Hot Starting Issues

[Jeff Balazs]

Since it seems like we are going to have a blazing hot summer here I decided to put the mechanical fan back on the truck. I had forgotten how much air it moves compared to a electric pusher fan. The difference is substantial. I suppose I can use both if I get stuck in traffic and things really heat up.

 

I am going to flush the radiator and engine one more time and then closely monitor the temps and starting conditions. If I have a another episode of hard starting when hot then I will fit the composite heat shield / carb spacer I have made up and see how things fare. There is a pretty good chance that it won't happen again now that I have better air flow and my fuel mixture and pressure straightened out.

 

Jeff

[Jeff Balazs]

Some progress.

Flushed the radiator again. This time it was pretty clean. Should be good from here out.

 

I took the carb apart again and focused on the step up piston. It appears to have been hanging in the up position which made it run rich. I spent some time cleaning the bore and put a slight bend in the cross piece which seems to have cured the binding. The truck is running much better now. No gas smell at the exhaust. Pulls away from a stop in third nicely now. So perhaps I finally found the problem I have had from the get go.

 

I let it idle for about 20 minutes and the temperature never got above 165. I recently remounted the mechanical fan and it is definitely more effective than the electric pusher fan ever was at idle. We have another heat wave due next week. Temps in the high 90's........so I am all set to give this a good test.

 

Jeff

[Jeff Balazs]

An addendum.

 

Earlier this summer I fitted a small aluminum heat shield below the float bowl. This effectively eliminated hot starting issues.

This week I decided to eliminate the heat riser as I have never been quite happy with the way it functioned. I had a buddy weld up the shaft holes in the exhaust manifold and I made up a SS plate to fit between the exhaust and intake manifolds. I put it all back together but left the heat shield off.

 

Getting rid of the heat riser appears to have helped with the way the truck runs now. Idle which was pretty good for a 60 plus year old truck ......and now is even smoother and more stable. Picked up about a 1/2" on the vacuum gauge too with no other changes.

No temperature rise at all in 95 degree weather and idling for 1/2 hour. But of course... the hard hot start reared it's ugly head again. I guess that little aluminum heat shield under the carb is a pretty good idea.

 

Jeff

[55 Fargo]

An addendum.

 

Earlier this summer I fitted a small aluminum heat shield below the float bowl. This effectively eliminated hot starting issues.

This week I decided to eliminate the heat riser as I have never been quite happy with the way it functioned. I had a buddy weld up the shaft holes in the exhaust manifold and I made up a SS plate to fit between the exhaust and intake manifolds. I put it all back together but left the heat shield off.

 

Getting rid of the heat riser appears to have helped with the way the truck runs now. Idle which was pretty good for a 60 plus year old truck ......and now is even smoother and more stable. Picked up about a 1/2" on the vacuum gauge too with no other changes.

No temperature rise at all in 95 degree weather and idling for 1/2 hour. But of course... the hard hot start reared it's ugly head again. I guess that little aluminum heat shield under the carb is a pretty good idea.

 

Jeff

Hi Jeff, sounds like you got this issue beat. Can you post a pic of your custom heat shield?

[Jeff Balazs]

Sure will do. I got the idea from some postings over on the car side this summer. Nothing fancy just a shaped piece of aluminum wired in place.

I will say that with the heat riser off and a plate between the manifolds the hard starting when hot was not as pronounced as it was before. I am really not sure that my heat riser was ever working quite as it was intended. The bimetal spring just seemed to keep it from opening all the way. And I found evidence a a small exhaust leak at the shaft bushings. Also the plate I put in probably blocks a bit of excess heat to the carb base.

 

Jeff

[HanksB3B]

Hi Jeff, sounds like you got this issue beat. Can you post a pic of your custom heat shield?

 

+1 on that

 

Sure will do. I got the idea from some postings over on the car side this summer. Nothing fancy just a shaped piece of aluminum wired in place.

I will say that with the heat riser off and a plate between the manifolds the hard starting when hot was not as pronounced as it was before. I am really not sure that my heat riser was ever working quite as it was intended. The bimetal spring just seemed to keep it from opening all the way. And I found evidence a a small exhaust leak at the shaft bushings. Also the plate I put in probably blocks a bit of excess heat to the carb base.

 

Jeff

 

Hats off to the car guys. Over the years I've noticed they really take their mills seriously. Some of the carb setups custom cams, heads and exhaust manifolds are really a work of art. I guess building a performance L6 sure would be fun, but I don't know how much my 87hp truck would benefit. I've yet to get a taller rear end and discs up front, that's first.on my to-do list, but the list is long and they are a ways down. Jeff I admire your ingenuity. I'm down for one.

 

Hank 

Edited October 6, 2014 by HanksB3B

[Jeff Balazs]

Hi Hank;

I will admit I do enjoy tinkering. The heat shield is a simple item. I will try to get some pictures tomorrow. Very low tech but it seems to help. Just a small piece of aluminum that is held in place with wire. Need it out of the way for some reason? then all you do is cut the wire. Dead nuts simple.

 

I too admire some of the builds I have seen on the car side. I really like those Langdon cast headers and I suppose if I came across an alloy intake manifold that was set up for a single 2 bbl I would probably go for it. Might pick up a 10% increase in available power if it was done correctly. You would feel that. A lot of times this "better breathing" type mod can actually result in improved gas mileage.

But for now this will do. I don't need to complicate my life any more than I already have.

 

Jeff

[Jerry Roberts]

Hi Jeff, sounds like you got this issue beat. Can you post a pic of your custom heat shield?

 There is a photo of a home made heat shield under the carb float bowl posted by Conroe Powdercoating  on July 6 th 2014 . Posted on the car side of the foreum . Vapor Lock or Heat soak the carb no mo' !

[Jeff Balazs]

OK so here are a couple of photos of the heat shield I have fitted to my truck. It is held in place with a couple of pieces of safety wire. Very....very simple but it makes enough of a difference. Under 15 minutes to make and fit.

 

Jeff

Edited October 7, 2014 by Jeff Balazs

[Jerry Roberts]

 There is a photo of a home made heat shield under the carb float bowl posted by Conroe Powdercoating  on July 6 th 2014 . Posted on the car side of the foreum . Vapor Lock or Heat soak the carb no mo' !

 Heat shield further progress . I also put a heat shield over my exhaust manifold . After a long drive and parking for 15 minutes , my fuel bowl was still almost too hot to touch . I then placed  the bottom third of a soda can over the underside of the fuel bowl  . It is held in place with a thin wire along the side , i could also wire it over the top if necessary . That seems to be helping a lot . Note ; my intake manifold is different than the others pictured previously as the others had the heat shield going right up to the base of the carburetor .   Also my engine runs at 160 degrees , my inner fenders are vented as are my hood sides . 

[john portala]

What would you recommend lowering the float about an 1/8 inch?

 

John

[greg g]

Couple 32nds usually does the trick.