vapor lock in carb??

[greenrt_se]

seems like we have a little vapor lock problem ,after driving and when motor stay stop abouth 15-30 minutes,it don`t start running
there is no room for any spacers under the carb (edelbrock rpm+Demon 750 carb)
so what else I can du to solve this problem(fuel return line ,etc)

[Ghoste]

Wrap the fuel line in some kind of insulating material.  There are some designed for this purpose.  Make sure that the fuel lines are routed away from heat sources like heater hoses and headers.
Make sure the fuel pump is up to the task as well.

[firefighter3931]

Edelbrock makes a carb insulating gasket....it's about 3/8in thick and will help. Make sure your fuel lines aren't resting against the block or a heater hose.

Ron

[Chryco Psycho]

use an alum plate approx 1/8" thick under the carb to deflect a lot of the heat

[greenrt_se]

Edelbrock makes a carb insulating gasket....it's about 3/8in thick and will help. Make sure your fuel lines aren't resting against the block or a heater hose.

Ron

I allready is that insulating gasket..no help  have to make cover for fuel line, just get right aluminium cover to make some around fuel line in motor room(the fuel line coming between heaterhose,so that is maybe problem

[69fuchs]

You could update your fuel system to the rt style.  It uses a 3/8" fuel line, and a 1/4" return line.  Instead of using a fuel filter by the fuel pump, chrysler used a combination fuel filter/vapor separator that connects the return line to the tank.  You also need the rt sending unit for the gas tank. This upgrade should keep the fuel cool!!!  All of this stuff is available--Try mega parts at (608) 452-2045 ask for jamie  Another option that would work just as good would be to use a holley fuel pressure regulator with two output ports.  Use one of the ports for fuel delivery to the carb, and the other port as a return line to the tank.  You will have to find a brass fitting with a very small orifice for the return line so you don't lose fuel pressure, and install a fitting in your fuel tank for the return line.  this modification works well with todays crappy fuels.

[greenrt_se]

Thanks,I think same,maybe I make return line .I use jegs fuel line in my carb,so I can make return line wery easy,they send properT-fitting whit it and I have a original fuel line under thew car allready and plumping it allready to the original return line nose (in the gas tank) maybe I make somekind of restriction in return line so fuel pressure doesen`t drop too much

[grouseman]

You need the insulating gasket.  Dont' worry so much about the warm air, it isn't 180F or 190F like the engine is.  You need to reduce the heat being conducted to the carb from the intake manifold. 

grouseman

[greenrt_se]

there allready is insulating gasket under the carb,between two gasket.I don`t have room for 1" or 2" spacer

[myk]

Using a return line system for the fuel lines doesn't keep the fuel cooler, it just allows the vaporized, overheated air to return to the fuel tank where it can then cool off and then become useable again...

[cudaken]

 What temp are you running? As we all know aluminum trasfer heat faster than copper or cast iorn. I had a vabor lock problem at 185 to 195 in the 68 Runner. Installed a 4 row (better way's to go now) and dropped the temp to 170 and no more vapor lock. 69 Charger with the 42sick was hitting 200 befor I did the cross radiator and never vapor locked.


Do you have the head heat riser's sealed or are they still going to the intake? More than likely your intake does not have the heat cross over but just a thought.

Have the engine shot with a thermal gun at the intake. Unless the gauges have been redone and new transfomer under the dash don't turst them.

Hope I might have been some help.

                                             Cuda Ken

[Ghoste]

Have the engine shot with a thermal gun at the intake. Unless the gauges have been redone and new transfomer under the dash don't turst them.

There are some words of truth Ken.  My car will peg the guage and you hit it with the laser temp and see it's only 180.  These guages are old and the infrared is becoming a tool whose expense is justified for most toolboxes.

[greenrt_se]

I have a autometer temp gauge(mechanical) under dash.Just driving from garage to drink some coffee,and after that car don`t start runnin,so I have to wait temp coming down

[cudaken]

 What is the temp?

                                 Cuda Ken

[greenrt_se]

when driving ,little less from 190f

[cudaken]

 I was having vapor lock at 190 with my Road Runner, now at a real 175 and no problems. Like I posted, the Aluminum intake trasfer heat faster but with cast iron I did not have that problem.

                               Cuda Ken

[greenrt_se]

yep,looks like ,when motor heat up the gasoline boils in intake,and then `smoke over carb`so the problem is too hot intake
carb give good shot fuel but that damn hot intake

[cudaken]

 I bought a new 4 Row off E-bay for the 68 Road Runner for $240.00 plus shipping. If you are not worried about stock look's do the cross flow. I bought mine for $169.95 buy it now, $30.00 for brackets, $25.00 to weld them on and $35.00 for a huge tran's cooler 12" X 14" off E-bay so total was $260.00 and was a steal.

Want to talk about running cool, used DFS68 3 Row in my 69 Charger with the old 42sick, was at 175 which was fine. Bought the cross over, 155 on the Road and 165 in traffic. That is some cooling.

