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Username Post: It's loading up        (Topic#358053)
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-15-19 06:08 AM - Post#2775555    

A stock 80 Chevy 350 with a newly rebuilt Q-jet originally for an 85-87 305/350. New fuel pump.
What does 'loading up' actually mean? I can guess but it seems there could be more than one cause?
Carb was installed by a Mechanic. He had to dink with it to get it right.

Another question - the carb doesn't kick teh transmission down when pressed into service anymore. Is it going to need a seperate/custom cable or something?

Thanks "loads"
Stan










It's all good. mostly




 
Mad Professor 
Contributor
Posts: 104

Reg: 12-30-08
09-15-19 06:53 AM - Post#2775557    
    In response to 4dr 57

Hi,

Chevy person here but know more about 4 spds.

Loading up is running rich. With a carb could be:
1) choke not opening, 2) float set too high, 3) needle/seat for float valve dirty damaged, 4) carb not matched to motor (jetting).

Choke issue could be a number of things depending on how it works.

My old SBC V8s I put a 4150 Holley on with mech chokes. Those you can check needle/float/float level in about 10 minutes with tools in your trunk.

Not sure how your "kickdown" works on newer Autos, old ones had mech link to throttle, simple but it worked.

I have a 1985/305 and I'm looking at building a simple 350 that does not have any bells and whistles to make working on troublesome. No sensors, single 4bb 4150 carb, vac advance set up for idle and partial throttle, single wire curved delco dist. Two vac lines, one for dist the other for PCV. Whoops one more it has power brakes, but I could retro that too.

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
89 S10 baja package







 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-15-19 08:02 AM - Post#2775560    
    In response to Mad Professor

Cool sounding project - hope it works out for you! 355? 383?

I agree with your reasoning. 3 or 4 would be the most logical at this point, especially the gunk in the fuel from the tanks gets past the filter. Some times it runs great with only a slight bog, other days it can die taking off from a light. with or w/o the A/C on ( higer idle.)

Oddly, I noticed the charge gauge and it relates to running poorly - or so it seems.








It's all good. mostly




 
gchemist 
Senior Chevytalk Moderator
Posts: 24929
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
09-17-19 04:36 AM - Post#2775687    
    In response to 4dr 57

4Dr 57,
Go here on how to adjust the detent cable: http://www.73-87.com/7387garage/drivetrain /detent....

To me loading up, means putting load on the engine. Like actually driving it, towing something, or hold the brake pedal while reving it up RPMs.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
Mad Professor 
Contributor
Posts: 104

Reg: 12-30-08
09-17-19 03:12 PM - Post#2775740    
    In response to 4dr 57

Water in fuel will make it run like a POS too.

A can of seafoam and a couple of drygas can't hurt.

62 Willys wagon
67 CJ5 Buick V6 w/OD
68 Camaro RS/SS , 69 LT1 350, M22
73 C10 292 6, M21 muncie/hurst, 3:73 posi
89 S10 baja package







 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-24-19 09:33 AM - Post#2776337    
    In response to gchemist


Thank You >gchemist< I appreciate it.
When the TH400 was first installed it adjusted like the 350 adjustment instructions, with no mention of a TH400 switch, so I am still in a quandary. NP, I will get it figured out.
Stan . . . rummages around for a BFH . . . .








It's all good. mostly




 
gchemist 
Senior Chevytalk Moderator
Posts: 24929
gchemist
Loc: Austin, TX 78748
Reg: 05-09-00
09-24-19 09:39 AM - Post#2776338    
    In response to 4dr 57

An out of adjustment switch or bad vacuum line are notorious for shifting problems. I'm actually looking for a TH400 switch. The installation for my truck is cut the A/C clutch at WOT or short speed bursts.

