Vapor lock driving me crazy

[68charger440]

I have been fighting vapor lock for quite some time on the real hot days.  I can watch the fuel boil in the glass fuel filter and the sight glasses on the carb don't show any fuel once it happens, so I am very confident that it is vapor lock.  The temp gauge runs at 180 or so, so that is fine.
I have the valley pan with the blocked off heat crossover installed
I installed a 1" phenolic carb spacer
I have rerouted the fuel lines away from all heat sources
I am at roughly 5500 foot elevation, so the gas boils real easy up here.
I have the carter high volume mechanical fuel pump, but the stock one does it too.
I could install an electric fuel pump, but then the noise and vibration might make me shoot myself.
The motor is:
440 bored 40 over with a balanced 500 inch stroker kit installed
Stock fresh 906 heads. 
10.52 static compression.
edelbrock performer rpm intake
Edelbrock performer cam
Proform 850 dp
Stock converter
3.91 sure grip
18 initial timing 34 total
3" exhaust all the way back from the headers with an X pipe in the middle
MSD ignition
I have heard that the fuel vapor separator may help, but that there used to be some that were made incorrectly.  Has that been corrected, and if so who has the good ones, or are they all good now?
Does anyone know of anything else to try to fix this?
Thx
Jim

[cdr]

you will need a fuel return set up  this is the regulator i used on mine, it is for a mechanical fuel pump. mount it up right before the line splits to the front & rear carb bowls & then run a return line to the tank off the regulator

http://www.summitracing.com/parts/qft-30-899/overview/

[68charger440]

So I can't use the vapor seperator with my mechanical fuel pump without a regulator?

[cdr]

So I can't use the vapor seperator with my mechanical fuel pump without a regulator?

you can try it, but there is a lot of line up to the carb exposed to a lot of heat.   mine works very well & i have been in over108 deg, my car is 512ci & ac. runs cool & no vapor lock.

[firefighter3931]

Hey Jim,

The return regulator that Charlie posted is the best option. Keep the fuel circulating to prevent vapor lock. Not a fan of those vapor seperators 

The fuel they sell at the pumps these days is terrible for carbureted applications. It's formulated for high pressure fuel injection and doesn't tolerate low pressure and heat very well 


Ron

[68charger440]

Sorry to be thick headed, but help me to understand...
1. I have always heard that an electric fuel pump will eliminate vapor lock because it pushes instead of pulls the fuel, and I guess that pushes the vapor out through the carb. Is that correct?
2. Does vapor lock on our old cars occur at the fuel pump, at that is why the pump can't pull the fuel? So if that same mechanical pump were in the back of the car, then it would act just like the electric pump and you would never get vapor lock unless the fuel somehow boiled to vapor in the back of the car?
3. If point 2 is true then wouldn't the regulator be too far downstream at the carb, since the vapor lock itself would begin at the pump before the regulator, and in that case the mechanical pump would still not be able to pull the fuel since it is trying to pull vapor still?

I probably didn't do a very good job of expressing my confusion as to how this would work.

[68charger440]

...and if all of the above is true then wouldn't the vapor seperator keep a cool flow of gas going through the mechanical fuel pump thereby keeping the pump from ever vapor locking to begin with, and then it would be able to push the vapor further down toward the carb out through the carb just like the electric fuel pump?

[cdr]

the heat in the fuel system ads up, from back to front it gets hotter & hotter, bleed off the hottest boiling fuel & it cools as it goes to the back. a electric pump will not help much if any on boiling fuel,, a return as close to the carb is what works.

[firefighter3931]

As noted above by CDR the main issue is lack of circulation. An electric pump can cause the same issues if it is run as a dead head system. Stock...these cars were basicly dead-head design fuel systems with no return line to the tank...only a simple vapor separator which is not as effective as a bypass regulator which keeps the fuel moving front to back. This circulation cools the fuel temps down and helps to suppress vapors and fuel boiling.

The basics of fuel ; Gasoline has a boiling point and flashpoint where it will ignite. As it gets warmer it produces more vapor which converts it from liquid to a gaseous state (vapor) and that is what causes the problem. Keep in mind that the fuel that these fuel delivery systems were built around are completely different from the current fuel formulations we have at the pumps today. The current fuels are more heat sensitive due to the additive packages and ethanol.

