cam size vs cid

I dont know much about squish and techinal cam specs but my nova has 9.6:1 comp with 220 cranking pressure in all cylinders and I run 87 octane all the time, Ive ran higher grades without any noticeable differences. Im not to concerned with detonation, even though its rated at 10.25:1 comp im sure true compression is 10:1 tops with the a cam that keeps me under 190 cranking psi I don't forsee any problems

 

Ok, well cant say I didnt try. In that case, go ahead and run the Crower 270 HDP, or the isky 262. Good luck.

 

the rover uses the Buick head, not the olds.

 

They (hotrodders) built plenty with Olds heads. Seems like the 215 tree was the SBC over there.....

 

I think we can all agree that a sbc is certainly capable of "charging" the cylinder sufficiently to detonate, right?

A typical, stock iron chevy head flows around 180 cfm at .400 lift, (the lift of the stock 929 cam) and its filling a cylinder of 43.75 ci. Lets round it off and call it 44 ci. So ball parkish, we have 4 cfm per ci, and I think most of us can agree that a 10.5/1 sbc is capable of filling the cylinder sufficiently to experience detonation at peak torque. You DO realize that cylinder pressure is highest at peak torque, not at peak HP, right?
So, lets look at the Olds. Here we have a 130cfm port feeding a cylinder of 27 CI,so we have 4.8 cfm per ci. hmmm, yup, I would say that it is at least as capable of filling the cylinder at peak torque as the chevy, and I think we can all agree (maybe not) that the sbc is capable of filling the cylinder sufficiently to experience detonation.

I am now going to spend my time on something more educational and enlightening. I'm going to go watch Family Guy.

 

In my opinion, it has to do a lot on heads, and valve size, when detroit scales motors up, we are typically using the same/similar flowing heads and lift on different cube motors, BUT the smaller motors don't need as much air. Everything should somewhat scale up, but when detriot cant fit big bores, runners, and valves in the casting we need to go with more lift to get enough air

 

Seems like a good idea for ya!

 

I was just showing my personal experience with cams and compression. I dont know much about cams and you appear to know what your talking about.

 

Here is a model in Dyno Sim. As far as spark knock, since you are living with the stock cam any increase in duration or later intake closing will lower your dynamic compression.

 

This is correct. And almost all the aftermarket cams that I looked at ( the Isky 262 was the only exception) under 210 @ 050 had an earlier closing point than the factory cams SAE published closing point of 58 ABC, and so would have a higher dynamic compression than the factory cam.

 

Falcongeorge, what happened to your post where you went through and explained I think three cams, isky crowed and crane I believe.

 

Here are 4 Cams, the stock replacement by Sealed Power and 3 others. The Sealed Power cam is not exactly what you have now. NHRA blueprints don't give duration's but the lifts for the Olds 215, and the Buick 215/300 are all different. The Unknown implies unknown to me.
Edit according to D&D you have the 43 cc heads.

This makes it it pretty unlikely it was 10.25. I have seen a 215 olds with the heads off and they for sure have 4 valve reliefs, and no dome. Guessing 9.5ish?





Estimated Nominal Compression Calculation



W/43cc head