Has anybody acuatally had first hand experance with this compression and 87 or 89 octane?

 

10.5:1 will run 91 octane perfectly fine and you can scrape by with 89 octane. I recomend using the aluminum head still.

 

If I run Dart pro 1 heads could I use pistons that create 9.25.1 compression and end up with 10.25.1 compression. I read that aluminum heads add 1 point of compression. If this is true could I use Hupereutectic Pistons to acheive this compression?

 

Yes or any piston for that matter, compression ratio is dependent on heads chamber volume, deck height (stock is 9.025), bore/stroke, head gasket thickness, and piston "surface volume" dome pistons take up volume increasing compression dish pistons add volume decreasing compession generally speaking.

 

Who told you that aluminium anything adds compression? The material the parts are made of has nothing to do with the actual compression. Aluminium will allow you to achieve higher compression on pump gas, but that's about it. What you need to worry about for compression is piston volume, like Griff said, combustion chamber volume, head gasket thickness, and piston to deck clearance, as all of these things affect the amount of BDC cylinder volume to TDC cylinder volume, which is where the compression numbers come from. The fact that it's aluminium won't change this in the least.

 

I assumed he ment he could get away with 1 point greater compression for the octane???

I dont want to muddy the waters to much but here is a good link on cam/compression dynamics
http://members.uia.net/pkelley2/DynamicCR.html .... I just wish I could understand all of it.

 

It does get a bit complicated, don't it?

 

Yea it does but I like reading through that kind of stuff, one thing I was kind of wondering about is that if the intake does not close prior to the piston coming back up wouldnt that create somewhat of a reversion pulse and if it does is the effect transfer to the intake as a pressure causing the lack of low rpm intake vacuum you see in some of the more radical cams?

 

That would make sense, wouldn't it? That's why we run external vacuum pumps on hot rods if we wanna keep power brakes.

 

Well they do have brake boosters out that are run off your powersteering pump so you always have consistent brake pressure.