Rear intake coolant bypass

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turboking15

turboking15

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Figured id post this up to show how i made my bypass setup and possibly help others. This intake uses the late t stat housing that is the same as the magnums with the smaller bolt pattern.

Total set up cost about $15
- modified magnum water neck
- 4× 1/4npt to 3/8 barb
- 3'-4' of 3/8 heater hose

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turboking15 said:
Figured id post this up to show how i made my bypass setup and possibly help others. This intake uses the late t stat housing that is the same as the magnums with the smaller bolt pattern.

Total set up cost about $15
- modified magnum water neck
- 4× 1/4npt to 3/8 barb
- 3'-4' of 3/8 heater hose

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This works well on a chevy , I did it 25 yrs ago on a hot 406 sbc , even helps purge air from the system when re filling radiator.
I also ram coolant lines off the water pump to between the center 2 cyls. , ---------
 
will any additional heat be put in the plenum? maybe some of the interior heat barrier on top of the hoses going under the runners and plenum?
 
Nice set up, I just plumbed it from passage to rear. Likes yours but that wouldn't fit on my set up. :thumbsup:

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turboking15 said:
Figured id post this up to show how i made my bypass setup and possibly help others. This intake uses the late t stat housing that is the same as the magnums with the smaller bolt pattern.

Total set up cost about $15
- modified magnum water neck
- 4× 1/4npt to 3/8 barb
- 3'-4' of 3/8 heater hose

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Pretty cool man, pretty cool indeed. Nice use of the noggin. How thick is that welded plate on the stat housing?
Also nice plenum work on the intake, spread to square.
 
abdywgn said:
will any additional heat be put in the plenum? maybe some of the interior heat barrier on top of the hoses going under the runners and plenum?
Click to expand...

Can buy the heat shields to go over them if one wanted to to help keep the heat out
 
What does this do? head coolant flows from the back to the front on out to stat, right?

<<EDIT>> just realized that it bypassed the stat so it flows regardless of temp...
 
Take a second look at the cool ET system, passages and flow areas.
 
rumblefish360 said:
Pretty cool man, pretty cool indeed. Nice use of the noggin. How thick is that welded plate on the stat housing?
Also nice plenum work on the intake, spread to square.
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Plate is .25" thick .750" wide x 1.500"ish long

Thanks, this is the 2nd one ive done. Like i tell all my buddies, "with a welder anything is possible!" lol.
 
The only possible problem I see are:
  • it completely bypasses the heads during warmup.
  • And then it bypasses some coolant flow past the heads when the t'stat is open.
  • Too much bypass flow in that path will lower coolant pressure in the heads, allowing easier boiling in the heads.

The normal bypass just bypasses the radiator, not any part of the engine. So this is potentially an issue with creating hotter spots in the heads.....
 
nm9stheham said:
The only possible problem I see are:
  • it completely bypasses the heads during warmup.
  • And then it bypasses some coolant flow past the heads when the t'stat is open.
  • Too much bypass flow in that path will lower coolant pressure in the heads, allowing easier boiling in the heads.

The normal bypass just bypasses the radiator, not any part of the engine. So this is potentially an issue with creating hotter spots in the heads.....
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-Heads are fed from the entire lower deck surface of the block front to back, not sure how this would completely bypass the heads during warmup.
-Thats the point, trying to remove hot coolant from the back of the head instead of sending all the way through the head then to the radiator
-Not sure how youre going to lower the pressure in the heads, its a closed system. Pressure will be the same throughout.
 
Good point on the head feeds but the main one is in the back.

No, coolant pressure is not uniform throughout. It is lowest just before the pump and highest just before the t'stat and in the heads. It is a difference of several psi. That is why guys who remove the t'stat and fail to put in a restrictor in its place often see temps rise, not fall. The t'stat is a restriction that creates the higher pressure in the heads; when that restriction is removed, the pressure in the heads drops and the coolant in contact with the hot head chambers boils more readily and things eventually get hotter.

Ain't trying to make this look bad.... just pointing out what is going on and is possible and how the standard flow is being changed. If you are not seeing any temp changes one vs the other, then that is a good sign. IMHO, never hurts to discuss these matters; we all learn. Tnx.
 