I have tried spacers, 1215 intake gashet which is still a good idea. But bottom line is heat is what causing the problem, get rid of the heat and the problem is gone.         

I have not installed my electric fan's yet, but one that turn then self on and off would help when sitting for a short time. Keep from buliding up under hood heat.

                                Cuda Ken

[Silver R/T]

upgrade your cooling system, radiator, water wetter, electric high flow cfm fans, aluminum water pump/housing

[grouseman]

You can make a great insulator plate using cabinet-grade plywood (I think it's called baltic).  Drill four holes through it to match the carb bores.  It's 3/8" or 1/2" thick, nice and smooth on both sides, very stable.  Intake/gasket/plywood/gasket/carb. 

If you are running an electric fan, change over to a clutch/viscous fan so that you ALWAYS have air flowing past the carb. 

My engines run at 195 and have no problems with carb boilout.  But they are setup as I've described above. 

grouseman

[cudaken]

 Warm is warm, rather fix the problem and not use a bandaid. Not trying sound like a Chevy Grouseman.
I tried spacers, could not use the air cleaner with the intake's I had, or problems with carb linkage.

                                 Cool is good.

                                             Cuda Ken

[greenrt_se]

I have a visco fan,motor running temp is 190 F,yesterday I made head shield under the intake,and it seems help

[grouseman]

Ken, your comments are a little too cryptic for me.  Bandaid?  Chevy?   

grouseman

[cudaken]

 Grouseman, first I cannot spell for Chevy. Second I normal dont miss spell foul words on the site. I use Chevy for S--t and fill in the center letter's.

As far as banaid, well just as I missed spelled. It is to try to fix something but not the real problem which is heat.

Grouseman, not trying to sound like Chevy hole but we just think driffrent and that is what I love about this site. Someone thinks this way, I think another and some where there is a anwser.

Fat a-s dragged around 400,000 miles behinde a BB Mopar and still learing Ken.

[grouseman]

Okay, I unnerstan your comments now. 

But I would say the bandaid solution is cooling the entire engine to solve the carb boiling problem.  Street engines need to run at least 180, preferrably 195, for the oil to do it's job and any moisture to evaporate out.  A drag car, sure, keep it cool.  But street driven engines should and do run at 195 all day long without carb boiling problems - IF they're set up properly.  There must be a substantial thermal break between the intake and the carb to reduce heat conduction.  The factory uses thick composite gaskets, typically 1/4" or so and open.  And the viscous fan keeps air moving around the carb all the time. 

Green rt, how are you doing on fixing the problem? 

Grouse Man

P.S.  Keep your chin up on that danged 440 you're fighting with.  You'll eventually win. 

[greenrt_se]

head shield under intake,1/2" insulating spacer under carb,tomorrov 170F thermostat,head are edelbrock alu,intake edelb,alu waterpump housing aluminium,visco fan whit tunnel

[cudaken]

 Grouseman, here again, we know something driffrent. I got my 68 Road Runner in 1973 from Mon and Dad with 48,000 miles. She never went over 180 wih 2 row stock in traffic and on the road 170. I will ad I still have her with the 4 row I spoke of.

My old 42sick with the good 3 row stayed in the in the 170 range as well. 1970 Cuda 383 with 3 row all so 170. With the cloged up 3 row the 69 Charger did hit 210 and did not vapor lock, but I  knew she was hot, oil PSI dropped like a rock.

I do think the Charger is running a little cool at 160. I know the pistons need to heat up and all that happy stuff.

Does not matter if you or I am right, just what we know. My self, 170 is where I like it for old cast iron motors.

                                        Cuda Ken

[Ghoste]

I think different engines like different temps too Ken for reasons that no one knows.  I had a 440 once that always ran best hot.  Just over 200 was where it ran the fastest, smoothest and got the best mileage.  Never knew why, it just did.

[greenrt_se]

the motor runs great whit 190F,but after shut down and around 30-60 min try to start again,then the problem is on.the intake is damn hot

[grouseman]

Looking back at the original post, I realized you didn't explain very clearly what is happening when the engine won't start. 

Is it harder to turn over when hot?  Does it turn over as quickly as when it's cold?  Does it struggle to catch, like it's flooded?  Does lots of black smoke come out if it fires?  Does it run rough until it clears itself out?  Will it fire if you keep it floored? 

I'm now almost wondering if you mean that the starter barely turns it over . . . could be over-advanced initial timing or starter/battery problems. 

Yes, the intake will be HOT.  Even 160F is HOT to the touch.  But the carb should be nowhere near that hot, you should be able to touch it and not think HOT. 

