[Half-Inch Stud]

Making it simple: Does EVERYBODY shift out of 1st gear after or before reaching the 60foot?

[tom s]

before on mine.Tom

[Cliff R]

"Cliff, you have a really good torque converter. Keeps the motor at pk torque despite 3rd gear load until it catches up. Self Averaging torque curve built into the transmission."

Excellent observation! Also keep in mind that those runs were made with our old engine, which made over 550ft lbs torque at 3500rpm's (stall speed) and was still cranking out 537ft lbs at 5100rpms (shift at 5200). The torque curve was nearly flat, so the engine really doesn't care where you shift it at, or if you go straight from 1st to 3rd gear!......Cliff

[Motor Daddy]

Originally Posted by Cliff R

"Cliff, you have a really good torque converter. Keeps the motor at pk torque despite 3rd gear load until it catches up. Self Averaging torque curve built into the transmission."

Excellent observation! Also keep in mind that those runs were made with our old engine, which made over 550ft lbs torque at 3500rpm's (stall speed) and was still cranking out 537ft lbs at 5100rpms (shift at 5200). The torque curve was nearly flat, so the engine really doesn't care where you shift it at, or if you go straight from 1st to 3rd gear!......Cliff

Nope.

Yes it matters, because up shifting too early means a numerically lower total gear ratio at a lower MPH. That means Cliff goes slower.

[Half-Inch Stud]

Yes it matters, because up shifting too early means a numerically higher total gear ratio at a lower MPH. That means the CONVERTER is MULTIPLYING the Engine TQ....again.


See, when the Transmission goes from 2.48:1 to 1.48:1 the CONVERTER goes from 1.2:1 back to 2:1...for an effective TQ increase that applies itself to the 1.48:1.

Lets ponder this together: 2.48:1 * 1.2:1 versus 1.48:1 * 2:1 Hmmmmm. HIS

[Half-Inch Stud]

IF your converter does not re-dip into TQ multiplying, then perhaps...the converter is mismatched from the desired upshift RPM....At the MPH that you upshift.

What matters for all of us is to really know the MPH that the car is rolling, for the upshift interval that our engine is saying "shift me now". See if the car "MPH'd-out" then the converter will not revisit the TQ multiply after the launch simply due to the Stator being locked to the Stationary Pump Neck. I think we want the Converter to revist TQ multiply during the 1-2 upshift. OR even the 1-3 upshift for those inclined that way.

Finally, if the Converter stall is TRULEY only for attaining the best 60foots, then Geez we'd run Clutch cars with 4.88 to 6.13:1 rear gear...and an OD gear.

I like the idea of a 3-series gear, and a Load-sensitive, MPH sensitive Converter. OD would still benefit at Highway MPH since the Stator knows the cars Driveshaft RPM.

[Half-Inch Stud]

Could ya imagine a 4500RPM stall converter with a HD locking clutch pack in a Sw-Pitch TH400. Now thaaat would do well in Street/Strip.

[Cliff R]

"Yes it matters, because up shifting too early means a numerically lower total gear ratio at a lower MPH. That means Cliff goes slower."

Correct, going straight from 1st to 3rd the car slowed up .02 to .03 seconds, same MPH.

We also found that by raising the shift points from 5200rpm's to 5500rpms we would pick up about .02-.03 seconds ET and .30-.50mph.

Still very little difference, but still it slows up if short shifted, and picked up if shifted up near peak HP. I raced the car for years and was very successful shifting at lower rpms, as there is no need to grind up the engine for bracket racing. In addition, having a couple hundreths available on the run would allow us to push our opponents hard enough they had little if any room to let off up near the finish line, when I didn't think we were going to get there first!......Cliff

[Motor Daddy]

Originally Posted by Cliff R

"Yes it matters, because up shifting too early means a numerically lower total gear ratio at a lower MPH. That means Cliff goes slower."

Correct, going straight from 1st to 3rd the car slowed up .02 to .03 seconds, same MPH.

We also found that by raising the shift points from 5200rpm's to 5500rpms we would pick up about .02-.03 seconds ET and .30-.50mph.

Still very little difference, but still it slows up if short shifted, and picked up if shifted up near peak HP. I raced the car for years and was very successful shifting at lower rpms, as there is no need to grind up the engine for bracket racing. In addition, having a couple hundreths available on the run would allow us to push our opponents hard enough they had little if any room to let off up near the finish line, when I didn't think we were going to get there first!......Cliff

The bold words say it all.

If you then used that power around the peak as the range of RPM your engine would see in the 1/4 mile, and you also had a higher numerical gear, your car would be even faster, because the rear wheel torque would be greater at every MPH.

[Cliff R]

Correct, in theory we could continue to increase the rear gear ratio, and raise the converter stall speed to provide more power on the launch. Both moves would improve track performance. Just keep in mind that it is NOT an easy task to hold over 600ft lbs torque on 9" tires, and we run over 120mph at the finish line. With our relatively short tires, we can't go up much more in gearing, as the rpm's at the finish line would be too high.

Higher stall speeds combined with taller gearing also makes the car LESS enjoyable to drive on the street. I've had a few of those cars, 4.10 gears and 4500rpm converters don't fair well with 50 to 100 mile runs down the interstate at 70 mph!

