engine bogging out at 3200
Printed From: CorrectCraftFan.com
Category: Repairs and Maintenance
Forum Name: Engine Repair
Forum Discription: Engine problems and solutions
URL: http://www.CorrectCraftFan.com/forum/forum_posts.asp?TID=2319
Printed Date: November-23-2024 at 2:42am
Topic: engine bogging out at 3200
Posted By: Guests
Subject: engine bogging out at 3200
Date Posted: August-24-2005 at 12:05am
i just rebuilt my 78 350. the problem i'm having is it keeps bogging down on me at 3200rpms. Ive found the sweet spot on my timming and it starts and runs good until i get passed 3200rpms. i have a supposely new quadrajet on it and seems not to have any vacuum leaks? can anybody help me with the problem? when i hit full throttle it boggs completely down. help please ive spent to much money on my engine for it to be doing this.
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Replies:
Posted By: Guests
Date Posted: August-24-2005 at 1:17am
| Sounds like the 4barrel metering rods are not adjusted corectly. You can bend them with a pair of pliers where the curve is. Our quadrajet was the opposite-it would flood out when you went to take off hard. Dont rule out an inadequate fuel problem either. Check fuel pressure/flow to carb. Usually though, a plugged filter/bad pump, etc, would cause it to bogg/die a bit after the 4 barrels open when it uses what fuel is available up. |
Posted By: JEFF KOSTIS
Date Posted: August-24-2005 at 1:24am
------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Jeff Kostis wrote:Posted By: stang72
Date Posted: August-24-2005 at 2:16am
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Jeff...my lake Decatur boating buddy! Swap on that rebuilt carb you have sitting in the garage!
A couple other things I thought of after leaving your house....Check all fuel line fittings and the fuel vent( and line).At higher rmps ,if there is an air leak in a line(even though it's not leaking fuel)It will suck air and not enough fuel passes when you need it the most! Jeff Kostis...makes good suggestions and knows your carb!...I too think your carb is not adjusted properly...and of couse I don't know squat about a quadrajet...so sell both your quadra's and get a Holley so I can pretend to be of some help! 
Please help this pathetic bast--d ,he's spent too much time , energy and cash not to be getting full performance...and he's sooo close! ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: nates78ski
Date Posted: August-24-2005 at 8:47am
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Number one don't bend any rods on a Q-jet. The problem you are having is a lag when the secondaries open. The most common cause is improper ignition timing. There is no "sweet spot in the timing". Adjust the timing with a timing light to 8btdc as a base line. take her out & see what happens. If the problem still exists but is better or worse advance the timing 2 degrees & retest. Do not exceed 12btdc. Also check the total advance @3000 rpm(can be in neutral at the dock), If you are not achieving 32-34 degrees total advance the secondary operation of the carb is effective. This is all because the secondaries on a OEM Holley, or Q- jet, or Carter are controlled by vacuum drop on acceleration. Any change in the timing effects the vacuum to the secondaries at any given point. Too much advance not enough vacuum drop and too little advance to much drop. There are so other minor things with the initial carb adjustments but this is the most commom problem for that 2800-3200 rpm lag. ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: Guests
Date Posted: August-24-2005 at 10:33am
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for nate 78 ski,
will i have to adjust carb when i set it to this timming. i did set it to what it called for in the book which was 8 to 10 advance. when i set it to that it wouldnt start or it would flood. i will try what you told me to. thanx |
Posted By: 79nautique
Date Posted: August-24-2005 at 11:22am
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Set the timing then re-adjust the idle mixture screws located on the front of the carb's base plate. Screw them in slowly one at a time until the idle drops then back it off a quarter of a turn, do the other side then redo both sides again until it is dialed in. Also make sure the choke stat is set correct. There is a notch/boss on the plastic choke stat and a series of raised bumps on the metal housing it is mounted to, the middle bump will be taller than the others that's zero, set it so that it is two notches rich. Also don't worry about bending any rod on a q-jet you have to bend them to get the choke pull off, accel pump, and secondary metering rods set correctly.
