Hey! I have a Gen 4 454 with a severly cracked block and I want to transfer over some of the parts to a Gen 5 454. My problem is the push rods and retainers, the Gen 5 had 5/16 push rods (which I no longer have) and I want to use the 3/8 push rods and guide plates from the Gen 4 but the the mounting holes in the 3/8 plate are larger. The Gen 4 had rocker studs that had a 7/16 mounting hole and the Gen 5 has 3/8 mounting bolt holes (guessimate on the sizes) My question is can interchange the two with drilling and tapping the rocker mounting holes to change over to mounting studs instead of the current bolts..

Thanks

So you want to re-drill the rocker stud holes in the head? I would if I could do it in house but wouldn't bother if I had to take it somewhere. The right studs and guides are not that expensive.

ARP sells studs with the smaller thread to go into the head to convert from the screw in style Gen V/VI to the Gen IV stud style. I don't remember the part number.

If I get the ARP studs will they still be non adjustable rockers? Right not they use a bolt and they are non ajustable. From what I understood the rockers with the studs on Gen 4's were adjustable.

what is this motor gonna be in and what rpm is it gonna spend it's life at? 5k? throw out the peanut heads. then see what you have for pistons. flat tops? you can run the 454 heads. if this mk4 engine froze, the heads are probably fine. if it spent 25 years as a raw water boat motor, the heads are junk anyway. dished pistons? you are looking for L29 heads or hard to find small chambered ovals. 3k to 4500? run the peanut heads and net-lash valvetrain. I measured them. they will handle any cam you are gonna put in that engine. where are you? there are probably many people on here who can set you up with stock valvetrain parts.

oh; 2700 Maxum. ok, the gen 5 heads will do the trick. where is motor from, a truck? the cam that is mainly designed to pass emissions needs to come out. if you aren't trying to increase power, use the cam and lifters from your orig engine.

The engine will stay below 3500 rpm most of the time. Everything is stock and I know this sounds crazy, but I only need the engine to run maybe 3 months then I'll be putting in a worked 8.1 496 that's at the machine shop now and will be ready for next season. This is why I'm avoiding throwing a buch of neww parts in it.

Both engines are mercruiser engines. Not trying increase the HP, just need a boat for a couple of months...

ok, buy a set of 5/16ths pushrods. or a set of gen 5 hi-perf pushrod guides and use your mk4 pushrods. you might wanna run your orig intake and carb just cuz you know it and it works and fits. or is this a boat you bought that somebody else killed? just check under water passage across front of intake. boat intakes rot there.

I think I found the answer... GM part number 12562369 3/8 push rod guides with 3/8 mount holes to be used with rocker bolts only, not 7/16 studs....