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-   -   1965 tripower idles faster after warmed up (https://forums.maxperformanceinc.com/forums/showthread.php?t=818101)

dlloyd 05-16-2018 11:54 PM

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?

dhcarguy 05-17-2018 01:54 AM

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

My442 05-17-2018 07:07 AM

Check for vacuum leaks.

Dick Boneske 05-17-2018 10:58 AM

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.

gtoguys 05-17-2018 04:43 PM

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

dlloyd 05-17-2018 07:51 PM

Quote:

Originally Posted by Dick Boneske (Post 5882816)
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.

Dick Boneske 05-18-2018 12:17 PM

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.

dlloyd 05-18-2018 06:19 PM

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

dlloyd 06-02-2018 06:02 PM

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.

Dick Boneske 06-02-2018 10:14 PM

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.

Geoff 06-03-2018 03:41 AM

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

Dick Boneske 06-03-2018 11:25 AM

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

dlloyd 06-04-2018 08:35 PM

Quote:

Originally Posted by Dick Boneske (Post 5889675)
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?

Dick Boneske 06-04-2018 08:53 PM

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

dlloyd 06-04-2018 09:59 PM

OK, I give this a try.

dlloyd 06-24-2018 01:28 PM

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.

Tripower67 01-08-2022 09:13 PM

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

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

Dick Boneske 01-08-2022 09:50 PM

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.

dlloyd 01-09-2022 11:18 AM

Quote:

Originally Posted by Tripower67 (Post 6309145)
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.

dlloyd 01-09-2022 11:22 AM

Quote:

Originally Posted by dlloyd (Post 6309243)
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


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