Hey CO. My bone stock '70 442 has a W-30 cam, stock manifolds etc. etc. When i first got it running I got the closest rods and jets for the carb that I thought would work. Those are a .069 jet and a .049b rod. I got the sizes off of another website. Well when first fired the thing barely wanted to idle, I had to have the idle mixture screws almost falling out to get it to start and idle acceptably. And it wouldn't tip in had to pump the pedal to get it unto the main circuit, at which it seemed ok but didn't try to drive it like that. So with some spare carb parts I put in a 72 jet, not much difference. Then a 78 jet and it starts and idles and drives but i know it's rich like Bill Gates. To compound the problem my carb somehow left the factory unstamped. It doesn't look to have been replated or had anything covered up just not stamped. It does have all correct fittings for late 60's early 70's olds carburettor.

 

jets and rods work in concert and need to be paired correctly. I don't have my service manual in front of me, but 69 is way too lean for a 455. You probably need more 72-74, but also need the correct rods. Wrong rods will give terrible idle, midrange and cruise, regardless of the jets. There were many different combinations based on which 455 and which numbered q-jet, so you need to provide a little more info. I have a full set of Rochester Manuals that lists all the parts for all the carbs so I can look up the correct "stock" jet rod combos. With the ethanol, you may need to go a little richer, but you need to start with something close to stock.

 

I'm not sure if you're mixing jets and rods in your post...try 48 jets with a rod between 76-78. With this setup you should be able to control the idle.
Keep us updated

 

some things to bear in mind: a '70 w30 MT carb. didn't use primary metering rods, a power piston spring, power piston, or 4m(quadrajet) jets. it used 2g(dualjet) jets. it also had different sized idle channel restrictors, air bleeds, and idle mixture discharge ports.
are you handy with very small drill bits? that's the only way you'll ever get it to idle right(and not be pig rich). the most likely reason your carb. doesn't have a model number is that the float bowl was replaced and the mechanic didn't bother to stamp the number into it. it wouldn't have left rochester without a stamp.


bill

 

Thanks. So how do I tell if this bowl was replaced with the right one? How do you tell the size of a q-jet without a number to go by? So I guess it's safe to say that this is not a w-30 carb, not that I thought it was but had no idea they were so different.

 

http://www.hotrodhigh.ca/PowerTuneQjet.html
You can read through this website for some ideas,I know it helped me out ,all pertains to Oldsmobile Quadrajets.

 

In re-doing the '79 Toro carb for the 403 last year, I noticed that there is typically about a 30 difference between jet size and needle size. That helped. I was -not- working with a unit lacking power piston like the '70 W30 carb. Can you verify if yours has the power piston, or has been altered to the more conventional setup?

What helped MOST was getting the TIMING right...
Is there anything in your enigne different from factory issue? If so, factory settings may not be even close to acceptable.

 

It's as normal a quadrajet as I've ever seen. No parts left over from the rebuild kit anyway. The only issue I had was the pump diaphragm kept running up onto the spring so I had no pump shot. I dug through some very old kits at the shop 'til I found one that works. It's not blue so I wonder how much of the corn-squeezins fuel it will put up with. Thanks for the link 61, I'll check that website out.

 

So any updates on your carb issues ?Did ya get it to work better?

 

Got jets in the mail just waiting for some time to mess with it. Life, job and other car stuff (daily driver) got in the way. Is running better because its it's cold out though. Thanks for the checkup, will be on this soon. Got to get the choke worked out in this weather also!

 

Good to hear ,keep at it you'll get it and once you do you'll be very happy and it'll be ONE more thing checked off the list !I found that once I changed my primary metering rods it was like nite and day to how well it idled and drove .