Rob Bromfield
GT40s Supporter
I have a Holley carb with 1850S stamped on the airhorn which makes it a model 4160.
However,sometime in it's life it's been converted to a model 4150 presumably by using the Holley 34-6 kit. I say presumably because the secondary metering plate has been swapped for what looks like a metering block and this new metering block doesn't have any idle screws so it's not some attempt to get four corner idle adjustment.
Because I'm an engineer I'm curious (or pehaps because I'm curious I'm an engineer) so I thought I'd try adjusting the two idle screws to get the maximum manifold vacuum at idle.
To my surprise I was able to screw both idle screws gently on to their seats without the engine missing a beat!
Aha! I though the powervalves leaking. So I took the primary side apart (someone has used the blue reusable gasket so this side has been taken apart several times in the past), extracted the power valve and used the not very scientific test of sucking on it.
There's no tear in the diaphragm as the valve actuates.
I'm assuming that there's no power valve in the secondary side as I haven't taken it apart (yet).
So out of curiosity, how does the engine continue to run with the idle jets screwed in?
However,sometime in it's life it's been converted to a model 4150 presumably by using the Holley 34-6 kit. I say presumably because the secondary metering plate has been swapped for what looks like a metering block and this new metering block doesn't have any idle screws so it's not some attempt to get four corner idle adjustment.
Because I'm an engineer I'm curious (or pehaps because I'm curious I'm an engineer) so I thought I'd try adjusting the two idle screws to get the maximum manifold vacuum at idle.
To my surprise I was able to screw both idle screws gently on to their seats without the engine missing a beat!
Aha! I though the powervalves leaking. So I took the primary side apart (someone has used the blue reusable gasket so this side has been taken apart several times in the past), extracted the power valve and used the not very scientific test of sucking on it.
There's no tear in the diaphragm as the valve actuates.
I'm assuming that there's no power valve in the secondary side as I haven't taken it apart (yet).
So out of curiosity, how does the engine continue to run with the idle jets screwed in?