i have a 66 383 2 barrel engine. to my understanding it should have 9.2:1. 4 barrel has 10.0:1.i have 516 heads i beleive.so the first question is what are the deck heights below the deck between the 2?im gonna do a garage rebuild on it.the machine shop is only gonna fix what needs to be fixed mainly to clean it and check for cracks.i will either use the 516 heads or get some 452 later heads. 2nd question is which should i do deck the block to acheive the distance of deck height of the 4 barrel version or shave the heads?i would like to run the 452 heads because of the unleaded seats and better flow.or to reach atleast the factory 9.2:1 compression so i wont loose that compression going to the open larger chamber heads?i am also planning on running the comp xe268h cam kit the one with cam lifters double roller timing chain ,valve spring etc..rpm intake,1406 eddelbrock carb,its going in a 66 newport 2 door tank lol.im sure it has highway gears its also a peg leg i know this because i smoked out the block this morning.id like to keep as highway freindly gears on it as possible.they say the cam will be ok with stock stall.how to i balance this out with this heavy car, highway gears and choosing a convertor to match?oh and i have stock manifolds which they say is good with a split duration cam.if i left any info out let me know.thanks will

The factory overstated the compression ratio, a 66 with closed chamber heads probably has a piston that is .080 below the deck, you do NOT want to cut the block that much.

I'm unsure what they did in 66 , but for 68-69 they had the same stated compression ratios for 2bbl and 4 bbl and the pistons had the same compression height between these two engines, the difference was the 2bbl piston had a dish to lower the compression. Your engine probably has closer to 8.0 compression, using 452 will make it a lot lower, it would be cheaper and better to just put hard exh seats in the 516's and install 1.74 exh valves at the same time .

well thats gonna suck if thats the case lol.i hope there is no dish but im not gonna count on it or find some std bore 4 barrel pistons

The 68-69 pistons in the 383 Mag were .020 above deck, which, when combined with the 906 heads gave
a cr figure very close to 10.00 to 1. The 67' and earlier 383's, 2 or 4 bbl, were right around 9.0 to 1 range with 516 heads. One problem is that you cannot put the 516 head on the 68-69 383
Magnum, (ONLY with factory pistons) WITHOUT checking deck height FIRST (closed chamber head vs open chamber head) since there may be interference with the higher compression height on those year only factory pistons. Otherwise, 516's aren't a bad way to make some power, you just can't make the bigger numbers like with the 906's and later heads WITHOUT doing some extensive rework to them.