Put clamps on the front segment and remove the clamps on the rear segments and take off the snubber.

One of these will help with being consistent
https://www.summitracing.com/parts/pro-67005sc/overview/

Oh you guys...I have an adjustable shift-light on my tach...sorry...I've gotten used to it so much that I had actually completely neglected to mention it. So when superchuck posted the link to the shift-light product the proverbial lights finally went off in my head...LOL.

I pre-set my tach to have the light go off at 6300 RPM, so by the time I react and the shift is completed the tach pegs up to about 6500 RPM.

My son put together a little compilation of that day's events, you can find it on YouTube.

My suggestion to jet the carb. up richer until the MPH slows down in the 1/4 mile is to verify adequate fuel delivery (EDITED Once it starts to slow down jet it back to the best MPH )T.Q. carbs can make a hoop of HP when jetted correctly, jet it up and try opening the rear door some more until it slows down

Since you average MPH is up I'd say your power is up. poor track prep and more power lead to more tire spin so loses down low. and weather and wind can affect it too.
And if you say your seat dyno around town tells you it has more low end the gain was probably gone in tire spin.
work one thing at a time try to get 60" more consistent and quicker then try moving rpms at shift up and down.
do a log.

Could be that you do not spin at the hit and start spinning after 10 to 20 feet as you come into power band and carry that spin past 60'

you may be detonating but not hearing it over other noises. I had a similar combo with a 340, iron heads, quick advance, 10.4 cr, 175 psi cranking, would run fine, no audible knocking but at the track it would run .5 quick on a 50/50 mix. I think it's worth a try.
you do need to get your 60' nailed down but your MPH will tell you if it helps.

IMO, those 60' times are terrible for a combo like that with a 4k converter.
If you're sure it's not spinning, then either the motor is really soft down low or the converter is suspect.
I would put a white stripe on the tire and have someone video the rear tires on the launch and verify it's not spinning.
No reason a hi-12/low-13 second car shouldn't be dead hooking.

The speed also seems low to me for what the heads flow, cam size, cr, etc.
How do the converter slip numbers look?

Fwiw, I think you're shifting too high, but that's easy to sort out.

If that converter really stalls at 4000 RPM I think all the torque you added with the RPM intake is going out the window, thus your 60 times that haven't changed. You're just losing a little top end, which is probably offset by your head work.

The tight shocks, clamped springs and sway bar explain why the car looked "stiff". Very little movement front and rear. The video confirms this.

I've never had a good handling car that I've taken to the track, so I am not sure how to go about getting weight transfer and hook. If the shocks are easily adjusted, you could maybe loosen up the front rebound at the track, then tighten it back up for the drive home.

pump swill? If it's got any ethanol in it you are really lean is my guess.

Don't pay attention to the AF meter, look at the MPH on time slip. That will tell you what the engine likes. I rarely have any engine on pump swill that like AF readings higher than about 12.4 for best MPH. If you are that lean, there is a TON of HP trapped in the poor tune up.

Not sure on rear tire height, but, 5700 through the traps and only 101-103ish is very weak unless the tire is only 25" tall or less. The converter may be suspect with a lot of slip if tires are taller.

Get the jetting correct, fatten it up and see how it does.

I am somewhat convinced now (given the forum feedback) that I still probably have a pretty decent amount of time spin @ launch. I will do the white stripe on tire trick next time out to really get a good measure of this.

The converter is a custom built (for this car&combo) 9.5" Dynamic Converters piece that's spec'ed out to stall at 4K. I believe it flashes to around 4K@launch, but I have always staged @ 3000 or 3500 and only did the 4K launch once.


I also think this is a tad slow for the combo I built..LOL...but I always attributed that conclusion to my "wishful thinking".

Regarding the converter spli numbers...umm...help me out, how do I calculate this?

The Nitton NT555R drag radials I'm using are 27.75" tall. Paired up with my 3.91 SG rear end, am I looking at calculating the theoretical speed @ given RPM and comparing that to what my gauge is actually showing?

As I sat down logging the 1/4 numbers into my spreadsheet that is what I started to think.

The street manners feel I referrenced earlier is that the Performer PRM is a much more responsive intake. The Strip Dominator on the other hand is soft down low, however, the benefit last time out to the track with that single plane intake seemed to have been that even with the full 32 psi tire pressure I am pretty certain there was very little (maybe none?) tire spin.

So as you pointed out I am wondering whether now I have moved to a better torque output and with the additional head-work I provided for a tad more flow to "keep-up" with the higher RPM performance of the single plane??? Sorry...all theory at the moment and really I'm thinking out loud on this one.

Driveshaft is only turning about 4800 when you are at 5700, IMO, that's a lot of loss.

