November 7, 201114 yr I want to clean up the intake manifold as much as possible on this webered ea81. I removed the anti- afterburner and am confused by something. I removed what was screwed into the rear of the intake right behind the A-AV, It appears to be just a metal plug with two plastic hose fittings on the outside. I do not understand why there is even a passage to the inside the manifold there. I searched the forums and I think I found a pick of the "plug" I am talking about. Here is that pic but note that one of the plastic nubs is broken off in this pic. I can post more pics of the part that will better illustrate my confusion tomorrow if needed when i have access to a camera. So is this truely just a plug? there is something here I am not getting. Also do you guys who have removed this stuff just plug the two manifold ports just to the drivers side of the opening for the carb base with vacuum caps?
November 7, 201114 yr Author I should add that the end of the threaded part of this valve looking thing that you can't see in this pick is solid and flat, no actual opening into the manifold. Perhaps there was something else in it's place on certain models? I can just replug the whole with this same piece and not have to even cap the two plastic hose fittings, correct?
November 7, 201114 yr Just plug the hole if you dont want it. All that is is a thermo-vac valve. It controls airflow from one port to the other based upon temp.
November 7, 201114 yr Author Just plug the hole if you dont want it. All that is is a thermo-vac valve. It controls airflow from one port to the other based upon temp. But my point is, why is there even a hole in the manifold there. This valve has no port (to within the manifold)
November 7, 201114 yr But my point is, why is there even a hole in the manifold there. This valve has no port (to within the manifold) The valve is designed to sense engine temp and to open or close an internal gate between the two vacuum ports. It is a way of turning on or off a device that is vacuum operated based on engine temp. For example - the EGR valve will only be enabled after the engine has reached operating temp. This valve interrupts the vacuum signal to the EGR valve (or whatever) till the proper temperature is reached. It does not itself supply the vacuum - only regulates if it's allowed to flow or not. Therefore it does not need an opening at it's base - just an appropriate metallic interface that facillitates the thermal transfer. Typically the bottom of the valve will be in contact with coolant..... GD
November 7, 201114 yr Author The valve is designed to sense engine temp and to open or close an internal gate between the two vacuum ports. It is a way of turning on or off a device that is vacuum operated based on engine temp. For example - the EGR valve will only be enabled after the engine has reached operating temp. This valve interrupts the vacuum signal to the EGR valve (or whatever) till the proper temperature is reached. It does not itself supply the vacuum - only regulates if it's allowed to flow or not. Therefore it does not need an opening at it's base - just an appropriate metallic interface that facillitates the thermal transfer. Typically the bottom of the valve will be in contact with coolant..... GD got it. thanks for the explanation. and yes it apears to be in contact with the coolant channel.
November 7, 201114 yr Author and the two ports right under the carb, are they just vacuum to be capped?
November 7, 201114 yr Are you refering to the small line that opens to to a squarish port under the carb base? That is the carb base-heater port. It flows coolant to heat the carb - it's basically an emissions trick. Hot air burns cleaner. It's typically blocked when installing a Weber as it tends to leak from ill-fitting weber adaptor plates. GD
November 7, 201114 yr Author Are you refering to the small line that opens to to a squarish port under the carb base? That is the carb base-heater port. It flows coolant to heat the carb - it's basically an emissions trick. Hot air burns cleaner. It's typically blocked when installing a Weber as it tends to leak from ill-fitting weber adaptor plates. GD No not the pre-heater, I am talking about the two ports next to the carb hole (just to the drivers side) on the manifold left empty when I removed the anti - afterburning valve. I can post a pic tomorrow, or if you are feeling curious, look in an ea81 FSM in the engine section they have a digram of a bare bones manifold. You'll see what I mean
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