Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Diagnose a Quadrajet carburetor problem => Topic started by: canadian nascar on July 24, 2010, 01:22:21 PM
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Hi Cliff,
i had my 301t built 8.5 comp, 262comp cam, roller rocker vt. i am having trouble getting it to idle, it will for awhile in park the it dies off and won't idle in drive. the exhaust is very smelly
i called you, Cliff the other day and you told me that my ilde tubes and channels are to restictive. can i just remove, then drill them out? or should i buy them?
you told me to look at the upper end of ilde mod reicipe #2
also i bought #77 jets in it and it runs good, but was wondering if they are enough and maybe should try some bigger ones?
thanks kevin
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the carb was rebuilt last year
thanks kevin
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The main jets have no effect on idle quality.
In most cases the idle tubes can be removed and re-used. If not, we have new ones available.....Cliff
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thanks for your help Cliff,
will do some disecting this week. i now understand if i do need mure fuel to use the APT screw during part thottle instead of changing jets.
kevin
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Correct, the APT screw raises the height of the metering rods. This only increases fuel delivery at part throttle/high vacuum. Fuel delivery at heavy/full throttle remains the same....Cliff
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Hi Cliff,
with the APT screw in is rich out is lean. I would like to know is for every full turn in how much of a jet size might i be increasing? or is it not known?
thanks kevin
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Hi Cliff,
read abit closer and understand the apt raises the rods not creating larger jets.
i was talking to a fellow 301t and he has 110 needle and seat are these avalible? and also you made a pair of secondary rods last year for me like dx rods but he is running ay rods which are richer?
removed my idle tubes and drilled them, the recipe you offered was #2 i didnt find .038 drill bit but found a .042 and tried it and it seems fine. it idles now in park and almost in gear, i just have to adjust the idle speed and screws abit more.
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We have .110" seats, .125's, .130's, .135's, .145's and .149's.
We also sell new idle tubes in any size you would want....Cliff
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Hi Cliff,
if the local boys can get me .145 needle seat will this give me any problems or should it be more application specific?
i am trying to learn how to make sure the secondaries are opening all the way. i have read from your book that emisson carbs like like mine are restrictive. so i might have some questions on that one.
thankyou kevin
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hi Cliff,
i am looking to open up the secondaries as i have some pinging and want to make sure i am getting all the fuel i can.
could you lead me the right way,
k hanger, custom dx and 77 in the primaries.
can run 5-6 lbs with gas only, did a test with water meth off, normally run 12lbs with water meth injection
thanks kevin
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Detonation on turbo engines is NOT a good thing.
You may need to pull out some timing as more boost is added.
How did you end up with .077" main jets, those are HUGE for that carburetor?
The only time you need a large needle seat assembly is when you aren't able to keep the carb full on hard runs. Sometimes a better fuel delivery system is needed, in lieu of a larger inlet seat.
I would doubt the little 301 would require a large needle/seat assembly, and is probably fine with a stock fuel pump/lines, etc.
Is there any evidence of running out of fuel on hard runs?.....Cliff
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Hi Cliff,
i purchased a sr kit, idle tubes, extra gaskets but air bleeds were sent with my package instead of the channel tubes for my 301t, do i reorder them channel tubes or don't worry about it?
should i put these recipie 2 air bleeds in or not?
i hope you have enough info on this post.
also stock came with 71 jets and i just bought 75 and 77 jets, tried them and 77s seem to be fine. doesn't flood or anything.
kevin
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Idle downchannel restrictions and the main airbleed restrictions are the same part.....Cliff
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thanks again
kevin
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The airbleeds (idle downchannel restrictions) have a very small hole in them, apprx .045", unless we pre-drill them.
They can be used at either location, for upper-lower main airbleeds, or for idle down-channel restrictions.....Cliff
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Hi,
so i put in the new accel pump, .135 needle and seat and took out the #77 jets and put back the stock #70s. now the response is good crusining but as soon as i put the throttle down it hesitates 2-4 seconds and is fine there up. what do i do?
i am thinking i should try and put the #75 jets in to see what that will do?
the idle is excellent now
thankyou kevin
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i am working from recipe # 2 as instructed by Cliff
kevin
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Describe "put the throttle down"? Going to full throttle from a standing stop, part throttle, heavy part throttle without the secondaries, etc?.....Cliff
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Hi
going full throttle at any position, did some reading and tried adj. the secondary a/v spring tension and that fixed the problem.
tightend the screw 1/4 turn from where it was.
thankyou kevin
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Good news, and one of the best features of the Q-jet....FULLY adjustable for secondary airflap opening rate, without taking the carb apart!.......Cliff
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Hi Cliff,
I am running #73 jets in the primary as called for in recipe #2, do you think they will be fine?
I have rich at idle because i was screwing around with the APT and I lost where i was which way do i turn the APT screw to lean out idle, light throttle.
thankyou Kevin
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Clockwise lowers the metering rods and leans it up....Cliff
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Hi Cliff,
Well sir over the course I have finally have this this running great according to the wideband, it is a little rich at 10.5 though.
