Re: IML: 68 No-start when hot

[<boboyen@xxxxxxxxxxx>]

Reset the float levels in the carb bowls.

On Tue, 11 Sep 2007 17:58:53 -0500
 Greg Krueger <box_89krueger@xxxxxxxxxxx> wrote:
>       Yes the car is in running condition i have driven it 100 miles at a time. I am fairly 
> certain it is in the fuel system not the electrical.  Black smoke will blow out of the tail pipe 
> momentarily after I get the car finally started.  We have replaced the coil, ballast resistor, 
> spark plugs, and wires.  We have checked for spark and it is there even when the car will not 
> start.  Also emedietly after I have realized the car wont start i check the carb's choke it is 
> working as it should.  I am fairly certain this is a boil over problem on a rebuilt holly 
> carburetor. any advice.  
>
>
> From: sosmi@xxxxxxxxxxxxx: mailing-list@xxxxxxxxxxxxxxxxxxxxxxx: Re: IML: 68 No-start when 
> hotDate: Tue, 11 Sep 2007 19:52:14 +0000
> Since there has been a lot of very good input, I would only add, spark, and fuel. The two easy 
> tests. It is possible the accelerator pump is in-active. The 68 should have a Holley carb, it's 
> possible the cold start is good because the choke is closed, and vacuum during cranking will draw 
> enough fuel to start, once the engine is hot it may be too lean to start. Then when the engine 
> cools enough the choke may close enough to start. A simple check to see if the accelerator pump 
> is working would be in order. And as others have stated, check for spark, however I have the 
> impression the engine will start, only with delay. If that's the case,it's most probably a 
> carb/fuel issue. A very low fuel pressure, or blocked fuel filter may also be a problem. You also 
> didn't say if the car was driveable .Ya'll have a nice day, Dave.
>
> -------------- Original message -------------- From: "Geoff Fors" <wb6nvh@xxxxxxxx> > It sounds 
> like the fuel is boiling and/or vapor-locking in the carburetor > bowls. I presume that once the 
> engine is running, it doesn't stall when > hot, it just won't re-start when hot? That points to a 
> fuel system problem. > I also presume this is running a Carter AFB series carburetor. > > Sounds 
> like the heat riser valve is frozen in position, and its thermal > clock spring may be rusted 
> away or missing as well. The spring keeps it > closed until the engine heats up, then it holds it 
> open after that. The > exhaust force will also push it open when the engine is brought above 
> idle. > It's possible to wire the heat riser open, especially if you live in a warm > climate. 
> However, the heat riser assists in rapid warm-up and reduces the > time that excess gasoline 
> enters the combustion chambers during warm-up. > You may have a valve which is rusted closed, 
> even though it appears to be > open from an exterior view. That would certainly account for this 
> problem. > Sometimes the paddle moves on its shaft. The only way to tell is to drop > the exhaust 
> pipe from the manifold and look, rather a pain. > > It's not unheard of for the heat riser paddle 
> to come off the shaft and fall > down the pipe, jamming at some point, plugging that side. I 
> haven't seen > this on Imperials but on 1960's Buicks it will totally plug the exhaust > system! 
> > > The gasoline sold today tends to vaporize far more quickly than 1968 > gasoline and thus 
> older cars without fuel injection can vapor-lock easily. > This is a perennial subject in other 
> make car clubs at the moment. > > The paint always cooks off on the heat r iser path section of 
> the intake > manifold after awhile. That's normal. It shouldn't come off the rest of > the 
> manifold, however! > > If we were to take a survey, I think you will find that there are quite a 
> > few of us running stock '67-'68 setups with working heat riser valves and > original carbs and 
> gaskets, and we don't have this hot-start issue. Thus I > think something is wrong. It wouldn't 
> hurt to make sure the choke is fully > pulled-off when the engine is warmed up. The setup worked 
> fine originally, > so if it isn't doing so now, something is not right. > > I don't see any point 
> in changing the intake manifold. The heat comes from > the riser tube, not the manifold design. 
> If you really want to eliminate > the heat, use a gasket that blocks the riser tube holes, and 
> you can retain > the stock manifold. And, it wouldn't hurt to use a thicker gasket under the > 
> carb. Bu t, it should run fine as a stock setup, and not get too hot. > > Geoff > Monterey CA > > 
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