I am in the final stages of going through the motions of rebuilding my 17059201 q.j. and have a question about chokes. It has a hot air style, but wondering if I should convert to electric.......or do I even need a choke at all? I have heard/seen some take the choke air flap and rod out along with the choke housing. Is this smart to do on my 65 wagon, non-daily driver? How would you plug the choke shaft hole (or would I need to)?

Also, what is a good baseline size for the idle mixture screw holes for a 496 with Merlin 320cc cast heads and 9.5:1 cr? Not sure of cam size yet, but will be a larger, long duration, probably 110-112 lsa style.

Any advice would help tremendously.:confused:

Rob

You live in Minnesota. Removing/disabling the choke is NUTS.

Tune the choke properly--it ain't hard--and you'll never regret it. A properly-tuned choke provides SEAMLESS operation in an engine using a stock/mild/moderate performance cam.

If the hot-air choke can be made to work with your manifold--there's nothing wrong with them and several things "right" with them. If you can't use the hot-air choke, an electric conversion is simple and inexpensive. Route power through an oil pressure switch so if the engine stalls the choke won't continue to heat.

Beyond that; the Cliff Ruggles Q-jet book is WONDERFUL; Ruggles knows what he's doing--and--he communicates it well.

It's a bargain at twice the price, except for the fact that it's printed in Communist China so the binding will probably fall apart in a few years like all my other Chinese-sourced books.

Amazon.com: How to Rebuild and Modify Rochester Quadrajet Carburetors (S-a Design): Cliff Ruggles: Books

You can put an electric choke in, cap off the vacuum tube at the front. Don't use a gasket under the choke, it won't work. There's a vacuum passage from the main body into the choke housing, you can plug it when using electric.

There's an early 70s Cadillac electric choke that work, comes off slower and has a standard male spade terminal instead of the funny "L" shaped one the later models have. I'll be darned if I can find the part number anywhere. Try NAPA Echlin.

you can buy the later choke electrical connector from gm

Just an FYI,if the q-jet your reffering is going on your almost 500 cubed bbc along with what you say is a larger cam then you may be SOL with that setup.

The MERLIN HEADS & LONG duration cam you mentioned your runing with basically 500 cubes is not generally q-jet territory IMHO.

Maybe a mild cam'd stroked 500 cid bbc with stock type gm heads would be ok but not a 500" bbc motor that's merlin headed with a longer duration cam as you put it which is likely a bad match.

Yes they used q-jets on lfg gm v8's like 454s/455s/500 cubes caddys but not with hi perf better breathing aftermarket heads and long duration high perf cams,that requires the q-jet to be worked away from stock calibration etc to run well in that situation.

Q-jets running on large 500 cid prefomance motors with cams running approx 228-230 deg int dur @.05 or more (which i would expect your is well over ) that will have lower idle and low speed intake vacuum generally need special attention to run well with respect to the power piston spring choice,larger needle & seat for more fuel flow into the small float bowl,the idle down tubes need to be drilled for the additional fuel that large motor needs at idle and to also avoid a lean stumble they can have going from idle to mains transition if the idle circut is too lean,different primarry jetting & meter rods & secondary metter rods too ,etc.

Dont get me wrong i really like the q-jets for street perf motors but in your case i suggest calling up someone like Sean Murphy or one of the other q-jet guru's here in t/chevelle that are experts as setting them up for large 500 cid perf motors like you have with hi perf heads & hot cam before you go any further .

I suggest this just in case they say its not doable for your setup or it will cost more then your willing to drop in the old q-jet.

But if your giving your stock q-jet just a std run of the mill at home garage rbld (with stock jetting/stock meter rods/smaller stock needle & seat/stock power piston spring)like you stated your doing and your not paying attantion to the items i listed above with it going on your modified 500 cid motor with better breathing aftermarket heads and large perf cam etc it will definately give you trouble and not do that motor justice in the perf dept without proper prep for your pretty hot setup by an experiecned q-jet builder .

So get a price to get it setup right by a pro and then wiegh that price against getting a new holley that may be a better choice in this case.

Just my 2 cent's there.

Scott

You live in Minnesota. Removing/disabling the choke is NUTS.

Tune the choke properly--it ain't hard--and you'll never regret it. A properly-tuned choke provides SEAMLESS operation in an engine using a stock/mild/moderate performance cam.

If the hot-air choke can be made to work with your manifold--there's nothing wrong with them and several things "right" with them. If you can't use the hot-air choke, an electric conversion is simple and inexpensive. Route power through an oil pressure switch so if the engine stalls the choke won't continue to heat.

Beyond that; the Cliff Ruggles Q-jet book is WONDERFUL; Ruggles knows what he's doing--and--he communicates it well.

It's a bargain at twice the price, except for the fact that it's printed in Communist China so the binding will probably fall apart in a few years like all my other Chinese-sourced books.

