Carb / Vapour lock question?

[NYCMille]

Hi Guys -

I am currently a Holly 850DP on my 440. The motor is mild, 906 heads .030 over, edelbrock dual plane intake, stainless valves etc. The main problem that I am having is VAPOUR LOCK!!

I put in a ceramic 1" spacer, heat wrapped the fuel and even checked to make sure my gas cap was vented properly. NO LUCK. Someone had suggested that I could probably go done in carb size to a 750/770, so I was thinking about the Holley  Street Avenger 770 CFM Four Barrel. If I did this though is there a chance that it could clear up my vapour lock problem. I feel as though I have already tried everything else.

Any help would be appreciated.

Cheers - Mike

[firefighter3931]

Hi Mike, sorry to hear about your problems. Have you tried changing the intake manifold gasket/valleypan ? The felpro 1215 is the one you want...it blocks off the heat crossover passage from the heads to the intake manifold. This gasket will prevent conductive heat transfer between the heads and intake. Make sure all your fuel lines are routed away from heat sources (block, heater hoses etc...)

Not familiar with a ceramic spacer ? The phenolic (composite) spacers are what i use.  

Ron

Ps. A smaller carb won't cure the vapor lock issues.

[NYCMille]

I did actually use the felpro gasket - and it is a phenolic spacer - sorry about the mistype - my fuel lines are about 4" from the headers, is this still too close?

[Charger4404spd]

Firefighter is correct. Change youe intake gaskets to the #1215's. This helps more than anything. These keep the intake alot cooler. The carb change will not help. I run the 770. I changed the intake gaskets and I use the phenolic gasket under the carb and mine will still vapor lock from time to time.

Hows your cooling system? What temp does it usually run at? Are you using a shroud?

[firefighter3931]

I did actually use the felpro gasket - and it is a phenolic spacer - sorry about the mistype - my fuel lines are about 4" from the headers, is this still too close?

Did you use the 1215 felpro intake bathtub or just the standard gasket ? There is a difference, especially when it comes to vapor lock issues. Charger 4404spd brings up some good points....how hot is it running ?

Ron

[NYCMille]

On the highway it rarely gets above 180 even on on really hot days. In traffic, if I sit it will start to creep up, but nothing major, maybe 200-210. I also run aux fax. Generally when it happens the temp of the engine is not over 180-185, its just after driving for an hour or more.

[Charger4404spd]

Is your timing correct?  Also, check the float levels.

Again, we ask, do you use the fel-pro #1215 intake gaskets? If not, get a set, I think that will cure your problem.

[SpudRacer]

I also appreciate the advise on the Fel Pro intake gasket set.  My 440 used to run hot ever since I picked up the car off eBay from Texas early this spring.  It had the wrong radiator, and I didn't know which radiator it had so I couldn't install a shroud, so I ended up replacing the radiator with the correct one from Year One, then I was able to install a factory shroud.  I also replaced the radiator fluid, installed a 180 degree high-flow thermostat.  Since then, the engine doesn't seem to overheat anymore.  I did top off the radiator after filling it, and most of my trips since have been around town until my last trip which was about 30 miles away to a car show.  I was quite embarrassed when I pulled in and shut it down only to watch it drain out about 1/2 quart of antifreeze onto the ground again in front of spectators and (more embarrassingly) my competitors!  I suppose the top radiator tank doesn't remain full, but has some space for expansion of the fluid.  Too bad these cars don't have an overflow or expansion tank.

I am having a devil of a time, however, getting this car started after it sits for more than 24 hours.  It takes 4-5 pumps on the accellerator, then cranking it over for a few seconds, then 4-5 more pumps before it finally tries to spring to life.  The choke appears to have been rigged up several times by bending? the linkage and is now nonfunctional requiring me to sit in the car giving it enough throttle to keep the engine running long enough to warm it up enough to sustain its own life.  However, once it heats up, it runs fine without any hesitation.  I am planning to (already on order) replace the carb with the Holley 770cfm Avenger.  For those running this carb (or the 670 or 870), can you please give me your input on installation, tuning tips?  Does this carb sit higher than the stock carb and will it rub my new moulded hood pad?

