Any of you tripower guys dealing with heat soak problems? My 3 webers seem to suffer from heat soak problems after sitting from a good run. It'll start and run but my AFR readings are all over the place going really lean. This only happens if I shut the car off and let it sit for a short time (5-10 minutes) after driven for about 10 miles. If I take it to work (13 miles) and let it cool all day, she runs fine. I've got phenolic spacers under the carbs, plastic insulating washers around the carb studs, insulated the fuel line, and wrapped the headers. My AFR is running a around 12.5-13 until I shut off and restart, then it jumps around - 12 to 16.5 wildly. If I'm going downhill with my foot off the skinny pedal, I can feel it trying to cut out and stumble. I thought of making a shield to cover the headers hoping to block some of the heat. Of course that could backfire and turn it into a big baking sheet...
Tri carb heat soak?
- Thread starter vssman
- Start date
What may be happening is that fuel is evaporating completely from one of the carbs and it is only flowing air for a short time after a hot restart. Or some of the lighter distillate components of your gasoline could be boiling off rendering your sensor inaccurate.
The heat shield is a good idea. That will reflect a lot of radiant heat away from the carbs. You may need to insulate the starter, though. If you could rivet some heat resistant insulation to one side that would help as well.
Another thing that could help is to add an electric fan on a timed relay to run the fan for a few minutes after shutdown. Thermo siphon effect will continue to cool the engine and reduce heat soak.
One thing that people forget is that originally the water heated spacer not only provided some heat to prevent carb icing in cold, damp weather, it also kept the carburetor cooled at 160-180F coolant temperature - important when you consider that the center carb is located directly over the center two exhaust port roofs.
The heat shield is a good idea. That will reflect a lot of radiant heat away from the carbs. You may need to insulate the starter, though. If you could rivet some heat resistant insulation to one side that would help as well.
Another thing that could help is to add an electric fan on a timed relay to run the fan for a few minutes after shutdown. Thermo siphon effect will continue to cool the engine and reduce heat soak.
One thing that people forget is that originally the water heated spacer not only provided some heat to prevent carb icing in cold, damp weather, it also kept the carburetor cooled at 160-180F coolant temperature - important when you consider that the center carb is located directly over the center two exhaust port roofs.
I also am thinking about that. If you remove the fuel pressure only if you have a mechanical fuel pump the return line would bleed off the fuel pressure.JackFish":1426bwl7 said:
The heat deal can be dealt with as Jack said with cooling fan, shields & phenolic carb spacers. The above combination has got to help with this problem.
The header heat is the killer.
kevinl1058
Well-known member
I had the same issues made heat shields (see Picture)
under each carb reduced heat significantly. Another issue I had was the the Thermo Tech Hood liner was bouncing the heat back down on top of the carbs. Removed the hood to install OEM hood liner and the car fired up even after 40 drive in 90 degree heat. Never overheating once. Hood is back on so I will take her out for a drive to see if the new hood liner makes a difference.
under each carb reduced heat significantly. Another issue I had was the the Thermo Tech Hood liner was bouncing the heat back down on top of the carbs. Removed the hood to install OEM hood liner and the car fired up even after 40 drive in 90 degree heat. Never overheating once. Hood is back on so I will take her out for a drive to see if the new hood liner makes a difference.I don't see how a return line could help. Fuel and vapor are going to escape out the carb vents, metering holes, and other places before going into a return line. A carb is an open system, not closed like EFI.
Even if you placed a return line at a regulator, it's only recirculating fuel from the regulator, not the carb.
Here's a delay-off relay that can hold the fan on for a set time after shutdown. Be warned! It is very pricey at $2.59......
Actually, it is only rated at 10A so I would use it to trip a 30A relay for a fan. But for that price, get a couple. Hook one up to your dome light and another to the radio! Maybe another to the headlights!
EDIT: Sorry forgot to add the link http://www.ebay.com/itm/1pcs-NEW-12...149?pt=LH_DefaultDomain_0&hash=item1e91b90ae5
Even if you placed a return line at a regulator, it's only recirculating fuel from the regulator, not the carb.
Here's a delay-off relay that can hold the fan on for a set time after shutdown. Be warned! It is very pricey at $2.59......
