milling heads, how much?

[coach71]

I havea a set of 360heads, #596 how much can they be milled, just for resurfacing without having to do the intakd side? also I think I read somewhere that for each .010 you take off the bottom you need to take / .0095 off the intake is that right? They are going on a 318, would milling them .030 help much on the compression? also does more compression = more gas/ less fuel mileage? I ask because in the 70's the mfg all lowered comp ratios and I'm not sure if it was for economy or so the hp #'s would come done( ie. insurance) can someone clarify that for me,
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Thanks for any and all replies and assistance.

[Steve Lahey]

COACH - I can't tell from your post what vehicle you have but I did the same thing to a '69 Dart with 3.23 axle behind a 904.
BEFORE: 318 motor with 340 cam and Edelbrok single plane & 600 Holley.
AFTER: 360 heads milled 0.030, same cam, E'brok dual plane & same Holley.
RESULTS: stronger midrange and no change in mileage (16-17 on highway).
BTW: you are correct on how much to remove from intake side of head.

[PLUM CRZY]

Hey Steve....that combo you have (318 w/ 360 heads) how is the the performance on the bottom rpm range of that motor say 1500-3000? I was consideing doing that to a 318 i have. With the additional port volume and cc size of the chamber i thought it might ruin the bottom end.....

[Steve Lahey]

PLUM - while milling I also ported & polished, netting around a 66 cc chamber. It's a little slow off the line but I'm running 235 R70 X 15 tires on the rear. I didn't set it up for the strip but a road cruiser instead. At 60 mph it turns ~2600 rpm and from 50-100 it is quick. Hope this helps & good luck.