Because my evac doesn’t work I had this welded up by a racer and positioned it directly in line and as close to a single primary tube in the collector as possible at a depth of 5/8”. I’m using the same ½” size metal tube from the evac valve to the collector as what Chad shows in his exhaust pics. I figure if this doesn’t work it won’t be any worse than what I presently have.

Chads exhaust uses cone type collectors and it’s unknown (top secret) where the ½” tube ends after it enters the center of the cone and what shape it is formed too inside. His system has hoses from both valve covers joined together leading to an oil catch box. I wonder if his system would work equally as well if only one hose from the valve cover was used.

Next race Sept 25… stay tuned !

I’ve personally seen up to -3” on the dyno but that’s not in the car.
Markemark, I would like to think minus 11 if correct that’s wild! All the collectors I’ve seen had the tube well behind the merge. ? I like Chad’s center point too. Your graph follows as I’ve seen our vac , it drops in high gear about +3+4 “ due to longer high rpm pull.
Also, any small leak at the motor negates anything. I spend hours making sure we don’t have any losses at the pan, China walls , intake seal,valve covers, rubber seals for breathers and fittings.

This message has been edited. Last edited by: BP758,

quote:

Also, any small leak at the motor negates anything. I spend hours making sure we don’t have any losses at the pan, China walls , intake seal,valve covers, rubber seals for breathers and fittings.

Agreed. One would need to do a smoke test to verify no leaks. But even if one had a leak and evac working there shouldn’t be any positive pressure at maximum rpm. I have 1.5 psi positive pressure at maximum rpm and no apparent fluid leaks.

I can add one of those cheap Amazon baby oil smoke machines are worth every penny!!!

Here’s the update to the evac valve relocation (with pic) that I posted on September 18.

Although small (using the kPa scale) there is now vacuum at all rpms with the change to only the right side (left side still as prior). The EVAC readings less than (below) Baro indicates vacuum. Considering what I had prior, to me this is a Great improvement and acceptable. Not looking for results that would pull any oil or need to have a catch reservoir.

Next test is to remove the left side EVAC valve connection and cap off the valve cover breather and valve at collector to see the results with only one side in operation.

I cannot modify the left side as it would put the EVAC valve in front of the O2 sensor.