| this is interesting , but many theories make no sense . I have a 60 buick 401 that has always done this . Hard start especially after sitting , carb was on and off several times . I thought a crack or internal leak , as even after a week it would take a very long crank , distressing to you if far from home . Carb was apparently empty . But you are not sure flooded or empty ? pulling air cleaner is often inconclusive as some gas has come up from first crank . Been there, add in ? closed choke etc First , even if fuel “ boiled in the bowls” which may happen just after shutdown , ( called “ hot soak” ) especially if you have typical rusted shut exhaust heat valve , — the boiling can’t be so aggressive as to raise bowl gas level enough to run into engine . Remember all paths to venturi involve air vents in their path ( those open brass tubes) and vacuum to lift the fuel up . That vacuum is not there sitting . Gas is below any path to venturi . I think modern gas has such a high vapor pressure it just rapidly evaporates, a matter of a day (?) leaving a dry carb . But within an hour choked a rich start would happen . If fuel pump is perhaps lower in flow than optimal takes time to refill maybe all this is normal , with 2023 fuel —what I think now ( if exhaust heat is ok) — just shut that heat off permanently unless you live in alaska . It goes back to 20’s and 30’s when fuel could be like kerosene . I am rebuilding a packard with stock 37 hot spot intake design like a slant six . I separated the manifolds and machined 1/4” off the exhaust and closed top hole with a bolted steel plate , threw away huge heat riser valve . I expect more hp and no problems with a cooler intake . See also Edelbrock air gap manifolds . They simply outperform heated ones . Right idea . Cool intake flow . Related , “ vapor lock” as a term is so misunderstood it is unreal . First , the line from pump to carb is under 3 psi pressure , if inlet float valve in carb opens any gas vapor air anything in that line is going to run right through pushed by pump and out that open end . When one sees THIS line insulated etc , it shows a lack of understanding . But , if suction line near fuel pump or pump itself gets warm , the suction impact will significantly lower boing point a lot and then you have vapor which the pump cannot move very well , flow stops . This is why electric pumps help real vapor lock by pressurizing what was the warm suction line . But don’t run it through the mechanical pump as a diaphragm rupture means a big fire 🔥 . This subject could go on , but i have fought random fuel flow stopping in a 50 stude with a 354 hemi for a long time . Finally got into it this week — electric Carter pump , changed it , large 100 micron SS alcohol dragster type stainless mesh filter stead of pump clean as can be no restriction still erratic flow . All lines good no mechanical pump . After gas tank in and out 2 nd time , we found the line inside the tank (!) was partially full of that same tan/ white residue one finds sometimes in our carbs . It can form a kind of mud deposit . I think ethanol is the culprit when sitting . Some chemical thing goes on with steel or galvanized steel yielding that powder ; also why AFB accell pump check valve sticks . I am going to try suggestion of marvel oil , i admit to cynicism but why not ? Nothing to lose . So insulate suction line near fuel pump , packard had a large thin steel wing between fuel pump mount and block sort of a hot air shield maybe 6 “ projection and heat fin . Jesse Vincent ( Packard Engine designer ) was a genius , we might copy that . Also stude V8 has fuel pump on top of engine with resulting long suction pipe in hot place . Guess what brand vapor locks all the time ? thoughts welcome John Sent from my iPhone On Jun 15, 2023, at 8:37 AM, dplotkin <dplotkin@xxxxxxxxxxxxxxxxxxx> wrote:
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