70 DeVille Carburetor Vaper-lock or "Heat-soak" issues
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RWD 19xx-1984 DeVille and Fleetwood,
1985-1996 Fleetwood and Brougham Forum Discussion, 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues in Past Cadillac Vehicle Discussion; After blowing my engine, (Valve broke-off and dropped into the cylinder) I rebuilt nice a 71, 472 and dropped it ...
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    jc4now is offline Cadillac Owners Member
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    70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    After blowing my engine, (Valve broke-off and dropped into the cylinder) I rebuilt nice a 71, 472 and dropped it in. Kept it as original as possible. However; This modern ethanol fuel is a real pain. I felt it was running a little too warm. I have a 180 degree thermostat and a mechanic used a fancy laser thermometer to tell me I'm running about 190-195 degrees going back into the radiator.

    The problem is, I stop somewhere for 20 minutes to an hour and it starts (If the battery can hold out that long) like she is flooded. I'm told it's "heat-soak" or Vapor-lock from the ethanol boiling-out of the fuel in the Carburetor float bowls and/or fuel lines. I've been looking around the web and I see race forms talk about a "Phenloic" Carburetor spacer to insulate the carburetor from the heat rising off the manifold. It looks like most are 1 inch thick. (I don't know if I have that much room under the hood to keep the OEM air cleaner) They also mention insulating the fuel lines near the engine and adding a electric fuel pump to add fuel line pressure. Some suggest buying marine or airplane fuel first. (Talk about BIG fuel prices, if you can get it.)
    I am told the ethanol in our gas will only increase in the coming years. Which will only make things worse for those of us with older carbonated vehicles.

    It's seems like the minute you change one thing you end-up changing 7 others to make it work. Is there a, relatively, easy fix to this? I'm not fond of the idea of converting to a fancy and expensive Fuel Injected System.

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    csbuckn is online now Cadillac Owners Master
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    I'd try to insulate the lines and move them away from anything hot before I do anything else. I dont see it being vapor lock if its parked for an hour and gives you problems on start up. The vapor lock I've dealt with would kill the car when driving. The guy had a second metal fuel filter in front of the engine. Hard starts when warm...

    What do you mean by starts like its flooded? Do you have to hold the pedal down to start it? How does it run after it starts?

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    The Ape Man's Avatar
    The Ape Man is offline Cadillac Owners Connoisseur
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    Have the carbonator well seals been sealed with epoxy instead of the problematic factory lead?

    Also take a long look at the distributor"s mechanical advance to make sure it does not bind. Very common problem with these engines. that can make warm restarts hell on the starter.

    Lastly, is the started to chassis braid connected?

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    carnut is offline Cadillac Owners Master
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    He means the "starter ground strap to the frame" in place?

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    jc4now is offline Cadillac Owners Member
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    Yes CS. If it sits for a while and if it doesn't start right away, I have to hold the pedal to the floor and it will start. It will run well until I turn it off. Like to go into a store or something. I get back out and have to hold it to the floor to start her again. In the morning (Or the next day I drive it...when she is cold. Pump the pedal a few times and pow. Starts right up.

    ----------

    Yes CS. If it sits for a while and if it doesn't start right away, I have to hold the pedal to the floor and it will start. It will run well until I turn it off. Like to go into a store or something. I get back out and have to hold it to the floor to start her again. In the morning (Or the next day I drive it...when she is cold. Pump the pedal a few times and pow. Starts right up.

    ----------

    Ok Ape Man. The Carb was working well before the rebuild. I just transferred it over. Runs like a champ when cold. Even warm, if I don't turn it off. But on a hot day and she gets good and warm...and I stop somewhere for a while, I got to hold it to the floor to get it started.

    Oh yea...I will park it in the garage when she is hot and in the morning it smells like gas vapors. Not quite like a gas leak. I've had those and I can't find any gas anywhere.

    I've only got 400 miles on the rebuild. I'm almost positive that ground strap is there. The guy who did the rebuild with me was all about properly grounding everything. It turns out my battery was not properly grounded and he corrected that issue.

    As far as the distributor binding. I will look into that.

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    The Ape Man's Avatar
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    Was a fuel well reseal part of the rebuild? Many times this doesn"t get done.

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    csbuckn is online now Cadillac Owners Master
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    Slight fuel smell when parked overnight and hard starts when warm...

    I'm not sure your hard starts are related to fuel unless a carb gasket is expanding with heat or you are running rich. Do you get the mileage you did before the rebuild? When having trouble starting, can you see a steady stream of fuel come out the carb when you pull the linkage back?

