A little help with a 400 cu. in. - Pontiac GTO Forum
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post #1 of 3 (permalink) Old 02-14-2014, 03:36 PM Thread Starter
 
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A little help with a 400 cu. in.


I could use some help and info on my 400. build date B063, casting #481988,
stamp on front 516672 under # YT.
The heads build date B032, casting #7M5
The intake build date B193, casting #494282,fire order 18436572
The exhaust build date B223 casting #490 142-8 & #490 143 2
Know reading a lot of threads here I've learned a lot, some of you guys really have a wealth of info. and its been very helpful!!
I got the build date down like B063 is Feb.6th.73
The YT under the stamp # I think is a 400 from 72,73,74
And the heads 7M5 are off a 455 I think?
Know with this info. before I start tearing it down for rebuild, is what I have worth the effort? And would I be able to get 380 to 420hp.
Any help will be greatly appreciated, Thanks Mike
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post #2 of 3 (permalink) Old 02-14-2014, 08:54 PM
 
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I'm using a 481988 block for a 461 stroker engine, year 71. They are good blocks.

The ones to stay away from are the 500557 blocks. They were designed with less material in certain areas to reduce weight which makes them weaker and only can handle about up to about 400 hp.

The 7M5 heads are from a '72 455 and should be 114cc. They made about 250hp on the 455 that year.

With the right head/cam combo you can easily make your hp goal.

I would look for different heads. Some of the heads will require dished pistons to keep the compression ratio down. The iron heads need to be around 9.5:1 to keep detonation from happening. Aluminum heads 10.5:1

I'm just learning myself and I'm sure more will chime in on suggestions. Happy building!
-Norm
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post #3 of 3 (permalink) Old 02-15-2014, 07:48 PM Thread Starter
 
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Norm,
Thanks for the info, I'll start looking for some different heads. any idea as to some #'s.
As for the intake should I keep the Q-jet, or replace intake and go with a holly? And what about cam and or pistons? Well thanks for any help. Mike
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  Pontiac GTO Forum > The 1964-1974 Pontiac Tempest, Lemans & GTO > 1964-1974 Tempest, Lemans & GTO General Discussion

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