7.4 mpi same mounts as small block

[QBhoy]

Hi

Does the big block 7.4 mpi have the same engine mount footprint as the short block 5.0/5.7 mpi would it drop right in ?

thanks.

 

[Scott Danforth]

they are close enough

however the exhaust manifolds and exhaust is much wider

 

[QBhoy]

they are close enough

however the exhaust manifolds and exhaust is much wider

thanks Scott. You mean wider bore from riser or just wider across the manifold ?

 

[Scott Danforth]

meaning you need a new y-pipe / exhaust. while the crank CL is the same, the flywheel housing pattern is the same, you can get both a 153 and a 168 tooth flywheel on either the SBC or BBC.

the mount surfaces are just a tad wider (not enough to matter)
the mount surfaces are about same spacing forward of the flywheel housing pattern. (not enough to matter)

however the SBC deck is 9.045" and the BBC deck height is 9.8". the SBC is about 21" wide at the exhaust ports vs the BBC about 25"......... so your exhaust will need to be addressed.

 

[QBhoy]

meaning you need a new y-pipe / exhaust. while the crank CL is the same, the flywheel housing pattern is the same, you can get both a 153 and a 168 tooth flywheel on either the SBC or BBC.

the mount surfaces are just a tad wider (not enough to matter)
the mount surfaces are about same spacing forward of the flywheel housing pattern. (not enough to matter)

however the SBC deck is 9.045" and the BBC deck height is 9.8". the SBC is about 21" wide at the exhaust ports vs the BBC about 25"......... so your exhaust will need to be addressed.

Ah. Thanks Scott. My exhaust is a full Corsa marine system. If it won’t fit the existing, I wouldn’t fancy changing all that too. Worth the thought. The hunt for a 6.2 mpi is maybe the way forward. Would prefer the 6.2 anyway. Keep it fairly modern over the older 7.4 mpi tech.
cheers for the definitive answer on this one. Cheers.

 

[Scott Danforth]

go new VVT 6.0 over the 6.2 mercruiser stuff. or build your own.

proper selection of parts and you will have a stronger motor

 

[QBhoy]

go new VVT 6.0 over the 6.2 mercruiser stuff. or build your own.

proper selection of parts and you will have a stronger motor

Oh man. I’d love to but I’d imagine it’s a hell of a lot of money for one of them. The idea currently is that now that the boat is in storage for a while and will only be used on nice days out...I’d like to do what I can to make her even more special than she already is. But within reason and without spending silly amounts. Although I don’t have the worry of the usual “not financially viable” concerns with resale value etc. I’ll be keeping her for as long as I last hopefully.
the perfect situation would be if I had a buyer for my current engine and put a little towards an engine of a similar footprint with more power. The current engine is as good as they come to be fair. Just I know the boat can take a little more and will be all the better for it.

 

[Scott Danforth]

drop a huffer on it.....

https://www.cpperformance.com/c-821-whipple.aspx

 

[QBhoy]

drop a huffer on it.....

https://www.cpperformance.com/c-821-whipple.aspx

This sounds like the answer. So the 555 can be remapped after all.