Vapor lock / incline issues

[Northpark70]

Took the bronco to Moody yesterday to break it in on its first trail run and it ran perfect on the road. Started Moody strong and a few minutes into the steep climbs in the beginning it would stall out on steep inclines. Then it would start back up, I would try again and it would stall out. I ended up having to back down Moody becuase she would go anymore. I tried to adjust the float levels and was encounted by a massive amount of pressure build up in the adjustment. Then went driving around fairly level ground to test it and it would stall out about every 15 minutes. Then it cooled down and I drove it all the way home with no issues.

Any recommendations for trouble shooting.

Small 2 barrel Holley by the way

[Viperwolf1]

Fuel boiling in the float bowl? Try a phenolic carb spacer.

[Jesus_man]

Yes, and insulating your fuel line, get the heat out of the engine bay, try an electric fuel pump, etc.

Also adding a 1/2 gallon of diesel to a full tank can help as well.

[Rox Crusher]

I still haven't 100% resolved my vapor lock yet but pretty well fixed it (99%) by;

- replacing water pump to reduce engine operating temp
- rerouting fuel line away from engine
- insulating fuel line in the engine bay with this http://www.jegs.com/i/Thermo+Tec/893/14010/10002/-1

I already had a phenolic spacer under the carb and a brand new radiator.

If I wasn't converting to EFI this fall I would eliminate the mechanical fuel pump for an electric set up.

[Northpark70]

Thanks for the tips. do you guys have problems with the pressure in the tank also. for example the bronco would die and I would let the pressure out of the tank and it would start again.

[Booger]

Thanks for the tips. do you guys have problems with the pressure in the tank also. for example the bronco would die and I would let the pressure out of the tank and it would start again.

You sure it's coming out and not going in? Cap should be vented.
I would reroute fuel line away from engine as much as possible, wrap it with fuel line wrap, if you have headers wrap them. Get an adjustable fuel pressure regulator and set the fuel pressure down to about 2 psi when wheeling. Raise the pressure back up before you hit the road or you will cause the engine to lean out and possibly burn a valve or worse. Also make sure you have off road needle and seat for the Holley, this will keep the float from bouncing when you bounce on a rock. Lower fuel pressure helps with this alot so you might not need it if you adjust the fuel pressure down. Set the float level so the fuel is just at the bottom of the sight glass hole on level ground.

Many yrs ago I had good luck with a Mallory pump that would pump up to 140 gph (gallons per Hour). It came with an adjustable regulator and had a port for a fuel pressure gauge. The pump would deliver 15 psi to the regulator and I would lower that to around 4 -5 on the road 2 -3 for wheeling. The higher pressure would help eliminate fuel boiling in the line causing vapor lock. I never had a vapor lock issue again. Problem with that is if you have 2 tanks you need two pumps.

[Rox Crusher]

Thanks for the tips. do you guys have problems with the pressure in the tank also. for example the bronco would die and I would let the pressure out of the tank and it would start again.

If your tank is pressurized due to heat induced expansion of the fuel it could be force feeding into the carb past the needle and seat.

When you release the pressure I would assume the surplus (expanded) fuel overflows the filler neck which relieves the pressure which was force feeding the carb.

This exact thing happened to 76Ford (Mike) on our trip home from Ouray. His was so bad it was actually coming out of the vacuum line that goes to the distributor.

Can you say 4 wheel drive molotov cocktail ?

[Gunnibronco]

I've never had vapor lock issues & I think it is because I use a fuel pressure regulator that returns "excess" fuel to the tanks:
http://www.summitracing.com/parts/MAA-4309/
So fuel is constantly flowing through the system, not backing up behind a regulator, getting hot.

I had originally installed a Holley Projection unit that required plumbing return lines to the tanks & used a fuel valve like this:
http://www.bcbroncos.com/store/product_ ... cts_id=212
It replaced the manual valve under the seat. I scrapped the Projection, but kept the valve.

I replaced the fuel gauge switch with a different one, so when you switch the toggle, it switches the valve & the fuel gauge. The gauge reads the tank you are using, like a modern duel tank truck.

I also use a high volume/high pressure mechanical fuel pump.

[Booger]

Gunnibronco I remember someone else telling me about doing just that yrs ago. If I remember right it was one of the guys at High Country 4x4 before they were all Heep all the time. Makes sense to me to circulate the excess back to the tank.

[ZOSO]

Thanks for the tips. do you guys have problems with the pressure in the tank also. for example the bronco would die and I would let the pressure out of the tank and it would start again.

You sure it's coming out and not going in? Cap should be vented.
I would reroute fuel line away from engine as much as possible, wrap it with fuel line wrap, if you have headers wrap them. Get an adjustable fuel pressure regulator and set the fuel pressure down to about 2 psi when wheeling. Raise the pressure back up before you hit the road or you will cause the engine to lean out and possibly burn a valve or worse. Also make sure you have off road needle and seat for the Holley, this will keep the float from bouncing when you bounce on a rock. Lower fuel pressure helps with this alot so you might not need it if you adjust the fuel pressure down. Set the float level so the fuel is just at the bottom of the sight glass hole on level ground.

Many yrs ago I had good luck with a Mallory pump that would pump up to 140 gph (gallons per Hour). It came with an adjustable regulator and had a port for a fuel pressure gauge. The pump would deliver 15 psi to the regulator and I would lower that to around 4 -5 on the road 2 -3 for wheeling. The higher pressure would help eliminate fuel boiling in the line causing vapor lock. I never had a vapor lock issue again. Problem with that is if you have 2 tanks you need two pumps.

I run this style set-up on my 79 and have yet to have an issue. The pump and regulator works pretty darn good.

[Northpark70]

Sounds like I will try a fuel pressure regulator, becuase when I cracked the screw to ajust the float level it sprayed all over the place. i must admit I also need vented fuel caps. I'm thinking about a possible carb swith to a four barrel. Has anybody had good luck with the holley truck avengers?

If so what CFM would you recomend for a stock 302 at our altitude?

[ZOSO]

search for the thread by ZEN on the TA carbs.

[Booger]

Sounds like I will try a fuel pressure regulator, becuase when I cracked the screw to ajust the float level it sprayed all over the place. i must admit I also need vented fuel caps. I'm thinking about a possible carb swith to a four barrel. Has anybody had good luck with the holley truck avengers?

If so what CFM would you recomend for a stock 302 at our altitude?

I agree with what ZOSO said about searching Zenzone.

If you check Holley website it will probably recommend 450 cfm or so. Go with the next larger 650 or whatever it is. 450 cfm is too small and will cause driveability problems.
I am running an Edelbrock and after doing a few mods to it works great fourwheeling.

[ClayJ]

I used to have a terrible time on hills. Stock 302 with the stock 2 barrel holley. Any sort of a hill would cause the engine to sputter and die.

I have now switched to a performer intake and a quadrajet carb. Granted, I don't do extreme wheeling, but everything I try now, the bronco just crawls up without a hitch. I can let the RPMs drop down to as low as 500 and it just keeps chugging up the hill.

[Rox Crusher]

I used to have a terrible time on hills. Stock 302 with the stock 2 barrel holley. Any sort of a hill would cause the engine to sputter and die.

I have now switched to a performer intake and a quadrajet carb. Granted, I don't do extreme wheeling, but everything I try now, the bronco just crawls up without a hitch. I can let the RPMs drop down to as low as 500 and it just keeps chugging up the hill.

wanna trade rigs ?

[ClayJ]

wanna trade rigs ?

You want a pink bronco?

[Rox Crusher]

wanna trade rigs ?

You want a pink bronco?

It would go with the purple window tint on my top