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#1 |
Registered User
Join Date: Jan 2008
Location: kansas city
Posts: 3
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402 HP and spec question
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 |
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#2 |
Senior Member
Join Date: Jul 2001
Location: Muskegon,MI,USA
Posts: 6,026
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Re: 402 HP and spec question
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
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1971 Shortbox step side 4x4, 350 sbc, 3:07 rear end 1965 Impala SS 400 sbc, Muncie rock crusher 1966 Impala SS 396 bbc, TH 400 1969 El Camino, 350 sbc, TH 350 1971 Snowplow built on a Blazer frame 1972 GMC Short bed, stepside, TH 400, 427 BBC |
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#3 |
Senior Member
Join Date: Jan 2003
Location: daytonabeach
Posts: 22,956
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Re: 402 HP and spec question
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
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71c-10 350/2004r/4:11 lowered3/4 longbed/dead by hurricane MEANING OF DEATH::::: SOMEBODY ELSE GETS YOUR STUFF DONT BELIEVE EVERYTHING YOU THINK TAKE MY ADVISE;I DON'T USE IT ANYWAY |
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#4 |
Registered User
Join Date: Jan 2008
Location: kansas city
Posts: 3
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Re: 402 HP and spec question
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.
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#5 | |
Registered User
Join Date: Aug 2007
Location: reno
Posts: 397
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Re: 402 HP and spec question
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.
Quote:
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A sweet 2000 Deville..... |
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#6 | |
Registered User
Join Date: May 2007
Location: Moore, Oklahoma
Posts: 2,396
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Re: 402 HP and spec question
Quote:
![]() just kidding - any big block is worth keeping --
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Are you retired too? Nonsense! I'm in my prime |
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#7 |
Registered User
Join Date: Jan 2008
Location: kansas city
Posts: 3
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Re: 402 HP and spec question
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.
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