Dasaki

As the title suggests, I need to replace the engine in my 77 Omega as I have a bad rod bearing and, while it drives still, I'm somewhat scared it'll finally throw the rod every time I go to work. The original engine is the VIN C odd-fire 231 V6 and it has the TH200 transmission sitting behind it.

There aren't any available 231s in my area though there's one about 200 miles away that would be good in it. However I'm unsure about the shipping process for motors and have been looking at what the local junkyard has available, mainly some 350 V8s out of large early-80s chevy trucks and TH350 transmissions.

Aside from the transmission, what else would need to be replaced under the hood if I were to go from the V6 to a V8, or should I just have a 'new' 231 shipped from Ohio?

1970cs

Welcome to C.O. IIRC that's a Buick designed engine. If you're going to salvage that engine, you may be able to obtain parts from those fellers?

Pat

M-14

Although a different engine swap isn't too hard on these you might want to tell us your budget. Its the little stuff that adds up.
Me, I'd go with a 350 or 403 olds & a th2004r trans, you should be able to get a lot of parts for the swap from junkyard cars like B & G bodied cars with 307 engines.
I'm not sure on the driveshaft for the X body.

joe_padavano

Another 231 is the only bolt-in engine replacement. Any other engine will require new mounts, new exhaust, new accessory locations and wiring, a different radiator, and possibly a different trans. We don't know your expertise or skills, so we can't advise without more info. A Chevy truck 350 requires Chevy mounts, a Chevy trans, Chevy brackets, etc. The trans from that truck will be a long tailshaft and will require mods to fit your car.

Dasaki

Ah, yeah, my skills are minimal for large repairs and my budget is almost nil. The joys of owning a classic and working at a gas station.

Sounds like the 231 is indeed my best option.

oldcutlass

Ask around to see if there are any decent volume engine remanufacturers. Or you may be able to find a Jasper engine dealer in your area.

captjim

Very true. The easiest V8 swap is a Buick 350, the Olds conversion is a lot more complicated.

joe_padavano

This website might be useful to you.

Dasaki

The yard actually has one of the Buick 350s, however it has a number of aftermarket parts and is priced at twice the cost of the Chevy engines.

oldcutlass

However when you consider the cost of installing the Chevy engine... You'll need a trans or adaptor, possibly a drive shaft or a yoke. Brackets, pulleys, starter, and all the incidentals. Its probably way more.

Dasaki

Makes sense. Now one more question. Will it make any difference going from an odd-fire to an even-fire 231?

I seem to have lost out on the odd-fire closest to me, however I have located an even-fire with 68000 miles for $350 with $150 shipping

joe_padavano

The even-fire will run more smoothly. Is the new engine complete? Things like the distributor will be different, so you can't use your old one. Balance will be different so you can't use your flexplate or balancer (I don't think, anyway). Tune up parts like the distributor cap will be different, so you'll need to remember to get parts for the engine, not the car. Assuming it's a carburated 231 from a pre-computerized RWD car (and not a 3800 or FWD or CCC engine from the 1980s), you probably can use it, however. If it is a CCC engine you'll need to swap your old intake and you'll need to find a non-computer, even-fire distributor.

Dasaki

The engine is coming off of a 78 Omega so aside from being even instead of odd, it should be identical, also considering asking if they can email me a picture of the rear door since I need that on the passenger side...

So I need to make sure it has the distributor and flexplate then or get those from another vehicle?

olds 307 and 403

Get the Buick 350 and the TH350 that was connected to it. It is worth twice as much as bone stock chevy. Supposedly everything swaps right over. The 3.8 is useless, gutless turd in non turbo or efi.

M-14

There's a good write on a 350 buick swap from a 3.8 (231) over at g body, I don't know if I should post a link. Is that against the rules?

oldcutlass

You can post the link.

M-14

OK, its a long one.
https://gbodyforum.com/threads/buick...50-swap.30492/

Dasaki

Thanks for that info on the 350 swap, going to keep that handy for the future as I don't plan on ever letting this car go for anything short of totaling it (gods I hope that never happens)

I'm just going to go for the 231 at present time as it's cheap enough to fit my budget and I just need the car running again as soon, and cheaply, as possible. Yay classic daily drivers!

