My brother just got a crane 227 cam (67* intake closing). The thinnest head gasket we could find that would work with aluminum heads is ".015

With these we got 11.55 static and 9.036:1 DCR. I figure he should be fine on 94 octane since it is only a shade over 9:1 (am I wrong?)

Also the quench would be 45. Any additional cooling needed? He is getting a 2" cowl and I told him to use water wetter. He has ceramic coated headers.

Would the dcr change with the addition of 1.6rr's? His motor and heads are stock. We used 54.5 cc for cylinder head volume but there appears to be dissention on what it is. Used 4cc for piston reliefs.

Here is the calculator we used http://kb-silvolite.com/calc.php?action=comp

Also, would a mail-order tune be adequate or does he need a dyno tune (he is leaning in that direction anyway). Is a tune absolutely necessary (as he will have to drive the car to the dyno if he goes that route-would he be okay driving it untuned?)

 

Well until we measure them we played around with 58cc combustion chambers and 4cc reliefs and the dcr with that is 8.6

If indeed they measure 58cc is 8.6 dcr safe enough for 93/94 with 45 quench? Should he get a 160* stat? If someone could tell me if my figures are right at least I would greatly appreciate it.

Assuming that we get no detonation will an increased dcr shorten the life of the engine running 8.6 (is high dcr bad for the motor in terms of wear even if you get no detonation?)

 

You will need to measure the heads and pistons. The Dart Pro 1 heads I have were supposed to be 64cc and are so marked on the ends. Turned out they were over 69cc. I had them milled and was told they were now 62cc. I have a friend with the equipment and we measured them twice and they are 64.2cc.

The flat top Speed Pro pistons I bought were advertised to be 3.4cc with the valve reliefs. We measured 2.8cc. That turned out to be good because it helped balance the bigger than thought head chamber. Bottom line is you have to measure. I'm going with a .35 quench, 10.74cr and 8.48dcr and 91 octane. This is a first gen. 355 motor.

Wish I could help answer your question but I don't have the knowledge. If the DCR turns out to be to high you can retard the cam a couple of degrees. I will retard my 218XFI cam 3 degrees to gain more power above 4000rpm. I'm not loosing that much below 4000rpm and the trade off is worth it. The above measurements include the 3 degree retard and has my cam closing 66 degrees ABDC. Hmmmm, that is close to yours.

 

thanks. they are stock lt1 (96/97 castings) heads and pistons. We really only plan on cc'ing the combustion chambers and figure polishing will take a little more out of there. With polishing we figure we will be just under 9:1 or less. I just don't want the motor rattling apart (I have heard that the pistons rattle even though no detontation is present with DCR??.)

 

When playing this close to max DCR ya got to measure EVERYTHING to get it correct.
9.0 DCR can be run with a GOOD dyno tune and a bunch of tweeking to get it right.