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Chevy C60

Started by bannerd, September 27, 2021, 08:03:03 AM

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bannerd

Hey all, I have a 1979 Chevy C60 with a holley on a 366.. it runs great but some days it just doesn't want to start.  It literally dumps 2 liters of gas down the exhaust and yup.. massive explosions when it does run.  What would cause this?  I've worked on diesels all my life and new to manual carbs, tempted just to buy a new one at napa for $199.

I've been through the carb with a carb kit but it never came with a flat.  the float does work, just not sure why it does it.

Open to options, would love to but a 6BT in the thing but not sure if the manual spicer tranny would hold up to the torque.

doc henderson

check spark and coil.  wires ect.  the hot rod guys will have a switch to turn off spark and coast in gear to draft fuel and air then turn it back on and boom.  not a great idea, but one possibility is intermittent spark failure with resumption.  could blow apart your exhaust or worse.  I am not a big engine guy, but others will chime in.
Timber king 2000, 277c track loader, PJ 32 foot gooseneck, 1976 F700 state dump truck, JD 850 tractor.  2007 Chevy 3500HD dually, home built log splitter 18 horse 28 gpm with 5 inch cylinder and 32 inch split range with conveyor powered by a 12 volt tarp motor

azmtnman

   Since it's intermittent, it's probably getting gunk in the neddle valve. I'm more familiar with the Quadrajets--not sure about the Holley--but the Quadrajets had a screen where the gas line connected to the carb. So, check your fuel filter. Old rubber gas lines can come apart after the fuel filters too. 
    I'd love to have a C-60 with a Cummins in it! I have an '88 R-30 with a 465 (not sure who manufactured that tranny) that has been in it for 27 years and held together without issue. It's not an ideal transmission for that motor (3rd and 4th are a little farther apart than I'd like) but it works, especially if you have a 2 speed rear axle.
   Just my $0.02! 
1983 LT 30, 1990 Kubota L3750DT, 2006 Polaris 500 EFI, '03 Dodge D2500 Cummins powered 4X4 long-bed crew cab, 1961 Ford backhoe, Stihl MS250, MS311 and MS661--I cut trees for my boss who was a Jewish carpenter!

mike_belben

2 liters of fuel just from cranking is a major amount of fuel.. a mechanical pump would take a very long time in starter years to fill a two litter bottle at cranking speed, unless someone has grafted on an electric.


either way that much fuel should be trying to start the entire time if spark is good.  to just crank and crank and crank then boom.. after being severely flooded tells me it has no spark while its filling and cranking.  get a timing light, tape the trigger down and stick it under the windshield wiper so you can see what the ignition is doing.  dont catch the wires in your fan.

intermittent ignition can be a lot of things, if its a breaker point distributor pull the cab and rotor and make sure the rotor shaft bushings arent shot.  that will drift the point gap and never last long.  if its a HEI GM i am not very fluent.  


how does the truck run when it is running?  

regarding swaps its nice to dream but you will probably be throwing good money after bad. the C60 is going pretty well extinct and an old OBS 450/550 "Fsuperduty" cab chassis would be a lot easier to keep together for less, and will do the same job IMO.  uhaul retired a mess of them if you can tolerate 2wd.  they had dana 80 rears with 10 lug, and 19.5 rubber will make it a pretty capable truck.  im sure theres a 6BT adapter kit for every granny gear NP or SM tranny by now and probably an engine mount kit for the 450/550 as well so just bolt it in.

Praise The Lord

bannerd

It has plenty of spark, I just put new coils on it but I did not check the distributor.  I can get about an inch to two inches of spark away from the block on all cylinders.  The explosion is because gas fills my muffler, it literally blew one apart.. wasn't a good day.  I drilled the other one and gas just pours out into a soda bottle... oddly enough I can tell it's doing it because it make s "FLUFF FLUFF sounds".  haha

I really think this is a carb issue but man.. when the 366 is running it runs strong.  Pulled about 20,000lbs up a hill with the pedal right to the medal, it did it.. no problems.  GM capability has it rated for 17000 so I'm not complaining.  The truck came from a town that only put 30,000 miles on it so it's in great shape.  They couldn't get the problem figured out, when I bought the thing.. my brother told me to tap on the carb and I drove the thing home.  I honestly never had issues with it.  (Tappy trick doesn't work now, :D)

I did check the fuel tank and there is a metal screen in there, besides that I don't see any pre-filters or in-lines.  Fuel delivery is from a lift pump which appears to ride a cam or maybe the crank?  It's pretty low on the block.

Also, when it does run it has a slight skip to it..I'm not sure why it does that.  I'm going to take the carb off and clean it, it's been a really good truck so I can't just junk it.  I just had the hydraulic dump cylinder rebuilt as well as the brakes.  I have a 6BT on the floor so it's not out of reach, but honestly this 366 isn't that bad of an engine.  Last year hauling sand I was getting 12mpg on the flats and about 8mpg up hills.  Not great but not impossible either.

bannerd

It was running this morning but only on choke, had to go to work but going to mess with it tonight.

sawguy21

It sounds like the float is hanging up or the inlet needle is not seating properly. Can you take the carb to an experienced mechanic, not a local shade tree? It needs to be set up properly to work.
old age and treachery will always overcome youth and enthusiasm

mike_belben

The issue is conflicting.  Running on choke is a sympton of lean fueling.  

