Manifold Bypass

While racing last fall, I wondered why the rear part of the intake manifold never seemed to cool down as well as the front when iced, and why the manifold heated up as rapidly as it did. I chalked the whole thing up to heat soak and a large aluminum intake directly over the motor as the culprit.
Upon further examination, I noticed coolant hoses attached to the manifold! These circulated a small amount of engine coolant through passages in the upper collector, or intake manifold.

The Fix

I bent a piece of 3/8" copper tubing with a plumber’s tool to simulate the locations of the existing outlets. Two radius bends did the trick.

 

Then I removed my intake tube (Z-tube in my case)

 

I clamped the coolant hoses using a pair or these nifty tools acquired for $7at the local auto supply:

 

I started here:

 

post quicker I'm waiting

 

Continuing:

 

Rear view:

 

Front view with bypass tube

 

If you’re wondering what a PMI is, check the “Poor Man’s Intercooler” post to follow.
I’ve only put a couple of hundred miles on it with the Manifold Bypass mod, but no leaks, drips or temperature spikes so far. Keeping air out of the system is important, so I tried to minimize the amount introduced.

The only difference I’ve noticed so far is a slightly cooler upper collector. The thing isn’t as unbearably hot as before, and cooler is better. I asked the head mechanic at the dealership what his impression of this mod was, and he replied that he saw no downside except slightly longer warm-up time during the coldest weather. He agreed with me that the design of running the coolant through the manifold was most likely a 50-state drivability consideration as well as an emissions aid to faster warm-up.

This is a first attempt, so please don’t flame too hard for the rough look. I would probably split some tubing to go over the tube for stealth or simply run a longer coolant hose point-to-point if I had to do it over.

The important thing is, with the price of mods and the scant horsepower most make, I believe in making the most of what I already have. See the “PMI – Poor Man’s Intercooler” post for more thoughts along those lines.
Wayne

 

Awesome job and very creative. Plus I learned a thing or two. Thanks for sharing.

 

One of the reasons for the coolant to run throught the throttle body is to keep it warm. Throttle bodies can ice over and that is not good news for the TP sensor or the actuator controlling throttle opening and closing. In southern california that is not going to be a problem, but somewhere like minnesota it will be. No biggie though, when it gets cold just pop the hoses back on.

And for the little bit of coolant that comes out when you pull the hoses, its not enough to warrant clamping the hoses. The coolant that spills out is whats in the throttle body and drips out, as long as you dont completly invert the hoses the coolant wont leak out and you will be fine. And that even if air does get into the system it wont be enough to cause a problem.

 

That's very interesting. So the coolant running through the plenum isn't actually meant to keep it cool?

Also, someone was telling me about a lower plenum gasket that resists heat transfer. This would in theory keep the entire intake manifold cooler, but I can't find any info on it. Anyone heard of it?

 

The maniford gasket is herehttp://www.nipponpower.com/engine/manifold_gasket/nextgear_gasket.html

I put it on along with a home-made upper insulator/spacer. You can see the lower insulator in the pix with the arrow. The entire thing (top/bottom) is ice cold even after a hard run. It works.

 

Try this http://www.nipponpower.com/engine/ma...ar_gasket.html

 

I thought originally that it ran through the throttle body as well, but upon further examination realized that it was recirculating through the upper collector (manifold).

I ran a bypass on a LT1 350 motor that had coolant running through the TB itself, and had no problems during 3 Chicago winters. Your mileage may vary.

W