1986e ironhead EGR and Coolant crossover passageway -- clarity needed!~!
01-31-2018, 01:45 PM
#1
Oil Producer
Thread Starter
1986e ironhead EGR and Coolant crossover passageway -- clarity needed!~!
I have read many threads on the 1986 early ironhead configuration for both the EGR passegways and the rear intake manifold coolant crossover.
EGR
The 1986 ironhead exhaust appears to have two passegways or routes to the egr valve. Both the cyl 8 exhaust tube to rear egr port by the distributor on tne intake and the and secondly, the two passegways that come up from the heads below between cylinders 3-5 on driverside and 4-6 on passenger side. The former routing is of the later aluminum head cars, and the latter routings are from the early ironhead 85 cars.
So my question is...do i block off entirely the 85-style egr passage and go with just the egr tube routing? this was what i found when i pulled the intake....there were two metal block off plates with 1/8th holes drilled in them. why the holes? are we wanting to let some exhaust gas through the 85's passageways? or none?
Obviously i can simply configure it the way it was when i tore it down but i wanted to ask what the factory setup was. i do not have the 86 manual. only the 87.
COOLANT PASSAGEWAYS at rear, including the "steam tube" connection from the rear passageway to the heater line.
What a gong show this subject is! Yes i've read all the threads. I've read Cliff Harris's comment who I believe also has the iron head 86. He seems to have tried with the rear crossover ports OPEN and then also he tried it blocked off with the 1/8th hole.
I read somewhere that another member upsized the hole to a 1/2" hole.
Is there any updated knowledge on the correct configuration that avoids heat building up in the rear of the heads? The configuration i found when i removed the intake was both sides of the egr crossover were blocked off with 1/8th pinholes.
And...both sides had comprimized gaskets at this area. the intake bolts were corroded and rusted and i can tell fluid had been leaking pas them for a long while.
The steam tube i*think* was designed so that if you get an air pocket in that rearward area the air (steam) is allowed to bleed off into the heater line. I've read others have plugged this off and no issues. Perhaps its only an issue if people do not correctly burp their cars and this was a failsafe attempt by GM.
Either way, I am keeping this car stock and unmodifed so I am leaving the steam tube in place. BUT, i am considering leaving both passageways open. Perhaps leaving one side blocked off and the other side open would encourage a flow from one side to the other.
I just don't know. why not leave them blocked off entirely. why does the head even need coolant in it?
On the other hand, if an engineer thought coolant should be in the threads, why block it off and restrict it? Is it because he wanted there to be a pressure graident in the very beginning of fluid forcing its way inside teh holes which would force the air up and out the "steam tube" which seems more like a "bleed tube" for the rear of the heads.
i know this has been discussed a thousand time, just wondering if anybody has had failures that were tracked back to either open or closed passageways.
thnx.
EGR
The 1986 ironhead exhaust appears to have two passegways or routes to the egr valve. Both the cyl 8 exhaust tube to rear egr port by the distributor on tne intake and the and secondly, the two passegways that come up from the heads below between cylinders 3-5 on driverside and 4-6 on passenger side. The former routing is of the later aluminum head cars, and the latter routings are from the early ironhead 85 cars.
So my question is...do i block off entirely the 85-style egr passage and go with just the egr tube routing? this was what i found when i pulled the intake....there were two metal block off plates with 1/8th holes drilled in them. why the holes? are we wanting to let some exhaust gas through the 85's passageways? or none?
Obviously i can simply configure it the way it was when i tore it down but i wanted to ask what the factory setup was. i do not have the 86 manual. only the 87.
COOLANT PASSAGEWAYS at rear, including the "steam tube" connection from the rear passageway to the heater line.
What a gong show this subject is! Yes i've read all the threads. I've read Cliff Harris's comment who I believe also has the iron head 86. He seems to have tried with the rear crossover ports OPEN and then also he tried it blocked off with the 1/8th hole.
I read somewhere that another member upsized the hole to a 1/2" hole.
Is there any updated knowledge on the correct configuration that avoids heat building up in the rear of the heads? The configuration i found when i removed the intake was both sides of the egr crossover were blocked off with 1/8th pinholes.
And...both sides had comprimized gaskets at this area. the intake bolts were corroded and rusted and i can tell fluid had been leaking pas them for a long while.
The steam tube i*think* was designed so that if you get an air pocket in that rearward area the air (steam) is allowed to bleed off into the heater line. I've read others have plugged this off and no issues. Perhaps its only an issue if people do not correctly burp their cars and this was a failsafe attempt by GM.
Either way, I am keeping this car stock and unmodifed so I am leaving the steam tube in place. BUT, i am considering leaving both passageways open. Perhaps leaving one side blocked off and the other side open would encourage a flow from one side to the other.
I just don't know. why not leave them blocked off entirely. why does the head even need coolant in it?
On the other hand, if an engineer thought coolant should be in the threads, why block it off and restrict it? Is it because he wanted there to be a pressure graident in the very beginning of fluid forcing its way inside teh holes which would force the air up and out the "steam tube" which seems more like a "bleed tube" for the rear of the heads.
i know this has been discussed a thousand time, just wondering if anybody has had failures that were tracked back to either open or closed passageways.
thnx.
Last edited by VikingTrad3r; 01-31-2018 at 01:50 PM.
01-31-2018, 10:45 PM
#2
Oil Producer
Thread Starter
im not restricting the rear coolant ports. im leaving the ports open. those holes are 1/8th or smaller. there is no way that coolant is being cycled and refreshed in there. i think thats what explains why the manifold bolts back there are always corroded. the coolants looses its corrosion inhibitors over time and is never cycled. i