Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: blazer74 on April 05, 2011, 08:16:13 PM
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Hello. Just completed rebuild on 17056228 large primary bore and mods using recipe #1.
Used Cliffs S/R kit + 2ndary spring and cam kit, rebushed primarys, Small notches in 2ndary flaps for Poe. Bushed main air bleeds to .070 airhorn and body from .120
Idle tubes .036
Channel restrictions replaced to .047, previous .055. Slightly larger than recipe calls for but thats the size the replacements were, driven in slightly below main bleeds
Upper Idle bleeds .069, lowers .076
Bypass air .080, Acc pump disc holes .026
Poe Wells .039, Poe Discharge holes .052, 2ndary bleed tubes .036
Green power piston spring, 1/4 float level
Cliffs 44 Primary rods, 72 jets, K hanger and CH rods. Pulloff at 2 seconds.
Mix holes .089
On first start up after warm up Idled slightly ruff (Choke completely off). Had to adjust mixture out 5 + turns min to get 14hg and a better idle, peformed Tip In (2000rpm) and had to adjust ADP up 5 turns to get slight rpm increase, after 5 1/2 to six turns no increase and less than 5 turns out get larger increase. Do not get rpm increase when removing small vac line.
Idles at 700, 650 in drive. Has a slight stumble off idle with light or hard throttle input, Acc pump shot is immediate and strong. Exhaust stinks, Runs strong otherwise, no hesitation at cruise, smooth transition to secondarys with a slight bog when open with spring at 3/4 turn. Had to put truck away and go to work.
Note: If ADP is less than 4 turns out will get lean pop when snapping throttle.
Idle is just slightly rough and stinks bad. Power piston is down at idle and 2ndarys closed tight. No apparent vac leaks.
Suggestions? Larger jets?
Thanks Craig
74 Blazer 355, 292 adv 214@50 449 lift, 111 lsa. Performer intake, stock 882 heads, flat top pistons.
Headers and dual exhaust 2 1/4. 2000 stall, 4:10 gears 35" tires. Timing 10 initial. stock vac adv can, Hei distributor
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I slight stumble at light throttle is usually part throttle fuel to lean. Raise the APT a tad more and it should correct that problem. If not, go up one jet size and test it again.
Always set the idle mixture screws for the best idle quality at the leanest settings. This is done by turning them in until you get a slight drop in engine rpm's, then back them out about 1/2 to 3/4 turns.....Cliff
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Thanks for the reply Cliff. Figured as much with larger jets, I had 73 jets in it at first but opted to 72 before I installed the carb. One of those unwritten rules first instinct. Going to swap jets and see what happens. Never had to turn mix or adp out this far before.
Thanks again for your time, Craig
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Nothing at all wrong with running the APT our 4-5 turns (or more) to fine tune the primary part throttle A/F.
All that means is that the metering rods have LESS distance to travel when more power is called for (vacuum falls off sharply)......Cliff
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Hey Cliff, Progress. No help raising apt , went with the 73 jets no help with stumble. It did give me NO control of apt during tip in. So I disconnect acc pump and problem gone, tried outer hole and a little better but too much pump shot. Mix still about 5 1/2 turns out and can kill engine with needles turned in as the same with the 72 jets.
What do I do about too much pump shot, Holes are at .026, and should I go back to the 72 jets also?
Thaannkks! Craig
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Try the punch trick and reduce hole size, try different pump? Seems to be what I'm finding in search.
Craig
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I would lean it up some in lieu of trying to reduce accl pump shot......Cliff
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Ok, Will try smaller jets. Off subject question, what would cause one carb to produce 14 hg at idle and another to cause 15 hg at idle same engine and idle rpm? Craig
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Idle bypass air, amount of fuel available to the engine via the mixture screws, etc.....Cliff
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Ok, Finally got back to carb. dropped down to 70 jets with all else remaining the same. This took care of too much pump shot. apt at 5 turns out with tip in. noticed that any less than that also lowers rpm speed during tip in and at idle speed. Mix is 5.5 turns out, less than 5 idle drops, more than 6 no change. Have slightly unstable and rough idle which I didnt have before I bushed the main air bleeds, acts like it has more camshaft in it than it does. lightly black tailpipes after driving a few times. Cant get as much idle vacuum or smooth idle with this carb vs my other carb 17057204 (large Mains) 77/52k other wise set up the same (stage 1). Did not check for nozzle drip. otherwise runs good. Idle will smooth some when closing choke to about 1/4 open. I have no vacuum leaks, ported dist vacuum. Pulling vacuum line of makes no noticeable change.
70/ Cliffs 44 rods
80 bypass air
036 tubes
047 channels
800 carb
main air bleeds 070
lower air bleeds 076 upper idle bleeds 069
base plate re-bushed. 089 mix holes
What do you think? Thanks Craig.
