hard starting when hot

Discussion in '1947-1954' started by 51 HHR, Sep 14, 2008.

  1. 51 HHR

    51 HHR Member

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    Im still having trouble getting the truck to start when it is hot.
    I replaced the coil and the points and reset the timing. Timing wasa bit ofa bother as it seems it would change as though I was not tightening the dizzy enough, Im not sure the clap holding it is really up to the job anymore maybe, but I cranked down on it and then took her fora drive fora about half an hour plus and then parked her without shutting her off and rechecked the timing and it was (as Brit may say) "spot on" rechecked the idle speed and it to was at 600 rpm as i had set it. Then silly me i shut it off and tried to restart without touching anything but the starter button, it jsut cranked and cranked. That was last night so then this morning i went out and she started right up without choking or steping on the throttle barely, I had to give her some go juice seconds after she fired but after doing that anda 10 second warm up she ran fine and idled at the same 600rpm i set her at the night before. I did not recheck timing as my light is 12 volt and the truck is 6 volt and i have to bring m silverado over to get a 12 volt source yadda yadda.

    So this all leads me to beleive and I am not certain but i believe that my carb is at fault i have seen a bit of fuel on the carb at the parting seam which made me reset the float level which reduced the amount of fuel coming from there but not stopping it completely I didnt want to go to far but I ama bit suspect that it may be letting to much fuel into the bowl still?
    It is a Rochester carb and I looked in the Shop Manual I have here but it does nto refer to the rochester by name only the G.M. Model B and gives a discription for settign the float level but I do not know if I can use those dimentions for setting it?

    Also teh Manifold heat valve is doing something I am not sure it should be doing Yes it is free moves quite smoothly maybe to smoothly as when it is cold and at idle the flat portion of the valve is parallel to the the ground and even when it is warm i have nto seen it move from there yes the spring is still hooked up to it but I am not sure it the tension is correct on it (book says 1/2 turn of the spring) I have not changed it. but here is what it is doing at Idle it sits there nice and prett but if i rev it it moves all on its own or with the change of pressure in the exhaust. The book also says that this will cause issues as the fuel/air mix will expand to quickly in the intake. Without taking the manifold apart I am not sure which osition the valve is in open(cold) or closed(hot)? I am thinking it is in the open position and staying there any Ideas about what temp this is closed at? I can check with a thermometer to confirm later this week.
    Bill
     
  2. vwnate1

    vwnate1 Member

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    Hi Bill ;

    Almost certainly you need to perform a hot valve adjust as they close up a bit when the engine is hot so there's not quite enough compression for reliable hot starting .

    Disconnect the heat risor spring and play with the weight ~ if you lift it , it should flop back down 1/2 turn when you let go of it ~ if not , use penetrant and graphite until it turns nice and easy (DO NOT FORCE IT ! it'll break) , then attach the coiled spring in such a way that it lifts the weight when the engine is cold but as it heats up , the (Bi-Metallic) spring loses it's tension and the weight drops and the flapper opens ~ the fact that revving the engine forces the valve to move now indicates the spring is on backwards and is causing the engine to heat soak and maybe even vapor lock .

    Yes , the ' Series B ' carby is the (in)famous Rochester , use the specs in the book to adjust it , after you've :

    A. adjusted the valves (again) when the engine is blistering hot

    B. fixed the heat risor and it's coiled spring .

    If you look in my older posts , I wrote a detailed one on how to use a vacuum gauge to set the carby mixture *perfectly* .

    Remember : no skipping the steps ! I know you've allready adjusted the valves or you think because they're not clattering they're O.K., but they're NOT , always begin any tune up issue with a fresh , HOT ENGINE valve adjust .
     
  3. 51 HHR

    51 HHR Member

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    Thanks Nate

    I will do later this week I need to get a rocker cover gasket to replace the one that is leaking now so it will end up being two birds one stone with setting the valves.
    Bill
     
  4. vwnate1

    vwnate1 Member

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    Good deal ! .

    I assume you allready have # 1 gauge battery cables and the ground cable is attached directly to the tranny or engine , NOT the frame....