As with most things in life, there are ALWAYS comprimises........Cliff

[Motor Daddy]

Originally Posted by Cliff R

Correct, in theory we could continue to increase the rear gear ratio, and raise the converter stall speed to provide more power on the launch. Both moves would improve track performance. Just keep in mind that it is NOT an easy task to hold over 600ft lbs torque on 9" tires, and we run over 120mph at the finish line. With our relatively short tires, we can't go up much more in gearing, as the rpm's at the finish line would be too high.

Get a smaller crank and make the power at a higher RPM. Shift the power band UP.

Originally Posted by Cliff R

Higher stall speeds combined with taller gearing also makes the car LESS enjoyable to drive on the street. I've had a few of those cars, 4.10 gears and 4500rpm converters don't fair well with 50 to 100 mile runs down the interstate at 70 mph!

As with most things in life, there are ALWAYS comprimises........Cliff

About those power leather seats....

[Cliff R]

Sounds good, but I'll stick with my "tractor" engine for now. It idles like a 350 making 200 hp, and runs well under the roll bar rule in full street trim, without power adders. Best part is we are using 89 octane fuel, and it's dead solid reliable. Lots of ways to go fast. I quit running Pro Stock sized cams and shifting at 7500rpm's years ago when I got away from Small Block Chevy's! Have a great weekend!....Cliff

[Motor Daddy]

Originally Posted by Cliff R

Sounds good, but I'll stick with my "tractor" engine for now. It idles like a 350 making 200 hp, and runs well under the roll bar rule in full street trim, without power adders. Best part is we are using 89 octane fuel, and it's dead solid reliable. Lots of ways to go fast. I quit running Pro Stock sized cams and shifting at 7500rpm's years ago when I got away from Small Block Chevy's! Have a great weekend!....Cliff

Well that's fine, Cliff, you are where you want to be, and feel the most comfortable. You have achieved your goal of your idea of a street/strip car. May I recommend a permanent disclaimer for your signature?

Be advised that these results were based on a personal desire to maintain a specific level of streetability at all times. In no way do these test results imply maximum performance, just a personal blend of street/strip. By no means are my results and parts combination the best way to achieve maximum performance, if one so desires to ignore such street factors.

[TIN TIGR]

now thats funny..cruel, but humorous..cliffs car runs well..he did his homework to optimize "his" combo..it aint no race car, but it works better than most pontiac bracket guys..

i like the 106-108 lobe centers..always worked for me, and we built our cars around that "violent" midrange..if i recall, my "stock eliminator grind" was like 244-230 at 050, and 106 lsa..??100 degree intake center??..however it came out, (17 years back), the same cammy held the l/stock record with a 4 speed..

the mild pontiac port responds well to tight lobes in a shorter stroke..i like them in 4.21 cranks too, but i have seen 113-115 lobes produce super smooth results as cliff has found..lower peak, but long pulls..for the street, his approch is more correct imo..and remember he runs a q-jet..the carb helps tell ya what cam to run

as for short cams, with tight lobes, i'd try it..but run 3.08- 3.31 gears, and a good 2 barrel, with adequate exhaust..

[Will]

A 2bbl over a Q-jet??? Why?

[speedshopmike]

minus the bull****, this thread could've been useful...

HIS, you're always looking for an absolute rule with everything you post - not gonna happen; too many variables in a given combo for "rules" to apply.
trends and indicators are what to look for (see cliff's methodology)
choose ALL parts to build on a motor's strengths and crutch it's weaknesses.

cliff - some people just like to argue; it's their nature; don't let people make you crazy.
i deal all day long with guys who gleaned all their "knowledge" from car craft magazine articles; it's impossible to change most peoples' minds once they're set.
my rule is tell customers 3 times, no more, no less, what i recommend, then sell 'em what they ask for if it's still different then my recommendation.

another thing i'll mention is i agree with the fella who posted vizard's LSA chart is not worthy of use; again, too many variables to use a line chart to choose a camshaft.
DV, someone i formerly greatly respected, "lost it" with that article on being a cam expert, in my humble opinion; that article annoyed me so much i literally burned the magazine.
by same nature, holley's carb cfm chart is "accurate", in which case every 350 inch motor oughta be running a 600 vac sec carb.

the bottom line is THERE ARE NO ABSOLUTES - trying to state things in those terms is an impossibility, and it's all about the OVERALL COMBINATION.
that includes gearing, weight, converter, etc.
most importantly, it means selecting parts to fit a given user's desires - want a smoky burnout in third gear at 1200 rpm from a roll - no prob, but it's not gonna run big numbers at the track.
want crazy track numbers - no sweat, but don't expect good manners as a street car.
we compromise all parts selections to achieve a desired result; it's that simple.
get the complete combo right and you'll have a happy ending.

last thing - LSA/overlap and it's effects are ENORMOUSLY influenced by the exhaust system.
overlap is all about exhaust scavenging to improve cylinder filling using negative pressure waves to pull in more mixture.
ever see a high-overlap combo that dyno's great big numbers, then falls on it's face when actually in a street car?
guess why.