|09-21-2006 11:03 AM|
|machine shop tom||
Check to see if your secondaries are opening fully. If they are, that may be your problem. The secondary butterfies are designed to work with that flat plate in the secondary holes. If the butterflies are vertical, the F/A ratio is compromised. The secondary butterflies should NOT quite open up to the vertical position.
|09-21-2006 10:47 AM|
You don't have to hack up your carb to defeat the lockout. Unless Edelbrock significantly changed the choke mechanism, the lockout lever is on a stub all by itself, captive between the vacuum break mechanism baseplate and the body. Removing this lever involves no hacking and assures that the secondaries will open whenever you want them open.
I have 2 Q-jets I use on my engine, one is a stock 7040207 Q-jet off of a 1970 350 Chevy that gets me 18-20 mpg, the other is an 800 cfm unit off a 425" Caddy and is heavily modified. When I go to the strip, I take the driver carb off and put the monster carb on, takes all of 5 minutes.
The 800 cfm unit cost me $8 at a boneyard, and $10 for a rebuild kit. I have removed all the choke horn, the primary metering rods are gone for area equivalent jets, the linkage is 1:1 on the secondaries, notched the air valves, drilled out all the passages per Doug Roe, etc. Throttle response is awesome, and it set me back less than $20, maybe $30 if you count the chemicals.
|09-20-2006 05:29 PM|
|1982 SS||The lockout is actuated by more than just it's weight alone. When the choke is off and the lockout is disengaged There is a pin on one of the other choke arms that pushes the top of the weight back swinging the bottom foreward. There is no way that that lockout can be engaged if the choke is off. Plus it does not have enough ckoke to be on more than about 2 1/2 minutes before the lockout comes off. The lockout arm also acts as a spacer and I'm not about to hack my linkages up.|
|09-20-2006 09:44 AM|
|onovakind67||I'm not talking about the choke, just the choke lockout mechanism. It prevents the secondaries from opening if the choke is applied, and can hold the secondaries out even when the choke is open if it is misadjusted. You wouildn't want this to come into effect at the strip as it will make a huge difference in the carb. Are you familiar with the choke lockout mechanism on your carb?|
|09-20-2006 09:30 AM|
|1982 SS||The choke is still in place. It sees a lot of street time, and very occassionally, someone else drives the car. It has to have some semblance of street manners.|
|09-20-2006 09:20 AM|
|onovakind67||Did you remove the choke lockout mechanism? Murphy's law will apply here.|
|09-20-2006 08:56 AM|
|1982 SS||One of the plugs could have been leaking but instead of dripping, sucking air. Who knows. I spent the better part of an hour just figuring which part of the secondary went where. Same with the idle circuit, but I didn't have a problem with that, I just figured if I was going to do it, I had better do it right. I'm back to where it was before now. Also, I had noticed my consistency was slowly disapperaing at the track, I wonder if this was something that had been there a while but had just gotten bad enough to finally seriously hinder performance. I still think I need to loosen the secondary air doors just a little though... Things to do, but not enough track time.|
|09-19-2006 10:56 PM|
|lust4speed||Glad to here the problem was solved, but I am guessing that the epoxying the plugs didn't solve it. The plugs should basically only give you a massively rich condition at idle. Quadrajets can be so wierd. I was chasing a bog off idle and went through it without really finding anything strange. Back on the car for a test drive and I almost ate the steering wheel at 4500 RPM, with it catching and pulling me back in the seat at 4300 and off again at 4500. That high RPM drop off wasn't there before. I haven't had the chance to go back through it, but I'm betting more on the top bowl gasket not positioned exactly, allowing a large enough air leak to prevent the secondaries from sucking fuel properly. You might have just positioned the gasket better and solved the problem on the last assembly.|
|09-19-2006 03:32 PM|
For those of you still following this stroy and those who want to get to the end of the post to see the answer...
A combination of a thorough rebuild and putting epoxy all over and around the plugs, it runs like crazy now. It works real good now, pulls clean to 5500 then next gear and 4700 to the end of the 1320. I may need to adjust the secondary air door tension a little bit, but it is very close to the tension it was when I pulled it apart.
|09-18-2006 09:05 AM|
|1982 SS||I know the needle and seat for the float are a "high flow" at .149". I have made sure that the needle and seat were clear. I will have the carb back together later today and hopefully a test run to see if it is any better.|
|09-18-2006 07:44 AM|
high rpm lean
Needles and seats for Q-jets come in different diameters. In the Doug Roe Q-Jet book there is a section on drag racing where the seats are progressively changed to smaller ones until a lean surge is achieved.
Not sure what Edelbrock is using but at one time four or five different diameter seats were available from GM.
|09-17-2006 09:18 PM|
Small enough to make the motor go rich rather than lean. It's a 10 or 11 inch round by 2 inches tall k&N with an Xtreme lid. As far as I can tell, it's just big enough for the motor as long as I keep it clean. I clean it about once a month and it had been cleaned about two weeks ago, so it has seen a good night of racing before this surging issue came up. It has been dirtyier than it is and still run like crazy.
Nothing interferes with any of the linkage. I had to get the velocity stack style base so it would clear the accelerator pump. And it seems small because it is all I have room for under the hood with a 1" spacer under the carb.
|09-17-2006 07:30 PM|
|GCD1962||What kind of air cleaner are you running?|
|09-17-2006 05:46 PM|
Here is a pic of what I have done.
|09-17-2006 05:36 PM|
I'm pretty sure they are opening up. The car runs 16.9's without the secondaries. It went 15.4 surging. The first thing I looked at was the lockout pin, it was fully away from the throttle shaft (you know what I mean, it was disengaged). I made sure it was disengaged everytime I made a test run of it.
Anyways, I have the carb disassembled and I am waiting for the epoxy to dry on the caps over the primary and secondary wells and one other cap on the underside of the main body. I did this in case it was sucking a little air past the outside of the caps.
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