Marine Block, Auto Block

Hey guys. I was just wondering what the differences are in a Chysler 318 Marine block, and a auto 318. Other than the cooling system/bolt on's of course. I am talking about the internals. Can you use a auto block, and use all of the marine bolt-on's? Thanks!

JoeinNY wrote: By block do you mean the block casting or are you talking about the short block including rotating assembly.

Sorry I didn't specify... I was talking about the whole short block(including assembly).

Isnt piston-cylinder wall clearance larger on a marine motor?

Marine piston to wall clearance should be higher. Forged pistion to wall clearance even higher. In general you should follow the piston manufacturers recommendation unless they do not have a specific marine recommendation if that is the case I would minimally shoot for the higher side of the tolerance range. You also need to go with a slightly higher ring end gap typically as well. In general the low end of the marine gap tolerance and the high end of automotive overlap so its more than possible that an appropriate automotive clearanced block will work.

Reasons that I have heard sighted for the differences include the extended full load operating conditions a boat sees compared to automotive apps, and the possibility in a boat of the thermostat opening up and allowing cold lake water into the engine where the the cylinder could shrink much quicker than the piston. Either way people do scuff new engines and lock up rings when they push the low ends of the automotive tolerances.

Now beyond that legend has it that chrysler produced some of the most marine of the marine versions. I have heard of more corrosion resistant alloys in the block all the way up to different cooling passages in intakes. If in doubt search it out on here it has been discussed by those who know...

Marine engine piston to cylinder wall clearance is 040. For an auto its 025.

That auto short block might be OK for cruising, but if your pulling slalom at 3200 to 3600 rpm it may lock up on you.

Thephantomkaw wrote: Do I have to use a marine carb/intake?

Carb, yes- its a safety issue. Intake, maybe. The marine Chryslers had a unique cooling setup. ReidP has shared the info here before. An aftermarket auto manifold can be used, but the cooling system requires some degree of modification.

I had my 66 Barracuda's 318 M Rebuilt and bored .60 over as it had sea water in it for a year. After boring we found the cylinders still pitted. We got a salvage 318 and rebuilt it from there As long as the rotation is right and therefore the seals. You should be OK. It now had about 300 hours on it without a problem. If you need a 67-70 318LM block there is a Speed Shop in El Cajon with one ready to go bored 60 over as they did one and then found out they had the wrong block