: 248 vs. 252



77-79 Cadillac
01-08-10, 02:58 AM
Hi everyone, I have a couple of questions I need help with. First is a 248 4.1 the same as a252 4.1? yes one is RWD the other is FWD. will the internal parts interchange, like crank, rods, main barrings, gaskets ect... On a 47000 mile engine can you replace the main barring and regrind or replace the crank? Or should you do a complete rebuild. I am on a tight budget. Any help will be great.

csbuckn
01-08-10, 10:53 AM
I dont know anything about the motors in question but if the bore size is the same, you may be able to swap the crank, rods and pistons but you may run into vavle clearance issues, depending on the stroke(if these two motors are related). A 47K mile motor that has a rod knock probably means it got low on oil so you would have to visually check everything thats affected by oil like...everything. But I think you should be good with just doing the crank.

I~LUV~Caddys8792
01-08-10, 07:14 PM
This is odd. The 252cid 4.1 was the Buick V6, all of the Cadillac 4.1 V8s have always been 249cid.

sven914
01-08-10, 07:45 PM
^Well I guess that's the answer. If the larger CID engine is an Buick 6, then none of the internals will work on Cadillac 8.

The Buick has a bore of 3.965 and a stroke of 3.401. The Cadillac has a bore of 3.465 and a stroke of 3.307.

The Buick's pistons and rods are too large to fit into the Cadillac block, plus the crank is missing two main bearing journals.

I suppose you could bore and stroke the Cadillac, but you might have trouble making the V6 rods fit a V8 Crank.

77-79 Cadillac
01-11-10, 12:35 PM
thanks everyone for your replies there was a main barring kit on e bay for a 87 eldo with a buy it now of a $100.00 the action has ended so I'm or we are still stuck with a 84 Fleetwood with bad rod knock. thank again John

csbuckn
01-11-10, 03:49 PM
ah, I see now. If your not ready to put a different motor in there, it may be time to let this one go. Maybe part it out before winter ends. But, I suppose the cheapest thing to do is fix it.

77-79 Cadillac
01-13-10, 11:04 AM
This 1984 6 door Limo is REALLY nice not one to be parted out yet. Its a good looking car. Its not mine, but I told him to buy it. A 350 FI from a 70's Seville will not work. What would be the best inexpensive way to go? Ols 403"s are hard to find.

greencadillacmatt
01-13-10, 12:23 PM
An Oldsmobile 307 will probably be the cheapest option. You can find them just about anywhere, they are VERY reliable, and they are cheap. I got a used one for parts (it came out of a running car) for $50. It will bolt into the car and to the trans like it came that way from the factory. Good luck, and post some pics of that limo!

77-79 Cadillac
01-13-10, 08:28 PM
Look for limoguy to post some pics soon its his car.

N0DIH
01-14-10, 09:10 AM
I just saw a 83 Olds 307 (the one with the GOOD heads) and a 700R4 (not sure on that, just what it said) on Chicago or Rockford craigslist, no price listed.

Me, get a 5.3L LM7 from a Chevy truck and call it done. Modern 300 hp muscle and able to knock down much better mpg than anything that you could put in the engine bay.

They are stupid cheap and low miles and run very very good. The heads and block designed are GREAT, highly recommended. And none of the stupid reliability issues the HT4100 had....


An Oldsmobile 307 will probably be the cheapest option. You can find them just about anywhere, they are VERY reliable, and they are cheap. I got a used one for parts (it came out of a running car) for $50. It will bolt into the car and to the trans like it came that way from the factory. Good luck, and post some pics of that limo!

77-79 Cadillac
01-14-10, 11:11 AM
I need a direct bolt in replacement , no headaches, with very few headaches. The Ols 307 sounds like the best way.

77-79 Cadillac
01-14-10, 11:18 AM
Greencadillacmatt, am I looking for a mid 80's olds. motor? Where did you get yours at? limoguy has made an album for one car, but will not the second, any ideas?

greencadillacmatt
01-14-10, 05:38 PM
I found my 307 on Craigslist. It didn't have a price listed, so I offered him $50. If you are willing to look around your area, you should find a decent lower-mileage 307 (try and find one that was recently removed from a running car.) The 307 is a long-lasting engine, but the 1987 (I think) and up models have roller rockers for the camshaft. This means less wear on internal parts. They seem to refuse to die.

If you want more power, go for the Olds 350. Same reliability and ease of instalation as the 307, but a bit more oomph. I am putting one in my '84 DeVille this spirng, and I paid $75 for it. It was also a Craigslist find. I rebuilt mine, but the instructor at the college said it looked as though I could have plunked it in and started it right then and there. The internals were CRAZY clean for a 34 year old engine. If you go this route, get one built before 1977. The '77 and newer ones have weaker internals.

Whatever your choice, they are VERY good engines. Best of luck to you! :thumbsup:

N0DIH
01-14-10, 09:04 PM
What he said....

Just that if you aren't racing or towing, the 77 up are ok (they had windowed main webs), but the 86-up 307's were the worst of the bunch for quality, the blocks were cast in Mexico and had lots of lifter valley cracking issues.

350's are by far the best, and given a choice, 76 and older for sure. Don't turn down a 330 either, some even had stock steel cranks....