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Re: 63 305 V6 Bucking
Oldgmc1963 #1413725 Sun Jun 13 2021 02:13 PM
Joined: Apr 2005
Posts: 10,194
Grease Monkey, Moderator General Truck Talk & Greasy Spoon
bartamos, some of us have tried to ride a full 8 seconds! eeeek


Martin
'62 Chevy C-10 Stepside Shortbed (Restomod in progress)
'47 Chevy 3100 5 Window (long term project)
‘65 Chevy Biscayne 4dr 230 I-6 one owner (I’m #2) “Emily”
‘39 Dodge Businessmans Coupe “Clarence”



"I fought the law and the law won" now I are a retired one!
Support those brave men/women who stand the "Thin Blue Line"! Hug a cop!
USAF 1965-1969 Weather Observation Tech (I got paid to look at the clouds)

Re: 63 305 V6 Bucking
bartamos #1413736 Sun Jun 13 2021 04:18 PM
Joined: Jul 2000
Posts: 1,332
G
Insomniac
Originally Posted by bartamos
I will never ceased to be amazed at experienced Stovebolt folks firing off a bunch of ideas from just the word "bucking".

It's a guessing game. It's all we can do given the limited info we have. I'm curious to find out who gets it right. Join in! Everyone is welcome to play. Don't expect a prize, though.


Gord
----
1954 1/2 ton 235 4 speed
Re: 63 305 V6 Bucking
Oldgmc1963 #1413739 Sun Jun 13 2021 04:36 PM
Joined: Feb 2004
Posts: 23,180
H
'Bolter
Oh, come on, now! Isn't everybody supposed to get a "participation trophy" these days? Getting rewarded for actually accomplishing something is so "1950's"!
Jerry


The murder victim was drowned in a bathtub full of Rice Krispies and milk.
The coroner blamed the crime on a cereal killer!

Cringe and wail in fear, Eloi- - - - -we Morlocks are on the hunt!
Re: 63 305 V6 Bucking
Oldgmc1963 #1413746 Sun Jun 13 2021 05:52 PM
Joined: Mar 2020
Posts: 209
T
'Bolter
could it be the clutch binding when it heats up?

my bad clutch will make my truck "buck" when accelerating at low rpms.


62' GMC Fleetside 3/4 ton 235 4-speed.
Time makes fools of us all.
Re: 63 305 V6 Bucking
Oldgmc1963 #1413764 Sun Jun 13 2021 08:36 PM
Joined: May 2005
Posts: 8,431
B
Sir Searchalot
OK, I'll join in. Could it be that the town has added speed bumps and you didn't notice?

A mechanic, a plumber, an electrician, doctors, scientist, engineers try not to guess. At least until after many questions, definitions of words and tests. Jerry knows this. So far, some folks have asked for tests. Very few questions. Many guesses.

I, too, am guilty of breaking my own advice.


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
I used to think beer was bad for me, so I gave up thinking.
Sometimes no nonsense makes sense, in a sense.
You can't teach a new dog old tricks.
Honk if you're Amish


Re: 63 305 V6 Bucking
Oldgmc1963 #1413768 Sun Jun 13 2021 08:58 PM
Joined: May 2005
Posts: 8,431
B
Sir Searchalot
I truly hope this is not another "fad away" new guy. Hope he stays engaged and checks the post. Some just don't realize that Stovebolt has a massive amount of knowledge that is put forth within minutes. He has 8 same-day responses. Several second day.

