compression

What is the highest compression that anyone is running on pump gas with aluminium heads. Im taking out my 9.5 slugs and want to go with 11.0, but I hear mixed opinions about what will work.

their's a guy here in h-town running like 12.3 Static
-brandon

I'll answer this before it gets moved....

I run 12.48 to 1...It's not the SCR that gets ya, it's the DCR....Mine is only 8.77....Many here have run 9 to 1 but you have to get everything right on for it...Heck, mine was hard enough to tune...and goes into hard detonation a lot easier than before...After lots of tuning it's all good....:D

What is the highest compression that anyone is running on pump gas with aluminium heads. Im taking out my 9.5 slugs and want to go with 11.0, but I hear mixed opinions about what will work.

Are ya running an LT1 with reverse flow cooling?

Jimbob
Get ya some good cooling and it will do better. There are people running 9.6 an pump gas but I will stay at 9.1 'cause that's the way it came out. My static is 13/1.

Jimbob
Get ya some good cooling and it will do better. There are people running 9.6 an pump gas but I will stay at 9.1 'cause that's the way it came out. My static is 13/1.

Well, if I used my theoretical .006 ABDC (using intake duration and ICL), I would be right at 9.18 to 1 (74.5*ABDC). I checked my actual ABDC and came up with 79*. Several times...on two different lobes....Makes sense, because I got a base duration of 295 instead of 289 listed on lobe chart :( The exhaust lobes were right on the money so, I did have two control lobes....Moral of the story.....our DCR's may not be as high as we think...

Are ya running an LT1 with reverse flow cooling?

Jimbob
Get ya some good cooling and it will do better. There are people running 9.6 an pump gas but I will stay at 9.1 'cause that's the way it came out. My static is 13/1.

I'm running this in my 540.

I'm running this in my 540.


It is the same rule of thumb.

i'm guessing scr and dcr stand for
static compression ratio and dynamic compression ratio
and i'm guessing static means the compression ratio calculated from total combustion chamber volume at bottom dead center to total combustion chamber volume at top dead center

what is dcr? and how is it calculated?

what is dcr? and how is it calculated?


http://members.uia.net/pkelley2/DynamicCR.html

Good write-up!

I'm running this in my 540.

If it isn't reverse flow cooled ya better stick to 8.5DCR or ya may have to run fuel in it.

It is the same rule of thumb.

Problem is how you get there... usually high compression big blocks take some dome to get, and that can cause issues on a pump gas high DCR motor.

The other side of this is how much VE can you make, the more you make the less compression you can run. Hell the less compression you need, everyone seems to think a Pro Stock motor is running some crazy SCR, but it's really around 15:1.

Bret

http://members.uia.net/pkelley2/DynamicCR.html

Good write-up!

:thumb:

If the dome is built right and has a fire slot it will be fine. Shouldn't take THAT big of a dome to get a 8.5DCR with a 75*IVC. Ya can always buy a small CC chamber head.

Hey: 15 to 1 will get it done...