Pontiac engine swap

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travis
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Pontiac engine swap

Post by travis » Sat Dec 08, 2018 5:04 pm

A friend of mine has a 1980 Pontiac Grand Prix with a 301/4bbl. The engine was rebuilt last year but burns oil like crazy...about a quart every 100 miles. My friend was able to get most of his money back from the builder eventually. It appears that the chrome rings never seated and the thing is .040 over with a really rough hone job.

We are mulling over options. One is to try rehoning the cylinders but the piston skirts are a little chewed up too. Another option is to go ahead and have it bored .060 over but I’m not really comfortable with this option. These 301’s are really thin and light compared to a “normal” Pontiac engine.

And then there is the option of an engine swap. I know a guy with a quality rebuilt ‘73 2bbl 350 that was in his ‘73 Firebird for $1500, but the option really being considered here is a ‘73 or ‘74 2bbl 400 in a big 4 door car. It needs rebuilt...if we go this route it will be a mild build.

I vaguely remember something about Pontiac engine mounts changing somewhere in the early or mid ‘70’s. Does anybody know about this? A quick search came up with nothing. I know the accessory brackets are going to be an issue due to the major deck height difference between the 301 and anything else. What about exhaust manifolds, or headers? What uses 3 port headers, versus 4 port headers? I know very little about Pontiacs.

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Re: Pontiac engine swap

Post by peejay » Sun Dec 09, 2018 7:42 am

What about having the bores honed properly (if possible) and having the piston skirts coated?

AFAIK the exhaust ports are basically three port, and Ram Air IV, which is getting common for headers because this is the pattern that Edelbrock used for heads.

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Re: Pontiac engine swap

Post by travis » Sun Dec 09, 2018 9:02 am

peejay wrote:
Sun Dec 09, 2018 7:42 am
What about having the bores honed properly (if possible) and having the piston skirts coated?

AFAIK the exhaust ports are basically three port, and Ram Air IV, which is getting common for headers because this is the pattern that Edelbrock used for heads.
I didn’t even think about getting the pistons coated...that’s just not something you normally think about on a 170hp engine :lol: Thanks!

The block is at the machine shop now to see if it is salvageable

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Re: Pontiac engine swap

Post by steve316 » Sun Dec 09, 2018 9:08 am

Not a Pontiac guy wouldn't 350 two barrel run as well as a 301 4 barrel?

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Re: Pontiac engine swap

Post by My427stang » Sun Dec 09, 2018 9:10 am

In 1986 or so, as a high school kid working in a Ford garage, I swapped out a blown 301 for a 389 then a 455 in a 1978 Grand Prix (one of the early small bodied GPs). First time out in the parking lot I killed the Metric 200 as any idiot kid would.

However, I do not remember any significant issues with the swap, I believe it was pretty much bolt in. I think the first version may even have been able to use the 301 manifolds, but I really can't remember the first version details.

I even was able to use the headers off of a 1971 Lemans that engine came out of. That being said, a 389 then 455 with 2.75 gears and later a TH350, a NAPA Performer Plus cam (or something like that) and a Torker intake, was no rocket ship, but could run the highway with the best of them!

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Re: Pontiac engine swap

Post by travis » Sun Dec 09, 2018 10:09 am

We swapped the metric 200 in this car 3 times in 2 years when I was in high school...and that was behind the 301! He eventually put a good built TH350 with a “tire barking” shift kit and a 1800-2000 converter in it, then 3.23 gears replaced the 2.56’s when the rear end got rebuilt. Those 2 changes alone actually made that stock 301 run surprisingly well.

There was “something” about the engine mounts but that may very well have been from earlier years. I just vaguely remember that little tidbit from something I read years ago. It may have have been chassis specific...I just don’t remember exactly.

That 350 2bbl runs perfect, but honestly it is a turd in stock form. The ‘73 Firebird it was in was a beautiful stock restoration...single exhaust and all. The 301 in my buddies GP would have kicked it’s arse :lol:

My friend is going to go grab the car with the 400 in it, yank the engine, and see if it will drop in the 301’s place. If so, then that is the direction he wants to go.

Anybody have any suggestions for a budget 400 Pontiac build?

