richsteve

Hey guys, I have an 84 camaro berlinetta with the 305 LG4 stock set up. The car is getting vapor lock during our hot arizona summers and I just purchased a 3/4 inch wood heat spacer for my stock carb. After I order it I started to worry that it might be to tall for the under-hood clearance. Does anyone know how tall I can go with a spacer before I run out of room? Thanks

sofakingdom

iTrader: (1)

Not bloody tall.

A better plan would be to figure out if it's REALLY vapor lock (if I was the betting kind, I'd lay 99999:1 odds that it's NOT); and THEN, figure out WHERE the heat is getting into the fuel (again, if I was the betting kind, I'd lay 99999:1 odds that it's NOT the carb); and THEN find a way to keep THAT PART cool.

Still have the stock fuel pump with return on it? When does it exhibit the symptoms that you're attributing to "vapor lock"? What symptoms are they?

richsteve

Yeah those cars are known for vapor lock. Does it after a hot soak. Drive the car around and let it heat up and than let it sit for an hour. when I crank it it turns over for a few seconds then cranks and wants to die. Have to gun it for a few seconds to clear it out. IT will also want to surge for a few seconds as well. Once I clear it out it runs great until I shut it off again and let it sit for 30mins or so. Gas could be boiling over in the carb as well. Already insulated the fuel line under the hood which helped but didnt cure it. My other camaro had a heat spacer and it never had that issue. Frustrating.....

sofakingdom

iTrader: (1)

No in fact, they are not.

Rather, ignorant people who don't understand what's going on, apply that obsolete term to a COMPLETELY DIFFERENT behavior than actual "vapor lock". Just because people SAY THOSE WORDS alot, doesn't make them true.

What "vapor lock" ACTUALLY IS, is the fuel boiling in the lines before the carb, and specifically, before the fuel pump, where the pump is pulling a "vacuum" as it "sucks" fuel out of the tank (remember, the boiling point of any liquid changes as the pressure on it changes); nothing but vapor being in the fuel lines; and nothing but vapor reaching the carb. The fuel bowl goes dry, and the car essentially runs out of gas.

I am not aware of ANY car having this problem in AT LEAST the last 40 or 50 years. Has as much to do with the fuel as it does with the cars; fuel simply isn't as prone to "vapor lock" as it once was.

What you are describing is THE EXACT OPPOSITE of "vapor lock". Instead of the carb running dry because nothing but vapor is being pumped into it, it's boiling over, and FLOODING the motor. You don't have "vapor lock"; you have "submerged lock". There can in fact be SO MUCH fuel gushing out of the carb, that it can fill up the cyls and "hydraulic" the motor.

2 COMPLETELY OPPOSITE sets of symptoms: in "vapor lock", the carb runs out of gas, and the motor leans out; in what you (and others with these cars) have going on, is the fuel being heated up BEFORE it reaches the carb, and boiling over in there, and spewing out of every hole in the thing, and DROWNING the motor in fuel.

Next time the car does this, STOP trying to start it, and get out and pop the air cleaner off, and ACTUALLY LOOK AT the carb instead of just assuming "vapor lock". You will see fuel EVERYWHERE, probably on top of the intake even, but CERTAINLY, you will see the interior of the intake DRENCHED in fuel and boiling fuel mist everywhere. THE EXACT OPPOSITE of "vapor lock".

Furthermore, had you looked at it RIGHT BEFORE you tried to start it, it would have been COMPLETELY NORMAL; it only starts to screw up when fuel starts to flow into the carb AFTER you begin trying to start it. Meaning, IT'S NOT boiling inside the carb, YET.

The ACTUAL ROOT CAUSE of this, is heat reaching the fuel pump. That's why it only does it when the car sits. What's REALLY going on is, the fuel in the pump gets VERY hot from the hot block, and stays liquid between the pump and the carb ONLY because it's under pressure; then when it passes the needle valve and goes into the fuel bowl, it's no longer pressurized, and all of a sudden its temperature is now ABOVE THE NEW BOILING POINT at this lower pressure, and it erupts into a full rolling boil INSTANTLY. It looks just like what happens to the pan of boiling spaghetti noodles when you let it get out of hand.

