Register or Log In To remove these advertisements. |
|
|
|
Thread Tools | Display Modes |
10-03-2024, 07:03 PM | #26 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
|
10-03-2024, 07:10 PM | #27 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
|
10-04-2024, 06:08 PM | #28 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
I checked for leaks around the intake manifold by spraying starting fluid then checking the bolts. No leaks found and all bolts were tight.
I advanced the timing to 6⁰ and took for a ride. Idle seems better but still off a little. Takeoffs were good with no backfires. The truck is a 3 speed manual. Seems a little off when I'm cruising at 30mph and I'm in 3rd gear. No problem accelerating from that speed or any other cruising speed though. Runs beautiful on the freeway at 65mph. So I was always under the impression that advancing the timing was a bad thing. Evidently not as it seems a lot of people do it. Should I advance it even more? |
10-04-2024, 10:02 PM | #29 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,732
|
Re: Rough idle and takeoff 250 inline
Of course!
Jump right in the deep end of the pool. Go right to 12. What’s your idle vacuum? Last edited by geezer#99; 10-04-2024 at 10:12 PM. |
10-04-2024, 10:55 PM | #30 |
Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,504
|
Re: Rough idle and takeoff 250 inline
What Geezer said.
About Advanced Timing. When these trucks were new, American gasoline was the best in the world. The Tetra Ethyl Lead created a cushion for pistons and valves. Zinc in the oil helped the lifters slide on the cam lobes easy. And Timing was good at TDC. Since we're dealing with a totally different blend of automotive fuels today, with additives and ethanol, we have to compensate by advancing the timing.
__________________
Every 25 years I like to rebuild that 292, whether it needs it or not. |
10-04-2024, 11:03 PM | #31 |
Senior Member
Join Date: Mar 2019
Location: Herculaneum MO (20 minutes south of St. Louis
Posts: 648
|
Re: Rough idle and takeoff 250 inline
The only danger in advsncing the timing is going to far & causing detonation. As Geezer#99 said go to 12 & test drive it while listening for detonation on acceleration. If you experience no detonation then your good. Then enjoy the increase in power and trouble free driving.
__________________
67 C10 283 T5 swapped longbed fleetside = wife's daily driver 67 C20 292 (originally a 250)4speed longbed fleetside w/original wooden bed=my project truck 67 C10 283+.060 (so a 292 as well)T5 swapped longbed fleetside=my DD 72 C1500 Sierra Grande 350 TH350 longbed fleetside=wife's fair weather truck Can you tell we are fans of longbed fleetsides & 67s Chris |
10-05-2024, 12:12 AM | #32 |
Registered User
Join Date: Jul 2007
Location: Toppenish, WA
Posts: 15,710
|
Re: Rough idle and takeoff 250 inline
Ran great until you got home from a 400 mile road trip?
Think back, where did you buy gas on that road trip? I'm a picky bugger and I don't care if I have to pay more but only buy gas at newer high volume stations or at Costco stations and never at old former gas station mini marts or cute/quaint out of the way stations. My brother in law drove fuel truck for several years and Costco is the absolute pickiest about fuel delivery. They don't let drivers stick the tank because the stick on the truck might have contamination on it. Most high volume truck stop or similar stations move enough gas that they never get water or contaminates. Before you go nuts run the gas in the tank out and down as low as you feel safe with and go fill up at the local station that you normally fill up and see how it acts. I wouldn't put it past dirt or crud in the carb but at least think back to where you bought gas on the trip and when it started acting up.
__________________
Founding member of the too many projects, too little time and money club. My ongoing truck projects: 48 Chev 3100 that will run a 292 Six. 71 GMC 2500 that is getting a Cad 500 transplant. 77 C 30 dualie, 454, 4 speed with a 10 foot flatbed and hoist. It does the heavy work and hauls the projects around. |
10-06-2024, 08:09 PM | #33 | |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Quote:
I have also gone through the carb twice and put a new filter in. Carb has a nice steam of fuel when I pump the accelerator. |
|
10-06-2024, 08:48 PM | #34 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Engine is idling worse and is getting worse under load. I advanced running to 8⁰ from 6⁰ and then increased to 10⁰. No improvement. I took the belt off of the smog pump so it wouldn't run and nothing improved. The carb has a nice stream of gas shooting into the carb when I pump the accelerator. I'm thinking the old truck didn't like the long 400 mile trip on the highway. I had never driven it that far in the highway before.
I'm going to do a compression check next. Any other suggestions? I'm thinking it's just tied and needs rebuilt at this point. Only 56k miles on it. |
10-06-2024, 09:53 PM | #35 |
Who Changed This?
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,680
|
Re: Rough idle and takeoff 250 inline
C'mon people, there has to be someone local to him who can sort this out!