The "old" gas could sit static in the fuel line for a longer period before turning into vapor so having the fuel system cycle the fuel front to back was not a requirement for reliable performance. Today's fuel is formulated for todays engines which run high pressure fuel injection with return fuel systems....vapor lock is a non issue with new cars for this reason. 

Mechanical fuel pumps are attached to a hot engine so running fuel through a mechanical pump only aggravates the problem. Having the fuel circulate will reduce the fuel temps and prevent the problem from occurring in the first place.

Circulation is the key 



Ron

[c00nhunterjoe]

Dont forget cavitation. Not really an issue on stockers but when people convert to electric and stick a 140 gph pump on the stock 5/16 lines......  it never ends well and they cant figure out why they still have issues.

[six-tee-nine]

And for the guys without a return line, should we fab something or are there parts available to convert?

[Tom Q]

Come on now, figure out what is broke. Engage the brain.

How hot is it under the hood? Measure the temp and get back to us.
Go to the home store and get a barbecue thermometer and mount it in front of the carb.

Insulate the fuel line [rubber hose cut down the middle] that runs along the frame rail. Be sure to be using metal lines from the fuel filter to the carb. Use a metal fuel filter. Is your fuel pump weak or fp pushrod too short?
Use the  Carter street pump

BTW 180 is too low of a min operating temp, 195 for today's fuel. But you guys seem to know more than me so just keep thinking 1970's

[1974dodgecharger]

Come on now, figure out what is broke. Engage the brain.

How hot is it under the hood? Measure the temp and get back to us.
Go to the home store and get a barbecue thermometer and mount it in front of the carb.

Insulate the fuel line [rubber hose cut down the middle] that runs along the frame rail. Be sure to be using metal lines from the fuel filter to the carb. Use a metal fuel filter. Is your fuel pump weak or fp pushrod too short?
Use the  Carter street pump

BTW 180 is too low of a min operating temp, 195 for today's fuel. But you guys seem to know more than me so just keep thinking 1970's

do you go in every thread and repeat the same thing over 

[cdr]

And for the guys without a return line, should we fab something or are there parts available to convert?

when i replaced my factory line from the tank to the pump I bought two 3/8 prebent lines & ran them next to each other.

[303 Mopar]

And for the guys without a return line, should we fab something or are there parts available to convert?

when i replaced my factory line from the tank to the pump I bought two 3/8 prebent lines & ran them next to each other.

  You will also need a new sending unit with a return.  Call Dave at Roseville and he will hook you up with the line and sending unit.  (http://www.rosevillemoparts.com/product_info.php/p/fuel-tank-sending-unit-68-70-b-body-3-8-with-return/products_id/8426)

I left my 5/16" line in and made that my return while installing a new 3/8" main line.  The pre-bent lines fit nice, and I just drilled a second hole in the frame rail.

[myk]

Come on now, figure out what is broke. Engage the brain.

How hot is it under the hood? Measure the temp and get back to us.
Go to the home store and get a barbecue thermometer and mount it in front of the carb.

Insulate the fuel line [rubber hose cut down the middle] that runs along the frame rail. Be sure to be using metal lines from the fuel filter to the carb. Use a metal fuel filter. Is your fuel pump weak or fp pushrod too short?
Use the  Carter street pump

BTW 180 is too low of a min operating temp, 195 for today's fuel. But you guys seem to know more than me so just keep thinking 1970's

He can't figure it out, that's why he's here, and we're here to help.  Sorry that we're not all ASE Master Certified Techs with a degree in snobbery like you are....

[68charger440]

Well, I guess I have some plumbing work to do.   I sure will miss the clean look of a single fuel line going into the chrome fuel line feeding the carb.  
I guess where my thinking was wrong above it that maybe the vapor separator doesn't keep a constant flow of cool fuel running through the pump.
The logic in my brain still thinks that if the pump is cooled down then it would not vapor lock and be able to push the vapor out through the lines above it through the carb, but you guys haven't steered me wrong yet, so I'll go with it.
Jim 

[68charger440]

I left my 5/16" line in and made that my return while installing a new 3/8" main line.
[/quote]

I think that is what I will do too.
At what point should I consider 1/2" fuel line?  Is 600 hp roughly the cutoff point for that upgrade?

