INtake Vent line

HI

I want to permanently vent the cooling from the rear of my Super Victor intake.
Just not shure which line size to go with.
I will use braided teflon hose either in Dash 3 or Dash 4.

Dash 3 = 3,17 mm ID ( 1/8"")
Dash 4 = 4,76 mm ID (3/16")

It will be vented to the top of my expansion tank.

What is your reco for sizing

Thanks

TOM

My understanding is that smaller is better in that location.

I agree.....smaller is better. You want air to move through it, but minimal amounts of coolant. I'd say either mentioned would do the job.....I would view them both as "small".

EGLITOM said:

I want to permanently vent the cooling from the rear of my Super Victor intake.
Just not shure which line size to go with.
I will use braided teflon hose either in Dash 3 or Dash 4.

Dash 3 = 3,17 mm ID ( 1/8"")
Dash 4 = 4,76 mm ID (3/16")

It will be vented to the top of my expansion tank.

What is your reco for sizing

Thanks

TOM

Click to expand...

If you do that then I'd go small.

My motor was plumbed so that it had a vent line from the rear of the intake to the top of the expansion tank, then from the bottom of the expansion tank to heater return on the water pump. The line from the back of the intake (it joined both sides together and then to the tank) was AN10.

What happened was the water would rather head out the back of the block and into the expansion tank and pressure built up in the tank. It'd blow a 18 or 20 lb cap up at high RPM. Besides that, the water temp was getting hot because the water would rather head out the back of the block and not go through the head to cool things down. There was no tstat in one of these iterations and the high pressure in the tank still happened.

So, we put a restrictor in the AN10 line (used a hose clamp and vice grips) and that helped out a lot. We kept from blowing the cap open but cooling was not optimal. I'd estimate the restriction took the line down to inbetween a -6 or -8.

After those track data collection episodes we re-plumbed the system. In the end what I'm doing, and I think this is working, is I have a AN4 line from IN FRONT of the thermostat back to the top of the expansion tank and we still have the lower line from the expansion tank to the heater return on the water pump. The back sides of the intake are blocked off.

Thus far it seems to like this setup. The motor burbles along at 180F for extended periods of time, doesn't get hot at all. With load and high RPM the cap doesn't get blown open and the water temperature doesn't increase.

Tom,

The purpose of the bleeds at the back of the heads is, when the motor is sitting horizontal or tail high, as in most GT40s, to expel trapped bubbles of air, or steam caused by localised hot spots . You only want the bare minimum size, -3 is more than enough. Feed it into your header tank and have that with a 5/8" or 3/4" drain into the bottom hose, or the heater return port in the pump. I also have a -3 bleed from my swirl tank to my header and use a 3/4" restrictor hole in place of a thermostat. My biggest cooling problem is to get it to run hot enough!

If you have large bleeds, they act as bypasses and not only reduce flow forward through the heads but the flow through the bleeds also bypasses the radiator.

Thanks gents for that valuable input.

I will go with a -3 line but will just drill a 2mm hole in the expansion tank where the adaptor bung is welded on.

I also will vent from my radiatior with a -3 line into about the lower Third of my expansion tank. This way the line still run upwards all the time and can purge the air out, but in the cool down stage it doesn´t suck air back into the radiator.

TOM