Cliff's Quadrajet Parts and Rebuild Kits
General Category => Quadrajet Carb Talk and Tips => Topic started by: ykf7b0 on August 20, 2017, 02:49:20 PM
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A couple years ago I did a Vortec head swap on my 76 L-48 Corvette and rebuilt the 17056202 Quadrajet with parts recommended and supplied by Cliff. The kit included 77 jets and 44 primary metering rods. I have since built a 383 stroker engine (10.3 to 1) to go into the Corvette and I am needing idea's on upgrades to the Quadrajet to meet the increased demand for fuel.
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........forgot to mention the installed DA secondary metering rods.
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What are the rest of the engine specs?
May not need much for tuning, at least for jets and metering rods. Depending on cam and compression ratio might need more idle fuel and bypass air.....Cliff
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383 stroker engine is 10.3 to 1 cr, camshaft is hydraulic flat tappet 279/289 with 225 and 235 @.050 duration, lifts are .465 and .470, factory vortec heads, aluminum dual plane intake, hei ignition, Hooker ceramic coated headers with 1 5/8 primary tubes and 2.5 inch true dual exhaust with Magnaflow mufflers, th350 trans and 10 inch converter with flash stall of 3200 and with factory 3.08 rear gears. I am also using the factory style snorkel air cleaner assembly for fresh air intake.
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Who made the camshaft and what is the LSA?
That is a lot of converter for 3.08 gearing, hopefully it is a custom built piece with very efficient characteristics above and below the stall speed......Cliff
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Believe he has a Howards cam: http://www.competitionproducts.com/Howards-Cams-Hydraulic-Flat-Tappet-Camshaft-Chevrolet-SB-225_235-050-465_470-110-LS/productinfo/112581-10/#.WZyDMSiGPIU
LSA is 110 degrees.
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It is a custom convertor built by PTC and it's spec'd by Kenny Ford himself. You are correct, it is a Howards cam with 110 LSA.
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I've heard PTC makes good converters but haven't ever used one here.
We have been selling converters for over 20 years, all built to custom specifications. We used Continental until they went out of business last year, and are now using TSP converters.
Not familiar with that camshaft so can't comment on it. I typically shy away from tight LSA for street engines due to increased overlap, degraded idle quality, stinky exhaust, and increased dynamic compression lower in the rpm range.
Some folks use them with decent success, but we build, dyno, street and track test most of our engines here and the wider we go with LSA the better the results have been. I know this goes against the grain a bit as most cam manufacturers use and recommend tight LSA.
I think is done more for the "bling" factor than anything else, as most folks want to hear some "lope" in the exhaust at idle speed instead of having it sound like a tractor engine......FWIW.....Cliff
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I went with a 110 LSA when almost all were recommending a 108 so I'm am a bit surprised to get a nod towards a 112 LSA or wider. Overlap with the 110 is 64 degrees.
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Mine is 107 in my 421, doesn't idle too bad.
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I get more complaints here to the shop for "tight" lsa cams than any other.
The very worst are from the Thumper and Mutha-Thumper cams currently being sold. The Comp XE cams get the second most complaints.
I also tune for a living, and we've had scores of folks bring their vehicles up here to custom tune. I've not to date been the first bit impressed anyplace with those cams when it comes to engine power and vehicle performance.
They sure do sound like they are going to get it done, but don't make the grade. Matter of fact we've had quite a few customers remove them and make a better choice, after getting tired of dealing with the stinky exhaust, poor idle quality, and lackluster performance......FWIW...
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I now have the engine in and the initial break in is complete. It will not idle on its on even with the accelerator idle adjustment all the way the in. Can I drill holes in the throttle blades with this 17056206 and rectify this problem? If not, how do I go about modifying idle fuel and bypass air? Thanks!
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First gotta ask how much initial timing do you have?
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You don't need to drill holes in the throttle blades as the Quadrajet carbs have this nice feature called Idle air bypass which does the same thing.
So if you feel you would need to increase throttle opening for more idle air, just enlarge the holes you already have, which you can see on page 29 of Cliff's book.
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I have the book and I am a bit unclear on this but if I can drill the holes in the butterfly's and get the same result as tearing the carb down and enlarging holes then why not just drill the butterfly's?
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With holes in the plates you're passing more air through the venturis & increasing chance for nozzle drip. Either way you are going to need to richen the idle circuit.
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what Cruiser said.
Holley guys can get away with drilling the plates because their boosters are not as sensitive as Q-jets.
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First gotta ask how much initial timing do you have?
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I've now got her idling but I'm getting a surge. Initial timing is at 17.
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With holes in the plates you're passing more air through the venturis & increasing chance for nozzle drip. Either way you are going to need to richen the idle circuit.
I have Cliff's book and I read why but I'm unclear of how to richen the idle circuit. Could you explain it?
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I have Cliff's book and I read why but I'm unclear of how to richen the idle circuit. Could you explain it?
Please disregard. I found the info in Ch. 6. I must admit I'm nervous about this mod and messing up a decent carb.
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Once you get the idle tubes out it's a piece of cake. Do you have a set of small numbered drill bits?
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Once you get the idle tubes out it's a piece of cake. Do you have a set of small numbered drill bits?
No. Where did you get yours? One other question if I may? Would it be possible to cure this idle problem by backing out the idle mixture screws a little? Thanks!
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Got mine here.
https://www.mcmaster.com/#drill-bits/=1994gik
This looks to be a good source too.
http://www.micromark.com/mini-hand-tools/drill-bits-pin-vises
http://www.micromark.com/20-piece-Drill-Bit-Set-41-60
http://www.micromark.com/20-piece-Micro-Size-Drill-Bit-Set-with-Index-61-80
You'll need to buy both sets to get the range you need, unless someone else has a better source.
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Thanks!
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To my surprise I was able to get the quadrajet to idle consistently by adjusting the idle mixture screws. Later on and after the total break in is complete I will really get into the secondaries and see how it goes.
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Drilling the plates could bend the throttle shaft if not careful. All the quadrajets I have seen, maybe 10, have had the body and top cover already set up with the bypass air channels cast in and open. The only thing you really need to do is pull the baseplate and drill the 2 holes out in the proper spot. I would refer to which recipe you are using, and start out on the smaller side of the hole. Once you do this, you could go larger if needed without pulling the base plate.
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I bought one set of my drill bits from Granger. Then hobby town for the smaller ones. Fastenal and Tacoma screw when I'm looking for exact sizes.
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The factory set-up on that carb would not delivery nearly enough idle fuel for that engine combination, even if you thru a ton of timing at it at idle speed it wouldn't have enough. Take a gander into the carb when it's idling as see if there is any fuel coming off the boosters (nozzle drip), and NEVER drill the throttle plates for bypass air especially from below with the baseplate still on the carburetor......Cliff
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To my surprise I was able to get the quadrajet to idle consistently by adjusting the idle mixture screws. Later on and after the total break in is complete I will really get into the secondaries and see how it goes.
Along with the idle issue resolved this engine is everything I had hoped for. Good vacuum for power brakes, not too lopey of a cam to run a/c, and runs very strong. Thanks to all for the recommendations and your sharing of experiences!