Rynda

Cleaning up the L98 manifold baseplate and...I removed the stainless steel cover over the EGR passages cast into the manifold. The oil was choked up on the manifold pretty bad under the plate. That means only one thing, the EGR system is dumping quite a bit of heat into the manifold. Kinda makes you wonder how effective those coolant bypass kits are [I guess every little bit helps].
I wonder if there is a small stainless steel radiator available that you could pass the exhaust gasses through and cool them on the way to the intake manifold. I'll bet the EGR Valve would last longer also. This would require a little creative re-routing, but should be doable.
Anybody else notice that, am I gettin goofy??

ol,RJ

the EGR system is a strange thing to understand.
If you have a factory service manual, take a look at what it says.
the hot exhaust gas's are routed into the intake because it actually cool's the combustion temp. (weird huh)
the theory is that it makes the mixture less explosive so it burn's slower and cooler (maybe it is used so they can run a leaner mixture and have less emissions).
I'm not sure if the temp of the gas's need to be high in order for it to work correctly, probably not.
you could just restrict it down with something, or do away with it all together.

Rynda

I am not in favor of doing away with the EGR all together untill I get really good at burning my own chips. I've burnt a couple of chips, and still taking baby steps. I do not think the gas has to be hot since it is only used to dilute the fuel charge in order to keep combustion temps below NOx formation. Reason tells us that lower combustion temps are less efficient (the Carnot Cycle). Anyway I'm am gonna give this a shot.
I was suprised at apparently how hot that part of the manifold was getting and had not seen any posts concering this, considering the pains we go through to keep the intake charge as cool as possible.

ol,RJ

I guess if I was going to try and reduce the temp I would start by getting the exhaust gas from farther back (near the cat). then you could install a small cooler in the line under the car.
that should help the passenger side, but I think the driver's side exhaust gas comes thru a passage in the head directly into the intake. only thing you can do with that one is block it off (the other side hopefully would supply enough).

Rynda

Great suggestion, I hadn't though of that.
On the 90 Vette, the exhaust gas is tapped out of the passenger side exhaust manfold, up and over the valve cover and into the intake manifold just ahead of and to the right of the distributer. The intake manifold has a central passage to reach all of the manifold runners.