American Dreamer

I currently have a 87' 454 330, carburated, Mark IV Block with stock heads.

Does anyone have experience putting newer MPI fuel injection system from a Gen V or VI.on a mark IV block of this style. I am pretty sure that the block and distributor setup are compatable, but are the heads? Do newer heads of a stock 7.4L MPI have a different ports or are they the same as the older ones.

Any issue that you may think of would be great.

Thanks.

JBmarine

I'll volunteer some info, from the intake up it should bolt with no problem. The intake from the MPI's is actually a rectangular port intake(same as the MPI Magnums). With regard to the heads;
....the early 7.4L LX MPI(say '94-'97 roughly) used the GM "peanut port" oval cyl head--it was a head with real small ports and didn't flow well(the motor hp was really over rated)
....however in '98-'01 the 7.4L MPI had the GM Vortec Head, much bigger oval ports, better flowing head, smaller combustion chambers, and higher compression (the motor made better power)
FYI, the Vortec heads will bolt up to a Gen IV block, must use a Gen VI head gasket and check that there are three coolant near the outer edge of the block between the cylinders(info about compatability is in a Fel-Pro Marine Gasket Book)
Get back to me if you have any questions or are looking for parts!?! Jason

boatn70

jbmarine, could you then tell me what to expect to find in my1998 7.4 300 carb motor. would you expect the peanut port or just the larger oval port?
thanks

American Dreamer

JB, thanks I'll get back to you.

JBmarine

Typically, if you have a Gen VI with the composite front timing cover(not the stamped steel cover) they had the Vortec heads. I have a post in the parts-for-sale thread (for a set of Vortec heads) where I'll be posting casting numbers compare your numbers to mine that would tell you for sure!!

boatn70

so.... is there a simple way to tell what gen block im working with. its a 1998 454 300hp, i understand that would eliminate the gen4 right? so it could be either gen5 or 6, id like to know what components i have in there. will the serialhelp out?

thanks
kevin

HPJunkie

Typically, if you have a Gen VI with the composite front timing cover(not the stamped steel cover)

behind the water pump (that stubborn hose) is the timimg cover,to distinguish the V or VI. You have to remove the valve cover to get the casting number on the head (that cheesy hose that goes to the air cleaner we were talking about connects to the valve cover on the other end. It has an oring on it and it can be reused and reinstalled. Maybe JB will post that casting no . on the Vortec.

crmax

I know the vortech heads were designed for the mpi injection with no heat exchanger , so I would say you have the penut port heads

crmax

if your looking for a stock fuel 7.4 310 mpi set up I have one distributor,computer and all

JBmarine

Vortec casting number--10141279