Plug coolant bypass and drill hole in thermostat
 

Hey Guys,

I have tapped and plugged the small "coolant bypass" hole between the intake and the timing cover. I then experimented with 3 different size restrictors in place of a thermostat. Since I blocked the coolant bypass I cannot run a thermostat because the coolant has to go somewhere until the thermostat opens.

Anyway, with all 3 restrictors my water temp never gets above 150 degrees. So tomorrow I want to experiment with drilling a small hole in a working 180 degree thermostat. The idea is that the hole will allow some coolant to flow through until the thermostat opens.

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Well I tried drilling 3 x 1/4 inch holes in the thermostat and the engine still would not get up to temp, even with a 180 thermostat and only 3 little holes. I have 2 temp gauges installed, factory and aftermarket. So I know the gauges are right.

Question. If I drill only 1 small 1/8 inch could this present a problem. I am concerned that if the thermostat is not open and the car is under load (5000 rpm) then to much pressure will build in the cooling system and "pop" something. The thermostat will not always be open and the engine could be at 170 degrees, if this happens will the high rpm and water pump cause the system to bust something? to much pressure? Is an 1/8 inch hole to small?

John

What problem are you trying to fix? I dont know what pressure the water pump can push, but its not much, 10-15 psi maybe. I think after that it would just bypass in the plate to impeller gap. I dont forsee it blowing any gaskets out. If your heater hoses are connected, its bypassing through the heater core anyhow.IMO ; )

I always drill an 1/8th inch hole in all my thermostats to act like an air bleed. Done this on lots of cars-stock and performance- over 30+ years with not one issue.

I have done the same in the last several years, for much the same reasons. I don't know if it helped.

I like your vid. We'll done. I enjoyed the systematic approach.

Cooling systems always seem to work like constraint management. After you eliminate one constraint or cooling limiter, you uncover the next weakest link and have to start whacking on that one.

Good video.

I also add the air-bleed hole in the 'stat.

A 1/8" hole is ok, nothing wrong with that. A lot of thermostats already have them, its called a "jiggle pin". Usually they are mounted horizontally with the pin at the top. Any more than that, and there is coolant going around the thermostat that it may not get hot enough to open. I would want the engine to be at
180f
I think some people would put an aspirin on the thermostat to hold it open, after filling it, the aspirin would dissolve and the air was bled out.
I would not do it on a newer (2000 and up) car. It may turn on a Check Engine light if the engine does not warm up fast enough.

Can someone post a picture of a thermostat with the hole drilled in it?

the high flow balanced sleeve type of stats like the Robert Shaw 330-xxx have an air bleed in them and an arrow indicating which way it should be installed, usually towards the front rad
it helps burp the system and acts a very small by pass without causing excessive cooling or reduced heating for those that need it
http://static.summitracing.com/globa...0-195_w_ml.jpg

here is one with some holes drilled in it
http://static.summitracing.com/globa...p-300_cp_m.jpg

I dont think position of a bleed hole matters on a Pontiac thermostat that is mounted flat. A lot of engines have them mounted vertically so yes, that would matter. A 1/16" hole is plenty. Its going to open and self bleed anyhow. But everyone likes an edge. ; )

SO,
The question I have is WHY would anyone block off the bypass?

In the video he mentioned it is done for race cars and when it is a leaking problem, I have never had one leak on my Pontiac engines even when reusing an "O" ring. If you instal it correctly you won't have leaks.


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Zim, Supercharger application...BDS recommends this procedure...I followed the advice from Craig Railsback....no problems...car runs at 160-170....all day....:) ...IAII block...BDS 8 71 ...plenty of air flow...When we designed and built the car, myself and Richie Hoffman at Hoffman Racing did plenty of "thinking and worrying"...I was very concerned about cooling issues.... the car is an automatic, with A/C and power steering.....Eric:usa2:

the reason to do it on a race car or even a stock car is so you can separate the coolant section of the intake manifold from the main body of the intake manifold. you can separate the two with a cut off wheel. once they are separated this allows you to change intakes at the track very easily without breaking into the coolant passage. another reason to do it is that these o-rings leak, if yours doesn't leak then you got lucky but I bet if you look right behind your water pump on the top of your valley pan there will be a little puddle of coolant.

Correction

The reason the bypass is blocked off has nothing to do with separating the water xover from the intake. The bypass can still be used [ or blocked ] whether the xover is stand alone or integral with the intake.

