17056228 First Test

[blazer74]

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   

[Cliff Ruggles]

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

[blazer74]

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

[Cliff Ruggles]

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

[blazer74]

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

[blazer74]

Try the punch trick and reduce hole size,  try different pump?   Seems to be what I'm finding in search.


Craig

[Cliff Ruggles]

I would lean it up some in lieu of trying to reduce accl pump shot......Cliff

[blazer74]

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

[Cliff Ruggles]

Idle bypass air, amount of fuel available to the engine via the mixture screws, etc.....Cliff

[blazer74]

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.

[blazer74]

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

[blazer74]

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

[Cliff Ruggles]

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

[blazer74]

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

[Cliff Ruggles]

Check to see if the throttle plate on that side is open further, or not seated as well as the other side.....Cliff