Technical V8 swap in a 1948 Pontiac

Hi! I’ve been thinking about doing a v8 swap in my 1948 Pontiac. It currently still has the straight 8. Does anyone have any advice about how to go about this? Also, where the motor mounts would have to be placed? Any advice would be greatly appreciated! I’ve been told that there is a conversation kit for 48 Chevy that would likely work, but I’m guessing I’d have to put a Chevy motor in it. We’re trying to stick with a Pontiac motor if possible. Thanks!

 

GM back then was not like GM later on, with "badge engineering". Unlike later cars, GM vehicles were actually quite different across the brands.

Parts for a Chevrolet might be able to be modified to work, but how much modification is hard to say.

In all likelihood, the mounts would need to be fabricated.

As for where they would be located, you'd have to suspend the replacement engine in the engine compartment, make sure that the fan is the correct distance from the radiator, and work from there.

Non like-to-like engine swaps, or swapping to a different engine, even of the same brand, if it was not an alternative optional engine, almost always requires welding.

 

Very doable with a Pontiac V8. A step by step here would be lengthy. There are books on engine swaps...look for one on Motor Books website. Also, an excellent post on a recent thread written by @ekimneirbo with photos and text. Plan on removing the 'front clip' (fenders, grille, radiator core support as a unit) for clear access to frame. Removing clip is not that difficult and pays big dividends.

Ray

 

Yup, plenty of room up there for about any engine, too.

 

Here in the UK, this lovely thing has a '60s era 425 Nailhead fitted in it......seems to make it move along the road quite well

 

Not sure where you located.

min Canada pontiacs where built on Chevy frames.

adapting engine mounts is no big deal
Most guys use the hurst front mount on these as it’s easy to install

 

@VANDENPLAS OP's car has "straight eight" .........not likely a Canadian build car.

 

Sheeat.... I’d put in 2 SBCs you got plenty of room. Seriously to make it easy, get an empty engine and trans and give yourself room around the trans and steering moving it a bit in every direction. good luck

 

I'm glad to see you plan on keeping it Pontiac (just my personal preference with a Pontiac).

As noted above the easiest way is likely to get or make a front engine mount.

 

Totally different frames if US manufactured; Chevy is top hat with bolt in front suspension so mounting kit won't work in a Pontiac frame which has open/boxed 'C' channel frame. A Pontiac in a Pontiac would be a nice touch. Whilst at at, don't skimp on upgrading your brakes, steering and/or suspension. Depending on what engine/trans combo you use, think about Hurst front mounts and also fabricating a rear transmission support member. I swapped a SBC into my 46 Olds frame (Similar to Pontiac) and had to fine tune eng/trans location to allow driveshaft to exit centre X-member with sufficient clearance for rear suspension movement.

48 Chevrolet


Pontiac (Example with V8)

 

Excellent info, Sir!

 

I am watching this thread. If the straight 8 in my 50 doesn't last I will probably swap to a Pontiac V-8.

 

Thank you. I’ll have to look into the website. It’s just called motor book?

 

PM sent.

 

I was in a car club in the '50's. There were 2 brothers with Pontiacs of that vintage, both had Olds V-8's with hydros. Not rocket science.

 

A really cool swap would be the OHV Pontiac 250 six.

 

This was common in Minnesota in the late '50's. early '60's.

Hydra-Matics rule!

 

Uh, NO. These are relatively heavy cars. Why would you want to cripple one with anemic engine like this and add parts scarcity into the equation?

 

Scarce? Yeah, you do see them though. Even in stock form a late one will have more than double the HP of the stock engine.

 

And the torque would be.....?

 

Torque moves cars......horsepower doesn’t......hp is a byproduct of torque. You can make a chainsaw engine produce impressive horsepower...IF...you turn 20,000 rpm.....but it would be useless.

 

260. The stock 1948 8 had 190.

Add headers and triple carbs (Pontiac did do this to a special performance engine) and claimed 315 HP. (No, I don't know the torque but one can roughly guess).

So while maybe OT a 1948 Pontiac is generally thought of as a low rider, not a stoplight car. With that in mind the OHC 6 would be different and kinda cool IMO. The last OHC 6 I saw for sale went quick.

 

Uh YES. The original worked for decades, and the OHC would run circles around the flathead six or 8. I put a Chevy 250 in my 48 Fleetline with a th350 and a 57 Chevy rear end. It ran great, ate up the hiway, chirped the tires in second gear when I wanted. So Uh, speak of what you know, not what you think.

 

3600 to 4100 lbs depending on model and engine. A 6 cyl Firechicken weighed 3080.

 

Since the car was originally a straight eight, how's about a compromise and stay with one? I envision a hopped up 320 ci Buick Roadmaster engine. I used to race with some guys that ran those. They bored 'em out a full 1/4" (!) and used pistons from an International Harvester tractor to give 356 cubes and added hi-lift rocker arms and 5 or 6 Strombergs (depending on how many they could find). If you could find an Edmunds head and intake, I could also see a 356 ci Packard.

I like different, interesting cars. My definition of interesting doesn't include a 250 ci 6 cylinder in a two ton car.

 

390 lbs torque @ 4000 rpm.

 

Though my post(s) did not endorse the Pontiac OHC 6 for this application, I am a fan of inline engines. I am member #057 of Inliners International, obviously dating back to their early days.

I am in fact currently building a ‘37 Chevy coupe with a 250 Chevy six that has been warmed up and dyno’d 258 lbs ft and 226 hp. It was modified specifically with an eye towards torque. The ‘37 Chevy coupe is a relative lightweight and for my purposes, I think will perform very satisfactorily. Nonetheless, as has been stated by others, the weight of the Pontiac in question is quite a lot heavier.

In addition, the Pontiac OHC engines, while certainly not extinct, don’t seem to be all that common. And most certainly the factory high performance versions were rare when new, much less fifty years later.

Further, the OP has indicated limited experience with engine swaps in general, and asked about the suitability of a Pontiac V8. Taking that into consideration suggests to me that the swap should be simple, straightforward and use readily available components.

Ray

 

yep. good advice

 

When born, my 48 Convertible had a straight 8. It was long gone and i wanted to stay Pontiac so this is my build with a 389. Plenty of room............

 

I LIKE that (except for the rear wheels; I expect they're only temporary).