The bypass serves two purposes:
[1] it acts as pressure relief valve, should the stat jam in the closed position.
[2] the bypass hole connects to the inlet side of the pump to heated coolant exiting the xover; the bypass gives faster warm up because some heated water is fed directly to the feed side of the pump.

so really the only reason to block off the bypass is if the seal is leaking between the intake and the bypass. or in racing situations to change coolant flow using restrictors. I was unable to get the engine to come up to temperature no matter what type of hole I drilled in the thermostat with a blocked off bypass

I have run both Thermostats and Restrictor plates in the past.

I have drilled holes in the EDGE ring of the T-Stat to allow air to bleed past the t-stat and help filling the cooling system easier.

I have installed bleeder type fittings in the water pump side of the timing cover to purge the air from the timing cover and help water pump efficiency. (Evans Cooling does this on all of their water pump modded vehicles).

Without the bypass from the cross-over to the water pump side of the timing cover it is possible to cavitate the water pump under some conditions. Pontiac Engineers did Things for a Reason.

Tom V.

Some old aftermarket intakes did not have the provision for the by-pass to match up with the timing cover.

My engine has an IAII block, an aftermarket timing cover, and E-brock water pump, and a Supercharger manifold from BDS...I blocked the by pass as per BDS's directions....Truth be told; I have no idea why it is recommended :)
I do therefore differ to the expertise and knowledge of the engineers...C.Railsback, T.Vaught, et al.....Whom I also thank for their patience, and information...Eric!

So then you must have the inlet from the back of the heads hooked to the timing cover inlet, and if not, then you have both inlet from heads and bypass plugged off and your not running any thermostat.

If that's the case your flow is from bottom rad hose through engine, heads and out to the Radiator.

You cannot plug bypass and inlet on timing cover from heater or back of heads and run a thermostat. If you do the coolant does not move in the block till stat opens.
In my opinion very dangerous because of locating of the stat.

charles

I had problems with leaks a long time ago and plugged the bypass. I run a 160 with 3 holes but I put an extender housing on top of it between it and the top radiator hose. I pipe both rear head into a y and into the extension after the thermostat. Thermostat works fine.. Block and heads cool fine. I have an old BeCool with a 3400 cfm fully shrouded electric fan. I welded an extra bung from the cool side of the radiator to a ATF heat exchanger and the coolant return goes to the small (heater) return on the water pump. I have a 67 FB conv - I only drive with the top down, and the heater is not plumbed.
It’s a 468 old EHeads that’ s a bit over 600HP and 640FtLbs. (Latest and hopefully last build). Converted from 850BG to Sniper for fuel earlier this year and just recently added the timing control. Ran fine all summer long - rarely hit 200 in the heat. Runs a bit too cool in the cold - I need to adjust the fan cut on temp., or have Snioer do it now.

My understanding is that the 'bypass' is actually the bleed, the stat is the highest part of the system, trapped air will naturally attract to that area. When the stat opens, trapped air moves to the rad, and the cap after X psi will 'burp' the rad.

The sleeves have the rubber rings on them because that is the pressure side of the pump. I see many confused about the direction of flow of the block holes. The water flows out the stat, or when the stat is closed, circulates in the block/heads/core/pump areas.

Intake to cover gaskets leak for a couple possible reasons:

* Shrinkage/dry rot of rubber ring
* Cover pitting where seal rides
* Incorrect installation/tightening sequence of intake bolts
* Use of incorrect bolt retainer/bolt length, bolt bottoming out

Causes when aftermarket intakes are used:

* Incorrect installation/tightening sequence of intake bolts
* Intake to head bolt holes not large enough to allow intake to be pulled forward enough to seal
* Intake seal area 'ridge' is too high, not allowing rubber ring to compress enough
* Cover pitting where seal rides
* Use of incorrect bolt retainer/bolt length, bolt bottoming out

I may have missed some, I'm still on first cup of joe, but that's what comes to mind at the moment.

I can't think of any good reason to block the bleed hole.

The only reason I can think of to drill holes in a stat is to maybe have more flow at a lower temp. Like you want to run a 180 stat, but also would like lower temps before the stat is FULLY open.

Cutting the crossover away from the intake runners is usually done to align intake/head ports, but also allows for easier intake swaps without breaking into the cooling system, like when testing intakes.

Personally, those 'high flow' stats do not work as well for me, and I generally see slightly higher temps across the board with them.



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I see many confused about the direction of flow of the block holes. The water flows out the stat, or when the stat is closed, circulates in the block/heads/core/pump areas.

So, if the cross-over bypass is blocked and the heater hose return to water pump Timing cover is blocked, and a thermostat installed, there will be no circulation in the block before thermostat opens? So then you have potential for the water pump cavitation. Thank you. What are your thoughts?