#1  
Old 05-16-2018, 11:54 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default 1965 tripower idles faster after warmed up

I have a butler built 65 421 and restored tripower by Mike Wasson.
My question is it idles around 700 RPM when I first crank it. After it warms up it idles at a 1000 RPM. Is this normal? If it is normal the why does the motor try to keep running when I shut it off?

  #2  
Old 05-17-2018, 01:54 AM
dhcarguy's Avatar
dhcarguy dhcarguy is offline
Ultimate Warrior
 
Join Date: Oct 2003
Location: pa., usa.
Posts: 1,364
Default

Doesn't sound like your choke is working properly. Just one reason. The first thing I would check

  #3  
Old 05-17-2018, 07:07 AM
My442 My442 is offline
Chief Ponti-yacker
 
Join Date: Oct 2009
Posts: 595
Default

Check for vacuum leaks.

  #4  
Old 05-17-2018, 10:58 AM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

If the choke is functioning properly, it should idle around 1700 rpm when first started (fast idle cam). When the engine is started and the choke pull-off sees engine vacuum, blipping the throttle should bring the idle down to about 900 rpm until the choke spring sees some engine heat from the choke heater tubes. Then, the idle should drop to whatever you have it set to with the idle stop screw. With a fairly mild cam on a 421, idle should be around 700 rpm.

It sounds like your choke may not be closing when the engine is cold, so idle mixture is a too lean. After the engine warms up, and can run on a leaner mixture than when cold, idle speed increases. I would expect this would also result in backfiring and poor throttle response when the engine is cold.

There may be a vacuum leak complicating the problem as well, but confirming whether you have an operational choke would be the first step in troubleshooting.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #5  
Old 05-17-2018, 04:43 PM
gtoguys gtoguys is offline
Senior Member
 
Join Date: Nov 2002
Location: Waunakee, Wisconsin
Posts: 228
Default

Run on is usually associated with low octane fuel for the engine or the idle is set to high.

  #6  
Old 05-17-2018, 07:51 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Quote:
Originally Posted by Dick Boneske View Post
If the choke is functioning properly, it should idle around 1700 rpm when first started (fast idle cam). When the engine is started and the choke pull-off sees engine vacuum, blipping the throttle should bring the idle down to about 900 rpm until the choke spring sees some engine heat from the choke heater tubes. Then, the idle should drop to whatever you have it set to with the idle stop screw. With a fairly mild cam on a 421, idle should be around 700 rpm.

It sounds like your choke may not be closing when the engine is cold, so idle mixture is a too lean. After the engine warms up, and can run on a leaner mixture than when cold, idle speed increases. I would expect this would also result in backfiring and poor throttle response when the engine is cold.

There may be a vacuum leak complicating the problem as well, but confirming whether you have an operational choke would be the first step in troubleshooting.
Dick, you really know your stuff!
You described exactly what is happening at start up.
I screwed up the choke setting by listening to a so called mechanic that told me I should set the choke wide open cold especially in the summer.
I am learning this stuff the hard way.
So tell me the proper way to set the choke.
While motor is cold do I adjust it fully closed?
Thanks so much for all you guys help!
I donít know what I would do if not for all of you guys answering my questions.

  #7  
Old 05-18-2018, 12:17 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

Adjust the choke dial so the choke closes when the engine is cold with the engine shut off. There should be gentle spring pressure holding the choke closed.

You need to open the throttle each time you make an adjustment or check the choke spring tension. The goal is for the choke to be fully closed at startup and wide open after a few minutes running time.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #8  
Old 05-18-2018, 06:19 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Great!
I will set it like you said and I will let you know the outcome.
Thanks!

  #9  
Old 06-02-2018, 06:02 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

I have the choke set correctly thanks to Dick.
This has solved most of my issues except the fast idle after warm up.
I am pretty sure that the hot idle compensator is the reason for that. Idle seems to be fine until I start hearing the whistle from the hot idle compensator.
I guess I need to pull the carb and plug the compensator.

