1972 GTO engine swap 400 cu. in.

[Fecklar]

Hello,

I was wondering if anyone could give me some advice on my 1972 GTO. I bought a 72 GTO that had a 400 cid engine in it at one time. I bought the vehicle with no engine. My neighbour has a 400 cid engine from a 1978 Firebird that he is willing to give me. I would rebuild it of course. I got the following info online and was wondering if there is any way around this?

"In 1977, the Pontiac 400 block was cast with revised motor mount bosses, and will only mount in late Firebirds or Grand Prixs."

Thanks in advance for the help.
Steve

[MrPbody]

Yes, Ames Performance and Performance Years both sell the "adapter" kit.

The post-'75 400s use a weaker block than previous versions. As long as you keep power under 550 HP and revs under 6,500, everything should be fine. Unfortunately, that '77 400 will be a "stone" compared to GTO engines. It CAN be upgraded to perform well, but it NEEDS attention!

I recommend Jim Hand's book "How to Build Max-performance Pontiac V8s", published by SA Designs. This is the only current study of the ol' Injun available today.

Jim

[Fecklar]

Thanks for the great advice Jim. I think I should stay with the stronger block. Would a 400 cid qualify from a 1975 Bonneville. I can pick one up for about $350.00 with 77,000 original miles on it and it has never been bored over. Or is that still the same as the 1978 Firebird 400?

[MrPbody]

Mid-75 was the "change". The casting number of the block should be readily visble on the passenger's side rear, above the bellhousing "flange". The "good" block number ends (last three digits) in "988" while the thin-wall is "557".

Unless you're going to plan a "future build" with lots more power, either block will do fine.

Jim

[Fecklar]

Thanks again, I will buy the book and I got the "988" block.