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Canadian Poncho Homepage -> Canadian Poncho -> 65-70 Full Size Power Train Tech Forum -> Worn throttle shaft. Vac leak? Strange miss? Poor idle? Bench solution.
Post Info TOPIC: Worn throttle shaft. Vac leak? Strange miss? Poor idle? Bench solution.
cdnpont


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Worn throttle shaft. Vac leak? Strange miss? Poor idle? Bench solution.
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If you have a intermittent miss you can't track down on your 350 with a 2GV.

It could very well be a vac. leak at the carb throttle shaft. Yes, we didn't listen to you guys. I've got my 350 sorted well now. Runs nice after three carb benching's and a good setup. No mis. I'm expert good at these now, I was kind of good at it when I was 18, but now I have the internet.

 

McGiver style, bench shaft vac leak repair. It's the pre send it out and pay some guy 300 bucks for bushings job.

 

Remove the two throttle plates from shaft. Go easy. The 4 screws are never meant to come out. They will with force, but pick your driver head well.

Pull the shaft.

 

Passenger side.

Trim 1/16" off the shaft end. Bevel and dress that shaft edge. Finely polish the shaft (don't sand, polish). The last 3/8 of the shaft is usually just riding in rust anyway so it's no foul to cut or grind it off.

 

Now go and tap the cast passenger side throttle base hole with your Chinese mega set 1/8 NPT fine tap. No tap drill required here. The NPT tap will take up. the hole is sized for it. Cut in just Just enough that it will catch the plug you will install.

Locktite on the thread, tighten a 1/8" standard grub screw in the threaded shaft hole. Just a couple of threads in. Stop.

The grub screw is a mile away from the shaft end. 

grub.jpg

Linkage side.

Clean the shaft where it rides in the casting, de burr the casting outside flat surface and also linkage lever inside surface to make it as smooth as possible.

Roll a suitable Viton O ring or fuel resistant down the shaft to the throttle arm. 

It's not jamming the throttle in the least, still leaks probably, but better.

vitonrs.jpg

Reassemble.  Place the plates through the shafts. Use locktite high strength on the 4 screws...or bad things.

 

Now you have less leakage. And no miss.

 

But it's only a stopgap to a loose shaft. Problem is a worn shaft obviously brings more issues. Like the throttle plates begin get caught in the bores. Tip in off idle you get that little rough pop in the gas pedal feeling.

We all know how crappy that rough pedal feels. I hate it and I really think that feeling is a worn throttle shaft.

Cheers.

 



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
LT1Caddy


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There is (was) a race guy near you that is a genius on the Rochester 2 barrel ....

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4SPEED427


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LT1Caddy wrote:


There is (was) a race guy near you that is a genius on the Rochester 2 barrel ....

 Doesn't look to me like Mark will need to call him! Once again Mark, well thought out and a nicely detailed how-to thread.



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1966 Strato Chief 2 door, 427 4 speed, 45,000 original miles 

1966 Grande Parisienne, 396 1 of 23 factory air cars (now converted to a "factory" 4 speed)
cdnpont


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I know it's totally a mickey mouse repair, but it seems to work and it's what I enjoy. It's just that little grab coming off idle thats annoying to me now. It kind of always had it, that grabby pedal.

I'm going to try to bush and hone it myself, and it would be nice to keep the car working in the interim. The carb in the car now is otherwise very nice.

 

 

 



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
cdnpont


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LT1Caddy wrote:


There is (was) a race guy near you that is a genius on the Rochester 2 barrel ....

 Thanks Bruce. I've heard of him. I guy I know who raced stock cars used him. The 2 barrel Rochester is still widely used in racing isn't it.



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
Canadian Poncho


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Have you considered maybe converting to a Holly EFI system? I've heard nothing but good things about them and they are pretty simple to install. I'm not sure if you can get a 2bbl adapter however a 4bbl intake would be easy enough to install. I'm thinking of this for your convertible and you'd have great driveability with it.

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cdnpont


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I have thought about it Todd. But all told, the car is running pretty nice right now, so backburner.

Cliff has one.

What do these systems cost all in?



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 67 Grande Parisienne 4 door HT. 69 Parisienne Convertible.
 
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LT1Caddy


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cdnpont wrote:
LT1Caddy wrote:


There is (was) a race guy near you that is a genius on the Rochester 2 barrel ....

 Thanks Bruce. I've heard of him. I guy I know who raced stock cars used him. The 2 barrel Rochester is still widely used in racing isn't it.

 It came to me just now. I think his name is Smith racing engines ( along that line) He's close to Cayuga, a guy maybe our age and now maybe his son. But if you were running the 2 barrel class in Cascar, if he hadn't done your carb you were "first in the losers".

He'll have your parts and I remember when I was racing talking to him on the phone and he was quite helpful....

HTH



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cdnpont


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Yes. Smith fabrication is it. It's an entire fab shop I think. Thanks Bruce.

 

 

 



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