Howdy all

I'm collecting parts for a 383 build.

I have a 383 block, .005 deck height, line honed, and AFR Eliminator 195 heads. Will be picking up an HSR as well.

I had picked up a Comp 268XFI roller cam, and had planned on using 12cc dished pistons to get a comp ratio of 10.1:1. with a .038/4.060 gasket, quench is .043 and the 268 gives me a DCR of 8.22.

I have been considering changing up to a 7cc flattop piston and using a 280XFI, bumping compression to 10.66:1 and a dCR of 8.27.

My questions were,

is 10.7:1 going to be pump gas friendly?

How much low end will I lose 268 to 280, if any?

Should I be upgrading the springs on the AFR's regardless of which cam I finally go with?

Thanks ahead of time.

~GP

 

when you know your DCR, you use that to determine octane requirements. SCR is no help to you now that you have your DCR figure.
Your loss of low rpm torque to the 280 is going to be nearly no loss at all since you are maintaining the DCR.
IDK the AFR spring specs off the top of my head, but they aren't beehives, so I would switch to COMP 26918s, and you will need LS1 retainers and locks because AFR is now using 8mm stems in their SBC heads.
The main advantage of the beehives is that they don't have any natural resonant frequency, thus you never get spring surge, so you get fewer and smaller dips in your torque curve. Whatever dips remain are caused by intake, headers, cam and tune.
You'll need to get your HSR Extrude-Honed or it'll be a choke, as cast it can't flow anywhere near what those heads can.
Do all that correctly, and expect an easy 500+ horses, and at least 500 ft-lbs. Probably a good bit more.

 

Holy bejesus.

So I shouldn't have any issues running on 91-93 octane?