Many thanks for the advise!

Tom
Bryson City, NC
60 R/T SE Turquoise

[Chryco Psycho]

the Holley is the same height [3.5"]
I would have used a 870 on a 440
tunign , I could write pages try this for starters http://www.cuda-challenger.com/smf/index.php?topic=822.0

[SpudRacer]

So many different opinions!!  I was told by others that without any changes to the engine, the 670cfm would be more than adequate and would provide a better throttle response than the 770 and esp the 870.  I was told by most that the 870 was way too much carb for a stock 440, so I opted to compromise and go with the 770.  I may install a hotter cam and headers in the future.

The 770 is on back-order right now as is a K&N filter.

Can I PLEASE get more opinions regarding the carb choice for a stock to mildly modified 440??  Thanks guys.  I'd rather change my order now, then have to return the wrong carb later.

Tom
Bryson City, NC
69 R/T SE Turquoise

[cudaken]

 NYCNilles, I think the temp is your problem. When my 68 Ruuner was hitting 200 210 in traffic it would vapor lock as well. Replaced the radiator when it started to run hot on the highway. Now 180 and no vapor lock.

Long time ago I was having a problem with boling the gas in the float bowls. Man could not figuer out what happing. When cool ran great, hit 180 fall on it faces, back fire and made life awful. I replaced everything, carb, intake gasket, distributor and wires. One day I stopped to get gas while I was riding my bike. At this point I asked anyone I could that worked on cars what could the problem be? Older man about 60 was sitting a rocking chair. Started asking him, when I got done he stated "It's your Carb gasket".

Told him, there was no vacume leak and it looked fine. Told me "beside sealing the carb it help's shield's the carb from heat". Well I left it at that and headed off. Following weekend what the heck, threw $400.00 at the car what was another $2.00. I be dam, took care of it. Learned one thing from that, just because it cant be the problem does not mean it not.


                             Cuda Ken

PS, 41 Husk drove is 68 Charger and broke down at my house, vabor lock. Replaced the Carb gasket and he was on the road again.
               

[8WHEELER]

I have found in the past that a mild street driven 440 will run fine with a 780 vavuum sec, or
an 800 double pumper. Now I know these are older carbs but I run an 850 DP now on the
street only and it runs a little fat at idle but great off idle but then again my engine is no where
near stock.

Dan

[firefighter3931]

So many different opinions!!   I was told by others that without any changes to the engine, the 670cfm would be more than adequate and would provide a better throttle response than the 770 and esp the 870.   I was told by most that the 870 was way too much carb for a stock 440, so I opted to compromise and go with the 770.   I may install a hotter cam and headers in the future.

The 770 is on back-order right now as is a K&N filter.

Can I PLEASE get more opinions regarding the carb choice for a stock to mildly modified 440??   Thanks guys.   I'd rather change my order now, then have to return the wrong carb later.

Tom
Bryson City,
69 R/T SE Turquoise

Inmo, the 770 will be fine. My built 446 (535hp) uses an 830 cfm modded carb and at wide open throttle (6500 rpm) it was only moving 800cfm as measured on the dyno. The 770 with it's smaller venturis will give you better throttle reponse than an 870 carb would. For a stock to mild build that would be my choice.

Ron

[SpudRacer]

Thanks for the detailed (fact-laden) suggestion Ron.

The carb shipped yesterday and should arrive today or tomorrow.

Tom

[grouseman]

Let's get the terminology straight.  Vapour lock occurs in the FUEL PUMP itself and so no liquid gasoline will reach the carb.  As the pump tries to appy suction to the fuel, it is just hot enough that it instantly boils under reduced pressure.  No suction, no pumping, no fuel.  An electric fuel pump will solve the problem.  So will keeping heat away from the fuel lines LEADING to the fuel pump, and keeping the fuel pump cool.  Do a simple test - pour cold water on the fuel pump when you're experiencing your problem, and if it cures it you've found the culprit. 

Yes, carbs can get so hot that they boil the fuel out of the bowls so that they're dry upon restart.  When running, that vapour gets sucked into the carb so it runs richer, but still runs.  Every carb should have some sort of insulator gasket/plate underneath it. 

grouseman