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#1
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Vapor Lock - Danger
I've owned my tri-power GTO for 4 years. In that time, I've never had an issue with vapor lock. It always takes 5-7 seconds cranking on a hot start feathering the throttle to catch, but nothing too bad. Cold start no problems ever. Once I'm moving, no problems with vapor lock.
This last month, including today's cruise, it will hot start after some cranking, but will die one or two times in the first 1-2 minutes of idling/driving. So, I was rolling out of a parking lot and trying to merge into heavy SoCal traffic and it is sputtering and dies. Not safe at all. Again, once I'm cruising and fuel is moving, no problem. Cold, no problem. WOT, no problem. I have a 5/16" feed fuel line to a mechanical pump. No return. The fuel line and filter are NOT in contact with the block. I have phenolic insulators under the carbs. Using the temperature gun, the exterior of the fuel bowls is 140-160F. The engine runs cool, <180F. The ambient temp is cool, maybe 65F. Dual electric fans, both functioning. 160F thermostat. The cooling system is beautiful. My next move is to buy a filter with a ¼" return nipple, and run a rubber line back to the tank. I'll need a new sending unit with ⅜" feed and ¼" return, and use a reducer on a piece of rubber hose at the tank to go from ⅜" to 5/16" existing line. Question, did something change in California gas? Anyone else suddenly having issues? I can't understand why now...
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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#2
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Have you checked the vent lately? Could be collapsed or plugged.
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'65 Tempest 467 3650# 11.30@120.31 |
#3
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No, I have not. Good call on that. I will check it out and report back.
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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#4
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Fingers crossed its that simple.
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'65 Tempest 467 3650# 11.30@120.31 |
#5
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From the troubleshooting section of my website:
http://www.thecarburetorshop.com/Tro...ardstarthot:// Jon.
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"Good carburetion is fuelish hot air". "The most expensive carburetor is the wrong one given to you by your neighbor". If you truly believe that "one size fits all" try walking a mile in your spouse's shoes! Owner of The Carburetor Shop, LLC (of Missouri). Current caretaker of the remains of Stromberg Caburetor, and custodian of the existing Carter and Kingston carburetor drawings. |
#6
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try putting heat insulators under carbs
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2008KRE Q16 Winner 2014 atco raceway doorslammer winner 86 grand am tube car 8.95 @152 455 eheads solid flat tappet cam Hoffman Racing building and racing Pontiacs for 35 years |
#7
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Richie,he has them!Tom
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#8
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Spent a lot of time on this. Gas starts to boil at 95F and your fuel pump eventually is 160+f. Try the ceramic insulator that Canton sells that goes between fuel pump and timing cover. I ultimately solved my issue with a in tank electric fuel pump and a regulator at 6 psi.
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#9
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Canton Racing Mechanical Fuel Pump Insulators 85-010
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#10
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Installing a return line is a good idea but I'd use a reproduction A/C 1/4" steel tube instead of rubber hose all the way back. You'll have to change out the sending unit in the tank or solder in a hose nipple to accommodate the return line.
Yeah, CA gas sux. That was the main reason for installing EFI in my '66 GTO. |
#11
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It may not be vapid lock, you now may have some bad rubber fuel line that's dry rotted and leaking air which the fuel pump draws in much much faster then fuel.
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Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
#12
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We use the same suppliers for gas here in Arizona, same crappy 91 octane.
As it stands right now I haven't noticed any issues on our cars. We daily 2 classics and both have been fine. One has a return line fuel system and the other does not. Temps have been hovering close to 60 up here in Prescott and 70+ in Phoenix and I've made the trip (220 round trip) with both cars recently without issues with fuel, filling up at different stations. With that said it could be a number of different issues causing problems. Could just be you got a bad tank of gas recently. One thing I've noticed is that the ethanol content is not consistent from one station to the next. Installing a return line certainly helps and not a bad idea to do so. This fuel does not like temperature AT ALL. Sounds like you have all the other bases covered. |
#13
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May have been the change from summer to winter blend fuel although that happened a few months ago.
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Ed 1968 GTO (Thanks Mom) 2006 Silverado 2007 Cadillac SRX 2015 Chevy Express |
#14
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If you didn’t have a problem before, I would think that something is failing.
I had a very similar problem on my 70 GTO and a new fuel pump took care of it. I believe the ethanol gas deteriorated the rubber seal. |
#15
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The problem has been going on for 1-½ months.
The carb vent is clear. I'm ordering the Canton fuel pump insulator from Jegs, and the fuel filter with a return provision from Pontiac Tri-Power. https://pontiactripower.com/collecti...th-return-line Regarding the return line, do you recommend buying a pre-bent one, or bending my own? The Right Stuff has a pre-bent one, but I have no experience with those. Going for a test drive now...
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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#16
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I should've been more clear, I was talking about the tank vent. I assume you have the small metal line on the tank with the short section of hose. That could be rotten, or have debris in it.
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'65 Tempest 467 3650# 11.30@120.31 |
#17
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I'll check the tank vent. I replaced the vent hose about 2 years ago, so I think it is OK. Also, if I had tank venting issues, I would expect the issues all the time, not just after hot starts... I will check though.
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1965 Pontiac GTO 455/469 w/ #48 Heads, '65 Tri-Power 9.25:1 CR Stump Puller Cam Muncie M22W 1st-2.56 2nd-1.75 3rd-1.37 4th-1.00 3.55 Rear Differential Front: 225/60R15 Height: 25.6" Rear: 275/60R15 Height: 28" |
#18
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The pre-bent lines fit well and save time.
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#19
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Absolutely / happens quite often years after the build one needs to go & tighten all clamps & possibly replace the rubber hose ends .
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#20
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Symptoms posted remind me of a 2bbl carb that the base plate to fuel bowl screws have worked their way loose.
That or a carb that's right on the verge of loading up. Not enough to flood over but enough to cause stumble when turning or crossing unlevel pavement at idle or minimal throttle opening. Homework before part swapping. Including basic engine tune Clay |
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