[Zooguy]

All right first things first if you just want to post about how I'm ruining the value of my car, or this is sacrilegious please keep scrolling I don't need your comments.

If you're genuinely curious and willing to offer some help please feel free to share your knowledge with me. Here's a little info to start.

I'm from Oklahoma City and I drove to Tennessee and rescued this 1966 Pontiac Star Chief Executive 4-door that had been sitting outside since 1993.

In my past I've had several different race cars but I just sold my last one which was a 1994 Pontiac firebird formula with a 350 cubic inch LT1 carburetor swapped and lots of nitrous. It did wheelies and it had a best pass of 10.177 at 129.9 mph. But for the last 2 years I I didn't take the car to the drag strip I found myself doing little local cruises and cars and coffee type events. So I got rid of the car and started looking for a late '60s land yacht to build a family cruiser out of.

After doing lots of reading I've learned that the 389 under the hood has a very weak block being a 1966. For this cruiser build I'm wanting a Roots blower sticking up out of the hood and some massively wide rear tires.

I've already got the back tires and appointment scheduled to have the car modified to fit them but I'm going to be running a 31"/18.5”-15” Hoosier QuickTime Dot.

I already have a stock 454 Big block Chevy disassembled in my garage and that has peanut Port heads and a nice low compression ratio for boost. I'm not wanting to build a race engine but just a fun weekend cruiser with a blower. I'm not after any specific horsepower numbers but I just want to make lots of low-end torque to move this big heavy car.

I've done a lot of searching but I can't find any really good write ups of people swapping big block Chevys into Pontiac b bodies. I already know the transmission won't bolt up directly but that's a very simple change with the bell housing. I think what I'm going to run into issues are going to be motor mounts and exhaust manifolds / headers.

Is there anybody in here who has put a big block Chevy into their full size Pontiac b-body? If you have please let me know I'm going to have some questions.

[Zooguy]

Here are some ideas and pictures I liked inspiring my build.

[misterp266]

While I’m not really familiar with Chevy stuff, I would consider replacing your front frame section from the firewall forward with one from an Impala. That way, all the Chevy stuff will work much easier. Like oil pan, motor mounts, and headers. Otherwise, I think you’ll be looking at lots of fab work.
Good luck, all blown cars are cool.

Road Kill did a blown BB Impala....

[b-man]

I’m not sure but I’d say do a trial fit with a bare block with crank installed along with the heads, bolted to the long tail shaft Chevy TH400 you’ll be using.

Take note of the position of the crankshaft nose from side to side and from whatever reference point for the height before pulling the 389. Then drop the BBC package in and use the original trans mount on the crossmember to locate that end.

Chances are pretty good that a pair of BBC Impala engine mount frame stands could be bolted to the front crossmember after finding the proper location.

I can’t imagine that there’s such a huge difference that you’re going to have to splice in an Impala front frame stub. Both the Pontiac and BBC engines have a rear sump oil pan so the BBC pan shouldn’t interfere with the Pontiac engine crossmember.

If that all goes well I’d say a set of headers made to fit a 427 Impala should work or at least could be modified to work without having to completely remake them.

Just get a little adventurous and test fit it all is what I’d do.

[Sirrotica]

B body Pontiac frame mounts are welded to the crossmember, they aren't bolt in pieces. It would be much easier to stick with the born with style of engine in a Pontiac chassis. Or find a chevy to put it in. Tubbing a 4 door car is going to be a little challenging also.

[Scarebird]

I would simply grind off the old mounts and get a set of these 1973-75 engine mounts.



Use the clamshell style mount. Bolt up to the engine, lower into place. Once you have it where you want, tack weld then pull motor. Drill out the 3 holes per side and bolt in.

[Scarebird]

Here is a shot with a stealth motor showing the mounts...

[Stuart]

The car probably isn't as heavy as you think - shipping weight on a four door Star Chief was 3,920 pounds.

