My car is still running rough.. I stopped at a garage and explained I changed my plugs, cap, rotor and fuel filter and I'm still getting this hesitation feeling. With the car off he took off the breather cover and with a small screwdriver he inserted it in the round tube type opening in the front of the carb. He said he should be able to push down on the rods from there since there's only a small spring holding them up and mine seemed to be frozen? Is this a true test? He said the top of the carb needed to come off and wd40 the rods and try to loosen them up being careful not to bend.. Emery cloth the rods and make sure everything moves freely... I wanted to check with you guys before going forward. The local autoparts said they don't sell just a top bowl gasket it's part of a rebuild kit which had way to many parts for my likings... :) Any help is appreciated! :cheers:

 

if you have a Qjet the power piston could be stuck in its bore.some times you can make a hooked tool and pull it loose. doug roe book shows how to do this but most of the time you must take the carb top off and polish the power piston and smooth out the bore it rides in. :chevy

 

Thanks.. Anyone have this book that can post a picture? He tried to push the rod "down" not pick it up? I've never taked a carb a part. Anything to go BONGGGG when I do so.. Any easy tips on doing this? Simple unbolt/unscrew some top screws and she comes off or do I have to pull the carb and do this on a bench.. How easy/hard is this? Also, do they sell just the bowl seal.? My local store only sold the kit and said his Felpro book didn't show a seperate gasket for it.. Maybe the dealer.... :eek:

 

I second what Mr. Zahrobsky said. You can try the same thing. Just take a small screw driver and press LIGHTLY down. The piston should have some spring to it.

 

with the engine off use a soda straw to try and push down thru the bowl vent,you should feel a spring action that you can push down. if not the power piston is stuck. please do not call me mr zahrobsky as it makes me feel older than my 68 years. i will scan you a picture of the doug roe article :chevy

 

steve,the scan was sent "thursday EXE" :chevy

 

Thanks.. What's involved in removing the top of the carb? Does the carb have to come off the car?

 

Removing the Carb from the car will prevent having to disassemble the engine to remove the parts that will be inadvertantly dropped!

You'll be so much happier doing the disassembly on the bench. :chevy

 

Sorry Clem! :D :cheers:

 

Does $200 for a total rebuild job sound expensive?

 

I think that is in the ballpark especially if they are gong to remove and replace it on the car. But, if you are somewhat mechanically inclined and money is an issue, you may want to rebuild it yourself. I had never even removed a carb before and I rebuilt mine last month. It took me way longer than it should have but it came out great. It really is just a matter of taking it apart, cleaning, reassembly and adjusting. I learned a lot from the process and am now much more confident about tackling problems with the carb.

 

Can we lube the bowl vent to prevent the above mentioned problem?

 

For $279, National Carbs will send you a rebuilt unit that's completely gone over and I think it's replated (I think they called it chrome polished - whatever that means) as well and has a lifetime warranty. I haven't bought anything from them, but their rebuild specs looked pretty good. http://www.nationalcarburetors.com Maybe someone here has had experience with them and can advise...

 

That is a valid test to see if the power piston is moving freely within its bore. If conditions are as they should be, a small amount of movement downward against the spring will be seen while the engine is not running. With the engine running at idle, vacuum is applied to the bottom of the piston and it is pulled down against the spring pressure. With the piston pulled down, the primary rods that are suspended on it are fully inserted into the primary jets. As you accelerate, the vacuum signal at the bottom of the power piston is reduced and the spring pushes the piston upward. This action pulls the rods out of the jets and allows more fuel to be metered into the engine. If no movement of the power piston occurs, the mixture will be affected. If it is stuck in the up position, the engine gets too much fuel. If stuck down, the engine runs lean. There are a few tricks to working on these carbs, but nothing difficult. Get a copy of the book by Doug Roe, and most things that can be a problem are pretty well explained. Trying to explain some of them without the illustrations is hard to do. I just looked at your posting again and I see mention of using emery paper on the rods to clean them. I don't think that is a good idea. First of all, the rods are not the most likely parts to be sticking, the power piston is. If you are heavy handed with the emery, you could change the diameter of some critical areas of the rod profile. That will affect mixture settings.


[Modified by blu73, 10:16 PM 5/16/2002]

 

Several points I can comment on.
- National Carbs is good. I have bought an 84 Olds and a 77 Chevy carb from them. Fast turnaround, quick credit on the cores and a support # if you need them.

- Taking the carb off the engine is the only SAFE way to go. Drop one little frickin' piece in the right hole and you will have a bad day.

- KOZ, do you a NAPA store near you? I have purchased several carb gaskets from them. Also, give it a try to rebuilt. $15 for a kit and $15 for the book and $10 for the Gunk to clean it. A good learning experience and what the worst that can happen - you need to order a rebuilt unit.

 

That was my thought too. AutoPalace had rebuilt units for $280. Don't know about warrantee but thanks for the link Chris81. I mentioned that to the shop owner and he said I'd be better off rebuilding mine so I know what goes into it.

Clem, thanks for the picture.. I believe he said to emery the power piston not the metoring rods.. Just my misunderstanding.. Metoring rods looked plastic?

Anyway I decided to pulled the carb and disect it to see what's inside. Sure glad I pulled it off.. Those two inside screws where just looking to fall into some where.. :lol: I got the top section off and saw the metoring rods and what I believe was the power piston which looked stuck down. I thought about getting needle nose plyers or tweaser to try and pull it out and then decided to bring it to the shop. The shop owner is the husband of a girl who teaches CCD with my wife.. Our daughters are best friends.. we just never got together until now.. Anyway, he said I could spray everything down to clean it but the best way would be to soak it over night to get into all the nooks and cranies.. With 90K on the car and since I'm in there anyway I might as well rebuild it. I decided to give it to him. I supose I could have just had him soak clean it but he's got to make a living too.. :blueangel:

He said he would set everything and give it back to me to install and then I would bring it back installed for the final adjustments. What final adjustments? I thought the only external adjustment was the idle screw?

Where can I get the Doug Roe book? Napa? Even though I'm paying someone to do the work I always like learning..

Thanks! :cheers: :cheers:

 

Hi KOZ,

The book on Rochester Carbs by Doug Roe is available at Summitt, JEGs, or most speed parts stores will have it. Another source that I have seen it is a Barnes and Noble.

If you friend is going to rebuild the carb he should set up the float and all internal adjustments. The "on the car" will be the idle speed, idle mixture, choke opening if electric, and vacuum pull-off. Good luck on your project.

Oh, $280 for a rebuilt is too much. National Carbs is much less, another source is Carbs Unlimited, and Recarbo, and Chicago Corvette Supply at about $180. They are all on the internet. If you can't find them e-mail me and I will give you the web addresses.