Question for VW guys

evanwebb

evanwebb

Well-known member
Hey all, is there any need to retain the cooling outlet on the end of a VW head versus just block it off? I'm wondering in particular about an early 1.6 8V engine but I guess the question could apply to other VW 4 cyl engines. I've seen high-horsepower prod and GT engines built both ways. I was worried that there might be a temperature gradient through the head without some flow from the far end, but looking at the way the coolant flows in the engine I think I can eliminate both the bypass hose that runs down the front of the block as well as the hose on the end of the head (that originally went to the heater core). Your thoughts? Thanks.
 
Hi Evan:

I run a thermostat and thus retain that front hose, I'm a big believer in thermostats. (I did drill a small bypass hole in the thermostat to help burp things and allow the system to be drained).

I use the rear outlet to connect to the expansion tank, so from a flow perspective it might as well be blocked I think. When I had the engine apart a year ago I saw no signs that #4 was hotter than #1. I'll confess that I did ponder this a bit but finally decided that it was OK.

Hey, I have an idea, I can sell you a bunch of thermocouples and you can instrument it! 8)

Al Seim
HP VW Scirocco 1.6
 
You can use a T/S and drill a bleed hole as prior descibed.

If you dont want to use the TS ,you must block the vertical bypass hose. I drill a bleed hole in the blank plate(freeze plug) also.

I have gone to all direct gauges and use the end of the head on all new builds. Just tap the water outlet.
I have seen all sorts of blanking plates on the end of the head. I use to worry about water flow from the outlet. Not anymore. Some time with your infrared heatgun will tell you the same,IMHO.
The hot jug is # 3 . always.
I am pretty sure tha t my book addresses this issue, but wil lhave to double check.
MM
 
Evan,

I have had the outlet blanked off since I built my car. We just had the engine apart and there was no sign of any overheating. The bushing at the base of the distributor was chewed up, but that's a whole other issue.
 
You can block the water outlet by #4. Use the one between #1 and #2 with a thermostat and you shouldn't have any problems.
Chuck Mathis
 
Foregot to mention that the VW oil pressure switch, can be used into the water outlet, to a dash idiot light ,to indicate low water pressure.
 
Thanks everyone! I'm thinking of blocking off the outlet by #4 and also getting rid of the bypass hose and just running a restrictor in place of the thermostat...
 
Thanks everyone! I'm thinking of blocking off the outlet by #4 and also getting rid of the bypass hose and just running a restrictor in place of the thermostat...
Click to expand...

That works, just be sure to warm it up before going on track.
 
I didn't like the fact that if the thermostat fails, it fails in the WRONG direction. I just took a stock thermostat, and removed the spring side of things, and used that as the restrictor.

Yes it does take a little bit longer to warm up, but so does the oil with the melling HP oil pump. I can't rev it too high with the cold oil at almost 100 psi or I'll blow out the o-ring on the filter.
 
Keep in mind that you give away power and durability with non consistent temp control.
Same with lots of oil pressure. Too much cost you power.
If you run carbs and it doesnt cough when it is cold, it should be addressed.
Stabilizing Temp vs fuel management is key to power.
 
Hey Mike, I will be aiming for cool water (180) and hot oil (220), and 10 psi of oil pressure per 1K RPMs. That's my understanding of basically getting it right, does that seem right to you?
 
I quit trying to keep the oil cool, way back racing on the ice. I just started using Mobil one and have not monitored the oil temp since. I am sure that it is way hot. Any of the good synthetics will work fine well up to about 300*. IMHO. I only use the stock OIl to water cooler, no additional coolers for me.
I cant remember having a oil related failure,( other than running out of oil,ignoring the light, in one of the Chumpcars))

I had a few drivers actually look at the oil temp gauge( back when it had a stock GTI gauge pack) and come in for 280*.

Sadly, I also dont look at pressure. Just run a low # light. The VW oil system has so much volume and plenty of pressure that a few pounds off makes no difference. Too much oil pressure, cost too much power and really twist the inter shaft as well as scuffing the pistons when cold.
I check the rod bearings every 25hrs. and the crank end play as well. ( I check the cranking compression and leak down every mon ,post race)
I run Rotella synthetic 5/40 now. ( 1200PPM zinc) Quick oil pressure to the rods and pistons.

As far as water temp, I like to heat up my engines as fast as reasonable. The only engine that I ran without a Tstat is the oval tracker. 8min race with the low RPM of 4800 builds plenty of heat.
All of the rest, I use a 160 , with a 1/8 in bleed hole. Stable high temps makes more power. The air temp gradient from intake to exhaust is what helps make power. If the head is too cool, your'e not getting full combustion and are missing some heat gain.
 
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