Now there has already been some bad advice given regarding your plroblem and adjusting a Q-jet properly. Bending the arm for the secondary metering rods will only open them up sooner and all Q-jet carbs have mechanical secondaries and are not controled by vaccum, open up the throttle fully and you will see the secondaries open up even if the engine is off and there is no vaccum. Also you can adjust the pivot point for the accel pump and effect how much and how soon it operates. I suggest you reset the timing to 8-10 btdc and verify that your total advance @ 3000 rpm is not over 32 degrees first, then re-adjust the idle mixture screw and idle as described above. Next I would check all fuel filters including the one in the carb, you'll need a 5/8 line wrench and 1" open end to do this. and Check fuel pressure as well. Once all of that is done if it doesn't fix the problem you will have to make additional adjustments to the carb and I can help you with it. It sounds like maybe the accel pump is a little agressive and the secondaries could be opening to quickly which is an easy fix. Where are You Located? Decatur, In? or is it in another state? ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: David F
Date Posted: August-24-2005 at 6:33pm
I hate carburetors
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Posted By: JEFF KOSTIS
Date Posted: August-25-2005 at 12:38am
I can say from day 1 with our omc 225 chevy 307 it never ran 100%. It would not take off like a holley did. After taking it to everyone, they said thats normal, put on a Holley. Im no Rochester fan, but after several days of taking it apart and playing around, I finally figured it ran awesome until 4 barrel time. Thats when I got out the pliers and adjusted (re-bent) the secondary metering rods down a bit and kept tweaking them, taking off hard, soft, and using a radar gun for max speed. Ill tell ya, it runs better than my holley on the other boat! The problem was that fuel can leak by the metering rods when the thottle plates are open, but the pull-off is still closed. The 4 barrels are so much smoother sounding no matter what. That baby will do 49 mph fully loaded! I was amazed at the difference. Everyone says not to touch them as they are pre-set, but as awesome as I got this to run, you bet I will do it with others!! I am actually impressed on how good a Rochester can run!  ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: JEFF KOSTIS
Date Posted: August-25-2005 at 12:40am
By the way, I dont know squat about Holleys yet. Just the Rochester!! ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Guests
Date Posted: August-25-2005 at 1:44am
i had to set my timming 15 btdc. i could not do 8 to 12 because it would either not start or flood out. 15 seems to start and run ok except when i hit 3200. i looked at my x-tra carb and it seem like the secondarys will open only at the bottom. when i went to my boat and open up the throttle the sendondary didnt not open at all. it was kind of dark so i have nt done anything except timming. i will try again tommorrow to see if the secondarys are opening. and that would be decatur illinois 79. thanks for the and ill try what you said to do.  
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Posted By: Guests
Date Posted: August-25-2005 at 4:29am
| I bet the whole problem is happening just because I am GAY! |
Posted By: Guests
Date Posted: August-25-2005 at 4:30am
| I bet the whole problem is happening just because I am GAY! |
Posted By: nates78ski
Date Posted: August-25-2005 at 8:51am
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The facts are all these secondaries work by vacuum or lack there of. The choke pull holds off the secondary air vane to richen the mixture as the secondaries open. This allows smooth transition because the secondaries have no accelerator pump. The secondaries are locked closed until the choke stat is fully warmed up when a lever on the lower right side of the carb moves enough to allow operation. I would advise you to have an carb expert set this carb to spec on a bench and then reinstall it to start the tweeking process. Also look at the mechanical advance system in the distributor for proper function.An engine should start eaiser a the lower timing setting.If this is a small block chevy it is also possible that the harmonic balancer has slipped causing causing false timing readings. You need to check this. Good luck ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: 79nautique
Date Posted: August-25-2005 at 12:09pm
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nates78ski
dude you are so full of crap I have never seen a Q-jet that has vaccum secondaries they are mechanical. The choke pull off is for the choke not secondaries. please not confuss the guy with incorrect information. Jeff screw in the idle mixture screws all of the way using light pressure and stop when they stop do not torque on the screws otherwise you'll damage them. Once they are fully closed back them off 1.5 turns and then reset the timing. An easy way to see if the harmonic balancer is slipped is to bring the #1 cylinder up to top dead center then look to see that the zero mark on the balancer matches the zero mark on the timing ear mounted to the block. If it doesn't then you need to replace the harmonic balancer. I'll look and see how far Decatur is from here and if it's not to far and you buy the beer I'll get you fixed up in no time. Q-jets are a little harder to adjust correctly but once they are they stay that way for a long time, holley's are easier but you have to re-adjust them regularly ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: JEFF KOSTIS
Date Posted: August-26-2005 at 1:27am
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Nates 78ski is somewhat correct. The choke pulloff is the vacuum secondaries for the rochester. They have done this forever on the quadratoilets. The pulloff allows the secondaris to open when there is little vacuum (WOT) and allows it to open gradually. It has nothing to do with richening the mixture. If you wire the pulloff in, the secondaries will never work and you have a 2 barrel only carb. 79 nautique seems a bit hostile toward this.
