The heads are off, swap them or not..

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They're stated to have around 57cc chambers according to my research, with most other heads being 67cc or larger. These are '67 920 heads. The 318 heads I have state that they're a 63cc chamber I think, but guys say they CC around 65-68cc on average. I'm not sure how much better non magnum 318 heads would flow, the heads I have look identical aside from the chamber. I may even do the porting myself since this is a low buck non permanent engine. Valve springs should be here today and I'm going to try to take the heads for their machine work tomorrow so hopefully we'll know how they do before too long. I just hope I don't have to invest too much in the 273 heads since they need a full rebuild.

I'm assuming I'll just need to do new guides, hardened seats, milling, valve job, plus seals and I guess I'll go ahead and do new locks plus the comp 901 springs.
 
I did, about five times, it's great! That's what inspired me to do my own porting on this budget setup. Looks like I'm going to pay about $400 at the machine shop for head work (just dropped them off) so the savings on the porting is very welcome even if I don't get it perfect. I'm really excited to see how this turns out, especially since it seems that the 273 heads aren't a swap that's done too often.

Here they are before cleaning....I'm picking up tomorrow to do the porting then back for guides, hardened seats, milling, 3 angle, etc. I'll be re-using the stock (~2000 miles) valves and retainers from the current 318 heads with the new comp springs.

img74781.jpg
 
It is interesting to note that while HP and torque improve with porting, it takes more RPM to get it. Unfortunately, while I can see the curves on the charts, I can't read them. What are the HP and torque readings @ 2500 rpm? @ 3000 rpm?

The early heads have the smallest chambers, followed by the 302s. While the 318 cop car heads have the biggest valves, they also have the largest combustion chamber volume. (Seems weird to me as the bigger ports and valves give more power, the big combustion chamber with a flat top piston gives it away.)

In the Edelbrock line, the Performer matches up with small valve LA heads the best. The Performer RPM or Air Gap is better suited to the big valve heads.
 
How about head gaskets ?
I would start looking for the thinnest gasket available,to boost compression.
 
Johnny Dart said:
How about head gaskets ?
I would start looking for the thinnest gasket available,to boost compression.
Click to expand...

I'm pretty sure I should be getting at least a point bump already. The cost of thin gaskets makes them out of the question for the budget build, the $ to HP ratio isn't there for me. I'll see if I can't get these CC'd so I'll have a better idea of my compression once they're done. I'll be really happy if I can get between 9.5 and 10.
 
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