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Also, Do you Have any 48k rods laying around for my 17057204 carb, 52k too much with 77 jets. I have to turn apt way out past spring tension to get rid of hesitation and to get tip in correct.
Thanks Craig
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OK, found i had nozzle drip on passenger side, turning in mix screw stopped it but makes mix to lean. Swapped from ported to full vacuum, backed out idle screw and readjusted mix to 4.5 turns out. Smooth idle no drip. Good news, but there's always a twist. If the truck sits after about 15 minutes after running it will not start unless pedal held wide open. Pumping pedal doesn't work, Swell.
Craig
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I'll have to look for 48K metering rods, might have some used ones in spare parts? I don't use they "K" series rods as they limit the control with the APT within a .005" range.....Cliff
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Hello, been messing with this carb off and on and still not right. currently have 72/44 combo, apt 4.5 turns, mix turns 5. Getting nozzle drip on the passenger side at low step of fast idle cam , getting black smoke when stabbing throttle and tailpipes lightly sooty. passenger side likes about a turn less on the mix for same result as other side. And slight hesitation off idle. I believe the nozzle drip is causing stumble of Idle. Otherwise runs good. Suggestions? Had nozzle drip prior on passenger side and went to straigt vac to distributer and back out idle screw, thougt I cured it but.
Thanks Craig
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Check to see if the throttle plate on that side is open further, or not seated as well as the other side.....Cliff
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Will do, Thanks
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Hello, Checked the primary throttle plates and they close fine. Tried another throttle body I have that is set up the same and still have nozzle drip if I use ported vacuum. Go back to straight vacuum and can stop nozzle drip. Drip starts on passenger side and drivers side drips just after that.
Using straight vac, 6 turns idle screws, 2 turns apt 72 jets, cliffs 44 rods, acc pump outer hole. idle 800 park, 650 drive, vac 14.5, 10 deg initial.
Now runs good, no stumble, pulls hard thru secondarys. Does still have some sooting of tailpipes and some black smoke . Going to try 71 jets and see what happens.? Also added edelbrock 3/4 wood spacer and helps with heat soak but didn't notice any other change.
Thanks Craig.
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Good news. Going back over the basic engine combination, the cam is a tad much for the "low" compression 355, and ground on a 111LSA.
882 heads are poor performing heads, with very restrictive exhaust ports, and huge combustion chambers. Even with the flat top pistons the static compression ratio is probably around 8.5 to 1.
A set of Vortec or SR Torquer heads would be a BIG wake up call for the engine. It would idle better, less timing needed everyplace, and more power at every rpm.
I've ran into what you are going thru a few times. Takes some effort to get everything dialed in, and often we are chasing the fuel and timing curves around quite a bit to make the engine happy.....Cliff
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Hey Cliff, thanks for going back over my info again. definitely agree on the heads, and step down to about a comp 268H cam. I need to pull a head a take some piston measurements to truly see what size cc head I need to get to about 9.1 due to not having specs on my current pistons (older trw's) Too hot right now for that with this 100 deg weather. But then again maybe its time to build a 383 or 400.
Thanks again Cliff for your input. invaluable!
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I'd stay away from any cam on a 110 or tighter LSA. There are some EXCELLENT cam choices out there for SBC's. I still have to this day to find a better cam for a 355cid engine with about 10 to 1 compression than the old 327/350hp cam. It has 222/222/114 specs, over 300 degrees of seat to seat timing. Idles pretty good, strong power from the moment you load the engine till you decide to shift it!
There are a couple of Melling cams that work just as good, with similiar specifications. The 280 duration .480" lift on 112LSA is a good one as well. These cams need at least 10 to 1 compression to be happy, but will lower the dynamic compression enough to use pump gas without any issues.
Another very good choice, is the GM LT4 Hot roller camshaft. It's a nice upgrade, and will produce over 1hp per cid with a good set of heads on a 350 engine.....Cliff
http://www.jegs.com/i/GM-Performance/809/24502586/10002/-1?parentProductId=761656
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Hello, Made some upgrades, Vortec 64cc head\intake setup from scoggins. Changed cam to Comps 268HE 218/454/110. Made a large difference in performance. Puts me just under 9:1 comp with pistons .040 in the hole.
Quadrajet 17056228 minor changes.
Basic Recipe 1
72/44cliffs
Idle tubes .035
Icr .047
Upper Mains .070 bushed
upper idle bleeds .069
Lower idle bleeds .076
Bypass air .086
Acc pump .026
Poe Disch .052
Air valve 3/4 turn/ with small notches in upper 2ndary blades
Adp 4.5
Mix 4.5
1.5" Edl wood spacer
Runs great except for hot start issue. Fuel seeping out of primary venturi nozzles and air bleeds after shut down requiring WOT to start after about 10 min. Seems like fuel is rising in bowl after shutdown.
