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I'm looking for suggestions on the rebuild of my Pontiac 400 engine from a 70 or 71 GTO. It currently has 'YS' heads which I understand are 96cc low compression heads good for 8:1 compression according to some references and 8.5:1 by the Pontiac specifications. I have read lots of comments on the 6X heads but I guess the YS was not very popular. So, one of my questions is weather this head will be equivalent to the 6X or similar heads. What are the differences and similarities?

Someone suggested earlier to build it up with the Eagle 462 stroker crank and that seems well worth considering. With the low compression are these heads suited to adding a supercharger?

The goal is to run on 91 octane but also lots of street power. It needs to idle decent and be well mannered in traffic. I want power to start at the lower RPMs so the car will pull away hard.

The engine will be followed by a TH400 trans. I don't know which tires yet, but that is the topic for another thread.
 

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Pontiac 400s are one of the best 0-60 engines made.

I would keep it fairly stock. Just build it for torque.

Headers are a pain. The gaskets blow out easy, and they are hard to change.

Block the heat crossover in the heads and it will get you another 20 hp.
 

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400 pontiac Build

I know this has been posted for a while,but it has been my opinion with my own Pontiac blocks that with a set of 87 cc heads such as the ram air 3 or even a good set of 6x heads,with the proper porting and induction,you can get around 400 horsepower with 9 to 1 compression.A set of 6.5 rockers on the exhaust lifters to help get the exhaust out faster is a great way to get these motors to breath a ltttle better,and a good set of headers with some fairly priced gaskets will be a great investment(Remember,a motor is just an air pump),just tighten the bolts again after your first 50 miles of drive time.
 

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Grumpy Old Goat Herder
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posted by firebird red: I'm looking for suggestions on the rebuild of my Pontiac 400 engine from a 70 or 71 GTO. It currently has 'YS' heads

Where did you find a YS head? I didn't know that Pontiac ever had such. If you are saying that the heads are off of a YS block, if the block were a 70 400 YS, the heads would be 13s, if off of a 71 YS they would be 96s.

Bill
 

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Ohio Firebird Member
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my 75 400 was zero decked, 30 off the heads 6x8's, ss valves, 68 N-crank, flat top's, cam intake,headers 73 q-jet carb 800 cfm . dino was at 9 to 1 and 382hp at 3200rpm it goes to 60mph in an easy 5-6 sec.

 
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