[firechickenman]

I'll bet that launch with the 8" converter did feel a little different! That 60' change should have made more difference in your ET but that converter is too loose killing your down track performance. I think a custom 10" would work best for what you're doing. I'm very happy with my 10" PTC. It drives really well on the street, flashes to 5000 on launch, and locks up fairly well at the other end of the track. It traps about 6500 at 132-133 in the 1/4 with a 3.73 gear and 275/60R15 (28") tire.

[GOAT8U2]

Ideally you'd want Real slippage % to see and give the converter company.

Take the rpm in 3rd gear and mph at 5500, 6000 etc and see how the converters coupling at those rpm ranges. It's possible you're seeing like 15% at 5500rpm then like 12% at 6000 and 10% at 6300rpm showing the converter would continue to couple if you could spin it higher (you wouldn't though unless you wanted).

There's a better chance a 9.5" true turbine ID converter fits your needs better than an 8" (probably a 8 3/4" turbine ID) due to your max rpm. You can install a different stator blade setup in the 9.5" to get it to stall and flash stall better than normal yet it'll couple at max efficiency sooner than the 8". The 8" is usually ideal for 7k+ rpm range engines.

[Half-Inch Stud]

Originally Posted by leeklm

.............Just for kicks, I am dropping my exhaust for a day at our local 1/8 mile this wknd running the loose converter. Supposed to be high of 52 degrees, so hopefully some clean air for a few fast runs.

Please plan to install Collector Extensions (about 13" long) for Torque and off-idle response .

See signature for 10" ATI 2800-3200 Converter ( super-tight on Street with 3.31:1 gear in 3650 69 Bird. 5200-5500 shift points and 5950 RPM at big end for 12.0. Super 60' too, and same same in '68 Strip .bird.

Relevant since the 11.0 68 Bird combo was destined for mid 10's with same 5250-5500 shiftpoints, and i forget trap RPM but definitely below 6200.

[leeklm]

"Please plan to install Collector Extensions (about 13" long) for Torque and off-idle response ."

Yep, ordered a few exhaust parts earlier this week . Sunday will give me a chance to compare 1/8 mile rpm vs mph, but from watching my 1/4 video, it looks like the rpm will be about 6k pretty much across the board! With the cool weather, hoping the track prep guys are on their A game!


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[leeklm]

New update... great racing weather at the 1/8 mile today! Removed the exhuast and replaced with a 2 ft pipe and turndown. I should be right around 3,300 lbs race weight. My car now sounds as obnoxious as the rest of them

I was rewarded with a new personal best 1.40 60ft and 6.51 ET @ 106.7mph. The car was launching great in time trials, but tires went up in smoke twice during Elims. Ended my day early but was fun nonetheless!

I am now really curious to see the results once the right converter is installed!

Attached are 2 runs from TT

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[firechickenman]

Dropping the exhaust really woke that thing up! You're right there with me in ET and MPH at the same weight with a much milder combo! If you really want obnoxious, take the 2 ft. of pipe off.... Attached time slip shows what your 1/4 ET and MPH should be.

[leeklm]

Nice time slip Greg! One caveat with my 1/8th mph here is that this track always registers about 1.5 mph faster than the two 1/4 miles I run on occasion. 1/8 mile ET is consistent at all 3, but mph always a little higher at this one.

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[Half-Inch Stud]

2' extension will sure avoid reversion lean-out. 1.40 is a measure of success: congrats!

[leeklm]

1/4 mile update... had good air last Saturday, place was packed so could not really do any testing, but got 1 good run in. I did set a new personal best, but you can see the converter slippage crossing the line around 6600 rpm. Bill did a great job balancing the rotating assembly as it feels this engine would sing well north of 7k!!

Again, looking forward to results with a tighter converter to see if I can maintain these 60ft times while providing less slipping on the top end and keep the rpm south of 6500.



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[AG]

What was your % slippage across the line? My converter is 6.8% across the line at 6700 rpm.

[leeklm]

Using the formula of 128mph x 3.5 gear ratio x336 then divided by 26" tire, i come up with 5,790 rpm at zero slip. Since i am about 6,600 rpm, that comes out to 13% slippage if I did that right.

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[Cliff R]

" the flash on this 8" PTC is too high for me, as it almost feels like I am driving a CV transmission with very little RPM drop on shifts."

Too much slip once past the stall speed and coupled, but for sure combo loves the high flash stall and additional torque multiplication to get the car moving. Even an 8" unit should be able to couple better than that...IMHO. That's a typical trade-off and exactly what I saw back when I was testing converters. From what I've seen with this sort of thing most companies don't have any trouble getting your PLENTY of flash stall, but getting the converter to lock-up past the stall speed is the tough part.

Since you already have an 8" "race" type converter you may want to have them tighten it up just a tad. That should be less than replacing it with another unit even with the shipping both directions. If all that fails you can always open up the wallet and go another direction.......Cliff

[AG]

Originally Posted by leeklm

Using the formula of 128mph x 3.5 gear ratio x336 then divided by 26" tire, i come up with 5,790 rpm at zero slip. Since i am about 6,600 rpm, that comes out to 13% slippage if I did that right.

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13.98% slip, ou should pick up some mph with less slip. That thing is flying.

[grandville455]

I do agree that it loved the flash, But It also appears to be happy in the upper rpm range keeping it at peak hp or above even tho its slipping, It should pick up, It will be interesting

[leeklm]

One last change for the season... i ended up having my 10" converter re-tuned with a different pump and some modifications to the stator. Was hard to read my tach video but looks like it is stalling at 4200.

Did not get much tuning accomplished on Saturday due to a large car count and a couple of extended clean ups. I was able to get 2 decent runs that provided a 1.40 60ft, which is 1/10 better than the original 10".

We had a strong headwind so was difficult to determine slip on the top end. Other cars were down 2-3 mph. DA was around 1500 ft.

I will not be street driving until next spring (making some changes to exhaust) , but the modified 10" is much tighter than the 8" I was trying out, and feels like it will still be fairly street friendly. All in all I am happy with the change and appears to be worth the effort!

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[Half-Inch Stud]

60' looks real good. 1/8 mile also real good.
Could MPH be a clue for mixture retune?

[leeklm]

Originally Posted by Half-Inch Stud

60' looks real good. 1/8 mile also real good.
Could MPH be a clue for mixture retune?

Based on mph results from other cars, I am likely down a minimum of 2mph due to the strong headwind. In addition, I had myself in the mode of shifting at a higher (6500) rpm from using the 8", which was probably hurting me here as it looks like I was dropping about 1500 rpm on my shifts. In the video, I could really hear the wide rpm drop, especially on my 2-3 shift. Bringing the shift point back to 6k should help.

This transmission has the low 1-2 gear set, so does have a wider gap/ratio on the 2-3 shift.

Looking forward to some cool air come April for more runs!! In the meantime, I plan on going through the motor this winter and possibly a little more aggressive cam as long as things are torn down

Can't see much here, but you can hear the shift points in this video...

https://youtu.be/BiJoHFv-z1A







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[leeklm]

Thought I would post this video from the most recent run discussed below with re tuned 10" Continental (done by Ultimate). Track video guy did a great job! The Camaro in the other lane is running a small block 383 putting out some good power.

https://youtu.be/P_wVOJSp-oE


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