The thing nice about adjusting the secondary rods on engine versus setting it to spec on the bench is that you can fine tune the mixture to compensate for the angle of the engine. The rear cylinders always get too much fuel, while the fronts dont get enough. ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Guests
Date Posted: August-26-2005 at 1:34am
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well im going to check a few things. i think everything is good on my timming.? i still think its my secondaries not opening i'll know for sure tomorrow because ill be able to go down to the dock during the day
what kind of beer do you want? |
Posted By: stang72
Date Posted: August-26-2005 at 1:49am
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79nautique...if the travel is not too far and Jeff takes you up on your most generous offer...I too will contibute to the beer...food too! I live about ten minutes from Jeff !The welcome mat is always out to members of this way cool site!
Where do you live? One state east perhaps? ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: skyhawkflyer
Date Posted: August-26-2005 at 11:56am
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Do you have a wedge plate? Everything revolves around wedge plates. My .02 worth....
From all my Q-jet experience, (and Holley) I'd rip the thing off your intake and throw it out on the dirt driveway. They are a constant headache. Put on an Edelbrock marine. They are simple to adjust and easy to rebuild when it comes time. Or better yet, convert to throttle body fuel injection. The money will be well spent. ------------- |
Posted By: 79nautique
Date Posted: August-26-2005 at 1:03pm
Now I have two Jack aces, obviuosly you don't like Q-jets, maybe it's because you don't know how to adjust them correctly. Maybe it's because you don't know that the choke pull off is connected to the primary barrels and not secondaries, maybe its that you don't know that most Q-jets have atleast two vaccum diaphrams and only one of them is the choke pull off. With any carb you have to fine tune it on the motor while running and no not always do you set it to factory specs. Mechanic's 101, maybe we need a carb's for dumby's manual. I looked at where you guys are located and it's about 4-5 hours away. I'm in Syracuse, IN so I'll have to map it out a little more and get back with you. I may have some free time next Thursday before the big week-end, Friday I'm going to the NHRA U.S. natioanals, in Indy. ------------- http://www.correctcraftfan.com/diaries/details.asp?ID=756&sort=&pagenum=1&yrstart=1979&yrend=1979 - 79 nautique |
Posted By: nates78ski
Date Posted: August-26-2005 at 7:43pm
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30 years of repairing ignorant wanabee mechanics screw ups have allowed me to earn good living. If you own a Qj, holley or an Edelbrock they have all a have to set up properly. All carbs do wear out with use. I suggest you take this carb to a reputable mechanic to check it on a bench. You may have to drop $300.00 on a new unit and if you do buy the Edelbrock. Easy to adjust & very turn key.Where you located in indiana. ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: captan1
Date Posted: August-27-2005 at 2:29pm
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Oh.... you'll have to let us all know how this goes.
------------- http://www.correctcraftfan.com/diaries/details.asp?ID=452&sort=&pagenum=1&yrstart=1978&yrend=1978 - 1978 Ski Nautique |
Posted By: Guests
Date Posted: August-27-2005 at 10:29pm
| looked at motor a little more today and i believe it is my secondaries not opening. they would not open even when i had full throttle. oh well ill probally get when i get my next day off work |
Posted By: JEFF KOSTIS
Date Posted: August-28-2005 at 1:26am
79nautique, im not a guy to argue, but I do like debates on a civil level. You are right about the choke pulloff rod going to the primary side and connecting the choke lever. But from there is a cam which wont allow the 4 barrels to open unless the bi-metal choke spring is hot, opening the choke plate fully. The other linkage that goes to the top of the 4 barrel secondary plates is tied to the pulloff rod. 79nautique, try holding in the choke pulloff in with a piece of wire and the 4 barrels will never open. By the way, the rochester on the boat is a 1974.  ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: stang72
Date Posted: August-28-2005 at 3:07am
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Debates are good for learning. I will watch this one and see what I learn!
