Carburetor Woes!!!

[americanmusc1e]

OK, right now my truck (383, vortec heads, 230 @ .050 cam) has a 600 Holley 4160 that I bought new about 2 years ago. I have had problems with the Holley ever since it was new. (float hangs and it starts flooding out of the boosters) and I have been told that it is too small for my 383.

so I pulled a Q-jet of of our '69 c10 and started to see if I could rebuild it. the secondary throttle plates were rusted shut, but after a lot of work i managed to get them free and I'm starting to piece the carburetor back together now. the carburetor is badly oxidized from sitting out in the weather and it has some wear on the primary throttle shafts.

SO, I started looking on ebay, and I found some pretty cheap edelbrock 750 carbs (1407) and a lot of the descriptions say that they were taken off 383's because they were to big for a 383.

so what should I do:

Keep the 600 Holley?

Rebuild the Q-jet?

get a 750 edelbrock?

get a 600 edelbrock?

OK, one last thing, I'm on a tight budjet and i don't have much money. So don't tell my to buy a BG Demon or a JET Q-jet.

[WorkinLonghorn]

Rebuild the Q-jet. Will be CHEAP and is a piece of cake if you go with the step-by-step instructions.

[71 super]

Get a 750 holley and go with it. 383 needs the cfm and the holley is much easier to tune and get right for the motor. you need to address why are the floats hanging on the other carb? Have you pulled fuel bowls and checked for trash from tank etc.? If you are having problems with the holley (they won't handle trash in the tank very well) you need to get a good fuel filter on it in line.

[geezer#99]

I ran a holley 3310 780 cfm vacuum secondary on my 383 with trick flow heads and a bigger cam than you have. Actual measured 11 to 1 compression. I was running a saginaw 4 speed behind it. In a 56 chev 210 sedan. Worked better than the 750 edelbrock it replaced. Took some playing with the float level, lower than normal setting worked for me. Holley's are more tuneable. Jets, power valves etc. more available. Q-jets need a good supply of rods, jets and hangers to work but will stay in tune better. What are you running for tranny behind it and rear gears. Stall speed can be a factor in carb selection too.

[americanmusc1e]

Originally Posted by geezer#99

I ran a holley 3310 780 cfm vacuum secondary on my 383 with trick flow heads and a bigger cam than you have. Actual measured 11 to 1 compression. I was running a saginaw 4 speed behind it. In a 56 chev 210 sedan. Worked better than the 750 edelbrock it replaced. Took some playing with the float level, lower than normal setting worked for me. Holley's are more tuneable. Jets, power valves etc. more available. Q-jets need a good supply of rods, jets and hangers to work but will stay in tune better. What are you running for tranny behind it and rear gears. Stall speed can be a factor in carb selection too.

the truck has a 700r4 with a 2000rpm stall converter, and 3.08 gears (only until I get the money for 3.73's)

[unclewatts]

Originally Posted by americanmusc1e

the carburetor is badly oxidized from sitting out in the weather and it has some wear on the primary throttle shafts.

There is a kit you can buy for very little that allows you to drill out the holes the throttle shaft goes into and press in bronze bearings to fix that worn throttle shaft. If you don't, you will have a vacuum leak there which will affect performance. Just my .02

[geezer#99]

Nuther question. Intake??. Will it accept the q-jet. Might need an adaptor to fit it up. To put the bushings in the primary you need to remove the small screws holding the plate to the shaft and restake them back in. Can be tricky. Bin there done that. Frustrating job. Looks like your combo is set for good torque. Lowish stall, O/D tranny, shortish gears. Best bet might be the Holley 600. Set the float so it doesn't flood and you should be good to go. Not sure what your elevation is there. The higher above sea level you are the lower your float level needs to be. Not a bunch, just a little. I had fun setting my float level at 3800 foot elevation on both my holley and edelbrock. Cheapest for now would be the 600. You know it works except the flooding. JMHO

[PanelDeland]

I see the carb as being just about right for a daily driver.Sure it doesn't flow all the cfm a 383 will use at WOT but it will have good street response.The 750 or maybe even bigger might help a full drag truck but will be a bit sluggish at part throttle on the street(JMHO).
I think the 600 is your best bet since you have it and learning to tune it should be fairly easy,there are tons of folks who have learned.The Quad is one of my favs because they stay in tune and require very little maintainence to stay good.It would be my second choice of the ones listed.