[firefighter3931]

Lots of guys run 3/8 line pushing in excess of 600hp so you're good to go Jim. A 3/8 supply line is fine for your application 

On a side note ; My old 446 making 535hp/540tq used the 120gph carter street pump with a single supply line and no return....dead head system. I used a metal fuel filter on the discharge side of the pump with braided fuel line up to the carb. I insulated the braided line with a chunk of conduit that was thermally protected and had no issues with vapor lock. Was it as good as a return system....definitely not, but it worked for me. We don't get as hot up here in the great white north so that probably helped a bit as well but I did drive it on several 100* days testing the cooling and fuel systems and never had a problem. 

This might be worth a shot before re-plumbing the fuel system 

This is the insulating conduit I used from DEI :

http://www.summitracing.com/parts/dei-010414/overview/




Ron

[68charger440]

Lots of guys run 3/8 line pushing in excess of 600hp so you're good to go Jim. A 3/8 supply line is fine for your application 

On a side note ; My old 446 making 535hp/540tq used the 120gph carter street pump with a single supply line and no return....dead head system. I used a metal fuel filter on the discharge side of the pump with braided fuel line up to the carb. I insulated the braided line with a chunk of conduit that was thermally protected and had no issues with vapor lock. Was it as good as a return system....definitely not, but it worked for me. We don't get as hot up here in the great white north so that probably helped a bit as well but I did drive it on several 100* days testing the cooling and fuel systems and never had a problem. 

This might be worth a shot before re-plumbing the fuel system 

This is the insulating conduit I used from DEI :

http://www.summitracing.com/parts/dei-010414/overview/




Ron

I think I will give that a try before replumbing.
I found this Holley regulator in my  garage. It has no signs of ever being used, but I can't for the life of me remember where I got it. Besides the blue caps it has blue paint on the adjuster threads.  Can anyone tell me if this is the right one for a carb application? Fittings are 3/8.

[cdr]

if no # on it  ?? I doubt it's one for a return , one for a return are made different inside.the one you need has a screw in jet.

[68charger440]

if no # on it  ?? I doubt it's one for a return , one for a return are made different inside.the one you need has a screw in jet.

Scratch the 3/8 fittings it is larger, probably 1/2. 
Anyway, the screw in jet?  Is that different from the hex key pressure adjuster on top?  Where is that located?

[68charger440]

There are no numbers on it.  Here is a better pic.

[68charger440]

Here are a couple more good pics. The second one is looking in from the bottom.

[six-tee-nine]

Thanks for all the tips... just to make sure I do it right the first time when I buy fuel lines and acommodating parts in the near future.

[cdr]

no that regulator is not for a return set up.





Cast Bypass Regulator W/JET - Features blue powder-coated top and is desgined for use with a belt driven or mechanical fuel pump. Adjustable jet provides tuning of low RPM fuel pressure. Comes with stainless mounting bracket. All threads are NPT

[68charger440]

Ok, thanks!
Anyone in the market for a shiny Holley non return line regulator?

[68charger440]

CDR... what wheel/tire sizes are you running?  I like the way it sits and the back wheels look like they come out close to the inner lip which is a look I am after.

[cdr]

295 50 15  on 15x10 5in backspacing , they dont rub

[68charger440]

Do you have a straight on view from the side picture somewhere on the site?

[cdr]

[68charger440]

Going by the measurments from my car using your wheel and tire combo I would have roughly 1/2 " space between the inner lip of the wheel well and the fattest part of the tire if the tire was sitting high enough in the wheel well.  Is that about what you have?