1. Does bucking mean the truck is lurching or hesitating or bogging down during driving? Is it rapid or large intervals?
2. Does it mean the motor itself is jumping all around while truck is not moving?
3. Does it do it only while going thru gears using clutch and then settles?
4. If you get up to 30 mph and push clutch in, does it coast with no bucking?.....while motor is revved a little?
5. Do motor mounts look OK? That motor is pushing 900 lbs on two rubber blocks.
6. Was it running good and all of a sudden did this? Was some work done just before this? I realize you did work after.
7. Can you describe bucking....what, when, where, how long. Trying to determine if "bucking" is the motor missing.... or the truck (motor mounts, clutch, tires, brakes, ujoints, wheel bearings and all that stuff). That would really narrow down "bucking".
8. Could you find a place to safely coast with motor off, clutch in?
9. Any modifications like mustang front clip, air bags, lowered, lifted, big tires, wheels, messing with distributor.
10. Those motors run better at more advance than spec now-a-days. Like 8-10 BTDC sometimes. Spec is 5.
11. If you have removed spark plug wires, recheck that you have them clocked for Firing Order 1-6-5-4-3-2 pix NOT 1-5-3-6-2-4 pix
12. "When a pump goes, it goes". You can't use that theory to eliminate the pump.

Another issue OldGMC1963 is we don't know your mechanical/electrical automotive experience, equipment or ability to test. Sounds like you are no rookie from all the tune up effort you've done. Let us know your approximate experience level. Sounds like a neat truck. I had a 1960 GMC with 305E recently. Yours is first year for coil front suspension and last year for wrap-a-round windshield.


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
I used to think beer was bad for me, so I gave up thinking.
Sometimes no nonsense makes sense, in a sense.
You can't teach a new dog old tricks.
Honk if you're Amish


Re: 63 305 V6 Bucking
Oldgmc1963 #1413770 Sun Jun 13 2021 10:04 PM
Joined: Jan 2014
Posts: 1,637
J
'Bolter
Bartamos is doing this the right way.....asking clarifying questions.

As for myself, I’m just gonna throw some more poo at the wall and see what sticks.

I like the motor mount theory, but the fact that it starts acting up after 20 mins doesn’t jive with that.

A couple other ideas I haven’t seen mentioned:

* I know nothing about the WW carb or what kind of choke it has. Maybe some kind of choke weirdness?

* Some sort of vapor lock thing?

* Perhaps a vacuum leak at the manifold or carb base that develops only once the engine gets to temp and things move around a bit?

Re: 63 305 V6 Bucking
Oldgmc1963 #1413779 Sun Jun 13 2021 11:03 PM
Joined: May 2005
Posts: 8,431
B
Sir Searchalot
I agree that acting up after 20 minutes is a clue. Not too much of a clue. Can mean what others have said, venting, vapor lock, floating tank debris, loss of pump pressure/suction. The WWs I've had all have cable operated chokes. Maybe he will answer the questions in order for us. 50 guesses does not give someone a direction. No info does not give us a chance to use our experience.

The problem with the pump tests, is that 20 minutes. The truck is going to start with any of the pump tests. I have, and others have, run a truck with a hose stuck in a gas container on the passengers floorboard, hose thru the firewall. This way you can drive for 20 minutes to see if pump begins to fail or carb somehow fails. Idling for 20 minutes is not fool proof. Need a load. This is what Jerry already said. That would be a good easy test and give lots of info. It sounds dangerous but what the h e l l.

Anyway, this is all guessing, if it was debris, it would be at the bottom of tank near the pick up, after sitting. A person could say that is when it should "buck"/starve for gas. Not after sloshing....


Watch out for careful drivers!!!
I'm away on an ego trip. Will be back on Feb 30.
I'm not an Auto Mechanic, but I play one on TV.
I charge $0.02 for every opinion and I take Paypal.
Plan B is always better than plan A, by definition.
I used to think beer was bad for me, so I gave up thinking.
Sometimes no nonsense makes sense, in a sense.
You can't teach a new dog old tricks.
Honk if you're Amish


Re: 63 305 V6 Bucking
Oldgmc1963 #1413894 Mon Jun 14 2021 07:59 PM
Joined: Mar 2020
Posts: 209
T
'Bolter
this can easily be a trans or diff issue as well, though fuel supply is a great place to start. I second the can on the floor method for initial test.


62' GMC Fleetside 3/4 ton 235 4-speed.
Time makes fools of us all.
Re: 63 305 V6 Bucking
Oldgmc1963 #1413907 Mon Jun 14 2021 09:33 PM
Joined: Mar 2019
Posts: 1,319
G
'Bolter
A shot in da dark..... Ignition coil is heating up and failing?

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