'83 Silverardo XST - ZZ4 powered
'95 Jimmy SLT (Bought @131,814)
'96 GMC Jimmy LS Ret. @236651 miles


 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-24-19 09:42 AM - Post#2776339    
    In response to Mad Professor

Thanx Mad Professor - Yes, that was suggested by my mechanic, in fact he was rather insistent about it. So I added the recommended amount of Sta-Bil 360 and a can of Heet foe a couple of tanks. No real improvement noticed, well maybe a little.

Messed with the adjustable vacuum advance canister on the distributor as well. Some improvement noted - more work needed in that area.
Stan

Something I have recently discovered that seems even more critical is the charging value! When the needle goes past 13 all is well. On 13 or below there is a bog and/or it runs like crap.

This leads me to my next question for Chevy Talk. . . . .

It's all good. mostly




 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
09-25-19 05:20 AM - Post#2776404    
    In response to 4dr 57

afaik "loading up" means fuel finds it's way to the crankcase - you smell it at the oil dipstick and also the carb is "wet" when you pull the aircleaner and look down...I once had this due to a leak of a poorly seating (stuck open) float needle, repairing the float/needle problem and then changing the oil is required in such case. how did you get the idea your engine is "loading up"?



 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-25-19 03:52 PM - Post#2776439    
    In response to BoniOni


hello BoniOni -

Two Mechanics said it was loading up - it can also cause a bog, hence the name carbburator nickname, Quadra-Bog. This causes puffs of black exhaust coming out and greasing up the tail pipe black at tip in, idling, and during operation if it's bad enough. No gas in the oil here, but thanks for the suggestion.

Loading up is gas in the carb getting thru, probably into the manifold then into an open valve. Sometimes this will cause the engine to turn as though it had high compression or a low battery sound. It happens when the vehicle is run for a bit, then shut off for a short while, then restarted.

Stock GM manifolds get really hot and evaporate the gas out of the carb. This causes hard starting the nest morning, even if the check valve in the fuel pump is working.

Yes, the needle and seat can be problematic on an old vehicle with old fuel tanks. Small particulate matter gets past even a 5 micron filter and there it is, wadded up in the needle seat area.

Carburators area pain in the azz - I love fuel injection, but I'm sure clogged injectors are expensive to replace - even my old '97 LT1 needed a set and cost about 250-300 dollars. GM injectors out, new Ford or Chrysler injectors in - problem solved.

DO yall have unleaded gas there as well? Cheers!
Stan

It's all good. mostly




 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
09-26-19 04:55 AM - Post#2776482    
    In response to 4dr 57

Hi Stan,

we have unleaded gas as far as I can remember backwards, and the bad is we have 5% ethanol in the fuel as dictated by law - do you have this "ingredient" too? if worried about diluted fuel, there's a water separator (also filters out particles) in the size of an oil filter, that can be installed somewhere between fuel tank and fuel pump, I have such on one car. On diesel engines it's usually pre-installed from factory and also marine applications use such separator.

I cannot agree that carburetors are bad in general, I prefer them over all injection systems. I have all types of Rochesters: Mono-, Dual and Quadrajet and cannot complain about them.

What you describe about the puff and black smoke..well it can be ignition related as well, for instance when you have an occasional spark miss or the timing is (over-) advanced or retarded so the fuel is not properly burnt in time, it can also happen in a certain rpm range only, when the timing curve is not set properly, this is what you do with the adjustable vacuum advance at the dist - what type of distributor do you have?

On the carb side, if the mixture is far too rich a spark miss and rough running (including bogs)is a symptom but can be easily fixed with a different jetting or simple by turning the mixture screws in (depending on the application, Quadrajet is usually 2,5 to 4 turns from seated as a starting point).

yeah it's true that the fuel evaporates through the mainfold as soon as the engine is runing fine again and gets hot enough (can be seen as a white mist in the engine compartment in a severe case). I recommend you fire up and after a short run shut down and then immediately take off the aircleaner and see inside the carb / manifold area if there is fuel condensed.

tell me about your experiences and good luck,
Gerald




 
4dr 57 
Valued Contributor
Posts: 4621

Loc: Texas Hill Country
Reg: 11-10-04
09-29-19 10:01 AM - Post#2776700    
    In response to BoniOni

Hi Gerald, the fuel here has a 10% ethanol content in it. Yes, carburators are ok.
That's a great tip on the fuel filtering, Thanks!

