Chrysler heads

Open up the heads (intake specifically) and go with s/s valves for marine applications. The valve seats are hardend because they are under extreme temperatures and can burn out very easily.

Here's a really good link on an explanation on Mopar (Chrysler) mods

http://www.allpar.com/mopar/4bbl.html

"One reason I never like doing the 360 heads on the 318 is because the chambers are so large that you have to shave the heads .060 to get the compression up, have to use the 360 intake so there are not any vacuum leaks, and there is usually a flat spot on the bottom end because the intake runners are too large for the size of the engine. A good port job works good for the 318 heads, headers work well, and a dual plane intake with a 600 cfm Holley, or Carter, work well. Really want to make it a little better, get the closed chamber 318 heads, get a set of 360 intake valves 1.88 vice 1.78 (one tenth of an inch is a lot for a small engine, but they work really well), and port the intake runner in a tulip fashion from the floor to the valve edge. The small runners keep good throttle response, the tulip design packs the charge really good and adds a good amount of torque on the mid to upper rpm range. Cam selection is really good in the .444 range. Not too big to kill the bottom end, not so small that it won't rev to 7000rpm, either, and you won't need a stall converter with an automatic. There is a cam that was for the 340 in about this size, very nice. Remember, this is a small bore/short stroke engine, so they rev well, but too much lift and too large a runner (as in the 360 heads) does not work unless you are running above the 4000 rpm range, which is not feasible on the street, only the strip."

These mods are for street but a lot of the info can apply to marine use.
I found it very useful when I did my rebuild.

Here's a good link on a forum discussing fresh/raw wter cooling
http://www.marineengine.com/discus/messages/12490/81387.shtml

I hope this helps.

Hey Todd,
I had hardened seats put in my 283 heads when I had all the engine machine work done....not 100% sure it was that necessary, but while they were doing a valve job, decided to.


As for other work, Are you hoping to get some more ponies out if the 318/or just good reliability? You planning on cam, intake upgrades, etc?


Do you know how many hours/miles are on the the heads your planning to use? In most stock instances, you shouldnt have to replace the springs. The machinist should be able to check the springs to verify their pressure is still in spec.

A multi-angle cut of the seats can help flow rates. Also some smoothing/polishing of castings can help.

This is kind of "generic" info... Im not that versed on the Chrysler stuff,hopefully someone can help a little more.

I always seem to run in fresh water. But in
maryland we have both. Alot of bracish to. I
always run the hose thru after a day in salt.
Is that enough to hold back rust? Dose salt
water rust out the inside of the heads as well?

Unless your engine has been fiddled with, its raw water cooled, meaning the water from the lake runs through the engine. Fresh water cooled is so named as it is in contrast to salt water cooled, should boats be run in salt water. Fresh water systems have a heat exchanger...sea water (salt water) flushes through the heat exchanger and back into the sea, cooling coolant or "fresh water" in the heat exchanger, which is circulating through the engine. You would know if you had such a system because it has the large (typically) cylindrical heat exchanger on the front or rear of the block. Not sure if fresh water cooling was a factory option on ski boats, might have been, I am guessing it was standard or optional on fish nautiques. You do hear of some fresh water cooled nautiques, but I would guess they are all or mostly after market.

Edit: Just realized pictures of your engine are above...you must have gone back and added them...I'm not that blind/unattentive.

Its raw water cooled.

I can tell you that I had stock components put back in the 318 Poly heads. They did put in the hardended valve guides to run unleaded fuel.
Parts came from EGGE Inc
They had everything in stock.
But they do not have the Marine 318 gasket set.

Those came from Marine Engine Parts and requires to kits....

Head Gasket Set
Marine Conversion Kit with Reverse Rotation Seals

They are Fel-Pro sets so you can order them from local parts stores.

Took me awhile to figure all this out..