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31pontiac's 1959 Bonneville

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Chuck Hoop

install chevy engine in 65 bonneville

Question

Has anyone installed a chevy engine in full size Pontiac?  Need info on motor mounts from someone who has actually made the swap.  and what else do I need to be concerned about?  Rebuilt chevy engines are plentiful, Pontiac not so much.  Money is another factor, don't have much but would love to get the Bonneville on the road.  Thanks for any  help.

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Them's is fightin' words Chuck. Or at least sacrilegious to us Pontiac faithful. But I think you know that too!

There is a surprising a lot support for Pontiac engines, parts, etc.. Granted, it isn't as cheap  as "Cough cough" Chevy parts but it is there (except for the Pontiac 265 and 301 V8s). So if the issue is finding parts for your Pontiac engine, let us know. Yeah, we know that Pontiac parts are not as cheap as Chevy. That is not up to us. 

Now I have not done this swap. I will be honest with you right up front. However, I would start with looking at the motor mounts between the '65 Bonneville and the '65 Chevy Impala/Bel Air/Biscayne. I would expect the Impala lower motor mounts to bolt into the Bonneville chassis. I would start there. If it doesn't, then you have to fabricate your own.

A Chevy engine usually means a Chevy transmission because Buick-Olds-Pontiac (BOP) cars had the same engine-to-transmission bell housing bolt pattern. Chevy had it's own unique bolt pattern. You might be able to find an adapter kit. Either way, your original Pontiac transmission won't just bolt up to the Chevy motor directly. If you go to a different transmission, it is possible that you might end up going with a slightly longer transmission tail shaft, which means you might have to shorten your original driveshaft. Maybe. You may also have to move your transmission cross member back. If you do that, you may have to drill holes in the frame for the re-positioned cross member. You may need a different transmission mount if you end up with a different transmission. Again maybe.

The stock automatic transmission cooler lines may or may not fit your new transmission and radiator. So budget wise, be prepared to get a custom set made, or bend/build your own.

You might also have to be aware of how your emergency brake cable(s) gets run. When I upgraded from a 350TH to a 400TH in my '72 Lemans, even though the case length didn't change, I still had to get a custom E-brake cable made to re-route it around the relocated transmission cross member. Anyway, something to be mindful of. You may or may not have this particular issue.

Pontiac engine has the starter on the driver side. A Chevy engine has the starter on the passenger side. So you will need to re-route and lengthen all your battery cables - including those going to the ignition switch. Most Pontiac battery locations are on the driver's side - closest to the stock OEM starter.  

Pontiac alternator is typically on the driver side. Chevy alternator is usually on the passenger side. Again, wiring for the alternator made need to be extended.

Any engine swap means you will have to tweak your exhaust or build some sort of custom exhaust (in some fashion), regardless if you run the stock engine manifold or headers. Even if this is just adapting it into the current exhaust system on the car. 

If your new engine is significantly more powerful than your old engine, you need to consider upgrading your brakes. The more "go" you add, the more "whoo" you need to add to be safe. Stopping a 4500-5000 car like a Bonneville should not be discarded lightly.

Check your radiator. Will it work with your new motor? Obviously the stock hoses probably won't work. Do you need a new radiator just because the car is old? Again maybe. Regardless the radiator has to be matched to the motor and transmission. Does the engine fan/clutch/shroud now meet up correctly with the new motor or does that now need to be adjusted or custom made, etc.

That's all the obvious things I can think of at the moment. I'll let my colleagues on the forum speak up too, especially if I forgot anything.

Edited by Frosty

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:badGT:

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Looks like Frosty pretty much has it covered...

Are you going with a Big block...Turbo 400 combo...Or a small block Turbo 350 and/or R 700 combo...?? As those different combos can present their own individual problems...As far as positioning everything in the proper place (crossmember location, drive shaft length...Which trans yoke to use...weather or not the trans is a manual kickdown or an electric lockdown switch....What color gears to use in the trans to calibrate the speedometer...Power steering hoses...ETC..)

Unless you have a donor car.....By the time that you locate and aquire all the correct parts.....Plus the details We haven't thought of yet...To do a properly engineered swap.... It might be just as economically viable if not more so...To redo the original Pontiac engine....Then just bolt it right back in.....

2 hours ago, Frosty said:

Them's is fightin' words Chuck. Or at least sacrilegious to us Pontiac faithful. But I think you know that too!

There is a surprising a lot support for Pontiac engines, parts, etc.. Granted, it isn't as cheap  as "Cough cough" Chevy parts but it is there (except for the Pontiac 265 and 301 V8s). So if the issue is finding parts for your Pontiac engine, let us know. Yeah, we know that Pontiac parts are not as cheap as Chevy. That is not up to us. 

Now I have not done this swap. I will be honest with you right up front. However, I would start with looking at the motor mounts between the '65 Bonneville and the '65 Chevy Impala/Bel Air/Biscayne. I would expect the Impala lower motor mounts to bolt into the Bonneville chassis. I would start there. If it doesn't, then you have to fabricate your own.