Mufflers full of gas would occur from a leaking float or float valve which could be intermittent i guess but either way thats also a rich condition similar to choke on so it should wanna run.  


I would still try the timing light to see what spark is doing when it runs.  That skip could be intermittent ignition too, happens all the time.

Edelbrock performer is a pretty simple carb especially compared to Qjet, and its idle circuits are adjustable with just a screwdriver fron the exterior.  Its been 20some years but i think most 4150 type 4 barrel holleys had to come apart for jet change.  I could be wrong. 
Praise The Lord

grabber green

If your  holley carb is stock to your truck and it backfired It blew your power valve inside the carb . . They make a little check valve to retrofit your older carb base plate  with and you can also buy a blow proof power valve. I went through this in the early 90s with my 69 c60 ,my 68 torino and my 66 f100 plus alot of other poeples stuff. Your truck only running  with the choke on sounds like a different issue.

bannerd

I have it running, it was popping like crazy though but after going down the road it seemed fine. Just seems like it's skipping to me.  There is also a hesitation now when I barely step on it.  It chokes then starts to go, almost like fuel loss or something. I have a master mechanic coming over Saturday, this is beyond me.

There is also a bunch of electronics on this carb, vacuums too which I'm not sure what they do. Looks like this;

Ebay link removed, refer to posting rules.

See what he thinks.

snowstorm

a 366 or 427 with a holley carb. had a governor set at 4000 rpm. i knew a guy that was really good with those carbs. he has been gone for years. i remember him saying they do wear out if a kit dose not fix it if it was done right. put a new one on.you may have to retard the timing compared to the stock setting cause the gas isnt what it was in 79. if it has points set the dwell them timing. new plugs wires cap and rotor 

Cub

Was always told the only good Holley is the one on the other guys truck. Always thought they were great. But constantly fiddling with them. Air temp changes 10 degrees get the screw driver out to adjust. Humidity changes, adjust.  Then I bought an edelbrock. Set it once n ran it for 10 years with no problems. Same with the q-jet on my 70 chev pickup. Get rid of the Holley n put an edelbrock on. My .02

reride82

Quote from: bannerd on September 27, 2021, 08:33:25 PM
I have it running, it was popping like crazy though but after going down the road it seemed fine. Just seems like it's skipping to me.  There is also a hesitation now when I barely step on it.  It chokes then starts to go, almost like fuel loss or something. I have a master mechanic coming over Saturday, this is beyond me.

There is also a bunch of electronics on this carb, vacuums too which I'm not sure what they do. Looks like this;

Ebay link removed, refer to posting rules.

See what he thinks.
Holley's are great if you want to tinker. I'd switch to an Edelbrock or Carter. It sounds like it started with an small/under-sized accelerator pump within the Holley, but a backfire has ruptured said accelerator pump and it leaks fuel into the intake. The accelerator pump adds more fuel under near wide open throttle conditions and now you have a hesitation. I love a Holley on my hot rods, but a truck doesn't need it. How does the engine oil look/smell?
Levi
'Do it once, do it right'

'First we shape our buildings, then our buildings shape us'
Living life on the Continental Divide in Montana

sealark37

My 64 Ford C-600 had the same problem with a 2-barrel on the Y-block 292.  After months of tinkering, I drained the tank, and filled with alcohol-free gas and two cans of Seafoam.  After a couple of days hauling, the problem disappeared. 

bannerd

Just want to let everyone know, he stopped by and there is two adjustment screws in the back of the carb.  The one on the driver side is so loose the spring wasn't putting tension on it and it was threading in/out on idling.  He had springs so we replaced those on both sides, a little bit beefer.  In the back was a brass screw he took off which a bunch of fuel came from that was adjusted so the fuel was slowly coming out (tip of a lead pencil that is sharp!).  I don't know, $50 later and this thing is so responsive.

There is a fuel filter in the tank but he put a clear one up near the carb that way I can make sure it's primed, common issue is fuel loss so I can tell if the lift pump is no good.  Should be good for awhile!  He said I would get a lot better mileage because it was running lean on one side and very rich on the other, perhaps why the muffler exploded.




mike_belben

glad to hear that! money well spent. 
Praise The Lord

barbender

Geez, the guy even charged you a period accurate mobile service charge😁
Too many irons in the fire

moodnacreek

I still have 2 old gas trucks, v8's and both have Edlebrock carbs. 366 in a Chevy '60' is a good cheap to fix truck. If I had that truck and needed it, it would get fixed at any cost.

johndozer

Didn't most GM products from that era come with Rochester carbs? If fuel lines are good, floats are good and set properly, needle valve and seats are good might be time to try another carb. Some spark plugs will test fine when removed but may not fire as strong or at all under compression but this would be more of a rough running than no starting issue. Possible mechanical damage to carb? Something cracked or distorted?

chet

Bannerd,  buy dat mechanic a beer, he's a keeper. ;)
I am a true TREE HUGGER, if I didnt I would fall out!  chet the RETIRED arborist

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