Quote:
Originally Posted by PontiacJim1959
The #17 heads are shown to be 72CC's and found on the 9.2 compression 350CI. They are most likely about 74-75 CC's as Pontiac added a few more CC's to take into consideration the carbon layer that would build up on the chambers and piston tops with the leaded gas of the day.
The XE cams are good with lower compression builds as they tend to build cylinder pressure, pull hard, but peak out a little early. Ran the XE274 in a 1972 400 with the 7K3 heads and those rebuild kit 8 eyebrow pistons and the engine pulled extremely hard to about 5,400 RPM's and was done - but it would rev to 6K, but it was no longer making power. Had no issues smoking tires with the 3-speed, 3.23 gears, 28" tall tires and ran on regular gas without issue. I would use this cam again on any low compression 8.2-8.5 engine. I would not run this cam in a high compression engine unless I planned on high octane gas or an additive.
The concern for your friend should be the high compression. No problems in my book honing the block with a drill hone/stone if there is little wear/ridge. Have done this a couple times "back in the day" when many of us had no money and freshening up the engine to stop the high oil use with new rings and valve seals was what we did to get more miles out of the car/engine. So go ahead and hone the cylinders, just make sure to be anal at cleaning up the cylinders after the honing to get them clean.
The heads will also have the press-in studs which means being reasonable on lift. If you go over a certain lift on the cam, then you will want matching springs which mean higher spring rates and this could pull studs up. So I would select a cam having a stock lift or a little more, but can use stock spring pressures.
Small valves, screw-in studs, won't provide any big HP improvements, and add to that the high compression and an EX cam spec and you friend is building for disappointment. However, the heads can be upgraded at cost and that's where most will say to just go with the 6X heads and get the compression you need along with the improved upgrades - then he can go with a bigger cam and get more HP/TQ.
So point out that his choice of parts are not entirely compatible and he may wind up with time/money put into the engine with disappointing results.
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Just to back pedal as I let this slip my brain, "Heads are #17 small valve with 7/16 studs and a 3 angle valve job set up by Kaufman"
Ok, so your friend is good to go with higher lift cams, just match springs to lift (and they may alraedy be good to go) and then make sure plenty of valve-to-piston clearance. I believe the consensus is to keep lift under .500" and there should be no issues.
Are the 7/16" replacement Big Block rocker arm studs? I am assuming so since Kaufman set them up. The heads should be using poly lock? This will allow the rocker arms to be "zero lashed."
Yes, CC one of the head chambers so you know exactly what the CC's are and then you can use the on-line Wallace Compression Calculator to get a good idea of what the actual compression will be.