• When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.

combustion chamber question

gtxrt

Well-Known Member
Local time
3:08 PM
Joined
Feb 18, 2021
Messages
333
Reaction score
183
Location
central ny
if you have a tight quench pistons up high with a good combustion chamber like close chamber 915 heads would you need more fuel [jetting] or less to make power. am thinking it burns more efficient so it would need and handle more fuel ?
 
You can probably burn a leaner mixture more efficiently. But id think it not change the optimal afr ratio.
 
Buy a stand alone A/F tester and don't guess. Or take it to a drag strip, do some runs while pulling plugs and trying different jetting. Otherwise it's just guessing.
 
I think tight quench and closed chamber, high swirl combustion chamber along with high velocity intake port will make the engine more octane tolerant and need less timing advance to make maximum power. Just my thoughts.
 
For a drag strip car, it is just testing. Not sure an A/F will tell what the motor wants. Time slips tell the tale. I never got anything from trying to read plugs. Time slips.
 
I think tight quench and closed chamber, high swirl combustion chamber along with high velocity intake port will make the engine more octane tolerant and need less timing advance to make maximum power. Just my thoughts.
The OP was talking about OEM iron heads.
 
My brother built a 440 with pretty much what you describe.
I think it was a true 10.5:1
Ran great made tons of torque.
Unfortunately after it ran a bit and got some carbon in there the cylinder pressures were so high it began pinging.
No efforts at timing or mixture changes could cure it.
A cam change might have helped/cured it but he didn't want to guess.
He put aluminum heads on it and changed the cam as well.
So be careful.
 
If the question is theoritical, less jet. You will be utilizing more of the fuel in the combustion process with a more efficient chamber.

In reality, it's unlikely you'll be able to find the difference.
 
Auto Transport Service
Back
Top