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
10-06-2024, 10:20 PM | #36 |
Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,504
|
Re: Rough idle and takeoff 250 inline
68gmcdude -- They sell little brass plugs that thread into your head to seal off any leakage from an inactive A.I.R. system. Also the steel tubing, pump, and bracket are dead weight now. It never did much to improve air quality. It just had the _appearance of doing something positive_ about air pollution. They were political, not engineering, ''improvements.''
I appreciate your desire to keep the truck original. At only 56,000 your rings should still be tight. L6s are bombproof. I ran my second 292 L6 to 250,000 -- by then I was blowing big blue smoke rings of Valvoline 50 weight. Do the compression check, and get back to us. Good luck.
__________________
Every 25 years I like to rebuild that 292, whether it needs it or not. Last edited by '68OrangeSunshine; 10-06-2024 at 11:29 PM. |
10-06-2024, 10:30 PM | #37 | |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Quote:
Last edited by 68gmcdude; 10-06-2024 at 10:45 PM. |
|
10-06-2024, 11:26 PM | #38 |
Who Changed This?
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,680
|
Re: Rough idle and takeoff 250 inline
Air pollution arguments notwithstanding, we'll need to see a picture of your engine to determine the type of plug you need after the remove the AIR injection manifold. The threads are straight pipe with a shape of double flare 5/16" b-nut like a brake line fitting. I'll go on record right here with stating that the AIR system on any vehicle produced with it did not cause rough idle or take off. I'd like to hear credible stories of people who had this problem. Millions of vehicles were produced across ALL vehicle manufacturer's products where no complaints were lodged. I worked on those vehicles back in the day as a certified mechanic, and this was not an established issue, ever.
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
10-06-2024, 11:29 PM | #39 |
Registered User
Join Date: Aug 2009
Location: Bowser
Posts: 13,732
|
Re: Rough idle and takeoff 250 inline
Redo the lifter adjustment.
Only do 1/4 turn from zero lash. |
10-06-2024, 11:49 PM | #40 | |
Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,504
|
Re: Rough idle and takeoff 250 inline
Quote:
I'll look around. Roughly about 3/8'' IRC.
__________________
Every 25 years I like to rebuild that 292, whether it needs it or not. |
|
10-07-2024, 07:58 AM | #41 | |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Quote:
|
|
10-07-2024, 07:59 AM | #42 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
|
10-07-2024, 10:24 AM | #43 |
Active Member
Join Date: Apr 2021
Location: Santa Cruz, NM
Posts: 115
|
Re: Rough idle and takeoff 250 inline
You said you were missing the spring behind the fuel filter, correct? That would mean the gasketed side of the filter wasn't sealing to the surface of the inlet nut. How long was it like that for? I think you got some debris passed the fuel filter, and into the carburetor. ...something into the idle circuit or primary circuit.
|
10-07-2024, 10:39 AM | #44 | |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Quote:
|
|
10-07-2024, 12:48 PM | #45 |
Registered User
Join Date: Dec 2005
Location: Kalifornia
Posts: 354
|
Re: Rough idle and takeoff 250 inline
When you changed the condenser and points did you use a reputable brand?
|
10-07-2024, 01:06 PM | #46 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
|
10-07-2024, 08:32 PM | #47 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
Ok. I discovered something tonight. I starting pulling things off to pull the valve cover and when I pulled the air cleaner pipe out of the valve cover, the rubber grommet came off with it, and it's pretty torn up. Is this the cause of my issue?
|
10-07-2024, 10:16 PM | #48 |
Who Changed This?
Join Date: Jan 2013
Location: Simi Valley, CA
Posts: 10,680
|
Re: Rough idle and takeoff 250 inline
Nope. Worst case, you'd see oil leaking. No oil on the valve cover below that means that your PCV system is working, and you don't have a lot of blow-by.
__________________
~Steven '70 Chevy 3/4T Longhorn CST 402/400/3.56 Custom Camper Simi Valley, CA |
10-07-2024, 10:19 PM | #49 |
Registered User
Join Date: Jun 2017
Location: Painesville, OH
Posts: 181
|
Re: Rough idle and takeoff 250 inline
|
10-07-2024, 11:12 PM | #50 | |
Senior Member
Join Date: Feb 2002
Location: Tucson, AZ USA
Posts: 7,504
|
Re: Rough idle and takeoff 250 inline
Quote:
Cornet....3/8 - Inverted Flange Plugs...p/n: 106-6....$1.60 [each] x 6 =$9.60 Prices may vary nationally. Other manufacturers may offer similar products with different prices and quality.
__________________
Every 25 years I like to rebuild that 292, whether it needs it or not. |
|
Bookmarks |
Thread Tools | |
Display Modes | |
|
|