Never assume that the tire circumferences is accurate using a math formula If you don't have access to a seamstres tape buy one and measure both tire circumferences and use only that as your actual tire circumference Make sure and get the circumference within 1/4 inch of each other also, I use pressure to get them there
I've seen 3.5 inches differences in circumference on three different sets of the exact same size of new slicks at the races

Going off a 27.75" diameter, the moroso chart shows about 4880rpm for 103mph and 3.91 gears.
That's close to 16% slip, which IMO is way too high for a combo like that.
Should be well under 10%.
3600lbs, 103mph shows just a tick over 300hp on the moroso chart.
The motor combo should make an easy 400hp at the flywheel.
My experience is that if the car is working even remotely good, you should be able to run within 10% of the predicted ET for a given power/weight ratio.
In your case, 360hp(90% of 400), 3600lbs...... Shows 109mph.

I'm going to dig out some of my old VHS tapes and see if I can find some passes from my Dads old 79 Cordoba...... From around 1993.
The combo was .040 360 with some of the old flat top trw pistons for a 71 360 application(8.8:1 actual cr), home ported( by my dad) 1.88 360 heads(don't recall the numbers.... Might have been J heads) converted to 2.02(probably flowed a max of 225-230).
Torker II intake, 650dp Holley, crower solid cam(#31312)that was 250-254@ .050,108lsa, .540-.550ish lift, hooker 1 3/4 headers.
9" Fairbanks converter I bought at a swap meet, 4.56 gears, 10.5 x 28 slicks, 3900lbs race weight.
I'll double check this if I can find the videos, but as I recall it ran 12.60's and I think the speed was in the 106-108 range.
That shows about 365hp on the moroso chart, which would work out to 405hp if you figure a 10% loss for being in the car.
That motor was dyno tested prior to that with a mp509 cam in it instead and made right about 400hp.

For a comparison with another car with a known hp, that's also not set up for drag racing at all.....
I have a bone stock 2012 mustang gt. 6 speed, 3.31 gears, oem tires.
The only thing that's not as delivered is its had a few oil changes and I put in a pcv system catch can.
Horrible tire frying launches(2.10 best 60') and less than stellar shifting on my part netted a best of 13.42 at 109.8mph.
The car weighs 3500lbs + me, and I'm 240.
The moroso chart shows 380hp for 3740 and 109.8mph.... Motor is rated at 412hp.

IMO, you really seem to have two issues...... The 60' is off, and the speed seems pretty low.

On the other end of the spectrum, to show how good things can run without a bunch of fancy parts, when the car is purpose built to go down the drag strip.
1980 Dodge Mirada running in I/SA. Low comp 360, 308 heads with 1.88 valve and no porting.
Stock intake and a TQ carb. .420-ish lift cam, headers.
8" converter, drag shocks, slicks, 4.56's(I think).
Min weight is 3410....... It's gone 11.70's at 113-114.
That shows 385hp on the moroso chart.

(Quote) My hands are pretty tied here. I am actually running a set of KONI adjustables all around (front & rear). They are set pretty stiff for minimal chassis movement. The car handles great with the HD sway bars both front and rear. So very little chassis weight shift to the back. The springs are replacement M-body 5 leaf setups, clamped in factory locations. I do not want to play around with this due to the road-handling characteristics.(Quote)

I watched your video. The front end on your car does not move enough to transfer weight to the back tires. Until you get the front end to snap up you won't get the car to hook with any consistency. If I had to guess the front of the car is moving maybe 3" and it needs to move approximately 5.5" and quickly. I sniped 2 pics of your car from your video and at rest and at full extension. You can try to disconnect 1 side of the sway bar and loosen the adjustment on your Konis to help this and I'm sure your 60' times will be quicker and more consistent and you'll be able to reconnect the sway bar and readjust the shocks for the ride home. Until you can make the car hook consistently your really wasting your time trying other things.The only other thing I would try with your combo is to lower your shift points to no higher then 6200 RPM. Get the front to move first then work on the rear suspension and tire pressure then work on the rest of the combo. I would think this combo should be consistently in the high 1.70's to low 1.80's for a 60'. Good Luck!

All good advice to address the poor 60' issue..... But still need to find the missing 6mph.

I totally agree that this car is definitely missing MPH but getting the car to leave consistently will help to quantify other changes so you know if your losing ET/MPH due to tire spin or something else. If the car can't repeat how do you know if your making good changes or bad? Properly setup his combination at 3600 lbs. should be capable of going in the mid 12's at somewhere around 105-107. Of course Track elevation, barometer, density altitude, temp and humidity will be a factor.
One question for the OP. You mentioned that you have 1.6 rockers that you want to try. Do you know that there will be enough piston to valve clearance for the additional .035/.036 valve lift?

For sure, it needs to be verified if it's spinning or not as the first course of action.
If it's dead hooking and still only runs 1.9-2.0 60' times, to me that would be an indicator that perhaps the poor 60' times and low mph are related to power output.

Fwiw, my heap always worked better leaving at a much lower rpm than the op is.
I like to leave at the lowest rpm I can and not have any kind of bog...... Usually 1800-2200, which gives the motor a chance to get a run at the converter, and can often be worth another 1-200 in flash stall speed.