    (yes , it makes a HUGE differance)
     
  5. 51 HHR

    51 HHR Member

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    #1 cable

    yes #1 Cable A+ goes directly to starter Ill have to check the Ground to be sure but Ill work on it this weekend
    Bill
     
  6. MISurfer

    MISurfer Member

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    Had the same problem with my panel for the longest time. Tried most everything mentioned here until we got another carb off a donor car and patched together a working one. Try this: Starts fine when cold but won't even after running 3 to 5 minutes, pull the choke about 1/3 of the way out, and hold the gas down slightly. Seems mine restarts almost all the time that way. Occasionally it gets touchy and won't restart unless it sits for 20 minutes. Follow Nate's directions and hope it works out. I dread stalling in traffic! Brian
     
  7. 51 HHR

    51 HHR Member

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    Valves adjusted

    Nate I adjusted the valvs as per the chevy book .015 on the exhaust and
    .008 on the intakes sounds like a sewing machine now valves were set way to tight it seems. Also confrimed operation of the heat riser it is working as it is supposed to and moves freely. My Tach broke so i could not reset the idle speed so I did it by ear on the high side.
    It now starts when hot and good thing to because it decided to stall at every single traffic light i came to as though it was starving for fuel. I did pull the screen on the carbby and it did have a bunch of rust and other particles in it cleaned it out before driving it home.

    Also the grund goes to the frame and is not a cable but a p braided flatwire about two inches across and ten inches long then similar from the frame to the tranny. I cleaned where they attached to the frame witha bead blaster and re attached and the engine turns over much faster maybe 30% faster.
    I didnt have access today to new cables so Ill pick them up later and install, as the positive is only #4 wire and #1 would handle much more current, I will olso run the ground to the same attach point on the tranny as the ground is now.

    I wanted to recheck ingition timing but i could not since my dwell tachometer crapped out on me so Ill run out and pick up a new one so i can reset the idle and dwell
    this stalling problem i think is fuel related no quite sure how yet Id push the clutch in and coast and pump teh go pedal but it would just "choke" is only way i can describe it like "ahhhhhh " but then it would start right up and and idle fine then when i went to go through the light just as i was about to shift it buck like a MF. some fast working the clutch and throttle would kep it running and id be on my way.
    But teh big thing is it now starts when hot i tink i can go to the milk store and restart it afterward and get back home
    thanks for your help
    Bill
     
  8. vwnate1

    vwnate1 Member

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    You're Almost There !

    Good deal Bill ;

    Often the ground strap can be positioned to reach from the nagative battery post to the tranny , do that as ground straps are fine for passing current .

    That joint between frame and ground starap really hits it hard in hot or below 40° starting .

    Expect to re-adjust the valves again in 100 ~ 500 miles , no more as they WILL close up again .

    You don't need a Dwell/Tach to set the timing , just idle it down as low as you can and set the timing to Ball on Pointer , re-set the idle as necessary and check & adjust timing again , you're good to go .

    If you have a timing light with advance dial , set the fully advanced timing to 32° @ 3,000 RPM's or so and finish with a Throttle Ping Test , adjust a tiny bit if needed , you'll love the extra power and easy starting .

    Brian ~ get some aerosol brake cleaner or starting fluid , be SURE to get the kind you can stick a little plastic snorkel into the nozzle , warm up your engine fully then spray around the intake manifold to head joints while it's idling , be sure to burn your hands by spraying the joints from underneath too as that's where my leaks were , underneath , not on top . fixing those intake leaks , stopped all my hot idle and stalling issues , increased my power and fuel economy etc. , etc. ~ give it a try , you should need NO CHOKE on any hot start ! .

    Using a vacuum gauge or two gas exhaust analyzer to set the idle mixture , is wise , I know most here won't have an exhaust gas analyzer so find some old cheap vacuum gauge and connect it to the vacuum port on the intakle manifold , adjust the idle mixture delicately to the highest steady vacuum reading you can , might be 15" (I hope not !) might be 21" if you're lucky and your engine is tip-top .

    Remember : " Caburator " is a French word that means " LEAVE IT ALONE ! " :rolleyes:

    It's the very LAST thing you touch during tune up and no , you do NOT touch it when the engine begins spitting back out of it ! .
     
  9. brit 50

    brit 50 Member

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    Nate

    Lets just make things a lot easier, why dont we all jus drive round to yours one sunday Nate, an we will fire up the bbq an put the beers on ice while you tune up our trucks.:cool:
     
  10. GrandpaGlenn0

    GrandpaGlenn0 Member

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    Tune up

    Neil, we want to see you drive yours to Nate's!
     
  11. GrandpaGlenn0

    GrandpaGlenn0 Member

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    Great idea-- Neil, we all want to see you drive to Nate's!
     
  12. vwnate1

    vwnate1 Member

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    AD Across The Pond

    Neil ;

    DON'T DO IT !! the Cuban guy tried it twice and the damned Coast Gaurd machine gunned him.... :eek:

    Sank a perfectly good , well maintained '51 1.5 Ton Chevy AD...... :(

    I guess Tune Up is also fast becoming a lost art , that's too bad .