Actually, it is only rated at 10A so I would use it to trip a 30A relay for a fan. But for that price, get a couple. Hook one up to your dome light and another to the radio! Maybe another to the headlights!EDIT: Sorry forgot to add the link http://www.ebay.com/itm/1pcs-NEW-12...149?pt=LH_DefaultDomain_0&hash=item1e91b90ae5
Thanks for the ideas guys. Kevin, I like the heat shields and may borrow the idea. I've been looking at the layout to see if I can shield the headers below the linkages. I think it would have to be mounted very close to the block so that it doesn't create a chimney effect next to the head. My fuel lines are on the drivers side. The main line runs from the regulator that is mounted to the old coil mount (I'm running a DUI) and goes toward the front around the valve cover before it branches off to each carb. What I really need is 3 throttle bodies that look like carbs and go over to EFI...
When I added the header shield on the crossflow Mustang I used 1/2" wide strips of aluminum bar bent in a "U" shape. I clamped one leg of the "U" to a tube and used a sheet metal screw to attach the shield to the other leg of the"U". I was just trying to keep radiant heat off the intake hose and it worked pretty well.
But the post shutdown heat issue you have is probably not related to the headers - those cool pretty quickly. I think it's the heat soak from the rest of the block and cylinder head. That's why I like the idea of the delayed fan for this problem. Not only will it get some cooler air into the engine compartment, the coolant will cycle itself thru the system too.
But the post shutdown heat issue you have is probably not related to the headers - those cool pretty quickly. I think it's the heat soak from the rest of the block and cylinder head. That's why I like the idea of the delayed fan for this problem. Not only will it get some cooler air into the engine compartment, the coolant will cycle itself thru the system too.
theman1990
Active member
Kevin, what did you use for the shields? Also, what fuel pressure regulator are you using with the triple webers?
kevinl1058
Well-known member
Aluminum sheets I picked up at a local hobby store. Using a Mr. gasket adjustable pressure regulator set to 2.5lbs..
theman1990
Active member
How did you fill the ICH fuel inlet and change it to the other side like the ICT's are? I have the ICH at home and am ordering the ICT's soon.
Drilled & tapped the blank side. Used a pipe plug on the one that came with the carb. Little bit of Teflon tape too using care not to let the tape hang over the top of the plug into the carb. Just watch how tight you get the plug as you don't want to crack the carb. I haven't solved the heat soak nor added any shields yet. For now I've been popping the hood to let the heat out. I rarely drove it last year. This springs project is a T5, 8", and a new front end with hopes it'll be a bit less wandering and geared better for more driving time...
I use a elect. fan .With out one I am sure the plactic hood would melt after shut down. Cools the engine compartment down quickly.Turbo power Baby!
that is why I run a port divider, even on a cast manifold,less exhaust to suface area to cook carb.
kevinl1058
Well-known member
Problems reoccurring fuel was flowing from the base of the carbs (2 and 3) at shut off. Quick cure was turning on the fan to cool the motor. I'm beginning to believe that you get what you pay for and the Mr. Gasket fuel pressure regulator just wasn't doing the job. I recently ordered a Holley 0-4 psi regulator to see if that will help. Going to rebuild the carbs with new needle valves, reset the floats and see where we go from there. I like my tri-power but a v8 may be around the corner.
To reduce under hood temps, try putting a small vent in the hood:
. 
... if appropriate, T bolt type bubble offers good under hood convection cooling after shutdown with headers and hot carbs'. I was worried the engine heat would separate the bonding of the fglas', initially elec rad fan was not switched so would run after shutdown with heat rise but now it's on ign. switch. After shutdown it gets hot but SFSG'.
.
. . 
. 
. 
. 
the inappropriate cowl induction hood scoop and others probably also could work ..
(PS former 'Mr Gskt' regulator ruptured pumping fuel on hot eng/ headers)
haev fun
. 
... if appropriate, T bolt type bubble offers good under hood convection cooling after shutdown with headers and hot carbs'. I was worried the engine heat would separate the bonding of the fglas', initially elec rad fan was not switched so would run after shutdown with heat rise but now it's on ign. switch. After shutdown it gets hot but SFSG'.
.
. . 
. 
. 
. 
the inappropriate cowl induction hood scoop and others probably also could work ..
(PS former 'Mr Gskt' regulator ruptured pumping fuel on hot eng/ headers
) haev fun