Ken, I know what you mean, some engines and cooling systems just handle things better than others, while others struggle.  But there should be an explanation for it all.  A buddy's 350 Pontiac (new to him and rebuilt right away) overheated from day one, even while idling.  The needle would just keep climbing - 230, shut it down.  Put in a 160 thermostat, no change.  Took out the thermostat, no change.  He put in a big alum rad, no change.  He put on an electric fan, no change.  Went through the timing and found the balancer had spun, which accounted for a lot.  But it still overheated.  Finally realized that there is supposed to be a plate sandwiched in the water pump which was missing - directs flow around impeller.  Put it in, and suddenly his problem was it wouldn't go past 150F!  I know it's not related to this problem, but there's a solution to be found here.   And the lesson learned was don't assume anything, and brainstorming was the key to solving it. 

grouseman

[greenrt_se]

it just no start,starter turning motor ok,like cold engine,when temp going down no black smoke,just normal start,when hot after driving,pedal to the floor don`t help,squiters give a good shot of gas  ,after cooling no rought running

[cudaken]

 Green RT, this is going to sound a little dumb, but want to try my cross flow? As you may know from my posting here my fresh 440 is coming back out. I figuer if I am lucky it will only be down 2 weeks, and that is if I am lucky.

You would need to drill some holes to use it, but I am 95% sure it will fix the problem. Besides, more likely to get hurt sitting around in the garage than on a Charger. If you have a 727, I will send the cooler as well.

Send me your address and it's on it's way.

                     Cuda Ken, the Cool

[cudaken]

 I will also send the hose's as well. No reason for you to spend any money for them.

                                   Cuda Ken

[deputycrawford]

I had the very same problem with my 69 charger. It also has a Race Demon, Edelbrock PRM intake and a Carter 120 GPH fuel pump. I would shut the car off and try to start it 30 mins later and fuel would boil out of the rear bowl. I started to shut it off and open the hood for the 30 Mins. it fixed the problem. I called Paddock and ordered the fuel sending unit for 1/2 inch feed line and the built in 1/4 inch return line. From the fuel pump I run the 3/8 inch fuel line because I went to NAPA auto parts store and ordered a fuel filter with  3/8 inch fuel line in and out and a 1/4 inch fuel return line for only $8. I ordered the 1/2 inch aluminum fuel line and the 1/4 inch aluminum return line in universal coils and ran the lines myself. POOF, problem solved. The sending unit cost around $135 and the other stuff cost around $60 but the car never did it again. Well worth the money. And I should never have to upgrade the fuel system again. I hope this helps. I even run the fuel log attached to the carb and a fuel pressure regulator. The stock vehicles had the same problem and the factory made a factory alumiinum foil rapped pillows to put under the intake when new. The return style system of the R/T fixed the problem when new. It worked for me when old too.

[greenrt_se]

thanks.when I made new fuel line ,I keep original line still in place under car.so now I have to just made return line from carb to end of the old line

[greenrt_se]

also I made spacer under the carb

[deputycrawford]

No problem. Like I said, I even have the Demon carb and the same 8AN fuel log I see in your picture. Just make sure your old line isnt too big. 1/4 in is plenty of line. Bigger than that and you wont hold any fuel pressure on the bowl seats in the carb. I also have the Carter 120 GPH mechanical pump with an electric fuel pressure guage. At idle it barely keeps 6 lbs pressure. If I had the bigger return line the fuel pump couldnt keep up. You had the right idea when you first  posted your problem. Run with it and Im sure you will work it out.

[cudaken]

 Timo, here is a little test for you.

Bring the engine to say 170, shut it off. Let it sit say 5 minutes. Start her back up, is the problem still there? I will bet it is not.

Humm, Finland. Does my cross flow need a pass port?

                                Cool Ken, posting again

[greenrt_se]

I put yesterday 170F thermostat,and it seems to help to solve my problem,but right now the wheater here is cold,and maybe it better at I
buy during winter good aluminium radiator.
cudaken.just drive to Alaska,and throught the Russian,it`s only 20minutes to drive my house after Russian.And thake yours radiator too

[cudaken]

 Hope that soulves the problem Timo. Lets see, if I leave right now I should be there in Januray.

                                        Ken

[greenrt_se]

ok.sauna is on ,and while you drive through Moscow,buy some vodka and caviar

[cudaken]

 Timo, I must say I had fun with this post. Hope to hear the problem is gone this summer, as well as mine.

                      Your friend Ken

[greenrt_se]

ok driving around town last night,stop the motor let is stay 5min-30min, start great.meet guy who make aluminium radiator and intakes from aluminium,he make radiator for me in next winter
so I have a lot of work for winter
-keisler 5 speed
-dash refacing
-chance carb jet a little smaller

[Ghoste]

I love that photo.  I don't know why for sure, but there is something about it that is just very appealing to me.

[greenrt_se]

damn,it make it again ,shut down hot (170F) motor ,and after almost 1hour don`t start defore I put a lot of gasoline in (pushing gas bedal to the floor many times) and then it fired up very slow.The carb is rich side(I have a A/F meter in center console) and plugs are NGk bcp5es

the intake isn`t hot,like it was whit 180f thermostat

[grouseman]

Is there a crack in the carb bowl, letting the fuel slowly drain out into the intake? 

grouseman

[greenrt_se]

carb is brand new demon,iwhile motor running I been searching vaacum leak around carb no found

[greenrt_se]

and the fuel level is ok in the bowls