350 or 455 into a 83

austingta · May 24th, 2009

Is it possible and practical to put a 455 or maybe a 350 (Buick ) engine into a FWD Riv?

TIA

Frank in Austin

ROA 10634

RivNut · May 25th, 2009

In the first year of this body, there was a 350 engine option, so anything is possible. If you're looking for a performance upgrade, why not stick with what came with the car as the V8 option and build from there. Because most all of the V8's that came in this body style were 5.0 Liter (307 cu. in.) Oldsmobiles, why don't you take a look at a 403 (6.6 liter) Olds. They're the limit of how far that particular "small" block was built. Oil pans, motor mounts, etc are all the same. The 455 Olds is a little different. There are LOTS of aftermarket options available for that 6.6 liter motor. (FYI, the 6.6 liter Olds engine was what Pontiac used in their Firebird Trans Ams that had the Automatic transmission - remember the Smokey and the Bandit movies?)

Edlebrock makes aluminum intakes, and heads, and there are builders like Mondellos http://www.mondellotwister.com/ who specialize in Olds performance. The weak link you'll need to deal with, with more power in this chassis, will be the driveline. I have no idea what can be done to a 325-4L transmission to strengthen it. The transmission uses the BOP bellhousing so any of the motor could work. The Olds engine has a rear mounted distributor unlike the Buick; installing an Olds motor would not require butchering your wiring harness. This swap has been done before. I think if you were to do some internet searches, you might find some info on them. Or, perhaps Jayson (Mr. 6th generation Riviera) Pruitt might know something more about this.

Check out this Oldsmobile FAQ website for other Oldsmobile info and perhaps some other options - like their 180 hp 5.0 liter motor. http://www.442.com/oldsfaq/oldsfaq.htm

Ed

CTX-SLPR · May 25th, 2009

Would an 83 be the TH325-4L or would it be the 3spd? Wouldn't an older TH425 be a close fit as well?

RivNut · May 25th, 2009

All Rivieras starting in '82 had the 4-speed automatic o/d transaxle (TH325-4L.) The transaxle in the T-types had a better final drive ratio than did the non T-types. I think, but I'm not sure, that the standard final drive was something like a 2.79 ratio and the T-type's was a 3.23. The TH325-4L is nothing like to older Olds Toronado's TH425. I can't imagine what all would be necessary to make that swap.

sosuzguy · May 26th, 2009

Ed's just about said it all. I wouldn't mess with anything more than an olds 350 or 403. I am planning on using one of these on a car in the future but at this time am still unsure which one. I think Tim McCluskey didn't recommend anything bigger than the 403 since I don't think the trans can handle the power. There is also the engine swap from the olds 4100 to 350/403 for the Eldorados that is helpful in this switch.

imported_tim63riv · May 26th, 2009

Frank,
Anything is possible, practical is another matter! Ed and Jayson are correct with their assesment of the situation. The Buick 350 and 455 were never used in a FWD application like the 79 to 85 Riviera. While the Buick 350 would physically bolt up to the 325-4L transmission, that is where the easy stuff stops and the difficulty begins!
The Buick oil pan and oil pick up must be modified or custom fabricated for this application,there is nothing available off of the shelf.
Exhaust manifolds or headers would have to be modified or fabricated as the drivers side exhaust has to go straight out to avoid the transmission.
You would have to modify or fabricate the differential and right axle brackets to mate up to the Buick engine. Then you would have to modify or fabricate the front engine mount while still providing oil filter access.
Finally you would have to plumb in the AC, power steering pump and other engine accessories, wire it up and go for a drive!
I don't want to make this sound like an insurmountable challenge or make the Buick engine out to be a lesser engine than the Olds. It is just easier to swap a 350 or 403 Olds in where a 307 Olds used to be! ( I may be selling my 85 T Type with a fresh Turbo Charged 3.8 Buick V-6 in it, that would offer another option to keep the car All Buick!) [img]<>/smile.gif[/img]
HTH,
Tim McCluskey