Exhaust Systems

I killed my 318 and picked up a replacement. Unfortunately it is a few years older than the 69 that I killed. The heads are flat on the older engine which changes the angle on everything. As best I can tell the engine was made in '64. Any ideas where I can get exhaust manifolds which would fit under a Barracuda hood? Or...would I be able to use the 69 heads on the 64 engine? The 69 heads have an extra water hole at the front which the 64 block does not have. Confused and getting frustrated.    

Engine Plate says 318BXRX   
Model 327

I beleive that if the sparkplugs are above the manifold and they are rounded they are from an M style motor 19?? to 1967 If the sparkplugs are below the manifold and they are square they are from an LM style 1968-197?

My two cents have been jinglin in my pocket all afternoon. Here's what I uncovered with a little research: Rick is pretty much dead-on but I'll take it even further. Just about everyone knows "Polyhead" on this site. He took his name from his 318 engine which was the original style 318 manufactured "for autos" from 1959 to 1966. Everything on at least the top half of this motor is completely different from the later 318 used in vehicles up to just several years ago. Similar to the differences in 351 Windsors and Clevelands. As was common with the marine engines displacements, you could find some of them being installed in boat model years after it was discontinued in cars. This 318 Poly was installed in a number of '67 model boats as we have one which according to CC was built in Nov 66. We also have the old white/red 67 SN which was built in early 67 and it has the modern 318, so it appears that they changed over sometime around the end of 66. Everyone check your 67 Mopars.

As to "M" verses "LM", Rick looks correct here also according to my older and newer doc's. But back in the early 60's, all of Chryslers marine engines carried the prefix "M" for Marine, I guess. When used in cars the early Poly 318's were referred to as "A" engines while the later 318's, along with the 273, 340 and 360 engines were "LA's", which I just read stood for Light. While however, the modern 318's were listed as LM, the 360 and 440 units still were referred to as M engines, even up to the early 90's, prior to ceasing production. Poly engines, even in cars, have the plugs accessible above the exhausts. I've yet to see a Poly motor in any boat later than a 67 that came with it originally, not to say they didn't do it. They were putting 312 Ford Interceptors in boats up until at least '65-66, when the last one went in a car about '62.

The brochure I feel is a 67 or older and somewhere I believe I saw a '67' designation.

There are still neat parts available for the Poly 318's such as aluminum intakes, etc, but I think sticking with the LM 318 might be the easier route, with parts everywhere.       

Bravo! Mr P. Outstanding! I would also suggest going with a later model 318. Not that I am not pleased with my motor, I went thru a few bottles of asprin rebuilding mine to keep the boat original. The right head on a poly is strictly marine, and you cannot find any, not to mention exhaust valves. One other thing to remember if it is a poly, the bell housing can only used with a poly. It is the same with an automotive application, the old torqueflite's were made special for poly's. And oh yeah! Good Luck! finding wet exhaust jackets for a poly!

barracuda. what is 99 SNOB ? please don't tell me what i think it is.
i have only seen 1 . ever ! that was in northern ky a few years back.