I agree with Scarebird, installing a BBC is mainly going to be a matter of coming up with new motor mounts. Assuming you're planning on a TH400 automatic transmission, you may as well just find a Chevy version; the existing transmission would need to be rebuilt anyway to handle the additional horsepower.

What kind of rear end differential ratio are you planning on? The existing one is most likely something in the 2.XX:1 range, and steeper gears may be difficult to find. Since the rear axle housing is probably going to need to be narrowed anyway to work with your wheel/tire combo, you may end up having to go with something like a Ford 9 inch setup.

[Zooguy]

Originally Posted by Stuart

The car probably isn't as heavy as you think - shipping weight on a four door Star Chief was 3,920 pounds.

I agree with Scarebird, installing a BBC is mainly going to be a matter of coming up with new motor mounts. Assuming you're planning on a TH400 automatic transmission, you may as well just find a Chevy version; the existing transmission would need to be rebuilt anyway to handle the additional horsepower.

What kind of rear end differential ratio are you planning on? The existing one is most likely something in the 2.XX:1 range, and steeper gears may be difficult to find. Since the rear axle housing is probably going to need to be narrowed anyway to work with your wheel/tire combo, you may end up having to go with something like a Ford 9 inch setup.

Yes I'm probably going to go with it for 9 in rear axle 33 spline axle shafts and with the bigger tires. To keep the same RPMs allowing the speedometer to stay accurate that says I would need to go with a 3.08 rear gear... But I'll probably go with something like 3.25-3.70.

My race car I sold to help fund this project had a th400, 4000 stall, Ford 8.8 rear axle with 4.11 gears. I could drive down the highway at 3000 to 3,200rpms that would be between 60 and 65 mph with 28 in tall tires. So if I put a 2, 500-2800 converter in it with 3.25 to 3.70 gears and the 31" tires I'm fairly confident it would go down the highway at the same speed but a lot lower RPMs and still have plenty of get up and go.

[Goatracer1]

I used the later motor/frame mounts to install a Pontiac in a Chevy truck so using the pieces in reverse should work very well for you. Use the rubber frame mounts and the steel motor mount halves and bolt them to the engine and lower it on to the frame. Mark the bolt hole locations , remove the engine and drill out the holes. should work.

[Zooguy]

When you say later what particular years are you referencing or if you have part numbers that would really help.

[Scarebird]

1973+ to mount BBC or SBC in a Pontiac.

[Sirrotica]

I'd bet that those mounts will only be half on that crossmember, the Pontiac frame has the mounts behind the crossmember, not on it. The member under the engine is further forward on a Pontiac B body frame in 1966 than like years of chevys. The GM divisions moved the front crossmembers fore and aft during the 60s due to their motor mount systems.

I'm sure no one knows what I'm talking about because everyone thinks that GM made all their frames the same, not in 66 B body they didn't. They, (GM) didn't standardize the B body frame until 1971. Olds is the same way, the frame is nothing like a chevy frame is.

Furthermore the Canadian Pontiacs that actually came with chevy engines, used B body chevy frames under them, GM didn't try to modify the Pontiac frame to accept a chevy engine. It of course can be accomplished, with time, money, and effort, but the crossmember is in the wrong place to just drop chevy frame mounts on the Pontiac frame. On the Canadian Pontiac there was no Wide Track because they used the chevy chassis under the Pontiac body. There's more to it than just using the chevy mounts and drilling holes in the Pontiac crossmember.

Notice in the picture that the mounts are behind the crossmember, welded solid to it, not bolted on it:



Hopefully this illustrates what I posted earlier.......

[Goatracer1]

I was using mid to late 1970's mounts. If they don't line up on the crossmember you could bolt or weld a flat steel plate to the crossmember and bolt the frame half of the mount to that.

[Sirrotica]

As I said. it's not impossible to make it fit, but you're not going to just drop the engine in place, mark the crossmember and drill holes, part of the frame stand will be hanging over the crossmember in mid air. That was the purpose of the first post.

