Holley heat soak Question?

[Anonymous]

Finally got my cars overheating problems fixed by boiling out the system with muriatic acid

But after a extended cruise night tonite I ran into another problem... :x

After I've been cruising for awhile, (2-3 hours) the car starts to have a major hesitating problem and seems to be loading up. Once you get it out of town and can clear it out its fine again.

Problem is the carb bowl hanging out over the headers. A thermometer reading shows that the bowl is right around 170+ degrees and is too hot to touch on the bottom of it.

After you shut it off there is vapor coming out of the bowl vent and it seems to be boiling the fuel right out of the accelerator pump after it sat shut off for awhile because you have to pump it a few times after its running or you will get a major bog the 1st 3 or 4 times you give it gas.

Obviously I need some cool air ducting to the carb or a heat shield or both. I tried to make a shield a while back out of some aluminum stock but it seemed to make the problem even worse!

Should I make a sandwich out of some aluminum sheet and some really thick gasket material I have and glue it all together with my 3M panel bonding adhesive. You can hold a lighter up to it and it wont burn so it should work I would think?

BTW, Everything else is fine, not running lean or anything like that and my headers are jet hot coated allready and I am allready running cold air to the air cleaner and the hood scoop is functional too. Think that about covers it.

Thanks,

Doug

 

[80broncoman]

I'd make the heat shield L-shaped and have it come up in front of the carband also the side of the bowl. And make sure to block air that has went thought the raditor as well. Just make sure the shield does not touch the carb at all.
Also there are some 3/8s and 1/2 inch thick insulating gaskets you might try if you have the room, and don't already have one. The headers might be 90% of the problem or 66%. Shielding will work best if the headers are the main problem.

 

[Anonymous]

I'm pretty sure the headers are the problem. I'd have to measure but I think the float bowl sits 4-6 inches straight above them.

I allready have the 3/8 thick carb gasket.

I'll measure tommorow and take a picture too!


Thanks,

Doug

 

[wsa111]

Doug, living in south carolina the heat factor really affects the holley carb bowl.

I made a stainless steel shield under the accerator pump cover & that corrected 80% of fuel perculation in the accerator cover causing a hesitation on the first or second acceration attempts, I plan to make a larger heat shield which will eliminate all the direct heat to the bowl.

Do that & that should take care of your heat soak condition. Bill

 

[addo]

If you can snag a few to play with, the old asbestos tiles used in roofing are pretty good for insulator "sandwiches". They're the ones people used to fix in a diamond pattern. Cut them outdoors after damping down, and don't grind or sand!

Aluminium is a heat sink, too. If you had a plate out over the headers and then sandwiched between gaskets under the carb, it may have been conducting the heat to your carb base.

The best, most dramatic cure I have seen for carb heating was with a 1" phenolic spacer. Nothing short of amazing.

 

[Anonymous]

Bill,

Did you use any insulating material or just the stainless sheet? I have lots of aluminum sheet stock laying around and I tried making one out of that but it just increasced the problem after it heated up....just think hot stove and you get the idea!

I think thast is one of the problems....this has been the hottest summer up here since 1988

Thanks,

Doug

 

[Anonymous]

If you can snag a few to play with, the old asbestos tiles used in roofing are pretty good for insulator "sandwiches". They're the ones people used to fix in a diamond pattern. Cut them outdoors after damping down, and don't grind or sand!

Aluminium is a heat sink, too. If you had a plate out over the headers and then sandwiched between gaskets under the carb, it may have been conducting the heat to your carb base.

The best, most dramatic cure I have seen for carb heating was with a 1" phenolic spacer. Nothing short of amazing.

Adam,

Never ran into any of them tiles, although I have seen pictures of them before!

I made 2 shields so far...one (and the best) that attatched to the side of the head using the egr valve mounting studs and the other one that bolted inbetween the carb and intake...that one freaking blowed and actually caused the carb to heat up so much after you shut it off that it would start blowing fuel out of the bowl vent!

I must take pictures tommorrow!!

Thanks,

Doug

 

[wsa111]

Doug, I did not use any heat insulating material at all.

However summit sells an aluminized sheet of heat shielding which could be glued to the bottom of the heat shield. On my el camino i used this aluminized heat shield material & secured it with toyota FIPG engine sealer & have no problems with it loosing its bond. The hooker headers I have on that vehicle run within 2" of the evaporator box & the fabric reflects the heat without any burning of the plastic.

During your winters you will probably want to remove the shield to get some heat to the carb area. Bill

 

[xctasy]

Australians deal with hot fuel handling and heat soak problems more than Americans becasue they have humid and hot conditons. Holden V-eights and log head Falcon I6's were the worst.

The any sheild has to reflect heat towards the headers (shiney steel plate on the bottom area), and soak heat from the carb area (paint it black top side). A penolic or gas ressitanant HDPE spacer with do the rest.

Other points to note are that running high fuel pressure and not having a return line is very bad for fuel vaporisation. Bell engineers had a go with GM's fuel systems in the mid eightees becasue of waranty claims occordign to one University of Otago Physicist. They found the lack of return line and high line pressure was the cause. Since 1985, GM eliminated carbs on all new products, and they hada bare minimum of retrun line EFI with lower pressure throttle body injection.

