Hello everyone I have some questions about how static cr & cam timining adv/ret affect the dynamic cr of an engine. I was using the calculators here on the board to see if my 383 would be ok on pump gas but I'm confused. When I calculated the static cr it came out to 11.5:1 and when I used this along with my cam's intake closing point of 44* abdc the dcr caculator showed my dcr to be 10.44, or way over the magical 9.0 dcr for pump gas.
When I assembled my engine my machinist told me to retard the cam 4* to help reduce the cylinder pressure so I did, as well as to reduce the low rpm tq for better traction with my 700R4 and 3.89 gears. Anyway here is all the info on my engine/car: 87 Monte Carlo SS Aerocoupe
383 carbed LT1 11.5:1 cr, 6" rods, 3.75" stroke, GM 847 cam, Rollmaster billet timing set, R-series roller lifters, home ported LT1 heads 2.02/1.57 Manley valves Crane dual springs, home ported LT1 carb dual plane intake BG 750dp,Milodon oiling system.
SRP ft 5 cc valve reliefs pistons .013 down the bore, .039 head gasket, 59 cc chambers in the heads 6" rod 3.75 stroke.
Someone else told me to go back and advance the cam 4* but when I ran my combo thru DD 2000 it showed the most hp/tq with the cam retarded 4*, can any experts enlighten me please.

 

The motor is not going to like the cam retarded 4 degs.

If anything put it in dot to dot which is +4.

BTW DCR is based of seat to seat timing so you can't set it based on the .050 IVC that's going to show you some stupid high DCR.

11.5:1 and a 847 cam on a 108 ICL will be fine.

Advance will increase the DCR and retard will decrease it.

I would also look at a impala head gasket for your motor since you have the pistons .013 in the hole already. That would give you a .040 quench which is really dam good.

Bret

 

Thanks SStrokerace, I'll go back and install the cam straight up while it's still on the stand, the head gaskests I'll just have to live with until I get the money to get my AFR 210's done then I'll switch them.