Vapor lock or something else? - Team Camaro Tech
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post #1 of 17 (permalink) Old Jun 2nd, 15, 07:27 PM Thread Starter
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Greg
 
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Vapor lock or something else?

My daily driver is my 67 SS Camaro which I put a 454 in. Never had this issue in the last 4 years I've been driving it but here's what's going on. It's getting warm outside somedays, I keep the car in the garage. When I first start it up and drive around it's perfectly fine. On hot days if I get out, let it sit for a little bit and get back in, it'll start and idle fine, and high rpms are fine but accelerating or cruising it'll sputter, almost like a miss, kind of falls on its face. If I let it cool down in the garage for a few hours it's fine again. It's been a while since I did a tune up so I'm going to do that regardless. But if I understand vapor lock correctly it seems I might need to put some heat wrap on the fuel line under the hood. It's just strange that I've driven in hotter weather and the engine coolant never goes over 185.

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post #2 of 17 (permalink) Old Jun 2nd, 15, 07:33 PM
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Rick
 
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Re: Vapor lock or something else?

Winter fuel blend is probably the issue. Do you have an insulator under the carb?
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post #3 of 17 (permalink) Old Jun 2nd, 15, 07:36 PM Thread Starter
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Re: Vapor lock or something else?

Yes I do have an insulator. I was just reading on winter blends. I'm in Michigan so we're still having temps before 50 degrees F and sometimes days as hot as 85. I use mid grade gas.

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post #4 of 17 (permalink) Old Jun 2nd, 15, 08:01 PM
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Rick
 
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Re: Vapor lock or something else?

I tried a few things including insulating the fuel line. Be sure you have good airflow. Factory fan? Wood ended up being the best insulator. Sometimes you can get lucky just changing fuel brands until the summer blend hits. You might try premium.
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post #5 of 17 (permalink) Old Jun 2nd, 15, 08:14 PM
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Bill
 
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Re: Vapor lock or something else?

Hoo, boy...

I know I'm going to get flamed for this, but...

You can always try the potato on the fuel line trick, if it solves the problem you know it was caused by vapor lock. Then trace your fuel lines, especially the rigid steel portions, see if they touch or pass close to some sort of heat generating part. Like your tranny.

I used potatoes on my ghetto track racer to cool down the brake lines in-between heats.

Let the flaming commence!

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post #6 of 17 (permalink) Old Jun 3rd, 15, 08:45 AM
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mike
 
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Re: Vapor lock or something else?

Sounds like a tune up might just solve this issue, could be as simple as fouled plugs, bad distributor cap. I would do that first, then check back and let us know how you made out. If it has not been troublesome the way it is then don't change anything.
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post #7 of 17 (permalink) Old Jun 3rd, 15, 10:09 AM Thread Starter
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Re: Vapor lock or something else?

Ok thanks everyone, I have about a half tank of this gas I'll burn through, get some more at a different station, get the tune up done and check back in, thanks everyone.

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post #8 of 17 (permalink) Old Jun 4th, 15, 05:07 AM
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Re: Vapor lock or something else?

Fuel recipe has changed in the past years, more ethanol and who knows what else.
Lower vaporization point will come into play.
I would insulate the fuel line(s) and maybe plan in the future, add a return line to the tank. Moroso makes a return adapter in place of the filler tube hose for a simple return.

http://www.summitracing.com/parts/mor-65385

Also, pumps push better than they suck, if using a mech pump, plus the heat from the BBC. Pumps can't suck vapor if suction fuel line is vaporized and carb fuel line included. Some owners install a small elec fuel pump, ie, Holley 12-601 or a 12-847, for pushing fuel to the mech pump. Just something to push the fuel forward even during acceleration.

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post #9 of 17 (permalink) Old Jun 4th, 15, 09:52 AM Thread Starter
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Re: Vapor lock or something else?

Thanks for that info, I think I'll try a tune up and insulating the line first, that return line and electric pump sounds like a lot of time and money just to drive it like I'm used to driving it. I'm not keen on the pump idea because it's another part to go bad on me not to mention wiring it up so it's not on all the time with the key, I like to listen to the radio while I'm messing around in the garage and toggle switches just aren't my thing.

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post #10 of 17 (permalink) Old Jun 4th, 15, 10:01 AM
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Re: Vapor lock or something else?

You're welcome.
Understand your point and your decision, I respect this.
Another suggestion is add clothes pins, one every inch of length, to the hard line(s) as these pins dissipate heat.

If this science project works, then you know its a heat related problem and simple fix is used - take them off for fall and no one will know the difference.

Another suggestion is use neoprene fuel hose in place of hard line(s) as rubber dissipates heat better.

Also, as a flow gauge, install a see-through fuel filter and it should be full at all times.

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post #11 of 17 (permalink) Old Jun 4th, 15, 10:11 AM Thread Starter
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Re: Vapor lock or something else?

I have heard the clothes pin suggestion enough times to give it a go, I do have a transparent filter already. I'll dive into it with all this in mind, hopefully this weekend and report back. There's nothing more annoying than finding a thread that is all about the same problem you're having but the guy never comes back to say how he resolved it. Thanks again.

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post #12 of 17 (permalink) Old Jun 4th, 15, 10:15 AM
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Re: Vapor lock or something else?

Watch the filter, it should be full at all times.

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post #13 of 17 (permalink) Old Jun 4th, 15, 11:12 AM
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Re: Vapor lock or something else?

Mine used to boil out of the carb vent like a geyser. The insulator helped. Then I used the line insulation from DEI which helped. The total cure was a HD clutch fan (my cooling system is stock) which kept the intake area cooler at idle. At least it's gone for now.
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post #14 of 17 (permalink) Old Jun 4th, 15, 04:14 PM Thread Starter
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Re: Vapor lock or something else?

I might have to disagree with you on the fuel filter being full. I haven't checked it while the engine is running but I have a pick up with the same engine, carb, pump and filter, also 2 trucks with small blocks same carb and filter. They all have the exact same filter and I just popped the hoods, they're all about half full, I've never seen them completely full and I've had one truck since 1999. They all run perfectly fine, 2 of them have new pumps and filters. Maybe it's the style filter or maybe you mean when the engines running but never seen them full.

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post #15 of 17 (permalink) Old Jun 5th, 15, 04:51 AM
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Re: Vapor lock or something else?

I know what you mean, Greg. I had an '88 MCSS with Eddy carb from previous owner
and I placed a Pyrex glass fuel filter on the vertical section of the hose from pump to carb.
When engine was running, filter was full.
When engine off and sat for say a week, filter would be half full.
Before starting the MCSS, I learned the fuel bowl was dry - evaporated - used a Q-tip down the vent tube and was dry.
I would pour in 1/4-1/3 cup of fuel into the vent tube and engine would start as normal.
Filter was full by the time I got out to look at it, say 10 seconds.

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