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Re: Pontiac engine swap

Post by tjs44 » Sun Dec 09, 2018 3:29 pm

There is a issue with motor mounts,the 301 uses a very late pattern on the block and many of the early blocks dont line up.Im not sure what the cure is.Im running into it wanting to put a 301 stroker in a 69 bird.Tom

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Re: Pontiac engine swap

Post by rfoll » Sun Dec 09, 2018 5:37 pm

70 and later have 4 motor mount holes, the extra holes were to allow usage in the later Firebirds. I can't speak to the setup on the G body. Most Pontiac engines used flat top pistons and varied compression by changing combustion chamber volume. Large valve 350 heads could kick the compression up on a 400. There are 455 stroke crankshafts available to fit a 400 block. With a .030" overbore and that crank, you would have a 455. Compression would increase using the stock 400 heads.
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Re: Pontiac engine swap

Post by My427stang » Sun Dec 09, 2018 9:16 pm

travis wrote:
Sun Dec 09, 2018 10:09 am
We swapped the metric 200 in this car 3 times in 2 years when I was in high school...and that was behind the 301! He eventually put a good built TH350 with a “tire barking” shift kit and a 1800-2000 converter in it, then 3.23 gears replaced the 2.56’s when the rear end got rebuilt. Those 2 changes alone actually made that stock 301 run surprisingly well.

There was “something” about the engine mounts but that may very well have been from earlier years. I just vaguely remember that little tidbit from something I read years ago. It may have have been chassis specific...I just don’t remember exactly.

That 350 2bbl runs perfect, but honestly it is a turd in stock form. The ‘73 Firebird it was in was a beautiful stock restoration...single exhaust and all. The 301 in my buddies GP would have kicked it’s arse :lol:

My friend is going to go grab the car with the 400 in it, yank the engine, and see if it will drop in the 301’s place. If so, then that is the direction he wants to go.

Anybody have any suggestions for a budget 400 Pontiac build?
It really couldn't have been much of an issue, because the 389 couldn't have been any newer than 1967, but hey, it's been a long time

I just did a 400, it runs super strong. 67 GTO, 4 speed, 3.23s, we did basically a stock rebuild, but added a custom ground 279 advertised, 224 @ .050 intake, 280 advertised, 230 exhaust, 111 LSA on 107 hyd flat tappet with camsaver lifters, I forgot the lift but it wasn't much, typical Poncho. Most Pontiacs run real wide LSAs and guys have luck with them, but I wanted to try a more "common" cam and it worked great. We also recurved the distributor, bumped up the initial and swapped the vacuum advance to ported vacuum and limited its travel. Again, it loved it. Only other work was a set of long tube headers, the car really runs strong for what it is and behaves nicely in traffic, starts good cold, etc. The 400s don't take much to do well.
70 Mustang, 489 FE, TKO-600, Massflo SEFI, 4.11s
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Re: Pontiac engine swap

Post by Geoff2 » Mon Dec 10, 2018 4:46 am

The later blocks actually have 5 mounting holes per side, early blocks have two. You can buy adapters that will allow a two bolt block to be bolted into a later model car.

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Re: Pontiac engine swap

Post by mag2555 » Mon Dec 10, 2018 6:52 am

Those dam 301s with there Cranks with only single Counter weight at each end where strictly under 4000 rpm motors !
I can't to this day believe Pontiac had a hair Brain idea like that and Balls to slap a Turbo on those things, and this is coming from a Pontuac guy!
There goal was to knock 100 lbs out of the weight of the 350 and 400 cid motors of the day which they did and that was the only up side to those motors!

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Re: Pontiac engine swap

Post by tjs44 » Mon Dec 10, 2018 7:01 pm

The block is a lot stronger than most believe.Big Joe Sherman and I built a 383 301 stroker with a 3 3/4 crank and a set of SD performance #15 heads and it made 478 HP 2 6000 RPMs.This was a true 9.5 CR street engine.They were built for a purpose at that time,fuel economy and nothing else.FWIW,Tom

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Re: Pontiac engine swap

Post by grandsport51 » Mon Dec 10, 2018 8:28 pm

I had some family friends who worked for PMD and they said it was designed to be built as cheaply as possible because

GM wanted to standardize on one 8 cylinder engine throughout the company .

Remember this was just after they had to pay off a class action settlement for putting SBC engines in'77 Delta 88s

Without telling the buyers of the cheaper substitution.


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Re: Pontiac engine swap

Post by mag2555 » Tue Dec 11, 2018 6:11 am

Well Joe must have used the Beefer Turbo 301 block then for it to live at that power level.
I am surprised the with that motors shorter 4.9 whatever inch deck height that you can stuff a additional 3/4" of stroke in there!

Are you sure it was not based off the 1969 303 short deck block?

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Re: Pontiac engine swap

Post by John Wallace » Tue Dec 11, 2018 9:22 am

I believe Tom's 301 was a Turbo 301 block.
He has or had 303 RA V blocks also.
(and other RA V engines)

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