Olds 350 - Footprint Smaller than 6.2/6.5?

[joed]

I just picked up a 1948 Chevy 2dr coupe - has a rebuilt SBC gasser and TH350 auto currently, but I just can't get that excited about that set up.

So I"m thinking a diesel swap is in order...

For those of you that have had both a 350 diesel and a 6.2/6.5, is the 350 any smaller externally? The 48's engine compartment is a little tight widthwise; the SBC fits fine but there is not a lot of extra room.

Thanks.

Joe.

[AfterhoursFab]

I couldn't say for sure but ive heard the olds 350 is the same size as as sbc. The 6.5 is about the same size as a big block motor.

[More Power]

Don't know about cars of this vintage, but a 6.5 will fit fine in a late '40s or early 50's pickup truck. We did a story on a 1951 GMC with a turbocharged 6.5L some years ago. Jim

[AKMark]

I would stay away from the 350, as it's a BOP motor. Much easier to use a Chevy motor to help finding transmissions for it.

I've driven a few 350 Diesels, they aren't horrific, but the 6.2 is better, and a Turbo'd 6.5 is better than a 6.2.

[AfterhoursFab]

Ah yes the trans bolt pattern is different too. But i guess if you could source a 350d then id guess there could be a trans hanging off it as well. Your better bet may be a small 4cyl motor like an early 80s Benz. They use them a lot for Jeep swaps, would be cool to have in that car altho its npt bowtie.

[joed]

Actually, adapter plates to go from BOP to Chevy trans and vice versa can be had pretty easily for not too much $$, so that shouldn't be a deal killer.

I've thought about the 6.2/6.5, but am wondering if it would be too heavy. I was thinking the olds diesel would be lighter, although maybe not by that much. The existing car front suspension is coil sprung - I could probably get higher capacity springs.

I'd also like decent performance; not sure the olds 350 could get there. Probably need a turbo with low boost - even then it might not hold up.

The easiest would be a MB 5-cyl turbo, but I was hoping to stay all GM if possible.

Thanks for the input so far.

Joe.

[convert2diesel]

The 6.2/6.5 is definitely larger width wise. The 350 Olds is exactly the same as its gasser counterpart. It is an Olds engine and bears no resemblance to a SBC, including the engine mounts.

Did a 350 diesel conversion on an 86 Cadillac Fleetwood that had the 307 Olds (same block as the diesel) in it and the conversion was a direct swap, including the exhaust manifolds. Weight was within 100 lbs. so no need for spring work. Actually made the car ride and handle better.

Same story with the conversion on the Buick. Swapped out the SBC for a 6.2. Everything bolted right up but there were clearance issues at every turn. The final result was about 200 lbs. heavier but the front springs only sagged about 1/2 inch. Again made the car ride and handle better.

Good luck on your conversion and would definitely suggest the 6.2/6.5 over the Olds diesel. Anything made after 81 (DX block designation) were not bad engines, just underpowered. The 6.2 made for a more tractable engine and one you can still get parts for. Worth the extra fab work.

Bill

[MajMike]

Actually, adapter plates to go from BOP to Chevy trans and vice versa can be had pretty easily for not too much $$, so that shouldn't be a deal killer.

I've thought about the 6.2/6.5, but am wondering if it would be too heavy. I was thinking the olds diesel would be lighter, although maybe not by that much. The existing car front suspension is coil sprung - I could probably get higher capacity springs.

I'd also like decent performance; not sure the olds 350 could get there. Probably need a turbo with low boost - even then it might not hold up.

The easiest would be a MB 5-cyl turbo, but I was hoping to stay all GM if possible.

Thanks for the input so far.

Joe.

Everything I've read and every mechanic I've talked too said the Olds diesel was a total POS, a gas engine forced into a diesel configuration. The 6.2 was designed from the get-go by Detroit Diesel as a diesel engine, get a 599 block and build it up with good parts (or get a running engine with low miles) then can keep NA or add Banks Sidewinder turbo kit for another 60hp and 100ft-lbs. You won't regret it.

Oh yeah, this is a great site for diesels and so is dieselplace.com for the 6.2 and 6.5.

[convert2diesel]

Everything I've read and every mechanic I've talked too said the Olds diesel was a total POS, a gas engine forced into a diesel configuration. The 6.2 was designed from the get-go by Detroit Diesel as a diesel engine, get a 599 block and build it up with good parts (or get a running engine with low miles) then can keep NA or add Banks Sidewinder turbo kit for another 60hp and 100ft-lbs. You won't regret it.

