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Percolation?

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Old 07-21-2018, 01:20 PM
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emdoller
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Last week I drove my wife’s 69 Camaro to the gas station. It was about 105 degrees out and the car had been running in my driveway for about 20min prior to heading to the gas station to put gas in a can. I did not put gas in the car and can’t recall if I shut it off but I’m pretty sure I did. I had the AC running. Gas station is about 2 miles away. Car has original 350 engine with a Rochester 2bbl carburetor. Gas tank is not vented but cap is.

When I pulled out of the gas station it stalled and I was able to start it. That got me to a traffic light. I then hit the gas and about 50 yards ahead I died. I couldn’t get it started. I opened the hood and removed the air cleaner. With my goal being getting it started and trying to get home I didn’t pay too much attention to all the signs.

I noticed vapors coming out of the carb and some residual gas on the manifold. I tried several times to start it and thought I was going to run the battery down. I then put about 1/2 cup of gas (luckily I had the can I just filled up) into the carb and it fired right up.

Given everything I’ve read on this sight, it seems like it was percolation vs vapor lock. If im right, im going to buy a phenolic spacer.

I realize this isn’t about my Vette but seeing that everything I know about vapor lock and percolation came from this website, I thought I’d get opinions before trying a fix

thanks in advance!!

Ed



Last edited by emdoller; 07-21-2018 at 01:21 PM.
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Old 07-21-2018, 02:44 PM
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Originally Posted by emdoller View Post
Last week I drove my wifeís 69 Camaro to the gas station. It was about 105 degrees out and the car had been running in my driveway for about 20min prior to heading to the gas station to put gas in a can. I did not put gas in the car and canít recall if I shut it off but Iím pretty sure I did. I had the AC running. Gas station is about 2 miles away. Car has original 350 engine with a Rochester 2bbl carburetor. Gas tank is not vented but cap is.

When I pulled out of the gas station it stalled and I was able to start it. That got me to a traffic light. I then hit the gas and about 50 yards ahead I died. I couldnít get it started. I opened the hood and removed the air cleaner. With my goal being getting it started and trying to get home I didnít pay too much attention to all the signs.

I noticed vapors coming out of the carb and some residual gas on the manifold. I tried several times to start it and thought I was going to run the battery down. I then put about 1/2 cup of gas (luckily I had the can I just filled up) into the carb and it fired right up.

Given everything Iíve read on this sight, it seems like it was percolation vs vapor lock. If im right, im going to buy a phenolic spacer.

I realize this isnít about my Vette but seeing that everything I know about vapor lock and percolation came from this website, I thought Iíd get opinions before trying a fix

thanks in advance!!

Ed


I had percolation issues when I lived in Colorado Springs...given the lower barometric pressure, using today's fuel and the mechanical fuel pump (heat sync), my car would percolate on a mid 80 degree day. I did the spacer thing and it didn't work. I finally went with an electric fuel pump...a Carter pump and filter from Jegs...mounted near the tank and I bypassed the mechanical pump all together. Took an afternoon to figure out where to mount, fab brackets and run the fuel lines and electrical. Not very hard. Oh, if you go this route you also want to add the oil pressure cut-off switch as a safety measure. In case of an accident and the ignition isn't cut immediately the pump won't continue to run when the engine shuts off.

No more percolation problem.
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Old 07-21-2018, 02:48 PM
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The vapors coming from the carb and fuel on the manifold say percolation to me. My '61 with dual WCFB's does this occasionally, but is much better now with Masonite insulator plates under the carbs. Still, the ethanol based fuel boils in a heat soak situation very easily. No issues going down the road though. Just the same issue you have described after the car sits 5-20 minutes on a hot day.
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Old 07-21-2018, 03:08 PM
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Thanks. I’m going to try a spacer and see how that goes. I appreciate the ultimate fix but this car is fairly original and I’d like to try the least invasive fix. I could always stop driving it in 105 degree weather!

Ed
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Old 07-21-2018, 03:15 PM
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Ed:

When was the last time you put gas in the car?? Any possibility of gas still being a "winter blend"??

