Swapping '69 273 with '84 318 Into My 1969 Dart

CudaRay said

I appreciate everyone's help thus far, thanks for working with a complete newbie.

I am struggling to understand the compression situation. All the information I can find on these pistons are flat top, at most a 4cc dish. If I was to use a steel shim at .028, assuming a deck height of .069, 70cc for heads, and 4cc for the pistons, I am getting 8:1. Taking into consideration altitude as mentioned it will be even less.

With flat pistons, and .020 shims (as claimed with Fel-Pro 375-SFL8553SP) I am getting 8.44:1 before taking altitude into consideration.

I am just looking to get ~230hp out of this to match what I suspect the 273 had on a good day. And again, I'll be using a edelbrock performer intake and 4bbl carb to help out with that. Headers as well if they'll fit.

Am i getting closer on this, or still way off?

Click to expand...

If your 318 is factory (1984) your pistons should be pn 3698571 with no valve reliefs (flat) and a 1.74" Compression height. considering an aftermarket performance piston is 1.81" compression height that's close to "zero deck" you get the picture.

FWIW I have an 80's 318 like yours that has been "re-ringed" and uses the 1.74" compression height pistons along with 2843675 casting 318 heads which have 1.78/1.50 valves and 69cc chambers. Turning a Delta Cams 211/218 cam 425/435 lift on 112lsa with a cast spreadbore intake and a 800 cfm Quadrajet calibrated for 4700'.

The engine pulls my 1/2 ton Power Wagon down the interstate at 85+ with no more than 1/3 throttle. It doesn't blaze the tire, but its got plenty of power to pull the 5000# pig around with 3.55:1 and 29" tires. We use it at 7000' and it wheels fine. No reason to hate on a 318.

Good luck with your project.