[Louis]

My Chilton shows a 455 with 390 h.p. for 1970, did this motor ever make it into the Grand prix,?I 'm looking at buying a 70 SJ grand prix with the 455,any one knows if they are rare,how many produced? it's automatic.

Louis

[Louis]

My Chilton shows a 455 with 390 h.p. for 1970, did this motor ever make it into the Grand prix,?I 'm looking at buying a 70 SJ grand prix with the 455,any one knows if they are rare,how many produced? it's automatic.

Louis

[GP-K]

Louis,

Don't trust the Chilton manuals. The 455 in the GP was 370 HP with 500 lb ft of torque. The true HO disappeared entirely in '70. The only cars (in '70) with anything like the HO manifolds, HO cam, etc. were RA III & RA IV F and A bodies (Firebirds and Lemans/GTOs). The '70 455 is still a great engine. It was the only year the 455s came with high compression. The engine was very similar to the 370 HP 428 from 1969, just torquier.

There were about 65,000 GPs made in 1970, and about 1/4 of them were model SJ's.

If it is in pretty good condition, I'd buy it if had the opportunity.

Good Luck,

K.

[Louis]

Thanks for info,This 70 SJ I'm interested in buying is supposed to have the original engine,on the original bill of sale it says SJ option but no mention of engine size at all,does SJ mean it had to come with 455 370 h.p. and 12 bolt rearend or did sj's also come with 400 cu.in. and a 10 bolt? Also it is strange the 455 is only rated at 370 h.p. since it has 27 cu.in. more than the 428 which was also rated at 370 h.p. it should have an extra 20 h.p. due to extra cubes since it has basically same heads,valve size,manifolds,comp ratio.(4 bolt mains?)what's choking it up ?

[Louis]

Thanks for info,This 70 SJ I'm interested in buying is supposed to have the original engine,on the original bill of sale it says SJ option but no mention of engine size at all,does SJ mean it had to come with 455 370 h.p. and 12 bolt rearend or did sj's also come with 400 cu.in. and a 10 bolt? Also it is strange the 455 is only rated at 370 h.p. since it has 27 cu.in. more than the 428 which was also rated at 370 h.p. it should have an extra 20 h.p. due to extra cubes since it has basically same heads,valve size,manifolds,comp ratio.(4 bolt mains?)what's choking it up ? Why are all those G.P.'s green whith black vynyl top? I also have a 69 same colour.

['ol Pinion head]

Louis,
The '70 SJ's came std with the 455 & the 12 bolt Pontiac housing'ed Chevy rearend. The SJ's all got Rally guages & the leveling control setup & factory SuperLift shocks on the back.
The blocks were 4 bolt & the topend carried the 64 casting heads. Compression ratio was adverised at 10.25 to one but was actually about 9.9 to one. The manifolds were the standard log type manifolds, not the RAIII units. The automatic cam was the 067 (P) cam, never owned a WG with the 068 cam... I've parted 5 of these with original engines.

The 455 370 horse engine was available in the Model J's also. Currently have one of these model J 455 cars.

IMHO, the 455HO moniker is a misnomer. These just aren't as strong as the 71-72 455 HO roundport engines. Without better flowing heads, the RA manifolds AND at least an 068 cam I could never understand the sales literature & orderforms calling the '70 455 big valve engine an HO engine. I will assume this HO moniker was used to separate it in the publics eye from the small valve 15 headed Bonneville 455 engine. This HO moniker was especially important in marketing the 455 GTO in it's first year what with both the 455 GTO & the Bonneville being rated at 360 hp.

Colorwise, Green & Gold were popular colors for the '70 GP lineup.

If the car is clean & reasonably priced, I'd buy it too. [img]/infopop/emoticons/icon_smile.gif[/img]

[This message has been edited by 'ol Pinion head (edited 11-21-2000).]

[Half-Inch Stud]

I've had 2 YK 428s. Motors Repair Manual 1971 shows them to be 390hp.
Long branch manifolds, 48 heads, 4bolt, 068cam, ...shows the 70 455HO at 370 HP.