A Chevy engine usually means a Chevy transmission because Buick-Olds-Pontiac (BOP) cars had the same engine-to-transmission bell housing bolt pattern. Chevy had it's own unique bolt pattern. You might be able to find an adapter kit. Either way, your original Pontiac transmission won't just bolt up to the Chevy motor directly. If you go to a different transmission, it is possible that you might end up going with a slightly longer transmission tail shaft, which means you might have to shorten your original driveshaft. Maybe. You may also have to move your transmission cross member back. If you do that, you may have to drill holes in the frame for the re-positioned cross member. You may need a different transmission mount if you end up with a different transmission. Again maybe.

The stock automatic transmission cooler lines may or may not fit your new transmission and radiator. So budget wise, be prepared to get a custom set made, or bend/build your own.

You might also have to be aware of how your emergency brake cable(s) gets run. When I upgraded from a 350TH to a 400TH in my '72 Lemans, even though the case length didn't change, I still had to get a custom E-brake cable made to re-route it around the relocated transmission cross member. Anyway, something to be mindful of. You may or may not have this particular issue.

Pontiac engine has the starter on the driver side. A Chevy engine has the starter on the passenger side. So you will need to re-route and lengthen all your battery cables - including those going to the ignition switch. Most Pontiac battery locations are on the driver's side - closest to the stock OEM starter.  

Pontiac alternator is typically on the driver side. Chevy alternator is usually on the passenger side. Again, wiring for the alternator made need to be extended.

Any engine swap means you will have to tweak your exhaust or build some sort of custom exhaust (in some fashion), regardless if you run the stock engine manifold or headers. Even if this is just adapting it into the current exhaust system on the car. 

If your new engine is significantly more powerful than your old engine, you need to consider upgrading your brakes. The more "go" you add, the more "whoo" you need to add to be safe. Stopping a 4500-5000 car like a Bonneville should not be discarded lightly.

Check your radiator. Will it work with your new motor? Obviously the stock hoses probably won't work. Do you need a new radiator just because the car is old? Again maybe. Regardless the radiator has to be matched to the motor and transmission. Does the engine fan/clutch/shroud now meet up correctly with the new motor or does that now need to be adjusted or custom made, etc.

That's all the obvious things I can think of at the moment. I'll let my colleagues on the forum speak up too, especially if I forgot anything.

 

Edited by TWO LANE BLACK TOP
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Thanks Two-Lane and Frosty.  Obviously I didn't put as much thought into this as you did.  All I saw was the possibility of a healthy crate engine putting out some ponies for a few grand.  However, as you point out that would just be the start of the expense train.  I didn't like the idea of cross breeding either, but I am on a limited budget.  Thanks again guys for waking me up.  I guess under the circumstances, I will stick with Pontiac.  Maybe a 400 or 455 to replace the 389.  I would think either of those would match up with what I have?

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Chuck, the answer is definitely yes. The 389 can also be re-built for respectable horsepower or bored/stroked out to 421/428 cubes too. Just depends on what your budget and performance goals are for the car and what you are starting with from the 389. We'd be happy to help you out there too. 

Care to describe the situation with the car and the 389 in particular?

Pontiac engines in general are torque beasts if tuned properly. It is torque that gets you down the road, not horsepower. The other nice thing about Pontiacs is there never was a big block/small block program. All Pontiac V8s were dimensionally the same size externally (except the 265 and 301). So swapping a 389 for 421, 400, or 455 is literally a bolt-in swap. You also can swap heads around too.

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Thanks again Frosty.  Who are we? (can help). Things to ponder.  Totally agree with 1, 3, 7 and 8.

Oh, I have a tired 65 Bonneville 2 dr.  I've lost compression in two cylinders I suspect from running unleaded gas.  Suspect that rings are bad also.  Haven't had it on the road since I've owned it.  It has the 8 lug wheels so I don't believe it has a lot of stopping power, but they look good.  Body is rough, but it has a great interior.  I've about decided just to try to get it roadworthy and drive it as is.  Limited funds has a lot to do with that thinking.  Anyway, what co are you with?

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I work for the State of Michigan as an IT project manager. I am just a Pontiac enthusiast, like you, who happens to know a lot about Pontiacs. 

There are parts for the 8-lug wheels out there now. Again not the cheapest things in the world but they are available to help at least refresh the brakes if you need them. One of my car club buddies owns a '63 Grand Prix with the 8-lug system.

So you have a tired, probably well used, 389. So you have the choice of a complete rebuild or crate motor. Have you considered calling Jasper for a quote on a reman replacement motor? They are not known for hi-performance motors but they are known for quality reman rebuilds, which sounds like what you want given your funding limitation. So if you get long block, transfer both manifolds, put on a new water pump, transfer your brackets, you might be motoring down the road next spring. Food for thought. 

Edited by Frosty
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