pontiac lemans engine swap

[Appollo]

thought i would start a new topic as to not hijack the other members thread.


I am starting the same swap on my 81 grand lemans with the 4.4 v8. finding any pontiac motor is very difficult so i want to use a sbc 350. i assumed the motor mounts, transmission, manifolds, rad and brackets would all bolt up. Are you absolutely sure about this, as i have to make some major changes, considering i already rebuilt the sbc 350. The only pontiac motors around seem to be 301's which are not too exciting, any guidance would be appreciated.
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Appollo
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Re: 1981 Buick Regal 4.3 V8 swap options
Postby Appollo on Sat Sep 06, 2014 8:32 pm

i've just located an olds 403 engine, would this be a simplier swap in my 81 pontiac lemans?
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pencero
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Re: 1981 Buick Regal 4.3 V8 swap options
Postby pencero on Sat Sep 06, 2014 11:20 pm

the 403 is much better for a street driven daily driver b/c it makes a boatload of low end torque but it's more expensive to rebuild at the shop unless you know how to do rebuild the engine yourself. You should bring someone who knows alot about engines before buying a 403 or you could buy a headache by mistake. I think to sum it up, its better to have an old 403 than an old 350, but of course a new 350 would always beat an old 403... it's really what all a person has to spend at the end of the day.
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olds307 and 403
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Re: 1981 Buick Regal 4.3 V8 swap options
Postby olds307 and 403 on Sat Sep 06, 2014 11:24 pm

It will move the LeMans nicely. You will need Olds brackets and frame mounts.

88 Cutlass Supreme Classic, Mild Olds 350, 2004R, 3.42 open for now....94 chev Z71 4x4, TBI 76 350 Olds, 5A heads,A4,204/214 cam,Sanderson's and duals, rebuilt 4L60E,3.73 gov lock, 2010 Challenger SE, Stone White, leather, 18" wheels, 2000 Dodge Dakota Sport Club Cab 4x4, 3.9 v6 and 3.92 no slip.

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Appollo
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Re: 1981 Buick Regal 4.3 V8 swap options
Postby Appollo on Sun Sep 07, 2014 12:46 am

i can build the motor myself, aside from the machining etc.
the sbc 350 i built for this car is .30 over with flat top pistons, mild cam, 64cc heads, edelbrock performer intake
etc. which i would really like to hear run. Can someone confirm that the transmission, manifolds,engine mounts and brackets will not transfer from my original 265 v8. I imagined being a v8 car, that most of it would transfer. I was also told by the previous owner that the car has a turbo 350 transmission, but maybe it doesn't?

 

[Appollo]

I've been reading up on the 403 and there seems to be two types pontiac and Oldsmobile. I wonder
If they are the same motor. Bone stock it's pretty mild at 180 hp but the 340 ft lbs of torque makes up for it.

 

[deanlemans81]

Hey Appollo, Glad to see another Lemans going together, I`ve got an 81 also myself.

Your 265 is a low deck Pontiac engine, practically identical to a 301. The good news, any Pontiac engine will bolt in with only minor mods to your accessories due to the higher deck height of a 326-455 Pontiac engine. If you use a 70-up block, your 265 mounts will bolt right up and it will drop in. Blocks 69-down will fit but you must use adapters since not all bolt holes are present for the mounts. The adapters are easy to get from most Pontiac specific vendors.

Now the bad news. While a SBC will easily bolt in it`s place, you MUST CHANGE EVERYTHING for it to go in. Not one part will interchange between the 2 engine families. That means engine, trans, starter, front accessory drive, fuel lines and electrical harness and all the other associated stuff with it. I`m going the otherway, from a chevy 3.8l V6 to a Pontiac 400. It can be done but it`s a b*tch. the easiest way would be to find a rusted-pos-junk sbc equipped g-body so you will have every little part needed for the swap.

If you want to go the 403 route, I believe most of the driveline parts will be able to stay (trans back) but you will still need to change most of the front hardware. One of the Olds experts here could better answer that part than me.

Hope this helps, have fun and post some pics of that Lemans for us all to drool over.

deanlemans81

 

[Bonnewagon]

I also advise you stay with a Pontiac motor. I know Pontiac V-8's are getting scarce, but they are out there. You already have the correct mounts, trans, though I'm thinking the older V-8 accessories will be needed too. A complete motor w/brackets would be ideal to find. Don't be discouraged you can't find a 400 or 455 because even a 2 barrel 350 is plenty for our cars.

 

[Appollo]

here she is before paint. roof and trunk have major clear coat peel, no rust at all and the rest of the paint is pretty decent. Frame rails are good as are floor and trunk. The reason I am restoring her is because it was my dad's first car and now it's mine. She's not my first choice by any means but whenever I drive it, I am grinning like a kid in a candy store. I guess it's just reminiscent of the old days gone by.

The original 265 V8 is a good runner but just so boring. I sure would like to wake it up and figure if I'm stuck with it, I might as well make her fly.