I've read that the Q-Jet is fine for Hi Performance use with some modifications needed.
Holly just has too many gizmo's that can go wrong with it for me, but a lot of guys/racers swear by them, and rightly so. You can't buy a NEW Q-Jet here in the States, just "new rebuilt." The $200 versions are rough as a cob and actually need an experienced (getting rare) carburator man to get running. The $400 versions just have a few less problems I was told.

Do you happen to have the equipment, know how and time to tune a carb to the point that the fuel delivery source to the engine stays in the idle circuit up to 2900 rpm or so?
I know if I did I would probably love Carbs!

I did a cold compression test on the weak side (RS) of the engine yesterday and found the same two weak cylinders as always, within 10% of the the two better cylinders. #4 and #6 were the weak ones at 140 psi, down from 150 psi for #2, #8. #4 didn't jump right up until the 3rd go-around.
The plugs are 45TS, the distributor is stock except for the ACell in cap coil and the Taylor 8mm wires. The engine runs without a gigantic miss but may be a little ruff. It seems to be smooth at 750 rpm idle. My timing light wouldn't work n matter what I did. Drat! I remember setting it at 10* I need to put on that timing tape I bought too.
Would you suggest running the hotter 6 cylinder plug - 46TS?

I also need to work with the adjustable vacuum advance. But I think it needs to be run out on the road for 100 miles at least, at speed, as 50 miles a week is all local, low speed usage,for the last 10 years.
The last time I ran it like that (12 yrs. ago.) the oil consumption stopped. The blue smoke out the exhaust stopped altogether after the valve stem seal R&R.

I checked under the air cleaner lid yesterday for some mist and didn't see any. I will check it a time or two more just to be sure. I should also crawl up over the engine and move the accelerator pump a little and see what's happening, if anything. Thanks for the motivation.

If I keep the truck I will need to install an electric fuel pump (Walbro) in line with the 3 line fuel regulator available thru Summit to eliminate the long starting time. But a newer truck at my age would probably be better. I have a hot rod to work on and don't need another project even if it is only an occasional one.

Say, have you heard any news about an increase in the (new) standard sea level rise there? Florida has but that may just be a local phenomena in one particular area.
It's turning into Fall in most parts of the country. West of the Rocky Mountains its snowing already.
It's been a little dry here but is still agreeable with 70 degree nights, 90 degree days.
Ya'll should be coming into Spring about now shouldn't ya? If it's not it sure is missing a good chance

Stan



It's all good. mostly




 
BoniOni 
Member
Posts: 31

Loc: Austria
Reg: 12-04-05
09-30-19 06:55 AM - Post#2776755    
    In response to 4dr 57

Hi Stan,

ethanol is a problem since it is hygroscopic and (like brake fluid) draws moisture from the air. ethanol by itself makes rubber fuel lines brittle and some gaskets (accelerator pump e.g.) may get warped, this is only true for the black (rubber) gaskets, the "blue" gaskets withstand ethanol. Next is that the water content makes the carb corrode inside, especially the float bowl, futhermore ethanol burns hotter.

from what you write it doesn't seem you have a problem with the carb flooding or the engine loading up. Problems with the accelerator pump show up as a bog on heavy throttle. What is a "long starting time"? do you have a choke installed? I have only mechanical pumps and they do their job well.

for the ignition, 10 degs of initial advance for ported vacuum (or vacuum plugged for setup) is ok. I recommend an adjustable timing light, so you need no scale on the vibration damper, just the zero notch. I cannot say much about the spark plug differences but I would start gapping them at about 0.045" for the HEI.

the compression values seem not too bad for an engine that has some miles on, I also do a leak down test which shows more details about where compression is lost.

hope this helps & greetings,
Gerald





 
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