Engine Advice

[k4gY]

I have an 85' Buick Regal Limited with a 231 V6. About a week ago, I broke the crankshaft. My problem is I don't know if I should get that fixed. I've had an estimate of $400 to replace the crankshaft and other associated parts, but the mechanic that I'm dealing with has a wrecked Olds Cutlass sitting in his shop that he is about to part out. He says he will pull the 307 from the Cutlass and drop it in mine for $500. $100 difference to go to the bigger engine. I've heard different stories and opinions on both motors, so I just want some advice. Should I have the 231 repaired or swap to the 307?

[NTX5467]

In many respects, the Olds 307, while bigger in displacement, was NOT much better in power than the 231 you now have. If you do decide to do that swap, also get: the COMPLETE computer and ALL related wiring harnesses from the donor vehicle, front coil springs (to compensate for the heavier engine weight), and most probably the radiator and transmission too. And that doesn't account for getting the exhaust and other things hooked up nor new motor mounts while you've got everything apart.

If you desire a bigger engine, a much better choice would be a 350 Olds or even a 403, but the same (or more) issues mentioned above would also be operative too. Or even a BUICK 350 (and transmission) from a larger LeSabre of that general era (for the computer items). But, if you get too far out of whack with the "power" thing, you'll need to find a heavier duty rear axle than the existing 7.50" ring gear unit in there now. None of these things are not out of the realm of "hot rodding", but it just depends on where your orientations are, how much time you can have the car "down", and how much money you have to spend.

In some respects, you could do a lot worse than just to repair the 231 V-6 in there now.

Just some thoughts,

NTX5467

[Bill Stoneberg]

I speak from sad expreience,

The 307 is a BIG pig. I cant get out of the way of a slow turtle on his worst day.

Go with something else. I will as I can.

[Buicksplus]

K4GY:

Your mechanic who offers to replace the engine for $500 or replace the crankshaft on the V-6 for $400 must be from another planet. I think most estimates for this type of work would be in the $1500 to $3000 range and is therefore not much of an option for fixing a 1985 car -- unless the car is highly collectable or has some special value to you.

Personally, if I did anything with this car, I would stay with the V-6. You are opening a whole box of pandoras with an engine change in a modern car like this.

Bill.

[k4gY]

Thanks for all the help guys. I've decided to go ahead with the swap for the 307, but I'm also keeping my 231 in case it doesn't work out. I do still have a few more questions though. I've tried researching on both cars, and doesn't a Regal and a Cutlass have the TH200 transmission? Or does the Cutlass have the 4R version? Also, the 231 makes 110hp stock. The 307 isn't coming from a Hurst, so it only makes 140hp, for now. Though the 30hp increase isn't that much, is there still a major risk of tearing out the stock rear end of the Regal? I'm not sure what ratios either car is running. Sorry for my ignorance in all these situations, but thanks to all of you guys for the help.

[Don B.]

It is hard to break a cam, sure it's not the timing gear?

A friend had a 307 and put a bigger intake and carb.

About 100 miles after that the engine started breaking rockers

when ever you got on the gas.

If you want more horses in the v6 find a 4bbl intake and carb

from a 252. If he replaces the cam the intake will be off anyway.

[k4gY]

It was the crankshaft that broke.

[NTX5467]

What was somewhat common, at least from my observations, was that the crankshaft didn't usually "break", but the middle main bearing journal wore excessively (making the knock you might hear) due to too much clearance. My machine shop operative relates that this was due to the way Buick machined/cast the blocks back then (noting too that one of the first things the Buick V-6 perofmance manual mentions is getting ONE long drill bit to enlarge the main bearing oil galley in the middle for one continuous galley of a common size).

In theory, the middle main bearing only requires "so much" oil to keep it lubricated, so using two larger drill bits that did not "meet in the middle" (more song lyrics!), resulting in a smaller galley section for just the middle main bearing, coupled with so-so maintainance over long periods, usually resulted in those engines needing a "crank kit" at about 70,000 miles or so. No breakage, just wear. Easily replaceable, but the engine has to be removed from the chassis.

As I recall, the only difference between the Cutlass Hurst/Olds with 165 horsepower was the exhaust system rather than anything internal in the engine. The Turbo200 is a three-speed automatic. The Turbo200-R4 is the 4-speed version with the 4th gear being overdrive. It's highly possibly that your Regal has a 2.41 rear axle ratio--which is NOT compatible with the overdrive transmission as it will make the cruise rpm tooooo low, further making the car feel "doggy" or "piggy" or just plain weak plus making the transmission "hunt" for a gear to stay in on the highway, which is not good either.

It'll take a good bit more power than what you have to cause problems with the 7.50" rear axle, but I mentioned that as a point of interest if you should desire to "get crazy" of something in the power deparment with other larger engine alternatives (like a 455 or something).

The OTHER thing to consider is how the engine swap will play out with your local state emissions checks too! If you change the engine from one vehicle from another, you need EVERYTHING from the donor vehicle on your vehicle--period. Everything that can relate and be affected by the engine in a particular chassis of vehicle, from the fuel tank forward. NO guess work here! Once those state inspectors see something has been changed, they'll start making a "laundry list" and then it's up to you to prove it's all been done to specs for that vehicle. In some cases, even putting an OD trans where it didn't come will affect tailpipe emissions due to the different cruise rpm levels (and related grams/mile of pollutants out the tail pipe).

That extra power from the 307 might seem enticing, but remember that you'll end up with a vehicle that's a little heavier (why you'll need the heavier duty front springs due to the additional engine weight!). Therefore, the additional engine weight combined with the marginally higher horsepower rating could result in a vehicle that you've spent some money on to make it better and "faster" that really isn't either. Much wrenching, flailing of tools and hands, more money changes hands, for basically no real benefit of the customer.

Also, make sure the intake manifold on the Olds is not aluminum. Many of them back then had issues with erosion in the seal area of the water passages in the intake manifolds where it mates with the cylinder head. They were very expensive back then and very hard to find in the salvage yards too--and that was 15+ years ago! Definitely NOT the $50.00 item they would have been for a Chevrolet!

Just some thoughts,

NTX5467