3X1 Weber heat soak???

[vssman]

Felllas:

I've been dealing with a tempermental engine this summer in my 63 drop top Falcon. I'm running a rebuilt 200 with a 3X1 weber/offy intake, DUI, yada, yada , yada... So it goes like this: It runs really good but from time to time it'll stall on me and I won't be able to restart it to save my life. After it cools, it'll start and run good. Farting around this past Saturday came to realize I may very well have a heat soak problem. I was running it around the neighborhood and it died. I jumped out and found my fuel pressure to be right on (3lbs) but heard a sizzling sound from the carbs (mainly the center one but I couldn't tell if the rear one was also doing it). I removed my air filter and didn't see any drips but clearly heard sizzling. Also the air filter was HOT - like taking a hot potato out of the oven hot... Timing is 15° and the headers are wrapped to the collectors. This got me thinking a bit more... It runs pretty good in the driveway with the hood UP but will start to sputter and die if I let it idle with the hood closed. I can't imagine making a heat shield that will fit under all of those linkages but if you think it might be heat soak, I'd try it. I may also try to make an air cleaner assembly that draws air from the outside too. Finally, could timing be doing it too? It doesn't ping but wouldn't too much advance cause the intake to be hotter?

TIA...

 

[MPGmustang]

Sounds like vapor lok to me...

I have a insulated fuel line from my gas pump to my carb to prevent what you described

IIRC when vapor lok occurs you would still have pressure in the line.

Test, when it won't start hot, drop some gas down the carb(s) (might need 2 ppl) and hit the gas, should start then die again (or coooled off enough to run normally)

solutions:
1) re-route gas line from pump to carb(s)
2) insulating the gas line from heat
3) electric gas pump (best if near the gas tank)

 

[vssman]

I haven't tried the fuel down the carb trick. I removed a few plugs and found them dry so I know I wasn't over pumping the fuel to try to restart it. I'm working on making 3 phenolic 3/8" thick spacers to go under the carbs. I'll try to locate nylon 'flanged' washers to insulate the studs too. I guess I can pick up fuel line insulating covers and put them on. My fuel line runs from the pump through a short line to a metal filter to another short metal line to the Holley regulator that is mounted to one of the bolts that used to hold the coil and then around the front of the valve cover to the driver's side of the carbs.

Any thoughts on timing? How much are you guys running? - I thought I was in the ball park. It doesn't ping so I figured it was OK. I know if I go a few more degrees forward (guessing 3 or 4) it's hard to turn over when it's hot...

 

[JOHN G]

have similar problems with mine-runs fine, but sometimes is very hard to start after it has ben shut down for a short time. let it cool and all is well. Carbs are very hot at this time and I get lots of smoke out the pipes when it does fire. This is no doubt heat related-I would like to know how the spacers work, but I think that the under hood heat from the engine/headers is just too much to overcome. My solution hopefully will be an electric fan with a thermostat. The ambient temp needs to be reduced, but I would be curious to see how the spacers will work.

 

[jahearne]

There's been a lot of talk about how a port divider may or may not help performance, but it's located right under the carb I think it would help a lot towards soaking up some heat. Any thoughts?

 

[powerband]

I needed this discussion on heat soak remediation for the 3X1 setup.

Slow speed/static heat rise with Headers seems to be key problem . An electric fan will pull/push the same amount at any engine speed and even when parked if wired for constant power. The 250/'61 project has no room for a WP driven fan, electric fan is temp' selectable high CFM primary - not supplemental, also "modern" mustang radiator with a lot more surface/sq" air flow capability through engine bay. Initially I wired it constant but would cycle long after parked . I have slow cranking and backfire sometimes after shutdown even with PMGR starter (10:1 Cr , 272 cam, @ 14 degrees timing).


I've considered an alum. plate angled over headers but heat still has to go somewhere (up), especially on shutdown and restart. even my mild built 170 with Headers throws a lot of heat up into carb/fuel/intake area . Header wraps are supposed to keep heat in for performance .






250 SixT'Bolt Comet project includes hood relieving for bubble hood with open ducts hopefully lessening heat soak.

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[vssman]

It looks like I may have solved my problem. I made 3 spacers out of 1/2" phenolic material and put them under the carbs. I also picked up a set of plastic washers that have a sleeve on them to isolate the studs from the carb body. The carbs are now fairly cool. They will get hot after I shut down for a while but not as hot as before. Good thing I think I got this fixed so that I can park 'er for the winter... :roll:

 

[MPGmustang]

can i ask where you got your material? I wonder if it will have keep my air cooler for better mpg

 

[vssman]

The machine shop where I work... I'll see what the material is and where they get it - probably MSC or McMaster Carr would have it.

 

[vssman]

I attempted to get the exact material designation from the machine shop supervisor with no luck (I'm not sure how he'll order more when the stock runs dry). Anyway, there's a numer of paper and cotton based phenolic sheets available from MSC, McMaster Carr and Grainger. They tend to have a high heat range of approx 250-300F and come in various sheet sizes. What I can tell you is that the material that I used "looked" like it was a paper based material and was 'medium-brown' and glossy on the outer surfaces in color. It cut easily with basic woodworking tools - i.e. 1 1/2" hole saw in a drill press. The shoulder washers were from Grainger and are PK40 Nylon shoulder washers (P/N 4DCA8) - those have a bit lower high temp rating of 185F but a friend of mine uses them on his racecar with good results. I held the carbs in place with 'nylock' nuts and got rid of the lock washers to prevent damaging the nylon shoulder washers.