ENGINE SWAP built 383 in and stock 454 out

[jchristy]

I am looking at a boat that has a stock 454 in it with a rod knocking. I plan on rebuilding the engine at some point. The boat already has a new bravo 1 out drive. I have a very healthy aluminum head 383 stroker motor sitting in my shop out of an old hot rod project. What issues will have swapping them out and what parts will I need. exhaust will be different manifolds. bellhousing should be the same I think. motor mounts should be the same I think. thoughts??

 

[alldodge]

The front motor mounts will need to be moved
Do not use alternator, distributor, carb, fuel pump, circulating water pump (unless closed cooling) or starter from the 383, must be marine

Bell housing will not fit
Need to change core plugs to brass or stainless steel

 

[Scott Danforth]

I am looking at a boat that has a stock 454 in it with a rod knocking. I plan on rebuilding the engine at some point. The boat already has a new bravo 1 out drive. I have a very healthy aluminum head 383 stroker motor sitting in my shop out of an old hot rod project. What issues will have swapping them out and what parts will I need. exhaust will be different manifolds. bellhousing should be the same I think. motor mounts should be the same I think. thoughts??

define healthy, especially the cam card and the compression.

what works well for a hot rod, really sucks for a boat motor. think less hot-rod, and more dump truck pulling a trailer up-hill in 4th gear in sand.

most hot-rod cams will suck water in on a boat. anything over 270 degrees of duration and you will suffer reversion or hydro-lock.

AD covered most of it, then there is the core plugs must be brass, and the head gaskets must be intended for marine use. having aluminum heads is also a detriment unless you have a heat exchanger.

 

[Bondo]

The front motor mounts will need to be moved
Do not use alternator, distributor, carb, fuel pump, circulating water pump (unless closed cooling) or starter from the 383, must be marine

Bell housing will not fit
Need to change core plugs to brass or stainless steel

Ayuh,...... The Chevy bellhousin' bolt patterns are all the same, from the I-4s to the BBCs,.....

 

[jchristy]

I figured the bell housing would be exactly the same. In a hot rod I can swap a transmission from a big block to a small block. bell housing on a chevy motor are the same. I guess I did know I need to install brass freeze plugs. I don't know what the cam card is as I didn't build the motor. it has a lopey idle for sure, but I have heard boats sound the exact same. why cant I use the accessories like alternator, starter, ect? 383 has the high dollar aluminum pulley serpentine setup on it. I really thought I could pull the 454 out and drop the 383 stroker right in and buy marine manifolds and I would be good. I know my 383 has way more power than the 454, but doesn't sound like it is going to work like I thought. sounds like my best bet is to have the 454 crank and rods turned and reconditioned and rebuild the 454 and reinstall.

 

[jchristy]

This is the 383 at idle in my old 37 ford truck. Swapped 383 out for a less angry 355

 

[alldodge]

why cant I use the accessories like alternator, starter, ect?

Marine items are ignition protected so you don't have an explosion. Its also the Law that only marine certified components are used

 

[Faztbullet]

Why in the world would you run the exhaust thru frame??? It will rust out like a muffler eventually..

 

[Scott Danforth]

I figured the bell housing would be exactly the same. In a hot rod I can swap a transmission from a big block to a small block. bell housing on a chevy motor are the same. I guess I did know I need to install brass freeze plugs. I don't know what the cam card is as I didn't build the motor. it has a lopey idle for sure, but I have heard boats sound the exact same. why cant I use the accessories like alternator, starter, ect? 383 has the high dollar aluminum pulley serpentine setup on it. I really thought I could pull the 454 out and drop the 383 stroker right in and buy marine manifolds and I would be good. I know my 383 has way more power than the 454, but doesn't sound like it is going to work like I thought. sounds like my best bet is to have the 454 crank and rods turned and reconditioned and rebuild the 454 and reinstall.

first, unlike a car, a boat bilge actually traps vapors, and using automotive accessories in a boat means you just built a bomb., marine stuff is designed to prevent fuel leaks and igniting of any leaks.

lopey idle usually means lots of overlap, cam centerline on a marine engine is such that there is little to no overlap. any amount of overlap and you start sucking water into the cylinders (reversion).

cam duration - anything more than 270 total duration with wet exhaust and you suck water into the cylinders (reversion)

your 383 is most likely built for high speed / high RPM street use and probably has over 10:1 compression, probably close to a 296 degree cam. absolutely wrong motor for a boat.

a stock 377 in a boat puts out 350hp at the crank and 320hp at the prop. with custom exhaust, proper cam, carb spacer, etc. 450hp is the max you can get out of a 377/383 with a wet exhaust system for a boat unless you bolt a supercharger on top. and that 450hp will be temperamental and not long lived.

what vintage 454? what heads?

 

[jchristy]

Why in the world would you run the exhaust thru frame??? It will rust out like a muffler eventually.

It is just a play toy. it starts to rust out, I can rebuild the back half of the frame in a weekend. The frame was coated inside and out with 2000 Degree BBQ grill paint. Small drain hole drill in the frame before the upsweep of the rearend to allow any build up to drain. It has been a year with NO visual signs of rust. Back frame rails are 1/4 inch thick and would take a lot of years to rust out with every day driving and this is only a play toy