Keep the 1406 Edelbrock or switch to a 1403

[natedogg]

A previous owner put a Edelbrock RPM Air Gap and a 1406 600cfm carb on the 305 in my 85 Silverado. I know the air gap is too much for it and the 600cfm is a bit too much also. I am going to switch to a Edelbrock Performer EPS and maybe a 1403 500cfm carb. My question is can the 1406 be tuned down to be more 305 compatible or should I buy a 1403? Thanks for any and all opinions.

[franken]

That dual plane manifold is supposedly fine for that engine and I'd guess the 600 carb is closer to good than the 500.

I'd say look at the plugs and see what color they are.

[natedogg]

All the plugs look about the same and are black. The truck has had a strong exhaust smell and you can see black smoke out the pipes at idle. My truck has headers with no cats, so I know it will have a smell. I just think it shouldn't be that strong.

[rich weyand]

The Performer Air-Gap is a great manifold. It keeps the carb from getting overheated, which the Edelbrocks are sensitive to. However, it will also slow the carb from reaching operating temps in cold weather. If you use the air-gap manifold, you should use the stock induction system that has a heat pipe down to the manifold to pull in warm air until the induction air reaches temp. I did that on mine, with a little creative jury-rigging to mate to the headers. The cold-air induction connects to the radiator bulkhead knockout with the stock fixture.



I used a 1-1/2" tailpipe extension with some slots machined in the back side clamped to the header pipe, and connected it to the underside of the snorkel with some bits and pieces of the original heat riser pipe and some 1-1/2" flexible tailpipe repair tubing cemented together with JBWeld.



The Edelbrock 1403 won't work any better than the Edelbrock 1406 unless you tune the carb, and if you are going to do that you might as well tune the one you have. Simplest is to get an A/FR meter and dial the tune in. Not cheap, but cheaper than another carb that will still run crappy if you don't tune it. Here's the A/FR meter I used. Amazon.com: NGK AFX Powerdex AFX Air-Fuel Ratio...

You need to crack the top off the carb and set the float height. If they are set wrong it will run rich all the time. It's in the manual, and it's pretty easy to do.

Then you need to start experimenting with the metering rods. Knowing when you are on the money is a lot easier with an A/FR meter.

But just buying another carb, any make or model, and slapping it on there is a waste of money if you don't tune it. You'll just be back in the same boat. Why not just tune the one you have?

[Dead Parrot]

Remember that the basic Quadrajet is a 750 cfm carb and GM put those on engines from 300 to 454+. Don't worry about 'over-carbing' a daily driver. Any reasonable carb you put on there will be operating at a fraction of its maximum flow most of the time. Tune the carb you have.

1. Verify that your ignition is working properly and replace those fouled plugs and install a new air filter.
2. Make sure the choke is working properly. A stuck choke can cause the too rich problem all by itself.
3. Make sure the power pistons are not gummed up. (can do this without pulling the top off the carb)(this too is in the manual)

If this doesn't fix it, you are at the open the carb up stage.

4. Consider getting a Calibration Kit. The one I have is Edelbrock # 1479. It has an assortment of metering rods, jets and springs to tune the carb for your vehicle and driving style.

5. What Rich said about the float levels. And check the needles and seats for small bits of stuff. And change the fuel filter.

6. Check the installed jets, rods and springs against the ones the manual recommends for your setup.

This should get you close. As mentioned, for best results you need an A/F meter.

[natedogg]

Thanks for the tips. Im still learning how to mess around with these old small blocks.