69 Coronet better E.T times

[505Coronet]

I recently acquired a 1969 coronet with a stroker 505 motor and a 5 speed manual, 8 3/4 rear end with 3.55s. i tossed on some 29x10.5 slicks and went to the track, im not a stranger to the raceway but i came from high torque diesels with 4x4 boosted launches and built autos. I grew up around old mopars (B and E bodies specifically) so im not new to mopars either, just never at the track.

I got the car down to 13.2 but i feel theres mid 12s/lower without driver error/better setup.

It has the factory leaf springs so i get bad wheel hop on burnouts, i cant seem to figure out how to launch at higher RPMs without breaking the beam and rolling.

Would a line-loc and a set of cal-tracs eliminate a lot of what im encountering?

Slip was as follows

60' 2.121
330' 5.749
660' 8.698
1000' 11.184
E.T 13.291 @106mph

And some photos since everyone loves those

 

[68Moparmaniac]

I recently acquired a 1969 coronet with a stroker 505 motor and a 5 speed manual, 8 3/4 rear end with 3.55s. i tossed on some 29x10.5 slicks and went to the track, im not a stranger to the raceway but i came from high torque diesels with 4x4 boosted launches and built autos. I grew up around old mopars (B and E bodies specifically) so im not new to mopars either, just never at the track.

I got the car down to 13.2 but i feel theres mid 12s/lower without driver error/better setup.

It has the factory leaf springs so i get bad wheel hop on burnouts, i cant seem to figure out how to launch at higher RPMs without breaking the beam and rolling.

Would a line-loc and a set of cal-tracs eliminate a lot of what im encountering?

Slip was as follows

60' 2.121
330' 5.749
660' 8.698
1000' 11.184
E.T 13.291 @106mph

And some photos since everyone loves those

View attachment 840775 View attachment 840776 View attachment 840777

Cal-tracs would be an improvement, help keep the pinion wrap up in check. You could play with your shock settings and check your pinion/drive shaft angles just to be sure their in spec. I've always liked the line loc set up, my finger seems faster than my foot... What tire pressure were you running?
I agree with you, with the setup you have should put you in the 12's...minus pilot error

 

[505Coronet]

Cal-tracs would be an improvement, help keep the pinion wrap up in check. You could play with your shock settings and check your pinion/drive shaft angles just to be sure their in spec. I've always liked the line loc set up, my finger seems faster than my foot... What tire pressure were you running?
I agree with you, with the setup you have should put you in the 12's...minus pilot error

i drove there on the slicks which were at 15psi cold, when i got to the track they were at 17.6, i went to 11psi so that could be 8-9psi cold. I didnt keep adjusting the tire pressure because i figured one variable at a time.

Ive been told cal tracs twist the tube on 8 3/4, is there any validity to this? if i break a ring gear/twist tubes im just going to toss a 60 under it and probably gear it a little deeper, since i have an overdrive and all

 

[Cranky]

It could do better using up graded leaf springs and better rear shocks. What's on it now? Original factory leafs or new ones? With a 505 and a stick, it for sure needs heavy duty leafs and if it already has that, you should do better with adding a leaf or even use SS springs. I'm not a fan of SS springs since they usually raise the rear up but have stacked my own and kept the rear at stock height. For stock type leafs, a very heavy duty 50/50 rear shock usually helped too. Getting wheel hop on the burn out says it needs more shock/spring. Keep in mind that more spring usually dictates more shock. I've had my best luck with a fairly stiff rear suspension with a lose front end.....

 

[NSS Guy]

Clamp the front segment of the springs to stiffen them up, this will help with wheel hop. I would leave just a few hundred rpm's over idle to get the converter to flash to whatever it will. The 106 mph shows it's possible to get to mid 12 seconds. I run 12-14psi in my 29.5x10.5 slicks.

 

[33 IMP]

@NSS Guy , he's got a five speed stick.
Your advice is still good.

 

[Cranky]

Clamp the front segment of the springs to stiffen them up, this will help with wheel hop. I would leave just a few hundred rpm's over idle to get the converter to flash to whatever it will. The 106 mph shows it's possible to get to mid 12 seconds. I run 12-14psi in my 29.5x10.5 slicks.