One thing I want to throw out there for debate...Vacuum secondaries or manual??? I am hearing two versions...I don't know the Qjet carb well at all,however I did look at Jeff's(who started the post) and it certainly looks to be a manual pull on the secondaries.
Nates78ski...agree..what ever goes on(holley, qjet or edelbrock)will usually require adustment...the carb on the boat is new and he has a spare rebuilt carb in the garage...I don't think he needs to spend more cash,but just wants to understand the carb and learn how to make the adjustments! Hopefully you guy's that have knowledge of the Qjet get get on the same page and and help solve that poor pathetic bast--ds issue!I can call him that...he's a friend ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: JEFF KOSTIS
Date Posted: August-29-2005 at 12:01am
Also an easy test to see if the secondary metering rods are delivering correct air/fuel is to tie the choke pulloff back with a piece of wire, as if the engine is idling and the pulloff is sucked in. This holds the top secondary butterflies with the metering rods shut. A test run at WOT will determine a 4-barrel issue. You will be running on just the primaries, obviously you wont get the power, but she should run good-no bogging. If it still floods on a hard takeoff (bogging and black smoke) then you need to lower the secondary metering rods. Even with the butterflies permanetly shut with the wire, you can get fuel when the secondary throttle plates open creating a vacuum up to the top butterflies and effectively sucking some fuel from those rods because they are not quite seated. This may or may not be your problem, but I know the factory Q-JET in our boat had that issue and no one could fix it. good luck!!
 ------------- MUSTANG COUNTRY http://www.correctcraftfan.com/diaries/details.asp?ID=1074 - 1974 Mustang 17 http://www.correctcraftfan.com/diaries/details.asp?ID=1093 - 1976 Mustang 17 |
Posted By: Guests
Date Posted: August-29-2005 at 12:52pm
| located in illinois 78 |
Posted By: skyhawkflyer
Date Posted: August-29-2005 at 2:11pm
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The Q-jet locks out the secondaries until the choke is pulled 100% full open. This is an anti-backfire feature that was incorporated for a cold engine. You don't want a carburator backfire when you have a rich fuel mixture. If your choke is not getting pulled open 100% then you should never be able to open the secondaries.
I don't know much about Q-jets but I do think it was a very bad design. The floats sink, the bowls and throttle body's have plugs that typically leak. The throttle shafts are noted for huge vacuum leaks. And it's not modular in any way, shape, or form. You have to disassemble to re-jet, and adjustments are made by bending linkages. Holley made a much better carb, but Carter truly is a great design with super easy adjustability. For that reason I never took the time to learn about Q-jets anymore than what I already experienced, because I knew I wouldn't stand for that kind of monkey motion taking place on my equipment. Spend the extra $$$ for a Carter AFB (aluminum four barrel), get the electric choke model. It dials in quickly, and you'll be back out on the water in a couple of hours. ------------- |
Posted By: nates78ski
Date Posted: August-29-2005 at 5:37pm
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There a series of steps to set up a Q-j properly. These include choke pull, choke thermostat, chock unloader, accelerator pump, choke holdoff or lock, primary metering rod, secondary metering rods, secondary air or vacuum vane windup spring & of course float height and float drop. Some of these require special tools to measure properly. Most of the time you get lucky and they don't need adjustment. If you do not have a history of the boat or do you know if the carb & spare are the proper match to the engine that presents another problem. I think the right path you are on is to make sure that the choke opens all the way enabling the lock out to come off. While the engine is first started cold make sure the choke pull is opening enough. Give me the carb number or look in the rebuild instuctions for this info. When these carbs wear with age & use these adjustment are you baseline. When starting cold if the engine runs rich adjust the choke pull off just enough to get rid of that condition. Now back the lock out lever the choke will take 5-8 mins to warmup @1200-1500 rpm. If it fails to open check that it is recieving warm air from the manifold tube or if it has an electric choke the proper voltage is there. If that is OK then the tension on the secondary windup spring may be wrong. Once again look in the rebuild spec for the proper turns to tension the spring. When you find that loosen the set screw underneath the air horn @the right side of the secondary air vane and hold the adjustment screw with a small screwdriver to adjust. This all sounds a little complicated but it really is not if you understand what to adjust in which order. Check the choke stat for opening & the pull off and let use know what you find before we mess with that air vane windup spring. Good luck!!1 ------------- Nathan http://correctcraftfan.com/diaries/details.asp?ID=1463&sort=&pagenum=3&yrstart=1978&yrend=1978" rel="nofollow - My '78 Ski Nautique <a href="http://photobucket.com/Nates78ski" rel="nofoll |
Posted By: Guests
Date Posted: September-02-2005 at 1:00am
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well my boating days are over for this year?
