318-340-or360?

[greghost]

Having a problem identifying this motor there are no plates on it anywhere.It is in a 1974 silverton Boat.The #'s on the block are 3418496/8860 manufacture date is on other side as follows 8/24/73.There is and R 1 on the block under the head facing the flywheel,right hand bank.Any help would be appeciated.Is there a site to look up block #'s?

[440roadrunner]

If this is a third party block, I don't know. If it's a Chrysler legitimate block, do the following:

Face the front of the engine, and look on what would be the drivers side. Look at the top of the block, close to the parting line (deck surface) between the head and block. There should be a number stamped (not cast) there, and IN THAT NUMBER in the first few digits, should be the cubic inches.

In this picture, the no. should be just below the head surface




Make sure you are facing the true 'front' of the block. Some boat engines are installed facing backwards.


If this is original, it won't be a 340. Also, be advised if you get the bright idea to replace a 318 with a 360--the rear of the pans are different, and the 360 is externally balanced, requiring a different flywheel and balancer.

[greghost]

These engines are not the originals and must be 3rd party blocks as there are no #'s on the front of the motor.Thanks for your time.

[440roadrunner]

There is at least one other way, if you can get to the back of the pan. The "half moon" shaped cutout in the rear of the pan is larger on a 360 that on a 318. If you can figure out a way to get a measurement on that, you can tell that way, but I'll have to go out and dig around for a pan. I'm not crawling under my old Landcruiser in this weather!!

I'll have to check in the garage later, but I THINK that the 318 pan has the same width cutout front and rear, which means the 360 is larger in the rear.

Another way you could tell, would be to get yourself to a parts store and look at a 318 and a 360 oil pan set. They may be the same part, and so may have the two sizes for the rear of the pan. You could easily lay them out and measure the difference.

According to this:

http://www.go2marine.com/product.do?no=90090F

it is one set, which means there should be three front/rear pan seals--two for the 318, and one extra larger one for the rear of the 360

[mr340]

This was an easy one...
3418496- 360 1971-1974 LA

[440roadrunner]

Would you mind letting the rest of us in?

[mr340]

Sure...

http://lightningjar.com/mopar/

Bob has lots of good info on his site...