Quote:

john, on your 383 in your dart,where your pistons down in the hole? i hear alot of folks talking about poor compression ratio on these motors in factory form. i have 3 complete 383 magnums here(2 are from 2 different 69 roadrunners/ 1 from a 70 super bee) all were very low mile cars,untouched,all stock,and all 3 of them have the stock flat pistons in them and are zero deck.
just curious how much variation there could be.



Technically yes they are in the hole, the CH on the stock 68-69 383 4bbl piston is 1.932, on a blueprint block they are .003 in the hole, the pistons in my Dart's 383 and another 69 383 HP I have are .003 in the hole. With stock heads from the factory which are in the 90cc range, the sets I have had cc'd were 90 - 92 cc, the compression comes in at 9.2 on an actual factory rating of 10.0.

I'm not sure about your 70 383, what's the assembly date, because the 70 383 has different specs per NHRA than the 68-69. Many claim that factory blocks can be as much as .020 TALLER than blueprint , the small amount of engines I have done have not been that high , all have been very close to the blueprint spec so who knows ?

the engine rules for the PS drags are changing for next year , the yare going away from the NHRA specs for a number of reasons and are now allowing as much as 1.5 over stock, but from the conversation I had it sounded to me they would like to see people build and certify to factory advertised which is what I am now doing . If you take a 69-69 383 , putthe piston at .003 to zero , steel shim head gasket and 80 cc heads , depending on the overbore , you can come in at 10.0 - 10.14 , My pistons will have very small valve reliefs and be .002 in the hole , with my heads I should be right at the 10.0.