He has a stick but clamping the front segment does help even with the launch. Thing is, the clamps won't stay very long if it's street driven as the bolts break....even grade 8's don't last long. In fact, I think grade 5's will stay on a bit longer.

 

[33 IMP]

With a stroker and a stick, if you are gonna race it, i would put a 60 in it, MUCH sooner than later. Wheelhop is a huge contributor to 8 3/4 failure, especially with slicks.

 

[PRHeads]

If you get the traction issue sorted out to the point where you can effectively leave at a fairly high rpm........ then yes, the 8-3/4 will have a short life......... if you start running the car like that regularly.

With 505 cubes, you should be able to leave at a pretty low rpm, along with some minor clutch slipping and get the 60’ times solidly under 2.0.

The mph is fairly low for a 505....... so either it’s a very mild combo, or there’s some speed left on the table.

Couple of good examples of how to walk it out of the hole here......orange TA and blue R/T Challengers...... running 11’s on repop bias plies.

In good fall air, both of those cars have been in the 11.30’s........ on those tires.

 

[68Moparmaniac]

i drove there on the slicks which were at 15psi cold, when i got to the track they were at 17.6, i went to 11psi so that could be 8-9psi cold. I didnt keep adjusting the tire pressure because i figured one variable at a time.

Ive been told cal tracs twist the tube on 8 3/4, is there any validity to this? if i break a ring gear/twist tubes im just going to toss a 60 under it and probably gear it a little deeper, since i have an overdrive and all

Nothing wrong with sliding a big D under the ole girl.. if you have one.

 

[dvw]

I ran my wife's 4 speed Challenger for a year. Hopped up small block with a completely stock drivetrain and suspension. It had wheel hop even on the street. An adjustable pinion snubber close to the floor allowed 5000 rpm starts with 9x28 slicks (12.50@110). At the end of the year upon inspection we found achipped a spider gear tooth and the stock axles twisted 1 spline. So before spending big $ on Cal Tracks (which do work very well) spend $20 and weld up a taller snubber.
Doug

 

[505Coronet]

It could do better using up graded leaf springs and better rear shocks. What's on it now? Original factory leafs or new ones? With a 505 and a stick, it for sure needs heavy duty leafs and if it already has that, you should do better with adding a leaf or even use SS springs. I'm not a fan of SS springs since they usually raise the rear up but have stacked my own and kept the rear at stock height. For stock type leafs, a very heavy duty 50/50 rear shock usually helped too. Getting wheel hop on the burn out says it needs more shock/spring. Keep in mind that more spring usually dictates more shock. I've had my best luck with a fairly stiff rear suspension with a lose front end.....

i have no reason to believe these are not the original springs

It has sway bars front and rear, bigger torsion bars in the front, upgraded shocks i believe the P.O was going in the pro touring direction of the car. I have no intentions of taking this car to a track and running against a 911, with that said its not going to be a trailer queen, i enjoy driving it and would like to keep it that way.

No issues adding SS springs and raising the rear a little, some clearance around that tire wouldn't hurt its damn close as is. No issues adding traction bars either.

I just dont want to throw money and hope it fixes it id like to attack it correctly, the raised snubber was an interesting idea i had not thought of that. So are stiffer shocks.

I dont have a 60 laying around, but a truck 60 with 4.10s and a posi are plentiful around me, easy to narrow that down and throw it in. I should say i dont have plans of getting rid of the 8 3/4 but im not going to put money into it either so if it lets loose itll get swapped.

 

[505Coronet]

If you get the traction issue sorted out to the point where you can effectively leave at a fairly high rpm........ then yes, the 8-3/4 will have a short life......... if you start running the car like that regularly.

With 505 cubes, you should be able to leave at a pretty low rpm, along with some minor clutch slipping and get the 60’ times solidly under 2.0.

The mph is fairly low for a 505....... so either it’s a very mild combo, or there’s some speed left on the table.

Couple of good examples of how to walk it out of the hole here......orange TA and blue R/T Challengers...... running 11’s on repop bias plies.

In good fall air, both of those cars have been in the 11.30’s........ on those tires.

There speed on the table for sure, i dont have a youtube to post a video but its got fully ported eddy heads, very healthy cam (does not like to idle/be under 1800), forged internals, balanced, FAST fuel injection etc

I believe its 95% my driving and 5% the tweaking the car

 

[Cranky]

No issues adding traction bars either.

