My 1969 Hurst (stock engine) has a Frankencarb (I saw that name and just had to use it). The carb number is 7025952 RM. I know the correct carb number should be 7025951. So the carb is from a 1969 Toronado. However, the base must have been /modified changed to accommodate the accelerator linkage on the Hurst. Otherwise the 7025952 should be the same as the 7025951. Overall, it looks in good shape….except….. The idle screws have no impact on the idle speed or running of the car. I have video down the throat of the primaries and gasoline can be seen flowing in above the throttle plate. Even then, the car actually runs pretty good. After running for a while, the idle might start to drop but otherwise it accelerates fine. I have a rebuild kit, including float and new idle screws, from Cliff’s High Performance, along with his book. I have several other sources of information on rebuilds.

I have started the rebuild process and I have a few questions.

1. Pulling the linkage, the secondaries only open about 60-70 deg at WOT. The primaries are at 90 deg. I can’t see anyway to adjust the secondaries to open to 90 deg at WOT. I read that in some cars the secondaries only open to 70 deg. What is the spec for this car and carb?

2. The primary rods are stamped 40, not 49B per the spec. Any thoughts on why the carb may have smaller rods, which I understand causes the car to run richer. I measured it, and it is 0.04 inch at the large end and 0.026 at the small.

3. When I removed the float, it was not attached to the needle with the small clip. Should the float and needle be attached by the clip for this application?

All ideas are appreciated.

Thanks,

 

Frankencarb. Yes indeed. All these years later, I doubt few are as delivered from Rochester. My findings are that airhorns get warped from overtorqueing, mostly the main bodies work just fine as long as they’re clean. Like really clean & rodded out. Antiseptic clean. What really wears are the throttle plates since they move constantly every time we drive.

For the idle screws, if you have some spares, test those. GM used a bunch of different lengths over the years. You might get some known good (i.e. correct) from a supplier just to be sure you’ve got the right screws in there. If yours are too long or (likely) too short, they’ll definitely affect the idle.

There’s a trick or 2 to try before gathering exotic idle circuit parts. First one is to go to your hardware store and get a couple of 3/32”s O-rings to block any vacuum leaks that might be in the screw holes from decades of use. Worn threads can lead to vacuum leaks, which can throw metering off. I’ve found tiny little O-rings help with this, but for GM it’s not factory. Apparently it’s common in the motorcycle world, of which I’m completely ignorant. Second idea is that there is thick stuff called “vacuum grease” which supposedly helps maintain vacuum while lubricating. I’m not sure it survives well in the heat of a hot throttle plate long, but might be worth a try.

Getting the secondaries to open all the way involves bending a rod on the driver’s side such that when the primaries are all the way open the secondaries are at 90°. Your call as to whether you want that, but I do that for my cars. I can’t recall the name of the rod, but play with the throttle plate linkage a bit and you’ll see what pushes the seconadaries all the way open (or not…).It’s the round rod that hooks into the secondary butterfly driver’s side slot. I bend the rod rearward with a pair of needle nose pliers to get to 90° when primaries are at 90°. Or bend it forward to get fewer degrees of secondary opening.
For rods and jets, I’d start with factory since the qjets were used on everything from Chevy Vegas to Cadillac 502’s. Rods & jets are a precise system, but you really want to start with factory parts for your car. Cliffs or other supplier should be able to hook you up with the right parts. I have a vague recollection that some of the 442’s were delivered with just jets, no rods. Your car may or may not be one of those.

For my later 170 series (74 & later) qjets, I always use the clip since that was the design. I’ve seen some carbs without it, but I believe you get quicker and more positive opening & closing of the needle and seat with the clip as opposed to without it.

For float levels I’ve used 9/32” or 5/16” measured at the rear toe point. See diagrams on line for just how & where to set this.

If the car runs a bit different after really warming up (not just the idiot light going out, after a good 30 minutes or more of solid running), metal expands and it can affect the mixture from tightening tolerances. I’m going through this right now with my 98.

If you really want to get into carb tuning, see my posts about using Innovative Solutions oxygen sensors to monitor exhaust gases the way EFI systems do. I found 02 sensors extremely helpful when carb tuning. Vastly better than vacuum gauge.

Don’t rush, make notes about the starting state of each experiment, what you changed and how it drove pre- / post changes. It’s very easy to chase your tail with carbs.

The world is gradually forgetting carburetors. Hope this helps
Chris

 

Page 89 in Cliffs book should help with the secondary adjustments to get to 90*
It doesnt hurt to run without the clip on the float, but I always use one. It is there so when float level drops from evaporation it will pull float off of seat and not get glue down.
I just found out from Cliff that that clip is a item that should be tuned.
Set it up so that with the smallest of movement from the float dropping the needle lifts.
One reason for the nozzle drip it sounds like you have is that the primary throttle plates are too far open and exposing the transfer slots.
If you can close them down so they are square as you look at them would be a good place to start.
Where is your timing at? A bit more initial will help you close the primary throttle some. I set the max 34* to start with someplace in the 2900-3100RPM
Let the initial fall where it may, but check it and use it for referance.
I would give Cliff a call and he should be able to set you up with the right rods and jets. Might as well get one of his choke pull offs as well.

 

Forgot to mention when using the clip do NOT hook it through any holes on the float arm. It just gets the hook centered in the float arm.

 

X2 Give Cliff a call. He still sells parts. He won't work on carbs anymore. His book is worth its weight. So is Doug Roes QJ book.

 

Cliff enjoys talking - I've spoke w/ Cliff several times over the years. You might also examine these/this kit(s). I bought one years ago - served me well, trays kept getting filled more & more over the years until I sold mine to a member who purchased a Quadrajet from me.

Quadrajet Ultimate tuning kit. Jets, Primary rods, and more

 

You might want to double check the number on your carb. A 1969 Toro carb is 7029252. The correct H/O carb (which was also used on every other 455 with a 4bbl that Olds sold that year) is 7029251. The fourth digit is the model year.

 

As an adjunct to what Joe stated, here's a list of of the carb #'s, along with the #'s for the jets, primary rods and secondary rods.

 

Chris,
With regard to your comment "3/32”s O-rings to block any vacuum leaks that might be in the screw holes from decades of use. " Which screw holes are you refereeing too?

Thanks

 

Lots of super advice. I did transcribe the carb number wrong the carb number on the car is 7029252- RM, which is the Toronado carb- my apologies. It does not have the correct H/O carb- 7029251.
I have both books that are recommended. The books have been a great read and resource- although I did miss the process of ensuring the secondary throttle plates align to 90 degrees on page 89.

The rebuild kit I have also comes from Cliff. Cliff complies the kit based on a phone conversation. If i run into more problems I will give him a call.

I am going to get all the factory rods, and jets, add the float/needle clip and restore it back to factory spec. In my mind that is the best place to start.

I also have the Innovative Solutions oxygen sensor to help set the mixture. I have used it on another car I have. It really does help.

Now that it is disassembled- time to clean it up and ensure all the passages are clean and surfaces are true- among everything else.

I see in the books that there are lots of details and measurements to check as I re-assemble the carb. I have rebuilt other carbs, but probably none with as many measurement points. Go slow and be methodical.

Thanks everyone.

 

I think both the 7029251 & 7029252 carburetors are 4MV divorced choke (remote choke) style 4 barrel Quadrajet carburetors w/ the choke element mounted on the intake manifold and connected to the carburetor by a rod. Is this correct?

So, which one you going to use (I may have been asleep at the wheel if you said which one you're using)?

 

A solid plus (+).

 

I'll be using the 7029252 carb. I don't have a 7029251. That is on my wish list.
Thanks,