She will get lowered with at least 18" wheels and I am considering removing the chrome mouldings. here is a photoshop.

 

[Appollo]

Hey Appollo, Glad to see another Lemans going together, I`ve got an 81 also myself.

Your 265 is a low deck Pontiac engine, practically identical to a 301. The good news, any Pontiac engine will bolt in with only minor mods to your accessories due to the higher deck height of a 326-455 Pontiac engine. If you use a 70-up block, your 265 mounts will bolt right up and it will drop in. Blocks 69-down will fit but you must use adapters since not all bolt holes are present for the mounts. The adapters are easy to get from most Pontiac specific vendors.

Now the bad news. While a SBC will easily bolt in it`s place, you MUST CHANGE EVERYTHING for it to go in. Not one part will interchange between the 2 engine families. That means engine, trans, starter, front accessory drive, fuel lines and electrical harness and all the other associated stuff with it. I`m going the otherway, from a chevy 3.8l V6 to a Pontiac 400. It can be done but it`s a b*tch. the easiest way would be to find a rusted-pos-junk sbc equipped g-body so you will have every little part needed for the swap.

If you want to go the 403 route, I believe most of the driveline parts will be able to stay (trans back) but you will still need to change most of the front hardware. One of the Olds experts here could better answer that part than me.

Hope this helps, have fun and post some pics of that Lemans for us all to drool over.

deanlemans81

thanks for the information, I am stoked on the idea of building a 403, my all time favorite motor is an sbc400, just for sheer torque. my problem is dropping another $2k on rebuilding another motor. I don't want to stick in a used motor, assuming i could even find a runner. And also I am pretty sure inserting a decent powered 403 will nuke the current transmission. so a new transmission is almost inevitable. However the more i learn about Pontiacs the cooler it is to have a pontiac motor in a pontiac.

 

[G-Body_Vet]

I'm also on board for putting a Pontiac back in it. My car was originally 305 equipped. I also have the wheels you photo shopped.....good choice! :lol:

Pontiac 400's make more torque than 403's btw. 403's have a big bore, but they also have terribly low CR's. The same can be said for Pontiac 400's when it comes to CR depending on the year you find. It's been awhile since I've looked at what's available for 403's but I believe you have a lot more building options for a 400, not to mention stroker kits. I hate to say it but $2000 doesn't go a long way for a decent performance build. That's more along the lines of a stock build, re-using as much as possible, with minimal machine work.

 

[Bonnewagon]

As long as the 265 is running well, why not just enjoy it while you scrounge up a bigger Pontiac V-8? What's the rush? By the way, it's not a coincidence the Chevy 400 has the same bore and stroke as a Pontiac 400, and the Pontiac 326, 350, 389, and 400 all use the same 3.75" stroke that accounts for that bottom end grunt. But the 421, 428, and 455 are real stump pullers. The 403 is a good Olds motor, but the only reason you find it in a Pontiac is because GM in it's infinite wisdom (insert eye rolling groan) discontinued the traditional Pontiac V-8 in '78 and used stockpiled '78 400's in the '79 tenth anniversary Trans Am. All other '79 6.6 motors were the Olds 403 because it was available and similar to the 400. In '80 and '81 the only Pontiac V-8 you could get was the 265 or 301.

 

[Appollo]

you're right ,there is no rush, just wanted to have all the parts ready to build it over winter. I just learned that the Pontiacs from 350 to 455 share the same block or are at least the same external dimension?!?!? if this is true then how can any parts from my current small block 265 be of any use, manifolds, brackets, flex plate, torque converter, starter even transmission? if I have to modify the car to fit a bb, than I should just get the biggest bb I can find, right? I never considered a 455 but I am upgraded the front springs anyway, so maybe it makes sense.

I agree $2k does not build a race motor. My goal is 250-300 hp. I figure almost any 350+ size engine with flat tops, mild cam, decent intake and headers should get me there.

 

[Bonnewagon]

Yes, externally all traditional Pontiacs share the same basic block dimensions going back to 1955. But there are small differences over the years and the 265/301 are probably the most unlike of them all. Only the cam, water pump, distributor, exhaust manifolds, carb, valve covers, oil pump, oil pan, motor mounts, and thermostat interchange with the older models. Mostly this is because of the single plane intake manifold and 1" shorter deck height. The heads bolt up, but again, the ports are different. The older flywheels will bolt up, but the 265/301 are balanced differently. Otherwise all Pontiacs can share flywheels. They all use the standard BOP bellhousing bolt pattern. The smaller displacements use a 3" crankshaft journal and a common 3.75" stroke, while the big boys use a 3.25" journal. But this is one reason why I love Pontiacs. I've had 455 heads and a 400 crank on a 350. Intake, cam, exhaust- all fit. Oh, and a word to the wise. Calling Pontiacs big or small block will label you as a Hoople. They're just Pontiacs.