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A 273 cylinder head question.
I was thinking about going with a 1.94/1.72 valve combination. I am building a 10.1:1 .030 over 318 with a 228 deg @ .050 .488/.488. 108deg CL Mopar Cam. Also, I would like to mill out a set of 273 heads to do this (I want to keep the closed chamber for compression and I have read that with some work to the runners, the 273 head does wonders). How much metal can I take off of the head, in all places. Whare and what should I watch for. How should I port them out also. I have noticed that in the April copy of Hot Rod, they milled out, shaved, and ported a set of '302' - 318 heads, like mad, to accomodate a 2.02/1.88 combo. Thanks.
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You need to talk to "cuda66273", he is using 273 heads on his bracket barracuda w/318.
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Yeah, hopefully he will run across this post. Thanks.
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I'm not familar with that write up. Those exhaust valve sizes look like big block sizes.
The 318 cam stock with 1.50 and the 340-360 with 1.6. These sizes are good to support big HP gains. There is also a problem with fitting these extreme size valves in the head. Theres not enuff room. The first 2 years of the 273 have small and off angle bolts for the heads to intake. An angle off the head itself is also not like the standard. You'll need to find a very special intake for these heads. Edelbrock did make such intakes for the 2 year run 273. |
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Quote:
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Gordonhill
There has to be a mix up on the valve size. 2.02 intake valve with 1.88 exhaust valves will require a valve guide spacing of 1.97" and push the exhaust valve way off center of the stock 273 port. A 1.625 exhaust valve could work with some work, but things will get tight. When the block is decked and the head is milled, any big cam will require some serious notches in the pistons. The problem with the 273 head is the port gets small at the entry to the bowl where the air needs to slow and turn down. The port restriction at this location increases the air velocity and does not allow the air to follow the floor of the port. To help slow the air down, the port needs to be raised and widened in the area on the port side of the valve guide. The guide can be contoured for better flow as well as 11/32 valve stems used. The pushrod pinch is not as big a problem as the port pinch deeper in hte port. Billy |
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I guess not many has ever used the 1.92/1.74 combo. 2.02 just seems like too much and then there is shrouding. Remember that I am also running an advertised 268 duration cam and I am also running flatops. I would'nt think that valve clearance would be a problem. Anyway, how much meat do we want to take out of the port, bowl side? Also, I have noticed that Hot Rod magazine opened up the valve throat quite a bit on those '302' heads, which are similar to the old '315' castings. Do you think we could do the same? I do have two sets of 273 heads. Actually three including the ones on my Barracuda. I do have some room for a catastrophic porting error. Thanks for the info Billydelrio! |
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