Need to check a few things Cliff recomended. Fuel pressure, Inlet side leak. Well plugs.
Will get back with results. Thanks Craig.
1974 K5 Blazer 355 sbc
Vortec setup
Comp 268HE
Headers, dual 2 1/4 exhaust
35's 4:10 gears
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Checked fuel pressure at inlet to carb. Found to be between 7-8 psi while running.
After shut down with fully warmed engine fuel pressure holds steady and then slowly rises after
aprox 10 minutes 9 psi, 15 minutes 9.5, 20 min 10 psi, using inline gauge non liquid filled. Heat soak at gauge could be a factor.
Restart fuel pressure goes back to 7-8 psi. After sitting 2 hours starts fine.
After approx ten minutes can see fuel in upper main bleeds and venturi nozzles.
Starts rough after about 5-10 min and hard to start after about 10-15 minutes.
Stock fuel pump typical 70987 2 lines.
Seems about right or just a little high for fuel pressure running.
Thanks Craig
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7-8 psi is fine for later carburetors. As long as the gauge holds pressure hot, it shouldn't be flooding, and how much fuel can be in the line after shut down under pressure that would make it's way into the carb and flood the engine. One would think if the pressure built up, and pushed the needle off the seat, the pressure would go down quickly?....Cliff
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Changed the fuel pump to edelbrock street pump. Puts out 5-6 psi. I don't have the hot start problem with this fuel pump. Pressure also drops off also after a few minutes of shut down. Seems the stock pump was holding pressure after shut down and was increasing with heat soak in the lines upward of 10psi. I also bypassed the stock metal fuel line on the block.
I think fuel was creeping past needle just enough to cause fuel to raise in carb just enough to allow fuel to drip and not showing on gauge do to heat soak, sounds good anyway.
It still does idle very low when started warm until given just a little throttle, but starts easy.
Going to go back thru the carb and install bottom plugs, replace and vac test needle/seat etc.
Going to open idle tube from .035 to .036 as per stage 1 of Cliffs book.
(Do you think .086 bypass air is a little too much or ok for a 268adv 218@50 cam?)
Thanks; Craig
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Should be fine....Cliff
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Went back thru the carb, installed bottom plug kit/with marine epoxy. Replaced needle/seat and vacuum tested. opened up idle tubes to .036 from .035 and installed Cliff's .044 2nd rods. Still using Cliffs .044 primary rods and 72 jets with dark power spring.
Seems to be a little less crisp of idle, but only drove it once could just be me, got caught in rain with full convertible blazer ( was fun tho). Going to readjust mix etc. Have not driven long enough to judge hot start issues which is considerably better with new fuel pump.
Thanks Craig
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Went for a run today, ended up turning mix in total of 1 turn and made big difference after opening idle tube from 035 to 036. Will see how it is cold next run.
Question about apt and mixture, relationship between the two. Should adjusting apt lower affect mixture? I've had stumble off idle in the past when apt adjusted too low. If I turn apt lower say 1 turn should I have to readjust mixture? Just a thought. Also went from CH 2nd rods to Cliffs .044 rods, Could be a tad to much on the 2ndarys. Think the CH rods are .054 tips.
Thanks Craig
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Lowering the APT leans up the primary side at light throttle only. It may develope a hesitation/stumble if you get them too low (lean).....Cliff
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Wow been 3 months, Had some issues with wide open throttle, popping and breaking up. Replaced needle/seat and float again, cured most of the problem but had to go 1 full turn on 2nd spring ( new spring). Seems to have cured that. Still have a little hot start issue, have to give it a little gas while cranking but not hard to start like it was. Did have the float every where from 1/4 to 15/32. 3/8 seems to work the best for me.
Ended up with 4 turns ADP, could probably go a little less.
3 turns mix
72 jets, Cliffs primary and 2nd rods
Set up with recipe 1
Thanks again: Cliff ;D
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WOT problems are usually fuel delivery related, or ignition. Takes a pretty good fuel pump to keep up with a strong running engine.
Glad things are going well.....Cliff
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on trucks from 73-87 and blazers fuels lines are close to the headers (unless there TBI) and on shutdown the heat under hood combined with heat from the headers can cause the fuel to boil and push into the carb then causing flooding and the need for WOT this has happened to me with 4 different trucks this era. make a heatshield for the fuel line or run a pump with a return if you can has fixed this for me all 4 times eather way works good
somethin you might want to check. GL
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Thanks for your input Zac, Have all that covered, Fuel lines rerouted using fuel injection hose, Edl 1.5" wood spacer, Edl fuel pump that bleeds off pretty quick after shutdown. The fuel pump was the best help so far.
Thanks Craig