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By NewPunkRKR - 15 Years Ago
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So I took the Fairlane to the strip for the first time today. Did 8 runs in about 35 mins, and the result was consistent and SLOW. Average Results: | R/T | 0.562 | | 60' | 2.672 | | 330' | 7.577 | | 1/8 | 11.595 | | MPH | 61.64 | | 1000' | 15.056 | | 1/4 | 18.091 | | MPH | 76.20 |
My first conclusion is I need a limited slip. Track attendant said right rear just spun all the way off the line But even once it connected, I didn't feel like it was pulling. Any advice on where I can get one and what's involed in swapping it? Has anyone had problems with the throttle linkage working properly with the Demon JR 525 carb? I feel like I couldn't get WOT? What secondary spring is recommend for that carb? I thought I had fixed my timing and fuel problems but driving it hard on the strip and then 75MPH on the highway home it doesn't seem to run right. Fuel ratio gauge doesn't even read at a cruise (goes below lean). I've spent a lot of time and money this summer and feel like I have taken steps backwards in how the car is running. I know guys on this site are running faster than what I did with little to no modifications. Very discouraging. - John
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By charliemccraney - 15 Years Ago
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Disconnect your throttle linkage from the carb, have someone push the pedal to the floor - or weigh it down with something, and see where the linkage is as compared to the carburetor.
Have you looked at your plugs? I too have an O2 sensor but the plugs have the final say on what is right. If it's lean at cruise, the performance will be sluggish.
Here is an excerpt from the instructions for my Holley concerning the secondary tuning:
"Many people have the misconception that opening the secondary throttles sooner will provide increased performance and quicker drag strip times. Others think they must “feel” a kick when the secondaries engage. Still others believe that they should disconnect the vacuum diaphragm and make the secondaries open mechanically.
Before going any further, lets discuss these points in a reverse order. First, if we could make our vacuum operated secondary carburetors perform better by opening the secondaries mechanically, it would be to our advantage to do so since all that vacuum actuating hardware is expensive and requires much time and money to calibrate. Mechanical secondary carburetors all utilize a secondary pump shot to prevent bogging when the secondaries are opened. Secondly, those who “feel” a kick when the secondaries engage are actually feeling a flat spot during initial acceleration because the secondaries have already begun to open and have weakened the fuel delivery signal to the primary boosters. The engine is struggling to increase speed and what they actually feel are the secondary nozzles “crashing in” as the engine finally reaches he speed where it provides the proper fuel delivery signal to primary and secondary venturi. Third, opening the secondaries early causes the situation described above. The secondaries must not open until the engine requires the additional air. This allows torque to increase along the peak torque curve. Performance is compromised less by holding the secondaries closed a little longer than by opening them a little too soon. If the opening rate of the vacuum operated secondaries is properly calibrated there should not be a “kick”, only a smooth increase in power should be felt."
"The secondaries will not open by free-revving the engine. The engine needs to be under a load before they will open. If you are still uncertain if they are opening, you can take a normal paperclip and clip it onto the secondary diaphragm rod and slide it up against the bottom of the secondary diaphragm housing. Go out and drive the vehicle, making sure to get into the secondaries. When you return you will be able to look at the position of the paperclip on the rod. If it is lower on the rod, you can tell the secondaries opened and how far they opened. This is useful in determining if you need a heavier or lighter secondary spring."
It sounds like the thing to do is to find the point at which you get a "kick" and then use the next stiffer spring. That's what I did.
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By GREENBIRD56 - 15 Years Ago
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John - have your significant other sit in there and plant her right foot on the floor (ignition off) - have a look, you'll soon know if the primary can reach wide open. Is the carb primary bowl fuel level right in the middle of the window? How about the secondary? Are they stable? Shouldn't change from run to run. What sort of fuel pump do you have on there now? Tank line good? Do you have air shocks on there? Put all of the air in the RH side - minimum on the left. What does the right rear contact patch look like when as she leaves a burnout? Equal heat on the tread face? Adjust the tire pressure. Run both the fronts up on the high end of recommended pressure. It going to take some thinkum to get her moving - not just parts, it all has to work together.