Oh yeah, this is a great site for diesels and so is dieselplace.com for the 6.2 and 6.5.

Mike:

Your information is mostly correct, especially those engines made pre-81. A good case of a good idea that was rushed through development and than handed over to the accountants for re-design. The modifications made to the original design for the sake of economics was the downfall and the list of things that fell apart closely resembled the re-design list.

By 81 they had worked out most of the issues with the final block (DX) with roller cams, beefed up lower end, improved fuel system etc. The only thing they couldn't get around was the number of head bolts. Just not enough room to add anymore, thus a continuing issue with blown head gaskets and cracked heads. This was largely corrected by de-rating the engine from 120HP to 105HP.

After 81, most of the issues could be traced back to the owners. If the engine was allowed to warm up properly and it wasn't used for drag racing, they would last at least as long as their gasser counterparts.

Had the occasion to talk to one of the design team that was hired to fix the problems and she made the following statement.

Our biggest problem was the suburban housewife (note she also was a suburban housewife with a degree in mechanical engineering).

Middle of February, minus 20, forgot to plug the car in overnight, in a hurry. Bundles the kiddies into the back seat, forgets about the wait light, just keeps cranking the engine till it starts to fire on a couple of jugs and ignoring the cloud of smoke emanating from the back of the car and the fact that the car is jumping up and down like a pogo stick. Finally gets it to fire on all eight, now really frustrated, backs out on the street and puts it into drive and floors it while the engine is still stone cold. Gets fifty feet and blows coolent all over the street from one or two blown head gaskets.

Calls hubby in a panic, hubby rescues her and either sells the car or has a friend swap out the diesel for a gasser. Spends the next 20 years telling anyone he knows what a POS that diesel was.

Wasn't a really bad engine, just not thought out well and not marketed correctly. That faux pas set the North American light diesel industry back 30 years. Realistically, if they had gotten over that hurdle things would have been much different. The afore mentioned 86 Cadillac Fleetwood with the 350 diesel would consistently give me 40+ MPG (Imperial) at 70 MPH, and that was in a 5,000 lb. car with all the endearing aerodynamic properties of a grand piano with the lid open. Would have given a Prius a good run for its money in a car you would actually want to drive.

End of history lesson.

Bill

[joed]

Thanks for all the input so far.

Another possibility might be the 6.5 rear turbo style engine, used in vans and hummers.

Anyone have any experience with these?

I seem to have some room behind the existing SBC - I'm not sure how much space the rear turbo set up requires, but there may be enough.

I've heard they can be more prone to head cracking/issues, but maybe that's due more to use in heavy armored hummers?

Thanks, again.

Joe.

[convert2diesel]

Thanks for all the input so far.

Another possibility might be the 6.5 rear turbo style engine, used in vans and hummers.

Anyone have any experience with these?

I seem to have some room behind the existing SBC - I'm not sure how much space the rear turbo set up requires, but there may be enough.

I've heard they can be more prone to head cracking/issues, but maybe that's due more to use in heavy armored hummers?

Thanks, again.

Joe.

Joe:

You'll need at least 4 inches (preferably more) of clearance from the front face of the bell housing and your firewall to accommodate the downpipe from the turbo. It exits over the right side of the engine but have seen some fabbed up units that is the reverse of that to exit on the drivers side.

I for one, prefer the center mount turbo set-up. One of the main reasons I bought the 94 Caddy. Had the needed clearance for the down pipe. Can't really comment on the reliability and the supposed heat issues but there has to be a compelling reason AMG stayed with the center mount for most of their development. If you are religious about heat blankets and wraps, can't see heat being an issue.

There are some compelling reasons to go with the center mount, the first is the exhaust routing. Both exhaust (inlet side) are of equal length and shape so that should boost efficiency of the entire system and remove some unequal backpressure that must be present in the side mount set-up (drivers side has to travel at least 5 times as far before hitting the turbo).

Of equal importance, especially if you are short of underhood real estate, is that you can easily reach things like glow plugs and injectors with the center mount, without major surgery. Not appreciably different than with the NA versions.

Only issue I had when working through the conversion on the Caddy, was routing of things like AC lines and heater hoses. Would probably have to re-locate the HVAC system or build some custom piping to get around the down pipe. Physically could not use the side mount in either the Buick or the Caddy set-up with the stock manifolds as they interfered with the passenger side upper control arm mounts. No way around it without fabbing up a custom exhaust manifold.

Good luck on your conversion. Sounds like fun.

Bill