Ford and Holden had huge problems in the early 80's. The draughts were very servere. There new more compact sixes and v-8 engines in there Falcons and Commodores had lower bonnet lines and less radiator area than ever before, but were becoming loaded with A/C, taller diff ratios, and yet more emission equipment. Ford solved there problems with plastic spacers, return lines on all 3.3 and 4.1 sixes, and had to restrict the 351 XE option mainly becasue of lack of engines, but it was also the worst V8 ever for awefull hot fuel handling issues.

Holden added the Varijet 2-bbl carb and HDT offered a anti vapouristion package with asbestos heat shield and re worked fuel ines in all there 4.2 and 5.0 v8 models.

Information is contradictory, but vapour problems happen when caviation occurs. If you rasie pressure, you create problems. We all know Holleys are diesigned around good fuel pressure and a higher float level, but Ford themselves in 1983 added the fuel return line on there 4180 series carbs, and elimiated hot fuel handling.

Mike, if you can get a 4-bbl 4180 front float bowl off a 83 to 88 5.0 or 5.8 Mustang or F150 truck, then you can blead off the fuel pressure via a half mm restrictor jet like Ford Austtralia did from 1982 to 1993 on there 2-bbl Weber 34 ADM carby engines. (You can use any Holley4150 four barrel vac sec front float bowl, it just has a press fit steel line to the back carb, which is then bleed off on the 4180 carb.)

You can then recirulate it to the tank like Does 10'S does in his Falcon, or ask someone to send you the Carter XE-XF Falcon crossflow fuel pump, which has the return line incorporated.

I know logic says good fuel pressure and heat shielding will fix things, but Ford looked towards return lines with 3 psi pressure, and ever since then, fuel percolation hasn't been a Ford I6 problem. Can't imagine Ford Australia in the cash strapped 1980's wanting to spend money on something that didn't fix the problem first.

 

[Lazy JW]

Aluminum is an excellent conductor of heat and will therefore absorb the heat and transfer it toward the carb. Remember the second law of thermodynamics states that heat travels from a hot area TOWARD a cooler area. If the headers are hotter (which of course they are while running) then the heat shield can actually make things worse. Stainless steel absorbs/transfers heat much slower than aluminum and somewhat slower than regular carbon steel. I still have some phenolic material that would be suitable for a carb spacer.
Joe

 

[kirkallen143]

Hey Doug,

I know it looks ugly, but thought about wrapping those headers? It comes in black, too. That is what I am doing for my turbo application on the inlet pipe to turbine and then also on the outlet exhaust from the turbo. 2"x50' runs about $36.00 from Jegs. Just a thought, later.

Kirk ' 73 bronco

 

[MustangSix]

The carb is going to run near engine temps anyway, unless you figure out a way to radiate some heat, but that level of temp is not usually a problem. Gasoline won't boil at those temps and shouldn't be an issue.

Where you probably have most of your current problem is from radiant heat coming off the headers. A heat shield between the headers and the carb is likely the best bet.

We had one on the crossflow at one point. It was simply an aluminum sheet fastened to the headers. It reflected most of the radiant heat downward and kept the throttle cable and air intake from melting.

 

[mustangsix2]

we fixed that problem with our ceramic coating but i suppose the heat shield held up ok.

 

[MustangSix]

we fixed that problem with our ceramic coating but i suppose the heat shield held up ok.

It's better, but we should still consider a heat shield. Maybe we can fab something up later to see how it looks.

 

[Soldmy66]

A couple of manufacturers make a product that is used to protect the starter on a small block Chevy from heat; since heat-related starter failure is a recurring issue. I think the shield used is two layers of metal, separated by some air space or some non heat conducting material - but I just don't recall. Looking at that/those product(s) might offer some suggestions.

 

[Anonymous]

Thanks for all the ideas!!

Heres what I come up with compliments of Menards....

I looked all over the place to find sheet stainless steel and finally found a piece at our local home improvement store. It measures roughly 10"x3.5".

It really cut down on the heat but I still plan on ordering some of that heat insulating material from Summit when I put my next order in.

Thanks guys!!

Doug

 

[Anonymous]

You could do one more, and get a 12v bilge ventilation fan from a boat supply (the kind idiots on ebay sell as "electric superchargers") and use it to bring colder air from in front of the car to blow directly onto the carb.

Aircraft use cool air tubes to cool accesories all the time, like the magnetos and vacuum pump. You could wire the fan to a switch used to turn on and off regular electric radiator fans, since that is the temp range you are dealing with.

 

[wsa111]

Doug, glad the heat shield helped. The small stainless shield with the heat insulating cloth really cut down on the heat transfered to the accerator pump cover.

I may do the same as you did & put a heat shield under the entire float bowl with the aluminized fabric heat insulating material.

Also when I get a chance I will get you a tube of the FIPG sealer I have been talking about & you will see this is a great product marketed by toyota & lexus.

Our technicians always have plenty of this sealer left over from previous engine jobs. So it will be a no cost deal.

Expect a care package in the mail in a week or two. Bill