Amazon.com: How to Rebuild and Modify Rochester Quadrajet Carburetors (S-a Design): Cliff Ruggles: Books (http://www.amazon.com/Rebuild-Modify-Rochester-Quadrajet-Carburetors/dp/1932494189/ref=pd_bbs_sr_1?ie=UTF8&s=books&qid=1229229784&sr=8-1)

LOL! I knew I would get that response at least once. Fortunately the car will only be driven from about May to September. I do have the book from Cliff, actually had him replate my carb. I have done all mods necessary except for drilling out the idle mixture screw holes. I will probably end up with an Edelbrock Air Gap, I'm guessing I should just convert over to electic choke. What should I plug the hole up with? Appreciate you weighing in.

Sorry guys, guess I don't know how to use the Multi quote.

Tom: You say to use an electric choke from a 70's caddy, how much difference is there on electric chokes, and how do you test their times?

Scott: I should have eluded to the fact that I bought Cliff's book, had him blast and replate the carb, and I have bought a kit from him that comes with larger jets, needle/seat, rods, and idle tubes. I gave him my specs prior to commencing this project, and he arranged the parts in my kit based on my specs. I also misspoke a bit, the heads are cast iron replacements from World Products, not Merlin. I did some digging on the paperwork for the heads and realized they are World Products, not Merlins, and are rec. port cast replacements. I have spent many nights with my nose buried in Cliff's book learning and re-learning this thing. Its something I just have to figure out.

I appreciate everyone's input. I have learned alot about this thing, and continue to keep learning with everyone's help.

WLL IF CLIFF set you up with the parts to modify/rbld your q-jet for you perf motor thats exactly what you needed to do to get the q-jet to work good for your setup.

With that said you should be ok,Cliff sure knows what he is doing being the expert q-jet person he known to be.

Yuo didnt mentione this so i hope you told Cliff your cam duration specs so he could set you up with the proper power piston spring for the approx idle/low speed intake vacuum he thinks that cam will create in your motor/setup,thats very inportant to get right.

If not call Cliff to get that right before completion of carb assembly.

Good luck.

scott

WLL IF CLIFF set you up with the parts to modify/rbld your q-jet for you perf motor thats exactly what you needed to do to get the q-jet to work good for your setup.

With that said you should be ok,Cliff sure knows what he is doing being the expert q-jet person he known to be.

Yuo didnt mentione this so i hope you told Cliff your cam duration specs so he could set you up with the proper power piston spring for the approx idle/low speed intake vacuum he thinks that cam will create in your motor/setup,thats very inportant to get right.

If not call Cliff to get that right before completion of carb assembly.

Good luck.

scott

Yah, I apologize for not giving the details. We talked several times and went into great detail on cam choices (that was the only thing not currently decided on for the engine build) and I feel good about the parts he sent me. I appreciate your feedback alot.

which style of hot air choke do you have- the older divorced style with the coil mounted to the intake and the rod going up to the carb, or the later style with the coil mounted on the side of the carb?
personally, i think the early remote style is the best setup, but the later style also works well if you get it set up properly.
either way, you need to have exhaust gasses flowing thru the intake manifold- which is a good idea year round up here in MN. even in the middle of summer when it's 95 degrees during the day, it can get down into the 50's at night.
i only like using electric chokes if there is no easy way to get heat to the coil from the exhaust crossover in the manifold.

Right now I'm sitting with the newer style with the coil that bolts onto the carb itself. I'm probably going to end up with a performer rpm air gap manifold. I'll check to see if that will accomodate for gases needed for the choke.

No, it won't. That's why it's an air gap.

No, it won't. That's why it's an air gap.

You have two choices, as I see it. Either one should work well.
1. Keep the hot-air choke; wrap copper tubing tightly around one header tube--several wraps--and have one free end attach to the existing fresh-air port on the carb, and the other attaches to the hot-air fitting on the choke housing. Clamp everything in place. Have fun changing valve covers--maybe you want to add a couple of splices to the tubing so you can remove the long sections that'd be in the way for engine service.

2. Drop the hot air choke coil like a broken rubber, remove the choke coil gasket, BLOCK THE VACUUM PORT in the choke housing, and block the fresh-air port on the back of the carb, install an electric choke coil. Route the power wire per my previous post.

2. Drop the hot air choke coil like a broken rubber, remove the choke coil gasket, BLOCK THE VACUUM PORT in the choke housing, and block the fresh-air port on the back of the carb, install an electric choke coil. Route the power wire per my previous post.

x2

Yeah that.

I,ve used NAPA 2-30076 electric choke and have had good luck. They also make the connector CTC100 echlin. I think that's the number, if not real close, fits that "L" style connector on choke perfectly. You can plug the small vacuum inside if cover with a round toothpick, and like they mentioned, no gasket. I just wire to ignition hot at the fuse panel with a 15 amp fuse.

the ones with a "L" shaped connector are going to be the emissions-legal type, completely off in 60 seconds. I use these with 10 Ohm power resistor to slow things down a little. These resistors are either in a ceramic block like a ballast resistor or some come in a metal shell with a bolt tab that's real handy.

I had a feeling that the air gap wouldn't have any provisions for the choke. I think I'll go the route of the electric choke.

I appreciate all of the advice on everything guys. I'll learn these qjets after all, with help of course.