Cliff's Quadrajet Parts and Rebuild Kits
Quadrajet Problem Solving => Dialing in your rebuilt Quadrajet carburetor => Topic started by: spluhar on September 23, 2014, 10:10:40 AM
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@ 4000 rpm, the carb lays down. It actually seems to be running out of breath before that, and by 4200 its all over. It's a 71 429 Ford, 10-1 compression, ported heads, 216/224 @.050, 519/513 lift cam, and Performer intake, stock exhaust manifolds into 2.5 duals w/ x pipe. Fuel pump is a Carter Muscle Car mechanical w/ 45 gph @ 5.5-6.5 psi., 3/8" rubber hose routed smoothly to the carb, 5/16" stock steel lines from the tank. I took off an Edelbrock 1407 750, which pulled strongly up over 5000 rpm, and I had a fuel pressure regulator on it set lower than it should have been (took that off).
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Certainly fuel delivery related. Pretty small fuel lines for that power level, as a 5/16" line is only 1/4" diameter on the inside.
Rubber hose on the pressure side is NEVER a good idea, it soaks up heat and can cause all sorts of running issues, not to mention leaks and fires, etc.....Cliff
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What size seat on the fuel inlet?
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Certainly fuel delivery related. Pretty small fuel lines for that power level, as a 5/16" line is only 1/4" diameter on the inside.
Rubber hose on the pressure side is NEVER a good idea, it soaks up heat and can cause all sorts of running issues, not to mention leaks and fires, etc.....Cliff
Small fuel line fed the edelbrock at this level w/ no problem. I'll change out the rubber once this is figured out
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What size seat on the fuel inlet?
.135
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Pretty small fuel lines for that power level
It's slightly warmer than stock. Mild cam, cleaned up exhaust ports, stock valves, regular performer manifold, no headers.
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Just double checked fuel hard lines: 3/8" (stock).
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older car?new fuel tank?my 72 ltd is set up real close to your setup. 9.7cr, perfomer intake ,isky 262 cam,17059212 carb . can't remember the spec id have to dig them out . car makes about 400 hp and 420 torque,pulled 5500 and then falls off . my cams only good for about 5500. my biggest problem was crud in the fuel tank . put on a new tank and problem gone . it kept plugging my fuel filter.all the lines are stock also the exhaust manifolds into the original y pipe connected to 3 in muffler and 3 1/2 tailpipe . i used a water pipe off a large haul truck that i had laying around.
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Small fuel line fed the edelbrock at this level w/ no problem. I'll change out the rubber once this is figured out
I'll bet you sucked to bowls pretty low in the E-carb as well.
The fuel delivery system needs to be adequate for the power level.
If you have installed a .135" fuel inlet seat and correct float setting, and are sucking the bowl dry, the fuel pump/lines/pick-up etc is pretty inadequate or restrictive.
I feed almost 600hp with a .135" fuel inlet seat at 7 psi with zero issues anyplace. Even with that said, I fought fuel delivery issues for years until I went with a good system to keep the carb full on hard runs. I even tried a Holley carb at one point, and the larger fuel bowls didn't help at all. They engine still "laid down" just past 5000rpm's, I went about 10' further with the Holley carb in place and it started to do the same thing it did with the q-jet.
I upgraded the fuel delivery system, and the car picked up nearly half a second at the track and 4 more MPH with no other changes, and with both carburetors.......FWIW.....Cliff
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I upgraded the fuel delivery system
To what? What do you recommend at this level? I'm on a tight budget and the car is daily driven, btw.
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That may not be enough pump, you might have to get something a bit bigger.
Maybe in the 100 gph range.
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45gph is 1 mpg @ 45 mph. That's not enough? 5/16" id (.3125) (3/8" fuel line) is waaaaay bigger than .135 seat size.
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The pumps are rated at free flow, so under 5-6 lbs. pressure they don't put out that much flow.
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spluhar did you ever get your problem figured out? what kind of rig is this in ? just curious.
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No, haven't dealt w/ it. I have a hard time spending another $130 on a $20 ebay carb. A new fuel pump may not even eliminate the problem.
It's a 76 Ford Elite. 1971 429 w/ ported stock valve heads and a mild cam. 3:25 rear, cast iron manifolds, c6 trans.
What did Ford do w/ the 429cj? What did Buick do w/ the GS455? Mine isn't that far off of these notable qjet cars.
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some thing doesn't make sense.my engine is real similar . my gear ratio is 2.75 i know its to tall what rpm are you running at 75mph?im asking cause i want to change gears.im looking for about 3000 at 65. anyway back to the problem. I'm only running the over the counter napa stock fuel pump i think it was 30.00 I'm thinking ether the float is to low or your needles are'nt coming up.what size needles and jets do you have ?i believe i have 73 jets with 52 rods . id have to dig out my specs to be sure. fwiw
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forgot to mention found a site that says a stock 429cj with/auto came with 72 jets and 50b rods hth
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just thought thought of something . i think thats about the year they changed primary rod length.fwiw
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My engine is not a CJ. My carb is off of a 75 Chevy pick up. I called Cliff and ordered a "kit". He spec'd it out. It came complete. It included a larger needle/seat. I'm going to try to add a little more float level, as it seems (after driving it for a while) to be running out of fuel often.
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my gear ratio is 2.75 i know its to tall what rpm are you running at 75mph?im asking cause i want to change gears.im looking for about 3000 at 65.
