Car won't 60

[slagburn]

Not really sure what's going on here so might as well start a thread? :shrug:

2013 GT, stock auto with Circle D 2C, Whipple 2.9, stock suspension except Roush upper arm/ bracket. 28" MT stiff sidewall slicks.
The car's been running pretty well and has been 60'ing consistently in the 1.52 range. If I lean on the tune a bit the best it's done is a 1.50. Not bad, but I'm trapping 131-133 depending on DA, ET's in the 10.4-.7 range.

So I thought perhaps changing up the gear might help get it in the 1.4x 60 range. Wrong! I put in a set of 3.55's I had laying around and the 60's now dropped to 1.58-1.60 consistently.

Only two things I can think of- converter's too tight and the deeper gear is loading it less causing a lower flash and less torque. Or my tires are going away. They do have about 75 passes and only a couple 32nds left in the wear holes. But, I'm not blowing them off, maybe just a little slip and slide. Unfortunately I have no video since the gear change to try to analyze.

I've seen the guys in the 1.3's with stock suspension and the same converter and I want some of that, what am I missing?

 

[01bluesnake]

Start with a fresh set of tires and go from there. No reason you shouldnt be hooking unless the track prep has been poor as hell.

 

[slagburn]

I've been looking at the MT Pro 275's. Hopefully they hook on a heavy car without LCA brackets, trying to avoid those.

 

[01bluesnake]

I haven't had a chance to run those yet, but hear nothing but great things. I've always ran the regular M/T radials with great luck.

Also, what are you running for tire pressure on the slicks?

 

[alex12gt]

I wish I had those 60 times lol and the street et pro is a nasty tire ran it last year think its actually why I bent my axle shaft lol but I switched to slicks this year

 

[slagburn]

I haven't had a chance to run those yet, but hear nothing but great things. I've always ran the regular M/T radials with great luck.

Also, what are you running for tire pressure on the slicks?

Been running in the 14-16 psi range. Leaning towards another set of slicks- anybody with comparable power having issues hooking a radial with marginal prep?

 

[90coupe5oh]

Stock suspension is actually decent, needs a set of shocks in the back in a BAD way though. They're way too soft. 100% stock suspension I pulled a 1.63 60ft with a set of old 26-11.50-16 et streets in a 6spd. I feel the biggest problem is it squats too hard and unloads quickly because the rear shocks are too soft. I'm gonna try a set of strange's.

 

[nosympathy]

Stock suspension is actually decent, needs a set of shocks in the back in a BAD way though. They're way too soft. 100% stock suspension I pulled a 1.63 60ft with a set of old 26-11.50-16 et streets in a 6spd. I feel the biggest problem is it squats too hard and unloads quickly because the rear shocks are too soft. I'm gonna try a set of strange's.

springs are some of that too from my understanding. From what I have read the Cobra Jet springs are some of the best for shifting the weight to the rear wheels too for added grip.

 

[Need4Speed03]

Stock suspension cars have been in the 9's...I say get the radial pros and your problems will be gone, I plan to go with that tire myself. That being said I know a guy who put lowers and relocation brackets on his car recently and the 60's dropped tremendously...he's on this board - another nitrous car.

 

[Torchy]

Ever thought about going a touch under 14psi (hot)? Might be a path to try. I've went as low as 10 before. Even been down to 8psi and that was NOT cool. Just a thought.

 

[FIFTY]

Slagburn, was this issue ever resolved?