Therefore:

The problem IS NOT "vapor lock".

The problem IS NOT caused by the carb itself; it is generated elsewhere, and the symptom merely OCCURS IN the carb.

Therefore, you CANNOT fix it by messing with the carb.

What you need to do, is insulate the FUEL PUMP from the block. You can verify this by simply putting an extra gasket under the FP. Go try that FIRST and see what happens. If it works, get one of these, instead of jacking around with the carb. https://www.cantonracingproducts.com...&category=8510

naf

iTrader: (7)

I have only recently, this Summer, begun to experience this problem with my 85 TA which has the stock fuel delivery system. I've put over 100,000 miles on this vehicle since 2004 with no heat soak issues until this Summer. Runs rich and rough for a few minutes after a hot soak, dwell pegged full lean trying to compensate. Clears up after a few minutes. I was edging towards blaming a change in the fuel that increased its propensity towards boiling...

kd5icr

iTrader: (2)

Has anybody here ever used a Fuel Pump Phenolic Insulator? And do they work? Also to sofakindom what I am dealing with is no doubt vapor lock I do not have fuel all over the place (intake ect..) the brand new pump just flat out stops pumping fuel untill it cools off and I mean it is dry. What I do notice is the mech pump is hot to the touch yet the carb is cool to the touch but then I did use a heat disapator between the carb and intake. To make it clear I do have shorty headers and the fuel lines are in the stock location both supply and return lines. This is a real problem and I am at a loss, I have never has this problem before and to me it is a serious problem and seems to be getting worse. I didnt get 2 miles yesterday and it died lucky for me I could pull off the road instantly. Even after little more than a hour with the hood open to speed up cooling the pump was still a little to warm to the touch. I had to get a tow truck to bring us (me and the car lol) home. After 4-5 hours it was cooled down enough to start pumping again. No it does not have a pusher pump in the tank it is a 85 Z28. Thats why I am asking because I have been all over this site and too many of the good people here all say something different . Maybe there needs to be some sort of sticky made about this.

sofakingdom

iTrader: (1)

Yes they work.

Sounds to me like the fuel lines back in your tank are plugged up with the crusties of age. Pop the tank out, remove the "sending unit", and rod it out with a coat hanger. You may find you need a new item of this sort (not this particular one, it's the wrong size). http://compare.ebay.com/like/3604912...Types&var=sbar

naf

iTrader: (7)

You can also insulate your fuel lines with heat sleeving. I've used some on my 87 SC where the headers run closer to the fuel lines than the stock exhaust did. Even though they're ceramic, the fuel lines still pick up a good bit of heat.

With the stock return style system you shouldn't be having a vapor lock problem while it's running. The system should be constantly running fuel through the lines, keeping them cool. It's when the motor is off and the fuel sits in the hot line that causes the lock. You can blow air through the feed and return lines and verify they're not completely blocked, maybe clear them out some.

kd5icr

iTrader: (2)

I do have the lines covered with heat sleeving, I have a set that you would use for plug wire boot at the plug, I used 2 of them to cover the lines were they run along the headers.
To sofakingdom.
What I did was, when the car did stop running, I pulled the fuel filter off of the carb and I sucked ( ok ha ha) a little and it filled right up with very little effort almost as much as taking a pull on a cigerette, so I would think the lines are clear and the fuel filter is as clean as could be infact the fuel is so clean you can almost not see it. Now I get it there are times when just driving around can at times dislodge any crap in the tank and send it floating around, but as the engine get warmer you can watch the fuel in the filter get lower and lower untill it is empty and the car dies. and as I said the pump is HOT to the touch yet everything else is cool the in and out lines as well as the carb.
Thats why I asked.