50 plus years of wrenching for a living, plus owning, building, driving and, driving my own race cars, I'm thoroughly familiar with fabrication.

I doubt anyone else on this board had a Jeep wrecker powered by a 455 Pontiac, I did, plus I built headers to fit that combo. That was the third Pontiac to Jeep swap I did, the first two were into Wagoneers. Picture of 455 Pontiac powered Jeep wrecker:



As I said, time, money, and effort can make most any engine fit any car. As I said it's not just a mater of dropping chevy frame stands, drill a few holes and it's done. There's more to it than meets the eye. Everyone was talking as it was just a simple GM swap, done with factory parts, only need an electric drill, it's not that simple was the point.

[72projectbird]

Originally Posted by Goatracer1

I was using mid to late 1970's mounts. If they don't line up on the crossmember you could bolt or weld a flat steel plate to the crossmember and bolt the frame half of the mount to that.

Bingo.

Grab a welder, or drill some holes and some large bolts and make it work. That's what hotrodding is all about

Bolt the engine and trans together, set it in the car with the driveshaft installed so you know exactly where it should be sitting, mark where the mounts need to be and get to fabricating!

[Zooguy]

Originally Posted by 72projectbird

Bingo.

Grab a welder, or drill some holes and some large bolts and make it work. That's what hotrodding is all about

Bolt the engine and trans together, set it in the car with the driveshaft installed so you know exactly where it should be sitting, mark where the mounts need to be and get to fabricating!

I am definitely not opposed to doing solid motor mounts I was I'm wanting something a little more comfortable but a little bit of plate still some grade 8 bolts and everything should be just fine.

[72projectbird]

Originally Posted by Zooguy

I am definitely not opposed to doing solid motor mounts I was I'm wanting something a little more comfortable but a little bit of plate still some grade 8 bolts and everything should be just fine.

You could mount plates to the frame and then put stock Chevy frame mounts on the plates to retain the stock rubber mounting system. Basically build a foundation for the stock mounts to sit on.

[misterp266]

Originally Posted by Sirrotica

I'd bet that those mounts will only be half on that crossmember, the Pontiac frame has the mounts behind the crossmember, not on it. The member under the engine is further forward on a Pontiac B body frame in 1966 than like years of chevys. The GM divisions moved the front crossmembers fore and aft during the 60s due to their motor mount systems.

I'm sure no one knows what I'm talking about because everyone thinks that GM made all their frames the same, not in 66 B body they didn't. They, (GM) didn't standardize the B body frame until 1971. Olds is the same way, the frame is nothing like a chevy frame is.

. . . . .

^ ^ ^ ^. THIS is why I suggested a front frame swap. Yes, with enough work, you can put just about any motor in any car but why make it difficult? Have the place that’s tubbing the back swap the front at the same time and square it all up. Otherwise, unless you talk to someone who has actually done it, it’ll for sure be more hassle that you think. Just my 2 cents.

[Sirrotica]

Originally Posted by misterp266

^ ^ ^ ^. THIS is why I suggested a front frame swap. Yes, with enough work, you can put just about any motor in any car but why make it difficult? Have the place that’s tubbing the back swap the front at the same time and square it all up. Otherwise, unless you talk to someone who has actually done it, it’ll for sure be more hassle that you think. Just my 2 cents.

At least someone grasped the relevance of not all GM frames were made the same in those years. When you suggested clipping the front frame, I knew exactly why you suggested it.

As I posted, when GM made the Canadian Pontiacs they used chevy frames without wide track, just to negate trying to deal with the different crossmember location, and the chevy frame stand location.

I never said it wasn't possible to do, just that it's not gong to be a 2 hour job like what was suggested.

Tubbing a 4 door sedan isn't going to be a walk in the park either, not saying it can't be done, but a 2 door body would simplify the process.