67442nut

Odd-fire, even-fire!!!!???????
What in the he!! does that mean???

Sugar Bear

Are you rather sure it is a rod knock? Those engines were notorious for bad timing chain tensioners that would cause a knock. It was a small spring on a rubbing block that would fail, an easy fix by pulling the front cover.

If you have the odd-fire version you could also use an early 225 Buick V-6, they were often in Jeeps and Outboard Marine Corporation (OMC) powered boats and were rated at 155HP.

A rugged engine in my opinion but not a ton of power. As mentioned a Buick V-8 would be an easy swap with good power.

M-14

When you base a v6 off of a 90 degree v8 you get an unbalance condition.
https://en.wikipedia.org/wiki/Buick_V6_engine
Read up on it, they tried off setting the crank journals to make it even firing (1977) but they still shaked. They really got smooth with the balance shaft in '88.

joe_padavano

Do the math. When you have cylinders at 90 deg apart and crank throws at 120 deg apart (as needed for a V6), firing pulses occur at 150-90-150-90-150-90 intervals instead of every 120 degrees. The even fire motors split the crank throws to even this out.

As an interesting bit of trivia, leave it to Ford to go the other way and build an odd-fire V8. The second gen Taurus SHO used a V8 with the cylinder banks at 60 degrees (for packaging reasons).

Dasaki

Yeah, I've had two different mechanics and the local junkyard manager tell me that it's the rod and two of the three have told me it's too late for a rebuild.

Plan on saving the old motor though, if nothing else I can use it for a core in a future engine purchase

67442nut

OK.
I understand the concept, although I honestly never considered it before.
Just never heard those terms before. (I'm still living in '67. )
Also, I didn't realize the engine being discussed was a "chopped off" V8.
Looks like the "off-fire" design wouldn't even run without modifying the crankshaft.
What about the Chevy 4.0 V6? Isn't it basically a chopped off small block V8?
Is it an "off-fire" also?
Thanks for the clarification/explanation.

joe_padavano

The odd-fire Buick V6 came out in 1961.

It is, but that alone doesn't make it an odd-fire engine. It's the odd spacing of the firing pulses that cause that. The whole concept was to lower cost of the V6 by building it on the same assembly line and with the same tooling as the V8, thus the use of the 90 deg bank angles on the cylinders. Of course, this also meant that accessory brackets, front cover, etc from the V8 could be reused on the V6, again to save cost. Ironically, the V6 was produced far longer than the Buick V8.

It does, but you get a "magic fingers" ride. Here's how the crank was modified to get the even fire engine. First photo is an odd-fire crank with conventional throws for the rods. Second photo is an even fire crank with split throws to even out the firing pulses.






There is no "4.0" Chevy V6. If you mean the 4.3, yes it's odd fire. It's a truck engine primarily, so vibration is less of a concern, though later versions did include a balance shaft. The 4.3 is essentially an SBC 350 (same bore and stroke) with cylinders 3 and 6 removed from the block.

olds 307 and 403

Olds 4.3 Diesel V6 was a chopped off DX with a Serpentine setup and extra head bolts. Was supposed to be the best of the Olds diesels.

Dasaki

Figure I'll give an update. If all goes as planned, I should have her back on the road by Sunday night! One of my customers at work does some mechanical stuff on the side, and even has a cherry picker to do the heavy lifting, and if there's no surprises he can do the engine swap for a mere $300!

And since this thread is pretty text-based, a picture of the old engine as a bonus.

QDgWxWy.jpg

D6QRWE9.jpg

Dasaki

The new engine, as it sat in the bed of my dads F 150 yesterday

hA60KU1.jpg

M-14

Boy, that bay has a lot of room, a 350 buick wouldn't be too hard to swap in. Maybe next time.

Dasaki

Good news: engine went in without trouble, car us driving again!

Bad news: new engine appears to have a bad valve cover gasket and I was making quite the smoke trail down the interstate!

Overall not too bad, since I was recommended to take the valve covers off the old one anyway, as the hose hole is on the opposite side with the new covers, and the hose barely reaches. So I can simply replace the gasket during that process.

oldcutlass

Valve cover gaskets are a relatively simple task. Glad your back on the road.