360 to 318 swap
 

Need to hear from the pro.s I just got a van to use for work. Its a 1985 that I have found has a 1976 318 in it. Its a 1 ton and id tags under hood say it had a 360. It purs like a cat and runs great till you get to 45 mph, then I get a rummbling at the torque converter area, or maybe trans. My question is I suspect that they may have dumped the 318 into the 360 tranny. I know there is a balance differance. Would it run out smooth till 45? Or am I looking at a differnt prob. If you were to missmatch eng. and tranny what would you be getting for symptoms? Thanks for any help on this. And yes for personal reasons I would like to keep the 76 318. thanks

I think you're on the right track. The 318 is an internally balanced engine and the 360 an externally balanced one. That being the case, a torque converter for a 360 has a counterweight on it while the TC for a 318 does not. If the 360 TC was not swapped out for a 318 one you will get significant vibration.

You can confirm this by removing the flywheel inspection plate and rotating the engine one full turn. If you find a weight welded along the edge of the TC then it's a 360 TC.

Thanks Alloro, if it turns out that my TC is wheighted can they be knocked off thru the inspection plate and will this solve the issue?

Before going forward I would be absolutely positive there is a 318 in there. I believe on the drivers side towards the rear of the block there will be a number. Within this number will be 360, 340, or 318. Obviously this will confirm the installed engine size.

If you can die grind the welds and get the weight off then go for it. Otherwise you have to drop the tranny and swap out the TC. Either way once the weight is off the vibration should disappear.

Unfortunately the vibration could've cause damage to either the rear main bearing in the engine or the input shaft bearing in the tranny. The amount of damage (if any) depends on how long it was driven this way. All you can do is get rid of the weight and go for a spin to see what you end up with.

I am sure. V.cover states that it was built in 76, and block cast # states its a 318. Cant find anything on the tranny though. I just suspect they dumpped the engin into what they had. I may be wrong. Will look at the TC. Thank you for your help