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By Hoosier Hurricane - 15 Years Ago
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John: What is your rear end ratio? Something around 3.00 is too high for good strip performance, something in the 4.10 or even lower helps get that 3500# car moving. But, then tires become an issue, a narrow hard rubber tire can't hold such a gear. Also, if you have a FOM, is it taking off in 1st? Manually putting it in LO will assure this. Aftermarket limited slips are available at most mail order speed shops and local speed shops. Yours will be 28 spline, can use the 9" Ford parts.
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By NewPunkRKR - 15 Years Ago
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Ok, so I probably over reacted a bit last night, but I can take my daily driver out and pull high 14's all day, so I was really hoping for better than 18's. Anyway, yes I have the linkage set properly as far as travel. However, I think there is more resistance in the demon carb (correct me if this is wrong) so the kickdown linkage has been engaging at 1/2 throttle. I changed the kickdown spring, but maybe I need a stiffer one. I can’t duplicate this condition without a load on the engine, but I know it was happening. Possibly now it’s only holding till 3/4??? I’ll have to check the plugs, I’ve been relying on the 02, but i guess that’s not a good program. If I am lean, this would be a jet issue? I’ve read that Holley article because I used to have a street avenger. I currently have the black (stiffest) spring in the demon, but I guess I should track back to a lighter one. I know all cars are different, but just curious what range people are using on the demon. I adjusted the bowls and they seem consistent, but last night I searched some articles and read people have recommended changing out the needles to Steel, so I’ll have to get those. Fuel pump is a Summit FE, fuel tank has been redone, fuel line is stock but good, I assume I shouldn’t have to go to a larger O.D. line I bought the Monroe air shocks, but they aren’t in yet. They are designed to be installed together for the same air pressure. I haven’t been able to find additional hardware at any store so that I can separate them. Anyone done this? Patch looks pretty good. I’ve got Cobra GT Radials, but I guess realistically if the strip is going to be a regular occurrence I need to get a cheap set of rims for the back and some different tires? Not sure on rear end. It should be stamped, correct? I built the FMX/FOM, so I’m starting in first. So any 28 spline 9” limited slip will work. I did a search last night at summit and came up with like 200 parts. Thanks already for your help. I just have a lot more work to do  - John
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By 63 Red Stake Bed - 15 Years Ago
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Regarding linkage;
I had a similar problem with the kick down linkage on my truck with the COM. I ended up using a lightly stretched return spring on the carb, & a lightly stretched return spring to the main linkage.(where the kick down & manifold mount is) I tweaked the arm that holds the kick-down return/stretch spring to strengthen it... Still trying to find a factory replacement. The weaker this spring gets, the harder it is to get the throttle to open in sink with the pedal if you are snapping it quickly.
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By y-block don - 15 Years Ago
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and only work on changing one thing at a time until you feel you can move on to something else i would start with the suspension get those 6o" down no matter how much power you throw at it it has to get to the grown or it will be useless good luck and keep chipping away the times will drop 
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By Hollow Head - 15 Years Ago
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For the rearend I would try something like Powertrax No Slip or Lock Right units. Easy to install and what I have read, they work fine.
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By NewPunkRKR - 15 Years Ago
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I looked at the rear end and the tag was actually still there... 3.10 gears That explains why I had a hard time launching, yet the car will do over 100 MPH on the highway no problem. What's a reasonable ratio for performance street (3.50 - 3.70?), but still drivable at highway speeds (75-80) for long distance? I'm thinking of buying a new complete unit w/ a posi for every day, and then taking the 3.10 and having it rebuilt as something for the strip only. Does anyone recommend a company to get a complete unit from, or do I try and just rebuild one myself. How easy is it to swap these out? Will it bolt right up or is there a lot of adjustments that would have to be done? I've watched them do rebuilds on the TV show "extreme 4x4" but they do the job in 45 seconds so its hard to tell how much precision work there is. - John
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By Ted - 15 Years Ago
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NewPunkRKR (10/21/2009)
I looked at the rear end and the tag was actually still there... 3.10 gears That explains why I had a hard time launching, yet the car will do over 100 MPH on the highway no problem. What's a reasonable ratio for performance street (3.50 - 3.70?), but still drivable at highway speeds (75-80) for long distance? How easy is it to swap these out? Will it bolt right up or is there a lot of adjustments that would have to be done? I've watched them do rebuilds on the TV show "extreme 4x4" but they do the job in 45 seconds so its hard to tell how much precision work there is. John. The 3.10’s are a good highway gear but not an adequate gear for the drag strip. A set of 3.50-3.89’s will be a good all around gear for both performance and driving around town. More gear simply allows the engine to get into its desired rpm band quicker.Changing out the pumpkins is reasonably straight forward. I've got it down to about 45 minutes from start to finish. Just insure you're using units designed for the same spline axles. Although you can set up ring and pinions yourself with some practice, it’s best to have someone that’s experienced with this to walk you through your first one. Pinion bearing drag as well as pinion depth and ring gear backlash are all critical in having a set of gears that do not make noise and have long life.
