GZ Tech Info

A common problem is pulling too much oil from the valve covers, much less often too little. The too much oil problem is usually due to the location of the inlet on the valve cover to the vacuum pump. This happens more so with vacuum pumps that pump more air, or have more air flow. Generally, the inlet should be on the front face of the valve cover to avoid over pulling of oil. When the pump inlet is in the top of the valve cover, it should be in the front, should not be over a rocker arm, works best with a stud girdle (as the oil from the valve train does not have direct access to the inlet). It is better to use a “pan evac” breather in this case as the inlet hole is larger (which reduces the air velocity coming out of the engine). If you do not have a stud girdle you may need to baffle the inlet with or without a Pan Evac breather (the baffle must be oriented properly to reduce oil flow out of the valve cover). Engines that are set up with the vacuum control valve on the opposite valve cover will tend to pull more oil IF the engine is set up with a high air flow vacuum pump and the valve is set at a relatively low vacuum level. This occurs because the total air flow going out of the motor is higher than would occur with a higher vacuum level, or with a smaller vacuum pump. The solution to this particular problem is generally to move the vacuum control valve to be in line with the pump. This can be done by relocating our VCV102 to our VCB100 (pan evac breather which was designed to allow the VCV to be installed in it, you need to drill and tap the top) or to our VCV102A/B (which is a billet piece that goes in the top or front face of the valve cover and has been designed to have our VCV102 installed in it). Of course inlet location, etc. is still of importance.  Another tip is to put some Scotch Brite in the baffle or panevac breather if still a problem. 

We have noticed that pulling alot of oil is also related to top oiling of the valve train. Mopar B1 heads and Ford “Yates” heads set up for road racing apparently have excessive top oiling. Remember, all that oil is splashing around and the pump will Suck up anything that passes the inlet hole if the air velocity is high enough passing out that inlet hole.

Lastly, the problem could be an inadequate vacuum pump coupled with an engine with alot of blow by. If the pump is overpowered by the blow by the pan pressure will build up to the point where alot of oil will be blown out . Inadequate can mean too small a pump , a failed pump, or an engine with really excessive blow by, which no vacuum pump will fix.