302 marine conversion

[Kernallklink]

Hello fellow boaters, just tested out my mercruiser 302 today and found that the block and intake manifold is cracked. I just got a line on a 351 Cleveland out of a 1980 mustang. Anyone here ever heard or done a marine conversion on an auto block? Could I swap out all of the marine parts from the 302 onto the 351?

 

[thumpar]

Re: 351 marine conversion

Re: 351 marine conversion

Just a block is easy. Swap the core plugs to brass. For the externals you may find hurdles. The flywheel and balancers changed over the years for one. What year are you starting with?

 

[Bondo]

Re: 351 marine conversion

Re: 351 marine conversion

Hello fellow boaters, just tested out my mercruiser 302 today and found that the block and intake manifold is cracked. I just got a line on a 351 Cleveland out of a 1980 mustang. Anyone here ever heard or done a marine conversion on an auto block? Could I swap out all of the marine parts from the 302 onto the 351?

Ayuh,.... The Cleveland block is Useless to ya,.... Ya need a Windsor block, they're very different,....

 

[Fleetwin]

Re: 351 marine conversion

Re: 351 marine conversion

Ayuh,.... The Cleveland block is Useless to ya,.... Ya need a Windsor block, they're very different,....

Agreed. Are you absolutely sure the Mustang block is a "Cleveland"? Only "Boss" 351's were Cleveland.

Windsor blocks have a removeable aluminum timing chain cover. Cleveland timing covers are part of the block.

 

[Bifflefan]

Re: 351 marine conversion

Re: 351 marine conversion

Only "Boss" 351's were Cleveland.

A Boss 351, is a 351 Windsor block with Cleveland heads put on it and Boss intake.
351 Cleveland's were found in many different cars and trucks.

 

[Fleetwin]

Re: 351 marine conversion

Re: 351 marine conversion

A Boss 351, is a 351 Windsor block with Cleveland heads put on it and Boss intake.
351 Cleveland's were found in many different cars and trucks.

For his question, the block is the difference. Timing cover identifies. Marine engines were Windsor. The marine gear (mainfolds, etc.) won't bolt up to a Cleveland. The Windsor later became the "M".

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

I'll have to take a closer look today, but I'll definitely make sure it's either a 351 Windsor or 351 modified. I'll keep u guys posted as to year and what not.

 

[Bondo]

Re: 351 marine conversion

Re: 351 marine conversion

I'll have to take a closer look today, but I'll definitely make sure it's either a 351 Windsor or 351 modified. I'll keep u guys posted as to year and what not.

Ayuh,... Ya need the 351 Windsor,.....

I might be wrong, but I believe Fleetwin is wrong, as the Cleveland, 'n the Modified are of the same engine family, not the Windsor,...
The "M" is a bigger displacement "C" motor,...

 

[thumpar]

Re: 351 marine conversion

Re: 351 marine conversion

I looked up the info so won't claim I pulled it out of my head. The C and the M are the same family. The M just used a W crank in a 400 block so the M and the C are compatible external wise. The C was discontinued in 1975 so unless the Mustang had an engine replacement it would either be the M or the W. From the articles I read the W was most common in cars but who knows. You will have to check.

 

[Bondo]

Re: 351 marine conversion

Re: 351 marine conversion

I looked up the info so won't claim I pulled it out of my head. The C and the M are the same family. The M just used a W crank in a 400 block so the M and the C are compatible external wise. The C was discontinued in 1975 so unless the Mustang had an engine replacement it would either be the M or the W. From the articles I read the W was most common in cars but who knows. You will have to check.

Ayuh,.... 'n from my foggy memory, the "W" was used in Alota cars, 'n ALL the Trucks,....

I also vaguely remember there bein' Way too many oil pan configurations,... :facepalm:

 

[Fleetwin]

Re: 351 marine conversion

Re: 351 marine conversion

Bondo is right, C and M are part of the "335" family.

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

Aye, thanks for the info. I do have a possible 351W. I guess I would have to change the rotation of the engine. Does anyone know if the stock or aftermarket intake manifolds are the same as the "mercruiser" intake manifolds? Just wondering if I can bolt up the 302 water pump from the 188 to the 351 intake manifold.

 

[thumpar]

Re: 351 marine conversion

Re: 351 marine conversion

Why would you need to reverse rotation?

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

Why would you need to reverse rotation?

I meant to say, just in case I have to, if the rotation is different with auto vs. marine.

 

[thumpar]

Re: 351 marine conversion

Re: 351 marine conversion

Reverse rotation is usually only put in when there are twins and one with run reverse. I would bet you don't have it. Figure out what you have and go from there.

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

Reverse rotation is usually only put in when there are twins and one with run reverse. I would bet you don't have it. Figure out what you have and go from there.

Good to know, thanks!

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

Thanks bubba, that helps out a ton. I'll keep this thread open and give you guys reports on my progress.

 

[jeromeb]

Re: 351 marine conversion

Re: 351 marine conversion

I'm fairly new in boating, but I do something about Ford engines
A Ford 302 and a 351W look somewhat similar. The 351 is wider and has a higher deck height. Intake, distributor, oil pan wont interchange,Bell hs and motor mts will.

A 351 Cleveland has the same bell hs and motor mounts but a different family of engine.

A 351 M, (or modified) looks like a Cleveland at first glance but is soooooo different. It has the bell hs and mts of the 429-460 family.

Why Ford say fit to do this is only known to them. Chevy, from 1955 265 cu in to 2000+ 8.1 all share the same bell hs.

 

[Kernallklink]

Re: 351 marine conversion

Re: 351 marine conversion

Closest motor I could get is a 1981 351 Windsor, according to guys on the ford truck enthusiast forum, the flywheel from the 302 should just bolt up, with the proper impedance of 28oz. The engine has been converted to propane, but the fuel pump assy should slip right in. I'm just not sure if I will have to do a cam or not. I could always leave it propane

 

[haulnazz15]

Re: 351 marine conversion

Re: 351 marine conversion

Also, check the heads at the rear of the engine. Some had a hole into the exhaust that's roughly 1/2" and went to "smog" equipment. It has to be capped off with a flat plate. (No real easy way to make a plug.)

Actually, it's incredibly easy to make a plug, because you can buy them for about $5 each (There are two). They are called thermactor plugs, and they sell them at many auto parts stores, or online at Jegs/Summit/etc.

The the OP, I will re-iterate what most of the others said. You need a Windsor block, not a Cleveland motor. The 351C was a completely different block/head from the 302/351W, and the 351C is in the M-family with the 351M/400M. There are no exhaust manifolds available for the 351C, not to mention things like engine mounts, etc all being markedly different.

That being said, the exhaust manifolds, distributor, fuel pump, starter, water pump, etc will all bolt onto a 351w. The main things that won't bolt onto it is the intake manifold, oil pan, and exhaust y-tube. The harmonic balancer will need to be the non-50oz version for the 351w.