OOooo kkk....most Mopar people shun traction bars but I'm not one of them. I'm all in favor of home built ones though. Home made ones because you ain't gonna find any that will fit a Mopar like they should. I like them to be as close to the spring as possible and make sure the bumpers nail the spring eye and not behind it! They have to be heavy duty though for that 505.....! If you've used slapper bars before and had good results, I think you might like what I'm talking about too. Slapper bars usually hit the spring behind the eye and well, that's not what you want. I've seen way too many bent forward spring segments over the years...mostly in the 60's and 70's because of store bought junk. And someone mentioned CT's. They seem to work pretty well for most but my one and only experience with them was on a nose heavy E body and we chased our tails with them. The car ran 10.0s and 9.30 on a small shot but man, it was never consistent. We talked to John many times and did all he said and it it still wasn't responding well. Finally pulled them off and went with ladders and nailed the set up pretty quick and then the car because consistent. This car was also street driven and it actually drove better with the ladders which surprised me.

 

[505Coronet]

OOooo kkk....most Mopar people shun traction bars but I'm not one of them. I'm all in favor of home built ones though. Home made ones because you ain't gonna find any that will fit a Mopar like they should. I like them to be as close to the spring as possible and make sure the bumpers nail the spring eye and not behind it! They have to be heavy duty though for that 505.....! If you've used slapper bars before and had good results, I think you might like what I'm talking about too. Slapper bars usually hit the spring behind the eye and well, that's not what you want. I've seen way too many bent forward spring segments over the years...mostly in the 60's and 70's because of store bought junk. And someone mentioned CT's. They seem to work pretty well for most but my one and only experience with them was on a nose heavy E body and we chased our tails with them. The car ran 10.0s and 9.30 on a small shot but man, it was never consistent. We talked to John many times and did all he said and it it still wasn't responding well. Finally pulled them off and went with ladders and nailed the set up pretty quick and then the car because consistent. This car was also street driven and it actually drove better with the ladders which surprised me.

ive had ladder bars on all my diesels and was a huge fan, i was wondering if this concept was still applicable to the car seeing as its was less torque (my last truck was in the 1300ft lbs range)

 

[505Coronet]

I should also toss out there im a compent welder and not shying away from coil overs and a 4 link to get a decent ride and better traction. This is a bastard car was a 318 auto, so i have no problem welding on it. Id rather spend the money right once and have it be what i want than band-aiding something to try and work

 

[451Mopar]

The '71 Charger originally had wheel hop. I took the stock springs to a spring shop and they added a leaf in the spring stack right above the main leaf and it goes all the way forward to the front eye bolt area, and is clamped. Also added an adjustable pinion and Gas shocks. I have been considering replacing the old KYB shocks with some Viking adjustable shocks, but money is tight right now.

 

[Cranky]

ive had ladder bars on all my diesels and was a huge fan, i was wondering if this concept was still applicable to the car seeing as its was less torque (my last truck was in the 1300ft lbs range)

No experience with that kind of torque lol What kind of ET's were they running?

I should also toss out there im a compent welder and not shying away from coil overs and a 4 link to get a decent ride and better traction. This is a bastard car was a 318 auto, so i have no problem welding on it. Id rather spend the money right once and have it be what i want than band-aiding something to try and work

A 4 link should work well.....

 

[PRHeads]

I would think the plans for a path forward would be based on what the target ET is.

Imo, the speed would need to increase at least 20mph before I’d feel like you were getting out of the happy zone for Cal-Tracs.
However, at that point, if the ET’s were commensurate with the speed..... imo, you’d def be well beyond having any real reliability out of an 8-3/4 and a manual trans.

Of course, the clutch starts to be a big player at that point too.
And then there’s the question of how long 3rd gear will hold up in the 833 with frequent 1/4 mild pounding behind a high TQ motor in a heavy B body.

 

[33 IMP]

The idea behind my suggestion was to replace the 8 3/4 before you break it, so it still has some value, to you or to sell to someone else.
Also, ladder bars work excellent, as you obviously know, and a lot simpler than a four link.
Edit: what gear are you doing your burnout in ? Second or third I hope.