Rafedial1
07-13-2009, 03:27 AM
while tearing apart some 6.5L NA and 6.2L NA cylinder heads I got my first good look at the pre-combustion chambers or precups. Now my question is, is the volume within the precups itself added to the volume of the main combustion chamber?
If so, that would mean if you increase the volume of the pre-cup, then more total volume. This results in lower static compression? I've been staring at these things awhile now lol and it makes me wanna modify them.
The 6.5 and 6.2 precups are different. Both are somewhat D-shaped and have the same volume (i think), but face different ways.
When operating, it looks like the fuel is injected and then deflects off the precup "D". But the inside looks at though the fuel/air mixture tends to swirl and combust inside the cup itself. So why is the cup separated from the main combustion chamber? i know i know...IDI...but why?
while on the topic of more volume. I also looked at the head runners today. i have to say, there isn't much meat near the intake runners to open em up any. The exhaust side looks promising though.
room for improvement?
thoughts....
side note: do all 6.2/6.5 heads have cracks between the In and Ex valves? :wtf:
here's a link I had saved for 6.5L specific problem areas. http://www.enginebuildermag.com/Content/Site302/SpecialIssue/11_01_2007/1898GM1107pdf_00000002283.pdf
it says the precups are indeed different. recommeded Gm Part #10183926 "diamond" shaped precups (comes in 6.5L Vin F 97-up). gmpartsdirect have them for $33 a piece X8. Now, if I had an image of that part I could duplicate it by porting, reshaping it in the 6.2L heads I am workin on. shape or size more important? hmm....seems there is some power to be made in this area.
If so, that would mean if you increase the volume of the pre-cup, then more total volume. This results in lower static compression? I've been staring at these things awhile now lol and it makes me wanna modify them.
The 6.5 and 6.2 precups are different. Both are somewhat D-shaped and have the same volume (i think), but face different ways.
When operating, it looks like the fuel is injected and then deflects off the precup "D". But the inside looks at though the fuel/air mixture tends to swirl and combust inside the cup itself. So why is the cup separated from the main combustion chamber? i know i know...IDI...but why?
while on the topic of more volume. I also looked at the head runners today. i have to say, there isn't much meat near the intake runners to open em up any. The exhaust side looks promising though.
room for improvement?
thoughts....
side note: do all 6.2/6.5 heads have cracks between the In and Ex valves? :wtf:
here's a link I had saved for 6.5L specific problem areas. http://www.enginebuildermag.com/Content/Site302/SpecialIssue/11_01_2007/1898GM1107pdf_00000002283.pdf
it says the precups are indeed different. recommeded Gm Part #10183926 "diamond" shaped precups (comes in 6.5L Vin F 97-up). gmpartsdirect have them for $33 a piece X8. Now, if I had an image of that part I could duplicate it by porting, reshaping it in the 6.2L heads I am workin on. shape or size more important? hmm....seems there is some power to be made in this area.