i tried working with the carb but still no power and bogging but now on top of it raw water pump is leaking and something is sqeeking and other noises which i hope is just the berring in the water pump instead of the motor. well thanks to everybody who tried to help but maybe next year. sad in illinois
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Posted By: stang72
Date Posted: September-02-2005 at 2:02am
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Get back on the dabnab horse and ride again!We have a month & 1/2 of usually good weather where there is less traffic!
I will make you a bet... that 62 we are getting rebuild will be on the water before you are running trouble free!You have a big head start...engine is still at the machine shop! Dinner and drinks(movie...Team America) for the winner!!!Get to work you pathectic bast__d. ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: skyhawkflyer
Date Posted: September-02-2005 at 1:39pm
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Take a look at what's wrong and get it fixed!
Git R' DUN!!!!! Maybe before you take it out again you should give the engine a thorough inspection. Get a piece of paper and pencil and write down everything you find, and then fix the problems one by one. Look for loose fasteners, bolts, loose wiring/terminals. Oil leaks/fuel/water. Inspect the hoses, belts, and plug wires. Go over every square inch, and make a list. Then get R fixed. Check all of your servicing too. Engine oil and fuel, and transmission, along with battery and terminals. You'll learn a little, get a few things fixed, and have fun in the process! ------------- |
Posted By: stang72
Date Posted: September-02-2005 at 2:37pm
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Right on Skyhawkflyer! ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: Guests
Date Posted: September-06-2005 at 5:31am
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nate
the carb number is 0437. but the original one was 2196. is there something wrong? I thought when you get another carb the numbers are suppose to match or is that just when you get a rebuild kit? anyway i've been trying to fix the problem and the stuff i've been told to do has not corrected the problem at all. i did see where the thermostatic coil spring looked a little worn would that have anything to do with my sencondaries not opening? |
Posted By: skyhawkflyer
Date Posted: September-06-2005 at 10:31am
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Yes,
Your thermostatic spring pulls the choke open as it warms up. If the spring is defective, the choke doesn't open. If the choke doesn't fully open then the secondaries are not available at any throttle position. Post a picture of the thermostatic spring. ------------- |
Posted By: Guests
Date Posted: September-07-2005 at 6:03am
| the reason why i say it could be the spring is because its pretty loose its the kind that is screwed into the intake manifold. their is no adjustment to it.screws on and off. im not even sure if i can get it off it looks like the original? ill try to get some pics taken of it |
Posted By: skyhawkflyer
Date Posted: September-07-2005 at 10:31am
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By your description, it sounds like the root of your problem, or at least a start!!! Take a picture, and soak it down with penetrating oil that creeps. You'll get it off. Patients! ------------- |
Posted By: Guests
Date Posted: September-08-2005 at 2:07am
| well i think it is going to be a bit the screw holding the spring together is stripped.so i'm going to get something to get it out. ill tell ya more later. |
Posted By: stang72
Date Posted: September-08-2005 at 2:36am
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Well...I saw Jeff's problem in action today!It does look like what Skyhawkflyer is on it! After the engine ran for a few minutes...the choke plate was not opening.
I am not familar with that carb...but was wondering if the sping tention is adjustable? Also...can you convert it to an electric choke? ------------- stang Face plants are not that funny when it's you face! http://www.correctcraftfan.com/diaries/images/3720/photo1.jpg" rel="nofollow - The Super Air |
Posted By: Guests
Date Posted: September-10-2005 at 5:03pm
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well my boating days this year are over.
my pistons are a slappin. the good things is that a friend of mine is a mechcanic and he is willing to let me use his garage and help me out with it this winter.
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Posted By: southwind 20
Date Posted: September-13-2005 at 2:07am
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Not to be a *** **** but the Predator I pulled off the drag car works really, really nice! ------------- Git One ON! |