3300 is 80mpg (about). I love the 3.25's. That's with a 28" tall tire.
http://www.wallaceracing.com/gear-speed.php
That is a gear ratio/mph calculator link. Don't forget that you'll get some slippage through the auto trans.
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thanks thats what i needed . i need to slow mine down . i had it wound tight about 5500 last week and thats a little fast for my old car .mine does not run out of gas it pulls all the way.its setup almost the same as yours. i don't like 75 or76 carbs.i only like 77 0r newer . the 75or6 had the apt in the left front corner standing in front.yes you can plug it but to me its not worth messing with.fwiw
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what do you have?
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i have a 17058212 and a 17059212 one on myltd 429 set up like yours and one on a 1979 ford f250 460 the ltd has the edelbrock intake i believe its the 7166 the pickup has the old cast iron manifold with a spacer . i will get rid of the spacer when i change intakes . i will not plug the exhaust crossover next time its causes me problem when its real cold and you let it sit for 15 minutes or so it cools off to fast. fwiw.
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What type of fuel pump do you have?
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it will take me a day or so to answer you. its below zero and covered in snow and i don't feel like digging it out . ha getting lazy in my older years. i think its an ac. i just went to napa and told them to give me a pump . nothing special just over the counter.ill try get back to you monday sometime.
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the napa part no. is m60036 he said its made by MPE 6.5-8 psi 30gph my cost 26.49 if you do a little searching i see carter has the same part no.m60036. hth
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Just for the Halibut. Have you tried running it with a fuel pressure tester hooked up. When the power goes away does it just fall flat or are there any symptoms like stumbling, backfiring, ............ Your sure the secondary's are opening and the rest of your linkage is operating correctly. (I know the E-brock performer intake is basically an aluminum version of a stock cast iron intake designed for 2v to 4v carb swaps) and is great for engines that did not come with or is very hard to find a factory 4v intake for. Having said that they are not always plug & play. Things like the throttle cable and bracket might bolt up but depending on the carb used may not function correctly. Especially if the car was equipped with a 2v carb from the factory ( I know you said you were using an E-brock AFB but that also might be different enough to cause a linkage issue with the Q-jet)
Engine off, air cleaner off. Have someone press the pedal down to the floor and look at the carb now remove the throttle cable and by hand open it up does the carb linkage keep moving if so then your throttle cable is not opening the carb fully.
I'm guessing at this point you have already tried pulling the fuel line off (both ends) and blowing it out. Also if there are rubber lines like from the sending unit/tank to the steel like that runs down the frame (factory type connections) see if they are cracked, brittle............... There is always the chance it could be sucking air. Or if your running a lot of rubber hose it could also be collapsing somewhere or crimped enough that the problem only shows up under load higher RPM's.
BBF after market intakes are square bore are you using the special gold colored adapter from E-brock with gasket top and bottom. The adapter they say to use when running a Q-jet on any of there non GM. dual plane intakes.
Just some food for thought (These are the phrases used when you over 40')
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I just thought of something else to try. Does it only do this under load or will it do it in park as well. if it does bypass the entire fuel delivery system by using a gas can (a marine gas tank works good) and a length of fuel line. Start it up and run it up over 4000 RPM What happens. Problem goes away focus on tank, lines.............. if problem is still there then your left with the carb.
As far as the Buick GS 455 they used a high capacity pump (long body) but for non GS 455's like a 455 in a 225 or wagon................ they used off the shell GM pumps. If you look at what came out of the factory back then early/mid 60's big blocks with 2x4's 3x2's cross rams...............they weren't running race pumps.
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Have not used fuel pressure gauge while driving. After 2 or 3 seconds of wot, it starts stumbling.
Secondarys are opening fine, I can feel them as there's a point where the end of the primaries where the secondary linkage needs a bit more foot to swing them open. Linkage is adjusted properly, am using the bracket off of the 2bbl 400 and a custom 2 hole 2 piece spacer to adapt the carb. I didn't want an open spacer due to the weaker vacuum signal, and a 4 hole was too shallow, with not a smooth transition from spread to square. I haven't blown down the fuel lines yet, but I just put in a new pick up and sending unit, a few months before I switched carbs.
I would not attempt to bring my engine up to 4000 rpm w/ no load. Too many things can go wrong. I've personally had engine component problems (when I was young and stupid) from revving engine w/ no load (possibly broken piston or ring, no compression and severe oil blow-by), and was close by my buddy when his fan blade broke off while revving engine in the driveway.
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Update. I hadn't run my car hard for a bit. I've changed out the in-carb filter for the in-line filter that I had on previously. I got on it the other day and it ran hard up to 5k w/ no hesitation.
I had the opportunity to go on a longer trip last week. 67 mile round trip, 80 mph the whole way (3200 rpm), on 4 gallons of super. 16 mpg average w/ a big block, 4500lb brick, running pretty hard.
The article that convinced me to try the Quadrajet was in CarCraft 08/01. I bought the carb in 07. I bought the kit in 2010. Now it's on and it works as planned!
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its nice to here when somebody gets there problem solved. thanks for the gear ratio post. I'm going to put in 3.25 that should be about perfect. as far as mileage my rig has to be run above 80 plus to get good milage about 16 above 80 .i only get 11-12 at 65 because my engine combo doesn't start to work till after 3000 rpm.