throttle shaft play - is this considered excessive

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thegermanfan
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throttle shaft play - is this considered excessive

Post by thegermanfan »

I have removed the 4300 from the engine and I am not sure if this throttle shaft play can/should be considered excessive. Interestingy shaft play is identical on primary and secondary shafts. So it does not seem like oridinary wear. What do you think?
And no I will definitively not change the carb to an edelbrock or holley. Only option would be inserting new shaft bushings. But I don't know how tight these will be.
https://youtu.be/YfVH7TOCinc
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Re: throttle shaft play - is this considered excessive

Post by action »

Throttle shaft play up and down in the hole should be close to zero.
Most of the throttle shafts are/were coated. (Teflon I think)
If the coating wore off that can be an issue as well.
This type of wear causes throttle position issues AND a vacuum leak.

If the play is axially or sliding in and out, that is not much of an issue.

I think you posted a link. That link did not not work. Difficult to make a judgement without knowing how much play.
(Don't blame you for not going down the Holley/Edelbrock hole. I would not go there either)

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JimA
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Re: throttle shaft play - is this considered excessive

Post by JimA »

Link works for me with the things removed from front and back.

https://youtu.be/YfVH7TOCinc
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Re: throttle shaft play - is this considered excessive

Post by action »

Looks excessive.
Especially the first push in the 4 to 8 second range.

The confirming test would be a measurement with a micrometer.
The quick and EZ test would be installed on the engine with engine running. Shoot some carb spray at the shaft where it goes into the carb. How high does the RPM go up?

What was the reason for removing the carb?

Looks like the carb has been sitting after a lot of use. The coating has worn off of the underside of the throttle plate. And the screw head(s) are rusted on the underside of the carb.

Action
Phoenix - Yeah, it's hot, however it's a dry heat
2006 Lincoln Navigator Limited 5.4l 3V
1996 Lincoln Mark VIII 2DR Coupe Diamond Anniversary 4.6l DOHC, 4R70W, 3.07
1970 Continental Mark III Triple Black 460 4v, C6, 2.80 (Used for Woodward Dream Cruise or just generally stored in Michigan)
1966 Lincoln Continental 4DR Convertible 462 4v, C6, 3.00
1966 Mercury Park Lane 4DR Breezeway 410 4v, C6, 2.80
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thegermanfan
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Re: throttle shaft play - is this considered excessive

Post by thegermanfan »

Carb was once cleaned with an ultrasonic bath. Hence some of the original coating was lost.
The car sat for some years now and I am in the process of resurrecting it. The accelerator pump was not pumping anymore, therefore I removed the carb to check and repair. Pump diaphragm had shrunken.

The tip - using carburetor spray on the shafts while the engine is running - I had no luck with that in the past. During engine running the intake manifold is heated by the exhaust gas passage underneath the card. If I spray the throttle shafts, much of the spray evaporates and gets sucked into the intake - raising idle speed. If I do the procedure with airfilter on, I have trouble reaching the shafts with spray. If I spray in the general direction underneath the airfilter, I see no change in idle speed.
I will try to actually measure shaft play. What number would be still considered normal? It can't be zero.
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thegermanfan
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Re: throttle shaft play - is this considered excessive

Post by thegermanfan »

I measured shaft play: maximum 0,0065" (or 0,17mm). Is this above allowable limit :?:
Would one of these bushing kits with reamer https://www.ebay.com/itm/232854380098 improve the fitment? No tolerances are given on these kits made in China....
The reamer looks somewhat short to be able to be guide from the opposite side shaft bore. :?:
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Re: throttle shaft play - is this considered excessive

Post by action »

.17mm is .0067"
Or 7 thousandths of an inch

Likely in the realm of excessive. Not sure there is a published spec.
I would want to see 5 or less, and there has to be some to get the shaft to move freely.

Of the material in there the soft to hardness are
The coating on the shaft
The carb body
The throttle shaft

Assuming the reamer and replacement bushings are the correct size (and the listing states it is) that would be a way to go.
And I would measure the throttle shaft to make sure. And measure in the area where the shaft passes through the body of the carb. NOT in other areas.
If the coating is not present on the shaft in that area, the brass bushing would be a very good material to have to get a smooth throttle shaft movement. The wear charastics is better as well. If it were me, before I would pull the trigger on the e-bay listing I would want to pull the throttle shaft out and inspect the shaft and opening.

Being in Germany, it usually is not about the cost of the part it is the cost of the shipping and time.
Buying the reamer and not needing it may not be that big a deal.

Action

Action
Phoenix - Yeah, it's hot, however it's a dry heat
2006 Lincoln Navigator Limited 5.4l 3V
1996 Lincoln Mark VIII 2DR Coupe Diamond Anniversary 4.6l DOHC, 4R70W, 3.07
1970 Continental Mark III Triple Black 460 4v, C6, 2.80 (Used for Woodward Dream Cruise or just generally stored in Michigan)
1966 Lincoln Continental 4DR Convertible 462 4v, C6, 3.00
1966 Mercury Park Lane 4DR Breezeway 410 4v, C6, 2.80
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Re: throttle shaft play - is this considered excessive

Post by tomo »

The reamer shown in the E-Bay listing has to be used very carefully in order to keep the 3 holes aligned. The reamer that I have seen used to do this job has an extension after the reamer to fit in the center hole of the casting. This extension keeps the reamer aligned with the center hole. The center hole does not usually wear very much. All 3 holes in the casting must be aligned or you will have binding.

The amount of play that you show may cause a slightly rough idle but the car should start and run reliably. Your other option is the find a carburetor shop in the EU that has some experience in rebuilding carburetors for US made Ford products.
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thegermanfan
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Re: throttle shaft play - is this considered excessive

Post by thegermanfan »

Just an update: I have used the reamer after modifying it for reverse operation. This way I used the reamer shaft as a guide through the remaining throttle shaft bores. I could insert 3 bushings, the 4th is not accessible due to the choke housing, which prevents inserting the tool from that side. But that 4th hole is very long and there wear of the carburetor base should be only very minor. I must say: the engine now idles smoothly like never before. Decent vacuum too.
The reamer must be used with very slow speed and good cooling and flushing out of the shavings. Otherwise the bores get too big. I used loctite to ensure airtightness and safe retention of the bushings.
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