402 HP and spec question

[big mike]

Can anyone tell me why the 1972 BBC 402 has such a low horsepower rating compared to the 1971 402 motor when both have the same casting numbers on blocks and heads. Is it compression ratio, camshaft, or what?

Will a change in the camshaft on a stock 1972 truck 402 improve the horsepower dramatically? Thanks

[JimKshortstep4x4]

Welcome to the 67-72 truck board from West Michigan!

The horse power rating was changed from "gross" to "net" for the 72 and newer years. The engines are basically the same only the rating system changed.

A cam by itself will probably not help performance because of the low compression the engine has.

Jim

[cdowns]

they changed the way they reported horsepower for insurance reasons back in the muclecar era so your 72 probally has just as much horsepower as the 71 i doubt theres any noticeable differance

[big mike]

Thanks for the replies. I was about to sell this motor off cheap because I thought it was just a boat anchor. Now I feel better about spending the money for a new valve job, a new cam and lifters and an aftermarket intake manifold.

[ofnaman]

I just (2 weeks ago) rebuilt my '70 402 and did a valve job on it and put a good cam in it. I also put an aluminum intake on it and HEI. Same crappy holley carb. I only honed the cylinders and reused the stock pistons. I cannot believe the power difference. If it was not for the crappy carb this thing would run great. Before the rebuild it ran good, I rebuilt it because the #1 cylinder intake valve lifter broke and I wanted to go through it anyway. I would never trash a usable 396 or 402, they are great running engines, and you could easily make a ton of power out of them.

Originally Posted by big mike

Can anyone tell me why the 1972 BBC 402 has such a low horsepower rating compared to the 1971 402 motor when both have the same casting numbers on blocks and heads. Is it compression ratio, camshaft, or what?

Will a change in the camshaft on a stock 1972 truck 402 improve the horsepower dramatically? Thanks

[streetstar]

Originally Posted by big mike

Thanks for the replies. I was about to sell this motor off cheap because I thought it was just a boat anchor. Now I feel better about spending the money for a new valve job, a new cam and lifters and an aftermarket intake manifold.

yep -- its a boat anchor alright. I'll be there tomorrow with $75.00 in my pocket, so have it swingin for me --


just kidding - any big block is worth keeping --

[big mike]

Darn...I misplaced that chain. I guess I'll have to invest some money into it and give it a topside rebuild. Now I need to decide what size cam to put in it without getting crazy.