  #10  
Old 06-02-2018, 10:14 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

I don't remember the idle speed going up when the hot idle compensator opens. But, that's the most likely cause of the increased idle rpm and the whistle.

Let me know how it works out.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #11  
Old 06-03-2018, 03:41 AM
Geoff Geoff is offline
Ultimate Warrior
 
Join Date: Jul 2005
Location: Australia
Posts: 2,437
Default

Your problem is likely a too rich idle mixture at operating temperature. The hot idle compensator adds air, mixture goes leaner...& rpm increases.

  #12  
Old 06-03-2018, 11:25 AM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

Geoff, that's a likely possibility---that may be fixed by simply turning in the idle screws on the center carb base.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #13  
Old 06-04-2018, 08:35 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Quote:
Originally Posted by Dick Boneske View Post
Geoff, that's a likely possibility---that may be fixed by simply turning in the idle screws on the center carb base.
Dick, How much would you turn the screws? 1/4 turn maybe?

  #14  
Old 06-04-2018, 08:53 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

You turn the idle screws for maximum vacuum, which will also be maximum rpm at idle. Do this when the engine is hot.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #15  
Old 06-04-2018, 09:59 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

OK, I give this a try.

  #16  
Old 06-24-2018, 01:28 PM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Update:
I adjusted the idle adjustment screws in by about 1/2 turn. It appears I have solved the fast idle at warm up. Time will tell. I will keep you guys posted.

  #17  
Old 01-08-2022, 09:13 PM
Tripower67 Tripower67 is offline
Junior Member
 
Join Date: Jan 2022
Location: Arizona
Posts: 4
Default

I'm having similar issues, hoping to revive an old thread.

About how many turns out did you end up with this all?

  #18  
Old 01-08-2022, 09:50 PM
Dick Boneske's Avatar
Dick Boneske Dick Boneske is offline
Ultimate Warrior
 
Join Date: Mar 2004
Location: Winneconne, Wisconsin
Posts: 5,246
Default

Have you looked to see that the fast idle cam is rotating clockwise as the engine warms? Iíve seen situations where the choke thermostatic spring is backwards, actually closing the choke, increasing idle speed.

Check that out before you do anything else.

__________________
BONESTOCK GOATS

'64 GTO Tripower Hardtop (Wife's Car)
'64 GTO Tripower Post Coupe (My Car)
'08 Grand Prix GXP LS4 V8 (Wife's Car)
'09 Pontiac G8 GT 6.0 V8
  #19  
Old 01-09-2022, 11:18 AM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Quote:
Originally Posted by Tripower67 View Post
I'm having similar issues, hoping to revive an old thread.

About how many turns out did you end up with this all?
My MSD distributor went out and I replaced it. I also removed front carb so I could get better access to idle screws and I adjusted the choke a little more to the left. After all that it run as it should. Not sure if all of it was contributing to the issue or not.
Ideas at about 700 RPM hot and cold after fast idle is complete. No rich smell out of exhaust like I was getting.

  #20  
Old 01-09-2022, 11:22 AM
dlloyd's Avatar
dlloyd dlloyd is offline
Senior Member
 
Join Date: Apr 2013
Location: Perry, Fl
Posts: 215
Default

Quote:
Originally Posted by dlloyd View Post
My MSD distributor went out and I replaced it. I also removed front carb so I could get better access to idle screws and I adjusted the choke a little more to the left. After all that it run as it should. Not sure if all of it was contributing to the issue or not.
Ideas at about 700 RPM hot and cold after fast idle is complete. No rich smell out of exhaust like I was getting.
I forgot to mention that I plugged the hot tile compensator with a 1/4Ē plug like the freeze plugs except 1/4Ē

Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -4. The time now is 03:00 PM.

 

About Us

The PY Online Forums is the largest online gathering of Pontiac enthusiasts anywhere in the world. Founded in 1991, it was also the first online forum for people to gather and talk about their Pontiacs. Since then, it has become the mecca of Pontiac technical data and knowledge that no other place can surpass.

 




Copyright © 2017