[cdr]

yes

[69wannabe]

I have been fighting the same fuel problem that you are having and I have done a few thing's that have suppressed my problem in a way that make it tolerable. It was worse on the warmer day's (90's+) but still doable. I am running a single 3/8 line from the tank to a carter street pump. then I molded a line similar to the original with a metal filter and then it run's up behind the alternator and up over the valve cover to the dual line tee. I cut a piece of rubber line and put over the steel line from the filter up behind the alternator and then put some of that thermo sleeve over that from the filter up to the tee. Then I put a cool carb technology's carb spacer under the carb which has helped and I put a 160 hi flo milidon thermostat in to help keep the engine temps down. It still run's around 175 degrees to 180 which is fine for a non fuel injected engine. Since the temp's have been down a bit from the 90's and in the mid to low 80's here the hard starting has pretty much went away. You can check out the cool carb technology's website and see how it works and the video that show's the temp's with a temp gun. It's not a cure all but it does help!!

[68charger440]

I did look at the cool technology stuff. Ron suggested it also, but I went ahead and ordered the bypass regulator because I have had to sit on the side of the road a couple of times for an hour while it cooled off and I just want this fixed with the most sure fire solution as possible.  I think the constant circulation will do it.  I saw some interesting DIY stuff on converting a dead head regulator to a bypass one with a replacable jet using the one I pictured above, but Ifigured I am tired of fooling with this.

[68charger440]

My bypass regulator came in and now I need to figure out where to put it.  CDR said to put it as close to the carb as possible.  With that in mind, does anyone have any pics of a setup where it is close to the carb, and looks clean also?
Thx

[cdr]

this is mine, i unwrapped the regulator for the pictures it aint purrddyy 

[68charger440]

Thanks... did you have to use that wrap to keep it from boiling too?

[cdr]

Thanks... did you have to use that wrap to keep it from boiling too?

no it did fine without it, but i am into overkill !!!! it gets very hot down here, did not want to take ANY chances of leaning out this engine I have way to much money in it to chance it. this is also my only car, so it gets driven!!!

[68charger440]

Wow! That's a beast of a daily driver.

[cdr]

also when you get this all on the car most of your afr readings will probably change. 

[68charger440]

Thats all I need, I just got it dialed in. 

[firefighter3931]

Thats all I need, I just got it dialed in. 

No worries Jim....you're a pro at rejetting that carb by now ! 

As for the regulator location ; You could mount it on the firewall just behind the carb and reverse the fuel inlet line to have it face backwards towards the regulator. Then run the return line down along the firewall to the frame rail where the return steel line will be plumbed. I'd insulate all of it with that DEI conduit to keep the fuel nice and cool. I believe you can purchase the DEI stuff in 20ft lengths 

Personally, I'm not a fan of mounting the regulator on the engine. Heat and vibration can cause erratic fuel pressure and aeration. I have mine mounted on the inner fender about 6 inches forward of the firewall with a supply line running to each bowl of the carb.


Ron

[68charger440]

I was considering other locations because the plumbing I was doing up front was looking kinda funky.  At least with the summer fading away soon, the vapor locking will probably not rear its ugly head until next spring even if I don't get it fixed with these mods.  I was hoping to have the car stable enough for some longer cruises, but until this vaporlock is fixed I have to stay close to home.  I'm jealous of my brother, he has a bone stock 69 4speed Charger that he hasn't had to do anything but general maintenance to for decades, and he can jump in it and drive it cross country with no worries. 
At least mine is faster until it vapor locks.

[68charger440]

The instructions on the bypass regulator says that you can install it with one side being the feed line from the tank, the other side being the output to the carb, and the bottom being the return line to the tank.  My questions are:
1. Does it matter which side the jet is on?
2. Wouldn't it make more sense to have the side with the jet as the return line to the tank since the jet restricts the flow? It seems like you would want the free flow going straight through to the carb and the jetted port only acting to keep the excess flow going back to the tank.  What am I missing?

[cdr]

i put the jet on the supply side ,   FOLLOW THE DIRECTIONS  THEY MADE THE REGULATOR ,THEY KNOW HOW IT WORKS  LMBO

if you look at my picture the black line is the return to the tank.

[68charger440]

Yup, I was going to do it their way. I was just trying to figure out why for my own understanding.

[cdr]

 

[68charger440]

also when you get this all on the car most of your afr readings will probably change. 

My afr readings did change.  Why is that?

[cdr]

less boiling fuel in the fuel bowls, i had to reset my float level also.