Discussion is good, partly why i posted this. There is not a whole lot of info out there, especially pertaining to the SBM in regards to this kind of stuff, so most of my research is adapted from SBC stuff. If there are any pitfalls or errors id like to catch them or know what to look for once this is up and running
 
So would plumbing it back into the manifold be a better choice to keep pressure in the system via a tstat or restrictor plate? That was my thinking and why I plumbed mine the way I did from back of head to front coolant runner below the tstat. As long as it works right and there's a difference.
 
I may have in correctly assumed this is a race only mod due to the T stat being by passed.

The hottest part of the engine is at the rear of ether cylinder head. Running 2 small lines passed the t stat is fine for a race mod. In the street, you would have to do research on how things work out and how hot & where.
You could introduce a restriction in the lines as not to circulate to much coolant in and out of the radiator without having sufficient cool down time.

For the street, I agree, under the T stat would be best.
 
Just a thought on a simple test:
Get a precise temp measuring device in the engine, and run it up to temp with the bypass in place with some significant loading. Then pinch the hoses closed and try it again under the exact same loading conditions and see if there is any difference. That is an easy test, and at least a first order check on things; takes some care to make the before and after conditions the same.

And I really don't know if there is an issue..... just sayin' that the flow paths are changing and that could effect how the system cools various part. Keeping hots spots from forming in the heads is an important matter (for detonation when things are being pushed hard). It is hard (for me at least) to imagine that this setup does not reduce flow in the heads at least a bit. But it might be such a small change as to make insufficient difference in head temps that have any real impacts.
 
In this intakes example, a Holley Street Dominator, there is a plugged water port at the rear where you can plumb water from the rear of the heads into the under the plenum water passage under the intake. (Same for the MP-M1-single plane. Noted by MP as a street strip manifold because of the ability to introduce heat into the intake for double duty/all weather driving)
Minor grinding under the T stat to open up the water passage in full would need to be done. Or close it off for no water heat under the carb.

Bottom picture is the MP-M1 single plane with a shot of the water passage (same as the Holley Street Dominator) that would need to be modified. Cut and closed off for no heat or cut wide open for max water flow and manifold heat under the carb. This water passage is not on the Holley Strip Dominator or the MP-M1-RACE intake manifolds.
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here is a blurb from Fel-pro about head gasket holes and the designed path of the coolant in a V8 (Chevy Rat but similar) I often wondered why the big *** hole in the front of the head was completely blocked off by the head gasket...It is to route the water to the block, stopping it from going up into the head in the front, creating a dead head for the rear to front flow.

WHY FEL-PRO USES SMALLER HOLES OR BLOCKS OFF SOME HOLES
The holes in head gaskets meter the flow of coolant properly through the heads. In most engines, coolant flows from the water pump at the front of the engine block toward the rear, goes up into the head(s), to the thermostat and finally to the radiator once the thermostat opens before returning back to the water pump.

An improperly sized or placed hole can create a shortcut which prevents coolant from following the correct path through the engine. If the coolant takes a shortcut because a coolant hole is too large at the front of the engine, the rear cylinders can overheat. If the holes are properly placed, but too large, the coolant can pass through the engine too quickly and fail to absorb enough heat, also resulting in overheating.
 
rumblefish360 said:
I may have in correctly assumed this is a race only mod due to the T stat being by passed.

The hottest part of the engine is at the rear of ether cylinder head. Running 2 small lines passed the t stat is fine for a race mod. In the street, you would have to do research on how things work out and how hot & where.
You could introduce a restriction in the lines as not to circulate to much coolant in and out of the radiator without having sufficient cool down time.

For the street, I agree, under the T stat would be best.
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I made a 1'' spacer out of a junk piece of alum. , and plumbed the lines below the thermostat, also ran them above ,which filled the block faster.
Dont remember which way I left them-----
the lines I drilled and tapped in between the 3/5 and 4/6 cylinders , were an idea I got from Bill Jenkins---------worked well !
I even thot about doing it on my 505 , but forgot it .
 
I see it as the water pump is pulling from the rad and filling through the front of the block. By having the bypass above the t stat its just going to circulate water through the block faster until it reaches temp. Once its up to temp and the tstat opens it really wont matter. Whats important is the temperature is even throughout the whole motor.
 
I'll be putting a heat barrier on mine before I fire it up since I ran mine by the fuel injectors don't need any heat if even very little affecting the injectors. Would have gone under the raise but that's where the pre fuel filter is and I put the insulation on the bottom of the runners and valley to help protect it from heat soak from the engine.
 
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