    I'm still in 'Vegas , I stopped to fill up my old Mercedes Diesl Coupe and a guy spotted me with the Bonnet & Boot open , came zooming over in his old Mercedes Diesel and picked my brains about Diesel Tune-Up for 35 minutes..... :rolleyes:

    Too bad my life's calling wasn't anything that would make me some money :p
     
  13. MISurfer

    MISurfer Member

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    Nate, thanks for the tip on the hot start. I'll try that this weekend. Have you ever thought about writing a book? "Everything you wanted to know about an AD Chevy but didn't know who to ask". I am somewhat serious here. If the information that you guys have shared on this forum was in a book form, it would be the best selling shop manual ever! There, you can make money at this Nate! I sure appreciate all the help here. I'll probably post more this winter when I stick this other 235 in and bring my panel up to 12 volt. Brian
     
  14. 51 HHR

    51 HHR Member

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    12volt

    Brian are you planning on replacing your wiring when you go to 12 volts or are you just going to convert teh genny and lights and regulator and install a resistor on the fuel gauge? Because if you are planning to change the wiring Id like to know whos harness you are going to use and why?
    Bill
     
  15. vwnate1

    vwnate1 Member

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    Wiring Upgrades

    The stock 6 volt harness is WAY overkill for any 12 volt conversion , you never , ever need to replace 6 volt wires except to correct physical damage as 12 volt systems use 1/2 the amperes 6 volt systems do , this is why 6 volt wiring harnesses are made with heavier gauge wires .

    My '49 3100 has the Taiwanese cheapo $99.00 basic stock 6 volt harness , installed (poorly) by the DPO's ' mechanic ' , early AD's have a multiple fuse fusebox thatis fine for most applications , even Hot Rods .

    A book huh ? . really , I don't give any information you cannot glean from shop and owner's manuals , it's all basic how to stuff I think .

    Keep posting and everyone here will continue helping you out , there are NO stupid questions . (some really interesting answers though :rolleyes: )
     
  16. 51 HHR

    51 HHR Member

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    Wiring

    Nate teh wiring in my truck is pretty ratty and kind of hacked up by only God knows who by this point that is the only reason I am thinking of changing it that and there are no Fuses that i know of or see with the exception of the horn
    Bill
     
  17. vwnate1

    vwnate1 Member

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    Wiring Harness Upgrades

    If it's the Kandy Red Panel Truck in your Avatar , you might want to consider lifting the entire harness and fusebox / relay panel out of a 70's / 80's vintage sedan or station wagon , this way you'll not only get lots of fuse protection but also some relays to power the various circuits , like the headlights as this will brighten them up a goodly bit and make the original headlight switch last longer , easier to add hazzard flashers etc. , etc.

    You'd then hang the new fusebox on the inside of the firewall where it's out of sight and well protected from the enviroment .

    Just a thunk , me , I like / trust / recommend the multiple fusebox of the '47~ '49's and the $99.00 Taiwanese basic plastic harness . :cool:
     
  18. 51 HHR

    51 HHR Member

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    research

    IM really not sure which direction I want to go in so Ill be doing research fora bit yet the last decent pre owned vehicle yard in the area just burned down this past week so locally there is no place to get used parts. I was thinking ofa prewired kit from one of the suppliers with modern day fuses and all. I do aircraft wiring for avionics as my career so running wires is not a big deal to me i had even thought about using some of the breakers and stuff i have removed and making a breaker panel up and wiring it for whatever i need but it would most definately not be stock
    I wish i hada photo of some of the wiring i have done on this computer I would post it maybe some before and after Instrument panel work that i have also done. Maybe this weeked
    Bill
     
  19. vwnate1

    vwnate1 Member

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    Bill

    Having worked with Rotary aircraft harnesses (L.A.P.D. Air Support) I heartily endorse you making up your own harness ~ just remember: use the _lowest_ value circuit breaker you can , like 10 A. maximim on most circuits and always have split circuits for the taillights , wire the passenger side taillight to the dash illumination so you'll instantly know if ever there's a problem (used to be industry standard) .
     
  20. MISurfer

    MISurfer Member

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    Bill, Sorry I didn't respond to your post about wiring in my panel. I forgot to check back to this thread last time I posted. I bought a Painless kit when I first bought the truck (two years ago). At the time, a lot of guys recommended the Painless as the easiest to work with. That may or may not be true because you can buy less expensive for sure. But it is ready to go and my extra 1957 235 goes to the shop to get rebuilt in about a month if my finances look ok. While the motor is getting done, I plan to do the wiring. My present wiring is original cloth and is really beat. I don't plan on going for perfection so no repro cloth wiring going back in. Next year I would like to get the Patrick's ring and pinion for a faster highway ride. Brian
     

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