[big_al_71]

I would go with a holley hp650 is exactly what I put on my truck, rejetted it and tuned it and it works super good...

[rico7769]

stay with the holley. I run a holley 80457-s 600cfm. Very easy to tune. Had problems with the first one we bought. Floats shot because we didn't clean the tank properly. Like the other post said, you won't get the response you would from a 750, but it would do great for a street/daily driver. I'd tear it apart and clean it really well and you'll get a great carb that is easy to adjust. If you want, I still have my other holley, has about 20 miles of driving on it (I know right, really filthy tank, sat up for years...$$$ mistake). I'll give you a great deal if you like. Just needs the floats to be cleaned/fixed/rebuilt.

[special-K]

Step away from the Holley 600.My sources all say they are crap.I`d get a Street Demon.You can decide which CFM is right for your set-up.I love Q-jets,but I don`t like to use adaptors to run an air gap dual plane.So I`m going with the Street Demon.I don`t care for Edelbrocks.I buy carbs from carb companies.

You don`t need money for a3.73 rear.There are so many wanting 3.08s for mileage/rpm drop @ hiway speeds that I`m sure you could find a swap deal.I`d want the gears in to get it dialed-in right once and for all.

[68Stepbed]

Well it sounds to me like your 383 isn't a big, nasty, narly engine, but more of a streetable engine making good torque and power for street use. If that's the case, stick with the 600. It will give you much better throttle response, mileage and overall better street manners, especially with that 3.08 gear.

That being said, the first thing I would do is order a 4150 conversion kit for it. The biggest problem with 4160 style carbs is the side hung floats and the secondary metering plate. There's just simply no way to tune the secondaries other than different vacuum springs.

The 4150 conversion kit will come with front and rear fuel bowls with center (or cathedral style) floats, a rear metering block, and all the hardware necessary for the swap. You could even take it a step further, and order a kit from places like The Carb Shop, Quick Fuel, or Proform that have billet metering blocks for highly adjustable tuning possibilities.

Holley has great tech support if you need any help with any of this as well.

Horsepower TV did a show about a year or so ago where they took a 4160 600cfm Holley, did a 4150 conversion and put it on a mild 383 on the dyno. It made some impressive numbers just by doing the 4150 conversion. Afterward, they put a 750 Holley on the same engine and it made less power and less torque with the larger carb. Bigger is not always better.

Another option, and a whole lot easier, is just buy a 670 Holley Street Avenger. The Street Avenger line of carbs is awesome. I've had my 570 SA for a few years now and not had any trouble from it. The 670 would be a good match up on that 383 as well.

[americanmusc1e]

thanks for all the replies!!!

Keep going folks, I still haven't made up my mind on this yet. Since I already have a jet kit for the holley, I guess I'll try to get it calibrated and fix the float hanging problem. But I'll still keep working on the Q-jet.

[mclairmo]

Fix the Holley 600 cfm. I love Holleys and have always had good luck with them. Yeah, your float might be sticking but that's not a design flaw. Get it fixed and it will run great. Make sure all is clean inside. Lots of little orifices that can get clogged, as with any carb.

[Roland]

Try replacing the metering valve in the Holley and install it very carefully. Use a 12 point socket to tighten it into the metering block. It is unbelievable how little stress it takes to tear the diagphram in these valves. Once they're right - they are right. Probably a bunch of really good carbs have been scrapped because they "couldn't be tuned". When this diagphram tears, fuel pours through and floods the engine.

[69GMCLonghorn]

Go with a 1000 CFM race carb! The barametric pressure of the entire US will drop the first time you floor it!