Oldsmobile Torronado '73 455, idling,air trouble!

[pauliq]

Hey everybody

I have some trouble with my carburator idling, or I should say still having trouble, did á lot of cleaning and rebuild it again with a kit, not the quality what your talking about on the forum, I know this now from Cliff, but stil...
I took the carb to a firm were they do utrasoon cleaning, it came back real clean and I could take out the tubes by hand, put everything back together again and gave it another try.
It dit run better and I could get it to idle quite well, But after a couple of minutes ( 15 ) it changed and fell down in rpm's and again dit not idle, like it dit before and when you put your hand on the airhorn it inmediately rises in rpm's and starts to run smooth.

I allready put in a new intake manyfold gasket and changed the vacuum hoses to rule all that out, today took out the gas tank to clean it and checked all the fuel tubes untherneath the car and also put on new fuel hoses on all the connections so thats solid to.....the reason that I checkt all that is that it also gives troubel now with full trottle.

I have an other question, I have been offerd a rochester quadrajet who looks almost the same as mine There is a slight difference, and that is that there's an extra tube on de rear of the carb, mine has only one tube on the rear and thats for the hotair choke thats on the manifold.
Does anyone have an idea what the other tube is for, and can I use this carb on my '73 torronado?
The reason I ask is that Its a stock 4MC quadrajet used for Oldsmobile 455,all type's '72 - '74 exept Omega and Toronado!,  so Im thold, can anyone tell me what's the difference with the other cars it's ment for,  mine is also 455, sure its a frontwheel drive, could that be the reason, I'm a bit puzzled here, and could use some expert opinion.
They tried to read the number on the side, but it's cleant and polished and rebuild and can't read it so real hard te tell witch type it exactly is, but it looks realy exactly like mine exept for that extra tube on the rear!
Another difference is that it has a electric choke, but it also has the connection of the hotair choke, the same as on mine, so i dont think thats gona be a problem.

Could realy need some help here...

Tanks in advance....Pauli

[pauliq]

By the way My carb is nr.  7043252.

Pauli

[omaha]

the rpm increase indicates that it is lean at idle. That said, there are various reasons that could cause this.  A vacuum leak would be one of the first things to c heck for. this includes any vacuum operated accessories. remember, things like power-brake boosters can develop internal leaks. Block these off to see if they are leaking. I once had a leak in my distributor-advance can. While the engine is running, pull the hose off the accessory and block the end with your finger. See if any change is happened. Do this for any vacuum operated accessory. eg; dist., brake-assist, pcv, egr, and even the carb-pulloffs. vacuum leaks are sometimes hard to show up sometimes. anyplace there is a rubber vac line or vac. operated accessory, there is a potential vac leak source. dont forget about warped baseplates or manifolds. Check these too. This is where I would start with first.
    If the other carb has an extra tube on the back side, it should not matter too much. It can be capped. However, how is the carb set up?  Is the idle tubes and bleeds similar to your old carb? how bout the jets? Rods and spring?  Having the number of the other carb might help to see if it is usable with your 455. Other than that, you may have to take it apart to investigate. 
   

[pauliq]

Thanks for your reaction omaha...

I did check all those vacuum users, and could not find any problems there and it did not gave a change in idling, so I think its in the carb itselve.
Did also do a test with carb-cleaner spray to find leaks in the system but no luck, the only reaction it gave was when ik came close to the airhorn, but thats becourse it suck's in the spray there.

About that other carb, they cannot read the number so its hard to tell what type it is.
And then you don't know if they made any changes, rebuilding it.

What would be the difference with the other 455 engines in other type cars of oldsmobile, I dont know about the omega but the toronado is a frontwheel drive, could that be the difference in settings of the carb becourse the engine is pulling the car, and in the other types pushing?
I'm quite shure it has nothing to do with the weight of the car, course it's weight is the same as the full size cars...!.....The torro is a two door car, a coupe, but has the same size as a full size familiecar.

When you differ the settings of the carb, it influences the carracter of the engine en the way you feel that the car is handling, but it still have to run good, and idle smooth or am I completely wrong here?
If so.....it must be possible to exchange carbs between those cars, and have good running engines, say it with a slight change in carracter!
Maybe it has to do with what options the car has, in relation to the connections needed on the carb, amount of tubes for vacuum users?

[omaha]

not that much of a difference in the other 455's of the rear drive versions of any particular year
I'm sure the other carb could be made to work correctly but if you knew if it came off another 455 it would make it alot easier. you would know thatr you were "in the ball park".  The Omega's used much smaller displacement engines not over 350 cubic inches so a carb off of one of these cars would have a different fuel curve.  It could be made to work just like any Q-jet could be made to work but you would just have to go through and measure everything. Then you might change a few things, maybe use the #1  recipe in cliff's book.     The 455 engine probably would utilize the "bypass air" feature used in many Q-jets.

[Cliff Ruggles]

Keep the original carburetor.

Completely/correctly rebuild it with good parts.

This includes pulling the idle tubes from the casting and cleaning in and under them.  Our HP kits come with new tubes.

Install all the new parts, and set the float.

Once running and fully warmed up, set the idle mixture screws for best idle quality. 

If the engine is "stock", the stock carb will have plenty of idle fuel via the mixture screws.

Full throttle power problems are usually caused by using a small fuel inlet seat, and not replacing the secondary plastic cam/spring during the "rebuild".......Cliff

[pauliq]

Thanks for the commend and tips omaha and Chris

Well.....I found out whats the problem with fulltrottle....I'm missing a part, thats the part that lifts the second metering rods, the part thats on the air valve shaft in the middle andpushes the metering rods up, for full power.

I'm affraid this must have happend when I took it to the company for Ultrasonic cleaning

Is this by any chanse a part thats in the HP kit?

By the way...the engine is stock...

An other question is I red about the tubes and that they have to be drilled in some ocasions, for some recipies out your book,  when I want the carb to be just stock, do I have to do that allso, or is the HP set for mine type carb for stock uses ready to build of the box?.....pauli

[omaha]

yeah that part is in the kit. (the plastic cam on the airvalve shaft) should always be replaced during a rebuild as the tend to get brittle after time.

[pauliq]

Thanks Omaha

I'm ordering a HP carb kit right now...and also a bushing kit......and ofcourse a copy of his book, and then rebuild it propperly like Cliff suggested.

Can't wait to start.....Pauli