Opened up my '72 low compression 340 because of a rear main seal leak and now I'm doing a full engine rebuild!! There were lips in the cylinder bores, one of the piston rings was snapped, and there were cracks in the valve seats that are getting ready to enter the water jacket!
I'm looking for some help working out what pistons to buy with the cylinder heads and if the cam and carb are too small. I drive the challenger to work everyday so I get most of my fun in the lower rpm range and I'm looking to build some low end torque, but I can't afford a daily driver that constantly needs filling up on 100 octane fuel either!
The first thing is to bring the compression ratio up from 8.5:1. My summers are about 95F. I considered a full new rotating assembly and stroking it as that would build a heap of low end torque, but that will break the bank too much!
My other thought was that ported iron heads would be better for the low end than new aluminium heads, but I can get a set of assembled edelbrock 63cc 60779 or 65cc 60179 with the extra .060" clearance. I have a friend who will sell me a set of either unused at a really good price. For pistons I was thinking hypereutectic aluminium by KB as I won't be making that much power and don't have plans to go bigger.
If I was looking for about 9.5-9.7:1 would that work on 87 octane pump gas with the aluminium heads and that cam?
To get a quench of 0.040" would I be better off using a flat top piston that sits proud of the block with the 60179 head or a shorter piston with the 60779?
Engine currently
-Bored: 0.030 over for 4.070"
-Carb: Holley 670 street avenger w vacuum secondaries
-Cam: Lunati 10200702. 220 int./226 exh @ 0.050" lift, total lift on stock 1.5 rockers 0.475 int./0.494 exh, lobe seperation 112
-Intake: Eddy 7576 performer rpm dual plane air gap
-Ignition: MSD 6AL, MSD Billet Dist, MSD Blaster 2 Coil
To reuse
-Cast crankshaft
-Forged connecting rods, #3418645 318/360 rods, fitted for 0.9842 floating pins. No offset. (jimynick)
-Stamped nonadjustable 1.5 rocker arms (jimynick)
Other components already on car
Tko600 trans, 4.10 diff gears, 2.5 inch exhaust and some no name aftermarket headers.
Cheers in advance. I've been working through a pile of books on hot rodding and rebuilding small block mopars, but I need some help understanding which way to go with it all!