not have the std 3 bolt mounting for the cam gear, it uses a stub with a keyway and pressed on, it also used a cam retainer plate much like the gen VI one(on a mark IV) as well. I assume as the gears are helical cut keeps the cam from walking out., pic below of what ft of cam looks like.