I would do a few things to help with this (likely vapor lock/percolation) issue:

1. Add your phenolic spacer under the carb.
2. Wire open or remove the heat riser. You can replace heat riser with a solid spacer sold for the FI cars.
3. Insulation your fuel line about 3-4 feet before the fuel pump and between the fuel pump and car. Include any external fuel filter also. Use the foam insulation.

The insulation can be removed in the winter if you don't like the look.

I used to do this to my performance cars back in the day. I also ran an electric pump, but you should try and use the mechanical pump if you can..........since I know you like your cars to be "original".

Larry


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Old 07-21-2018, 03:30 PM
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Thanks Larry. The gas line from the pump runs right between the water pump and the block. Not the best design in my opinion and not enough space to insulate but I’ll give it a shot.

Could be winter gas as it’s only driven 10 miles or so a week.

Ed

Last edited by emdoller; 07-21-2018 at 03:36 PM.
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Old 07-21-2018, 03:36 PM
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Larry,

I think you nailed it. Winter gas!! I’ll flush it and see what happens.

Thanks!!
Ef
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Old 07-21-2018, 03:40 PM
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Originally Posted by emdoller View Post
Thanks. Iím going to try a spacer and see how that goes. I appreciate the ultimate fix but this car is fairly original and Iíd like to try the least invasive fix. I could always stop driving it in 105 degree weather!

Ed
Originally Posted by emdoller View Post
Thanks Larry. The gas line from the pump runs right between the water pump and the block. Not the best design in my opinion and not enough space to insulate but Iíll give it a shot.



Sounds like you have a non stock fuel line routing from the pump to the carburetor.
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Old 07-21-2018, 03:47 PM
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FTF put an electric fuel pump, with bypass, on his 63 to address perc problems. do a search for him and percolation or electric fuel pump
Bill
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Old 07-21-2018, 03:49 PM
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Mike

this is for a 69 Camaro and I believe is correct. I’ll double check.

Ed
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Old 07-21-2018, 03:53 PM
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Originally Posted by emdoller View Post
Mike

this is for a 69 Camaro and I believe is correct. Iíll double check.

Ed

That is correct for a '69 Camaro. I forgot what forum I was on.
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Old 07-21-2018, 03:55 PM
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Yea, sorry about that. I just seem to get the best advice from this forum!! 😀

Ed
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Old 07-22-2018, 08:38 AM
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Originally Posted by wmf62 View Post
FTF put an electric fuel pump, with bypass, on his 63 to address perc problems. do a search for him and percolation or electric fuel pump
Bill
No bypass - turns out the electric pump can be used "in line" and has an internal one-way check valve - making installation much easier....

Of course, since putting a pristine new carb on the car I haven't had a vapor lock problem again (of course) and so I don't know if this is a cure yet or not...



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Old 07-22-2018, 02:12 PM
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I have that heat soak issue as well, Just last week I put a half inch plastic spacer under the carb and a hunk of insulation I got off e-bay around the fuel line from the fuel pump to the fuel filter, I also spaced the fue; filter up from in intake manifold maybe a half inch. Has not been hot enough to see if any of that worked.
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Old 07-22-2018, 04:13 PM
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Originally Posted by karkrafter View Post
I have that heat soak issue as well, Just last week I put a half inch plastic spacer under the carb and a hunk of insulation I got off e-bay around the fuel line from the fuel pump to the fuel filter, I also spaced the fue; filter up from in intake manifold maybe a half inch. Has not been hot enough to see if any of that worked.
And keep the inlet to the fuel pump insulated also, and away from the exhaust manifolds/pipes.

Last edited by Powershift; 07-22-2018 at 04:14 PM.
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Old 07-22-2018, 04:38 PM
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I have a fresh (1200 miles) 283 set up to 1958 specs,with dual Carters, 097 cam,etc. in my ‘54. I eliminated the heat riser and blocked off the heat passage under the carburetors. I drive in 90 degree weather a lot and never had heat soak or vapor lock problem. Hopefully those two fixes will help with your problem. I don’t see a need for spacers on my car. Good luck and Happy Motoring.


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