Boned up on a car purchase, need a 428/455
 

I bought this car at Mecum last week:

https://www.mecum.com/lots/FL0117-26...e-convertible/

It's clearly advertised as a 400, which I ignored, because the 428 was standard. And to be sure, I had the car documented by PHS and they said 428 multiple times. And the previous owner confirmed it was the original motor. I didn't go to Florida to check it myself, took his word it.

The seller was right, it's the original motor. But it's a 400. How did that happen? There was a ZERO COST option to downgrade from the nice 428 down to the 2bbl 400 economy motor. Since it's a zero-cost option it doesn't show up on the PHS invoice, so they incorrectly decoded it as a 428. While that annoys, I'm not a "sue PHS for my pain" kind of guy.

End of the day it's on me for not checking the numbers in person. I get that.

So that all aside, if I want put a motor in the car, should I:

a) stroke the current 400 out to 460 and put a 4bbl on it, maybe decent heads
b) find a 428 and do a completely stock rebuild on it
c) find a 455 and build that, convert it to multiport EFI, but badge it as a 428 and drive it

The irony is that since PHS docs the car as a 428 I could lie from here on forward, but I'm not -that- kind of guy either! If I don't stroke the 400 I'll hang onto the original motor.

Or, of course, I could just drive it with the puny 400. But I want a torquey land barge.

Re: Boned up on a car purchase, need a 428/455
 

Nice car.

Re: Boned up on a car purchase, need a 428/455
 

If it came with a 400 originally it should have the vin stamped on the block (making it a numbers matching car). If you put in a 428 the vin will no longer match (not a numbers matching car).

I think I would keep the numbers matching 400 and beef it up ( a little or a lot!)

Good luck, Rg

Re: Boned up on a car purchase, need a 428/455
 

I vote "a"...the stock 400 will feel pretty weak in 2017 terms, but adding some select parts will fix that.

Re: Boned up on a car purchase, need a 428/455
 

Not sure if this helps or hurts
https://tallahassee.craigslist.org/cto/5964846823.html

Re: Boned up on a car purchase, need a 428/455
 

That's a beautiful car! It's your car do what makes you happy.

If it were mine, I would leave it as is and enjoy it!

Re: Boned up on a car purchase, need a 428/455
 

That's exactly what I would do, and just cruise it. Beautiful Poncho!

Re: Boned up on a car purchase, need a 428/455
 

The 400 is going to feel like quite a sled. It shouldn't be that hard to put topgether a Ram Air III engine for it. The Ram Air III in the '70 Trans Am was rated at 345 hp. The same engine in the GTO was rated at 366. Corporate rules. It was 400 CID with the small mains that had far less drag than the 3.250 mains in the 455. The 455 was rated at 370 hp.
I put together a 428 engine from the SJ Grand Prix that I ran in a '70 Trans Am. With the Pontiac 9068 camshaft, the car got 16 mpg on the freeway and 13 mpg at 100 mph. it topped out at 145 mph and had great torque.
I transplanted a 455 into a Grand Prix that had a 389. It went from being a slow boat to slightly faster boat.

I also ran a 455 in a flatbotton boat. I ran a flex plate instead of a flywheel. It seemed to break a piston skirt every time that it came clear out of the water. They didn't have rev limiters back then. I had a set of Ram Air V heads but, never put them on. The good old Poncho days

Re: Boned up on a car purchase, need a 428/455
 

I find the car interesting as is, yet like most would prefer the bigger more powerful engine. However I would consider a gear change to get the torque "feel".
Had a 69 Impala SS427 with 2.56 or some such super high gear. Also had a 69Caprice 396 2 bbl carb car. It would have taken the Impala in the eighth mile no problem. On the freeway open the Qjet and the extra cubes would eat the Caprices lunch. :chevy: You get the idea.

My point is a gear change would get you the performance you crave yet retain the unique history of the car. A O/D transmission wouldn't hurt either.
Just a thought.

Re: Boned up on a car purchase, need a 428/455
 

Finally got the car and decoded the engine... not great. It's a 1976 Pontiac 400 with about 7.5:1 compression. At least the 6X-8 heads are decent, though they have huge chambers.

So odds are this car was born with a 428/360 but it went away at some point in it's life.

My plan is to fix all the little things wrong with the car (heater blower, a few power windows, that sort of thing), then decide on the motor. But I'll get everything else working properly first!