When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
I have a 75 small block. The vacuum actuator with a rod to the heat riser is bracketed to the manifold. The vacuum hose to the actuator is long gone. Can anyone tell me what vacuum port on the engine should be used to make the system functional?
On my ‘77 L-48 there is a hose that runs from the heat riser to an “F” shaped fitting on top of the thermostat housing. I believe it is OEM but I’m not sure what the difference may be between years. I have a pic but can’t figure out how to post it here.
It should be plugged into the bottom port on the on the “F” tree. It should supply vacuum to close the heat riser until the engine reaches operating temperature and cuts off vacuum so the heat riser can open.
If your heat riser is not functional and it is 'closed' presently, you NEED to get it operational or defeat it altogether. Operating your engine with a 'closed' heat riser valve will build a LOT of heat on that cylinder head. If you do any highway driving, it could damage the engine, blow a cylinder head gasket, and/or actually melt the exhaust manifold for the amount of heat that is restricted from being exhausted.
Unless you live in cold climates or regularly use the car in cold weather, you don't really need a 'heat riser'. If it isn't hooked up, just be certain that the valve is "open".
What engine and carburetor do you have? Could you post a picture of what components you do have. L82 & California build cars and L48 federal vacuum lines are routed a little different.
The 'default' spring SHOULD keep that valve open even if the system is disconnected. But, just like the earlier units that worked via a bimetallic spring, when that stuff gets rusted, It can lock-up in the CLOSED position. And there is nothing that will tell you that the valve is not open....
If your heat riser is not functional and it is 'closed' presently, you NEED to get it operational or defeat it altogether. Operating your engine with a 'closed' heat riser valve will build a LOT of heat on that cylinder head. If you do any highway driving, it could damage the engine, blow a cylinder head gasket, and/or actually melt the exhaust manifold for the amount of heat that is restricted from being exhausted.
Unless you live in cold climates or regularly use the car in cold weather, you don't really need a 'heat riser'. If it isn't hooked up, just be certain that the valve is "open".
How can I check if it is open or closed? When I apply vacuum to mine to the hose that is supposed to operate it, it does not hold. its like sucking on a straw. I do not know if it is open or closed now. On the video on my link below, you can see that the rod is all the way down. When I pull it up, the valve (door) on the heat riser moves, but I do not know if I am actually opening it or closing it. I believe it might be open all the time since the engine feels quite right and there is never vacuum on it and if there was, nothing would happen... Here you can see a short video clip: https://onedrive.live.com/?cid=58DB6...174115&o=OneUp
How can I check if it is open or closed? When I apply vacuum to mine to the hose that is supposed to operate it, it does not hold. its like sucking on a straw. I do not know if it is open or closed now. On the video on my link below, you can see that the rod is all the way down. When I pull it up, the valve (door) on the heat riser moves, but I do not know if I am actually opening it or closing it. I believe it might be open all the time since the engine feels quite right and there is never vacuum on it and if there was, nothing would happen... Here you can see a short video clip: https://onedrive.live.com/?cid=58DB6...174115&o=OneUp
Go back to Post #5 and look at the photo I posted.
The normal position for the actuator and heat riser is fail safe OPEN.
There is a spacer you can purchase if you want to remove the actuator and heat riser.
Some of the vendors carry that spacer.
Go back to Post #5 and look at the photo I posted.
The normal position for the actuator and heat riser is fail safe OPEN.
There is a spacer you can purchase if you want to remove the actuator and heat riser.
Some of the vendors carry that spacer.
Image # 1: the first one is the heat riser 'default", meaning how it is if I do not touch it. I would like to be sure it is OPEN. Image # 1: This is the Default: NOT pulling the rod up. is this OPEN?
Image # 2: The second image is when I am fully "pulling" the rod up, forcing against the springs tension. I believe that when I pull it up, I am CLOSING it, "simulating" what the lack of vacuum does when the switch reached the heat needed. Is this correct? Image # 2: This is when I pull the rod up. Is this CLOSED?
The video shows this movement better than the photos. Thanks!
Image # 1: the first one is the heat riser 'default", meaning how it is if I do not touch it. I would like to be sure it is OPEN. Image # 1: This is the Default: NOT pulling the rod up. is this OPEN?
Image # 2: The second image is when I am fully "pulling" the rod up, forcing against the springs tension. I believe that when I pull it up, I am CLOSING it, "simulating" what the lack of vacuum does when the switch reached the heat needed. Is this correct? Image # 2: This is when I pull the rod up. Is this CLOSED?
The video shows this movement better than the photos. Thanks!
I can't see the video because I'm required to log into some Microsoft site...
Photo 1 shows your heat riser in the OPEN position, just like my photo in post #5.
Photo 2 shows your heat riser is partially CLOSED/OPEN.
First, are you manually trying to pull the rod up with the engine HOT or COLD?
On a COLD engine If you are trying to manually pull the actuator rod up and that is the extent of the travel, pull the hose off at the actuator and try again, see if you get full travel so the finger stop is in the CLOSED position, again post #5.
There is a one way stop check valve in the EFE TVS switch, so by pulling the rod up you are deadheading energy against the check possibly limiting actuator travel.
I can't see the video because I'm required to log into some Microsoft site...
Photo 1 shows your heat riser in the OPEN position, just like my photo in post #5.
Photo 2 shows your heat riser is partially CLOSED/OPEN.
First, are you manually trying to pull the rod up with the engine HOT or COLD?
On a COLD engine If you are trying to manually pull the actuator rod up and that is the extent of the travel, pull the hose off at the actuator and try again, see if you get full travel so the finger stop is in the CLOSED position, again post #5.
There is a one way stop check valve in the EFE TVS switch, so by pulling the rod up you are deadheading energy against the check possibly limiting actuator travel.
Thanks for the detailed and quick reply. Here is a better link directly to youtube:
Thanks to your reply, I am glad to believe now that the "home position" for my EFE Actuator is normally open. By the way, my actuator valve does not work. If I apply vacuum or pressure t the hose, it does not hold vacuum or stop pressure. I'm just thinking of leaving it like this since I live in FL and do not believe I really need it. Even better, just take the actuator off and cap the hoses to and from the switch. Riser valve would be always open. Would this be a good idea?
Heat Riser Vacuum Actuator
