Wow! I sure did some responses that set off in all different directions! Maybe I will give more information and maybe someone that has pulled a 1972\1980 318 can give me an answer!
I have a 410 hot rod engine in my other car that runs low elevens and gets 23mpg on a run.
It is a 410 with 11/1 comp with forged pistons ,I beam rods, trick flow heads and a 340 victor port matched with 5 speed manual trans and 3.91 diff.
This is my other car that has 55000 miles on the clock and is a 1973 Australian Valiant charger 318 auto with air and steer and looks and drives like new with 95% factory original paint that is as good as the day it was built!
As a car like this is worth over $100 grand in aus I do not want to hot rod it but just keep it looking std but with a bit more poke. I have a spare set of heads that I have already worked on the ports and bowls and have ordered a set of 1.880 inlet valves and will be sending them to my head machinist that I have known for about forty years that will do a good 5 angle valve job and reduce the chambers to about 56CCs.
I am getting a roller camshaft and lifters for it but Mike at B3 needs to know a rough idea of compression to design a cam that idles like stock and has good low end response for me.
This car will have 360 exhaust manifolds and a 2.5 inch single system. The car at this time has a edelbrock performer manifold with an AVS2 500 on it but still sports the original 318 Fireball air cleaner that makes the engine bay look like stock.
I do not want to pull the heads off and let this car sit for months on end waiting for the parts to arrive from the USA.
All I am asking is has anyone measured how far in the whole was there 1971/1980 model 318 to find the average number that I can expect.
The small block mopar engines book that I have states the 1972 engines were .056 in the hole but I tend to think that they are generally further down and our Australian spec sheets on our 1973 318 says 8.2 to one compression. I will be machining down the heads to attempt to get about 56CCs and hopfully closer to near 9 to 1 comp.
Have a nice day!