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By NewPunkRKR - 15 Years Ago
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Thanks ted - If I purchase a complete 28 spine unit, will it need to be test fit / adjusted for my vehicle? Or is it a bolt in because the ring and pinion and would be set / tested before I received it. Is there a company that anyone has used and/or recommends for a complete aftermarket diff? - John
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By pegleg - 15 Years Ago
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John. You can try to find one on Ebay or Craig's list, Gears are available from Summit/jegs or a local Speed shop. There will be some one in the chicago area who can set it up for you. If not, we can work out something with a buddy of mine here in the South Bend/ Elkhart area of Northern Indiana.
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By Canadian Hot Rodder - 15 Years Ago
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FYI, I run a 3:55 Detroit locker and at 75 mph I am reving right at 3000 rpm on the highway. I am Running 225 R16 radials on the car. So far my best time with a stock (mileage unknown) 292 / FMX combo has been 17:02 @ 87mph. I know I can hit the 16's with some tuning and some slicks as I have been told that I am spinning the tires off the line every time. Hopefully that gives you some insight as to where you should be.
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By mctim64 - 15 Years Ago
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I bought a complete "Trac-Loc" with new 3.50:1 gears set up and ready to install for $350 + shipping three years ago on eBay, it was an easy swap and is working great to this day. I bought it from a guy in IN, maybe someone Frank knows.
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By NewPunkRKR - 15 Years Ago
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Thanks guys - I appreciate it. I'd like to think I can get to high 15s. (without building a new motor) Maybe i'm dreaming... Let me rephrase my previous post: What is a reasonable cost for a swap... I like the $350 that Tim mentioned. I see them online everywhere from $1300 to $150. Buying just new components seem to add up to approx. $600+
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By Doug T - 15 Years Ago
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When I had my truck it had a 3.73:1 axle and the engine was spinning too fast for my taste at today's highway speeds. So it depends on how you are going to use the car. If you intend mostly street/strip then 3.89 would be OK but driving on a longish trip would get on the nerves (at least on mine). If you are planning on longer trips than I would say 3.50 would be a fairly good compromise although the word is compromise. Who ever suggested checking the tire patch was on target because 2.6+sec 60' times indicate that you are quite slow at that point on the track. A locking rear axle will help but you need to check tire pressures no matter what and play around until both wheels spin at low pressure. One thing with radials, if you go too low with pressure they will only contact the pavement on the outsides edges of the tires. You will see this as two stripes of black from one or both tires. I run about 18 psi on my street tires with a Traction lok and I can get about 2.0-2.1 60' times, stickshift T bird. So far DOT slicks didn't help that much maybe 1.9 -2.0. There may be engine issues also but others are on them!
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By mctim64 - 15 Years Ago
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NewPunkRKR (10/22/2009)
I like the $350 that Tim mentioned. + I hope you know I ment a complete third member (pumpkin) not the whole rearend. 
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By NewPunkRKR - 15 Years Ago
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Yeah, that's what I'm looking for. I've never had any problems with the axel, so I'm assuming all the other components are in good shape. I looked online for diff. components and also complete 3rd members and it was typically around $700-800 for a rebuild unit. I'd like to find something for much less.
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By TriggerTorqueDave - 15 Years Ago
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John- You have probably checked this, but in case you have'nt, be sure the intake/carb spacer will allow your secondaries to open. The stock items won't allow throttle plates much bigger than stock to open. David C.
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