I have a set of 71 heads that I want to cut down to get smaller chambers. Does anyone know how much volume you lose with how much is cut off the head? For example, if you cut them .020, what happens to the head volume?
Thanks, Jim. How much can be taken off of a 71 head? Is it alright to take a 73cc head down to 68-69cc?
Sure, just make sure you check the CC accurately (with a Burrett) before you start milling. Just dynoed a motor today, with 73 heads, and I had to work pretty hard on the chambers, to get them UP to 68 CC.. These were previously done STG 1 conversion heads, so the size of the valve head comes greatly into play here. Typically, you can wack .030-.040 off an early head, without any trouble. JW
Steve, i "whacked" .060 off my 71 stage 1 conversions on my street car. With my pistons .070 in the hole, i needed to cut as much as possible off to maintain a whopping 8.6.1 compression. I also had the intake side milled so i would have proper alignment with the B4B. Would have been better to deck the block, & have better quench as well, but this was an extreamly low budget engine project. No problems running 12.68 on a 13 year old engine! Randy
Thanks for the info guys... I'm planning on setting the pistons at 0 deck, using 22cc dished pistons, with a .040" gasket, and getting the heads cut down to 69cc, if possible. That will give me 10.37:1 compression, which might be a little on the hot side, but I plan on running a pretty long cam. Where can I buy a burrett from? I'm aquiring tools as I do this project, and that's something I still need to get. The plan is to cc the heads and equalize all the chamber volumes. What is the best value for quench, and how close can you go on a 455? I was thinking of setting it at .035, but I didn't know if this was acceptable on these motors. I've heard that there is a lot of power to be gained from getting the quench as tight as possible. This is starting to get fun now... I just got some money to work with, so now my project might really see the light of day for the bpg nationals! :Brow: :grin: :grin: Randy, I really like your gold car. I saw it up at Thompson a couple years ago... very sharp! If I remember right, you drove it in and swapped on some slicks and ran some respectable times. :TU:
Steve, when you saw "the gold car" i had the good engine in at the time, got a best of 12.10 @ 110.5. i drove it to the track every time! That engine is now in the 68 now. Nothing better than an "all purpose engine" Randy
Good info. Outside of piston height, how far can you safely deck the block? If you have an 'average' engine, say a stock '73 for example, convert to Stage 1 valves, deck the block & cut the heads at aggressive(but safe) amounts what could you reasonably hope for in compression? Obviously affected by piston choice, head gasket, etc., but just a ballpark number?
