273 Top End Swap

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805moparkid

805moparkid

Slant and AFX Guy
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What is the situation of accessory bolt hole location when swapping 273 to 318 swirl port heads? What would be the casting numbers for those heads and is there a major compression change? looking for about 9.5:1.


also by going to 318 heads what would be a good small port intake?
 
The 273 920 heads are closed chamber just like the 302/308 heads so I don't know if there will be a gain,somebody will chime in with a positive answer.
 
From what I know its all about the heart shaped combustion chamber. The swirl port design makes HP with small ports (1.78/1.50) . The small 57cc chamber should raise compression.
 
A performer intake is a good one for the heads. The 318 302 heads are swirl port and have the harden seats already, win win
 
1970Duster said:
A performer intake is a good one for the heads. The 318 302 heads are swirl port and have the harden seats already, win win
Click to expand...

are these the 57cc chambers? if not what are they? and do you know what the 273 head cc's are?
 
302's are roller cam 318 closed chamber heads
308's are roller cam 360 open chamber heads
 
"302's" have the same chamber volume as the old '920 heads,,,the chamber shape is different, and they have hard seats already. Any small-port 273/318 dual plane intake, such as LD4B or SP2P, works great with the 302's.

302's have the same bolt hole locations as the 920's. When using 302's with stock manifolds, there is some grinding to be done at the back of the drivers head where the exhaust downpipe section passes by the head. You'll need to grind the head as well as the manifold, as just grinding one can cause problems. Also, you need to thread and plug the emission ports on the 302's.
 
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