#1  
Old 09-12-2021, 08:34 PM
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Default Pontiac V8's from another model Pontiac

I keep hearing references from GTO, LeMans and Tempest owners putting down engines from full sized Pontiac's and Grand Prix's. What's the reason for the put downs?

  #2  
Old 09-12-2021, 08:46 PM
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That’s where almost all the 455s and all the 428 and 421 engines come from, the big Pontiacs.

It’s the big Pontiac enthusiasts that decry the cannibalism of their favorite cars just so we can have their engines. I haven’t seen anyone putting down engines that come from full size cars, we like taking them.

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  #3  
Old 09-12-2021, 08:56 PM
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Default Engine Differences

I'll take a stab at this one, as I'm sure others will.

(1) SOME big car engines had smaller valves & cams than the same size engine in say, a GTO, of the same year model.

(2) I've read that SOME non-high-performance Pontiac engines actually came with lower quality engine bearings, than those that came in the higher perf engines that came in some Birds & Goats.

(3) SOME of the Bird & Goat engines came with 4-bolt main caps. MOST big car engines did not.

(4) BUT, I've noticed that SOME of the Grand Prix engines look to be almost identical to those that came in Bird & Goats that same year.

I'll edit this & post links to some info that may help show some of what I posted here.

OK, Here's a perfect example: In '69, the 350hp GTO 400, the 350hp GP 400 & the Bird 330hp 400 specs are almost identical. They can all use the big valve heads.

http://www.classracerinfo.com/Engine...4&MAKE=Pontiac

http://www.classracerinfo.com/Engine...3&MAKE=Pontiac

http://www.classracerinfo.com/Engine...9&MAKE=Pontiac

BUT, the big car 340hp 400 uses #46 small valve heads & a smaller cam.

http://www.classracerinfo.com/Engine...1&MAKE=Pontiac

Yeah, I realize these are NHRA legal specs, for Stock/SS drag racing. But, I think it gets the point across. The big B-body cars came with lower performance engines, in most cases.

This was NOT the case, with the hp 428 engines, since those never came in a Bird or Goat.

http://www.classracerinfo.com/Engine...9&MAKE=Pontiac

Then the 455's came along in '70. The 360hp B-body 360hp 455's show to have small valve heads. The 360hp 455 GTO engine shows to have big valve heads.

http://www.classracerinfo.com/Engine...9&MAKE=Pontiac

By '73, all the D-port 455 specs look about the same.


Last edited by ponyakr; 09-12-2021 at 09:45 PM.
  #4  
Old 09-12-2021, 09:14 PM
tom s tom s is offline
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ALL 421s were 4 bolt engines.I think 428s were only avail in big cars?Tom

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Old 09-12-2021, 09:51 PM
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"...engines from full sized Pontiac's and Grand Prix's..."


So, is a '69 -'77 GP considered a "big car", or an A-body, or does it have it's very own designation ?

"...The G-body designation was originally used for the 1969–1972 Pontiac Grand Prix and 1970–1972 Chevrolet Monte Carlo personal luxury cars, which rode on longer wheelbases than A-body coupes.

For 1973, the Grand Prix and Monte Carlo were folded into the A-body line, with all formal-roof A-body coupes designated as A-Special (and, after 1982, G-Special). These special coupes included the Monte Carlo, Grand Prix, Oldsmobile Cutlass Supreme, and Buick Regal.

For the 1982 model year, GM introduced a new front-wheel drive A platform for its mid-size car lines. The rear-wheel drive platform that had been in use since 1978 was re-designated as the G platform, and select models remained in production..."

Most of the junkyard 455's I bought came out of Grandvilles.


Last edited by ponyakr; 09-12-2021 at 10:09 PM.
  #6  
Old 09-12-2021, 09:52 PM
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Quote:
Originally Posted by tom s View Post
ALL 421s were 4 bolt engines.I think 428s were only avail in big cars?Tom
100% correct on both counts.

Quote:
Originally Posted by ponyakr View Post
"...engines from full sized Pontiac's and Grand Prix's..."


So, is a '69 -'77 GP considered a "big car", or an A-body, or does it have it's very own designation ?
They’re G-bodies by designation but are essentially stretched wheelbase A-bodies under the skin. For the purposes of this discussion they’re big Pontiacs. 428 and 455 engines were available n some of them.

A-body folks also like pirating the front disc brakes and rear ends out of them along with the big cube engines. The front spindles interchange due to their A-body roots, same for the rear ends. The ‘68 and earlier big Pontiacs (B-body) share nothing chassis-wise with G or A-bodies.

The G-body GP at least in the earlier years had base 400 engines that were pretty much on par with base GTO 400s, but in most cases came with one size smaller camshafts even though horsepower ratings were the same.

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1964 Tempest Coupe LS3/4L70E/3.42
1964 Le Mans Convertible 421 HO/TH350/2.56
2002 WS6 Convertible LS1/4L60E/3.23
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