73's and the apt 2.5 turns up
This weekend I am going to install a modified turbo housings that is now a te-62,
thanks for all your help and parts that I have purchased from you
later Kevin
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More air will help it as far as A/F ratio. Let us know how it works?....Cliff
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How do I get more air ?
I thought I would have to change the secondary rods.
Kevin
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The modified turbo housing should increase air flow to the engine, more air and more boost, etc....Cliff
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Hi Cliff,
So just put more boost, that's what you mean?
I thought there was a way to do it via the carb, opening the secondary flaps more.
Kevin
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One good thing,
the cruising a/f was 12 with the old turbo then went to 16a/f at cruising with the new, turned the apt 1/2 a turn and put it back to 12.. nice
Kevin
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HI Cliff,
I called you last week about my wot a/f of 10 , could you expain again how to get more air via the secondary enrichment tubes.
to what I see there are 4 brass tubes attached to the air horn that slide into the main body which are the ones you mean? and going from 36-40 that means what.
thanks Kevin
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Hi Cliff,
I am sorry but you told me that the float height and fuel pressure will affect the a/f also, I did some searches but couldn't find an explaination on these issues,?
my float height is 1/4'' and the pressure is 7psi
thankyou sir Kevin
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The long thin tubes are secondary air, the outer tubes are POE.
Fuel level in the bowl has an impact on how much fuel is metered with any particular fuel pressure and fuel inlet seat diameter......Cliff
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Hi Cliff,
I know which tubes you mean, so I will drill out the tip .036-.040. correct. to change the a/f at wot.?
thanks again Kevin
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Opening them up will have a minor effect on full throtte A/F, as it adds more emulsion air to the incoming fuel.....Cliff
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Hi Guys,
trying to launch from a stand still.
my car has a 2500 stall but is at 0 boost vacumm at 2100rpm foot braking and wot, i can hold the car to 2500rpm. at 2500 i have 3-4 lbs of boost but it will run on the primaries untill 3000 rpm then the secondaries come on but my 0-60ft is 4secs.
how do i get the secondaries to come in at 2200-2500 rpm?
the secondaries come in hard when they do and rolling at 20mph or higher they come in instantly.
thanks Kevin
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Yikes, 4 seconds is really lagging. Might want to contact some folks who drive and race the turbo 301's. I have no experience here with them, even though I build Pontiac engines and street drive and race my Ventura with a 455 in it......Cliff
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front choke pull off is 5 seconds to fully release, this is some of the problem. how do i adjust this?
thanks Kevin
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I was wondering if all you do is drill out the end that the vacumm line goes on, the larger hole allows more air to return. used as a air flow restrictor?
thanks Kevin
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We sell them already modified, really nice units with the straight inlet for easy access to the restriction......Cliff
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Hi Cliff,
I am getting closer, I recieved the choke pull off 3 seconds and it helped considerably,i can get to the secondaries during a brake stand now.
my next problem is I have a bad lean bog going to the secondaries, this was not a problem withthe old turbo, I have adj the sec. spring tension all over the place till the flaps wouln't open all the way.
I have read Cliff's book and he filed the sec. flaps to allow the secondary accelerator ports fuel to flow better so I did this and opened the ports up. stock size hole was .059 now .070 and still major lean bog with spring tension not helping. and cleaning all ports with brake clean.
How big can I go with the ports?
also the float is 5/16'' as 1/4'' would flood the carb at idle, should I raise it a little more?
thanks Kevin
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Hi,
just read that stock float height is 15/32, is 5/16 too high and causing problems?
thanks Kevin
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also forgot to remention inlet seat .135 fuel pressure 7psi
Kevin
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You should not experience flooding at any setting, if the float and needle/seat are doing there job?
Raising the float simply raises the fuel level, it wouldn't flood unless the float was hitting the gasket or being held down by something as it tries to raise up to seal off the needle....Cliff
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Hi Cliff,
I will try the 1/4'' float level again.
In the previous post I wrote that i have haveing a terrible time trying to get rid of the lean bog, last year it was so easy. I put JB weld in the holes and am going to redrill the holes according to your book.
took it apart again yesterday and the tubes were a little loose so i pulled them and checked for debris, didn't see any thing, put all back together and tried again. still lean bog tighened up the spring some again, anywhere from 1/2 to 1 1/2 tight and still lean bog with .07 POE hole.
Any ideas on how to get rid of it
stock turbo I was able to get rid of it.
later Kevin
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Have you tried shortening the primary accl pump shaft slightly? It may need a bit more fuel from the accl pump.....Cliff
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Hi Cliff,
It's been a while, I have no lean bog now in seat dyno, but the wide band shows one, when I go wot, I took a bit more than a 1/16'' off the accl pump.
I have a bit of smoke when I start the car, rich at idle but wideband shows 17-1 afr, idles starts good. Should I go leaner?
The 5 second 60ft was all fixed with going to a higher stall converter, was told by Buick 3.8turbo guys that I should have a 2800 stall but ends up a 2600 10'' converter. I can really lay a strip now, and if I cruise at 30mph and go wot it will start fishtailing.
Lastly the wot is 10-1afr for a moment then goes to 11.5-1afr. Some more fine tuning is needed but storage will be in a couple weeks.
later Kevin