The 72 Demon Follies....
Been awhile - time for a little update. Seems life got in the way of updating.
The track (Milan Dragway) decided to add some racing on Friday nights in October - called Footbrake Friday for footbrake only cars. Since I had been somewhat vocal about having a footbrake class, I surely wanted to support them so we took the car on Oct 14. It was some good fall air - with the temps ranging from upper to lower 50's all day. On the 2nd pass off the trailer, at 59 deg/DA of 1100, the car set some new personal bests of [email protected] mph. 60' was nothing great - 7.073 - but the cool air helped it make up for it down the track. I should add that with the 4.10 rear gear, the car is now going through the traps right around 6300-6350 depending on which run/what mph.
But the next runs were not so great. I had to lift when the car wanted to go left then continued to horizontally "porpoise" a bit. I'm no hero driver so I lifted. Not sure what/why but let's make sure all the suspension bolts are tight. Did that - they were all tight. Made another pass and car slowed a bit to an [email protected]. What/why?? Next pass had to lift again due to porpoising (car over-corrects itself when you try to steer it back from going left and starts to get quite violent like the rearend wants to come around). Starting to get concerned but got called up to the staging lanes. Dialed an 11.20 since it had gone an 11.199. Ran an 11.25 on the brakes so it seemed fine and on to round 2 we go. Left the 11.20 on it but took a nap at the light, ran it full out, and it slowed to an 11.35????? Time to go home and see what is going on.
Over the next few days, and with the car steering itself to the left, I watched lots of videos a friend shot of it. You can see on the hit, when it lifts the LF tire in the air and has the right one just tapping along, the right one toes in quite a bit while the left one stays straight. So from some recommendations from RRR and others here on FABO, I got the Mopar Chassis "bible" (9th edition) and read through it. Lots of talk about measuring toe-in at ride height and at various amounts of front end lift and what to do to make corrections. So I did that and you could surely see the toe-in increasing with lift but more importantly, it was really more the RF tire toeing in and the LF tire staying fairly straight. When I had the car aligned about 18 months ago, the printout showed they could not get any caster on the RF tire and only minimal on the LF. So I decided to get me one of those bubble alignment tools to see if I could correct it myself. Got the Joe's Racing Products one - seems pretty nice.
It came to me but not in time to where I could get back to the track the next weekend. I began to work both side's cambolts trying to improve the caster but basically could never get any success. So I set them so they had equally poor caster of about -0.4 degrees. Then I measured toe throughout the lift range and found that I could improve it but only if I re-centered the steering wheel like the Mopar Chassis book instructs (equal distance to wheel from lower tie-rod end grease fitting). When I had put my steering wheel on, this column does not have a master spline so clearly I messed it up. So I set the front wheels straight, pulled the steering wheel, and found it to be exactly 2 splines off. Re-centered it then began playing with the tie-rod ends to improve the toe-in on front end lift. Well...you couldn't make it perfect but I could get it where it was equal toe-out and then toe-in as the front end lifts. So I set to what I thought was a good compromise. The RH tire was pointing a tad to the right at ride height but let's just send it. Took the car out on some local freeways and hammered it a few times to see if it was stable at speed. It was and seemed to track straight so it should be ready to go...right? So it seemed....
Been awhile - time for a little update. Seems life got in the way of updating.
The track (Milan Dragway) decided to add some racing on Friday nights in October - called Footbrake Friday for footbrake only cars. Since I had been somewhat vocal about having a footbrake class, I surely wanted to support them so we took the car on Oct 14. It was some good fall air - with the temps ranging from upper to lower 50's all day. On the 2nd pass off the trailer, at 59 deg/DA of 1100, the car set some new personal bests of [email protected] mph. 60' was nothing great - 7.073 - but the cool air helped it make up for it down the track. I should add that with the 4.10 rear gear, the car is now going through the traps right around 6300-6350 depending on which run/what mph.
But the next runs were not so great. I had to lift when the car wanted to go left then continued to horizontally "porpoise" a bit. I'm no hero driver so I lifted. Not sure what/why but let's make sure all the suspension bolts are tight. Did that - they were all tight. Made another pass and car slowed a bit to an [email protected]. What/why?? Next pass had to lift again due to porpoising (car over-corrects itself when you try to steer it back from going left and starts to get quite violent like the rearend wants to come around). Starting to get concerned but got called up to the staging lanes. Dialed an 11.20 since it had gone an 11.199. Ran an 11.25 on the brakes so it seemed fine and on to round 2 we go. Left the 11.20 on it but took a nap at the light, ran it full out, and it slowed to an 11.35????? Time to go home and see what is going on.
Over the next few days, and with the car steering itself to the left, I watched lots of videos a friend shot of it. You can see on the hit, when it lifts the LF tire in the air and has the right one just tapping along, the right one toes in quite a bit while the left one stays straight. So from some recommendations from RRR and others here on FABO, I got the Mopar Chassis "bible" (9th edition) and read through it. Lots of talk about measuring toe-in at ride height and at various amounts of front end lift and what to do to make corrections. So I did that and you could surely see the toe-in increasing with lift but more importantly, it was really more the RF tire toeing in and the LF tire staying fairly straight. When I had the car aligned about 18 months ago, the printout showed they could not get any caster on the RF tire and only minimal on the LF. So I decided to get me one of those bubble alignment tools to see if I could correct it myself. Got the Joe's Racing Products one - seems pretty nice.
It came to me but not in time to where I could get back to the track the next weekend. I began to work both side's cambolts trying to improve the caster but basically could never get any success. So I set them so they had equally poor caster of about -0.4 degrees. Then I measured toe throughout the lift range and found that I could improve it but only if I re-centered the steering wheel like the Mopar Chassis book instructs (equal distance to wheel from lower tie-rod end grease fitting). When I had put my steering wheel on, this column does not have a master spline so clearly I messed it up. So I set the front wheels straight, pulled the steering wheel, and found it to be exactly 2 splines off. Re-centered it then began playing with the tie-rod ends to improve the toe-in on front end lift. Well...you couldn't make it perfect but I could get it where it was equal toe-out and then toe-in as the front end lifts. So I set to what I thought was a good compromise. The RH tire was pointing a tad to the right at ride height but let's just send it. Took the car out on some local freeways and hammered it a few times to see if it was stable at speed. It was and seemed to track straight so it should be ready to go...right? So it seemed....