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    jc4now is offline Cadillac Owners Member
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    I do not know how to answer that one Ape Man. I know the engine and heads were Magna Fluxed? and machined, Pistons .030 (30 Tho) over. Crank ground. New valves, Valve springs, Pistons.The intake manifold was all boiled out and cleaned. etc. etc. The carburetor was not really touched. New choke pull-off. and several new vacuum lines. Is the Fuel Well inside the Carb? We did not rebuild it. Just a new gasket between the Carb and manifold.

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    The Ape Man's Avatar
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    Ok. Gas can seep out of the carbonator if the fuel wells are not epoxied during a carb rebuild. That can cause vapor lock and associated hard warm restarts. So can fuel lines touching the engine.

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    jc4now is offline Cadillac Owners Member
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    CS: I'm not sure, Ive never had the air cleaner off when I get this and I'm not to comfortable getting my face too close to a Rodchester 4bbl in action. She could be a little rich. She seems to be DRINKING gas. I'm thinking 8 mpg, but I'm not thinking that is really that bad with this car. I've only put 400 miles on the new rebuild going to car-hop nights and car shows. I need to jot down the mileage and figure out the mileage I'm getting.

    However I'm going to run all of this by my mechanic friend (Not a full-time mechanic but he used to build local stock cars.) Like most he is all about the small block Chevy 350 and will tell me to ask the Caddy experts (You guys) and let him know what you guys think.

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    csbuckn is online now Cadillac Owners Master
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    For some reason, I didnt catch that this was a 472. I'm having the same issues with my rebuilt 500, hard starts when warm. I think the starter is getting hot. I was thinking about putting a heat shield between the exhaust and starter. When I was saying to look for a stream of gas when you are having the problem, I meant for you to do it with the car turned off. When its warm and giving you trouble, go under the hood and, while looking into the carb, pull the throttle linkage back to see if any fuel squirts out. You will be safe, nothing is going to pop up at you if the motor is off. If you dont see two squirts of gas going into the carb, then I'd think its vapor lock. Does it almost seen like the starter is having a hard time turning the motor? If so, that is probably gonna be starter heat sink, when the starter cools, it gets better. I know what you are going through as mine did the same thing. It doesnt do it as bad now but I dont know what I did to make it better(oh yea, I havent driven it much in the last couple years). 8 mpg is what your are gonna get no matter what you do. The best I've heard was 10 mpg.

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    cadillac_al is offline Cadillac Owners Connoisseur
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    I think it's more carb leaking than vapor lock. The points may need some tinkering. If it turns over slower when warm then there is another problem (starter/battery/alt). It does sound like a leaking carb though.

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    carnut is offline Cadillac Owners Master
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    These well plugs are like freeze plugs pressed into the underside of the carb base. If seeping, they will dribble gas into the intake manifold and give you a flooded restart warm. To seal, you remove the carb, invert it and apply epoxy around them, let dry overnight. reinstall carb with new base gasket. A better way to remove heat from the starter and solenoid is to wire in a Ford starter solenoid. Mount it on an inner fender and run the original solenoid wires to it with a short battery cable from it to to the starter.

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    The Ape Man's Avatar
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    Re: 70 DeVille Carburetor Vaper-lock or "Heat-soak" issues

    I used to get 8 volt starters made at the local rebuilder. They even started the 12.5:1 .30 over 500 I had in my '82 TransAm but it was not pretty.

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    jc4now is offline Cadillac Owners Member
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    So much to reply.
    Took her out a few days ago. About 8 miles, mostly highway. Picked up gf. Started right up. Took gf to Sonic for a burger, about 8 miles away on back roads. Sat there for about 30 min. (engine off) had dinner. Had to hold it to the floor to start and feather the gas for about 5 seconds so she wouldn't stall. Run good then. Back to gf. Stopped in for another half an hour. Again had to floor it to start. Back roads home. Got it in the garage and when I shut it off I could hear the engine heat soak. Top radiator hose bubbling noise. Lost about a qt of antifreeze via the overflow tank. Took a solid 30 min to stop bubbling noise.
    I keep hearing these 472 / 500 engines run hotter than most, but this is just plain annoying.
    I've replaced everything but the heater core. I've got a 180 degree thermostat in it. I've heard of a 160 out there but can't fine one.
    I think I've got a heat problem most if all. Which causes a host of other problems. I need to install a really good set if instruments to tell me exactly where I'm at. My car only has worthless idiot lights. When they come on, its to late.
    I'm getting frustrated. Not sure where to start. One friend suggested a set of electric radiator fans in FRONT of the radiator to push air through. Helping the factory fan. They had done this to a couple of older suburbans service vehicles with 454's in them that ran hot.

    I just don't know at this point.

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