[Half-Inch Stud]

Is the 1.50 60foot while leaving off-idle AND a Trans-Brake?
Be interesting to see if the 60 foot goes away when leaving off the Converter.
BTW, that's Test&Tune, not a hardware change.

The move to a 3.54:1 gear would be interesting because IF you can sustain the 1.50 60foot, then the rest of the track run ought be improved for upshift ratios allowing the Converter to fall-back-into its Torque-Converting mode.
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Me thinks the Converters (including Hi-Stall) have an optimal RPM band: defined as having a TQ-Multiplying RPM Range referenced to the Output shaft that shows the Converter needs a particular Rear Gear&Tire to center-up the TQ-Multiply ability

Me thinks the Converters "Saturate": Saturate defined as the "Fluid-Couple mode that occurs AFTER the TQ-Multiplying range has ben passed. The Fluid Couple-Mode can be come increasingly inefficent with increasing Input power.
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I know for sure that Converter Companies need to supply a "Converter Personality Plot" with their products. Such a plot would show Input RPM, Output RPM and resulting TQ-Multiply, for several sets of loads. The Plot is really simplified if put as a set of Efficiency Curves plotted against Vertical ("Y") axis from 0% to 100% , for ("X") axis Output RPMS. Input RPMs is gotten from Output RPMS/Eff.

[BruceWilkie]

The idea is to spend more of your time in the higher half of your powerband than the lower half. HP = how fast work gets done. I have no doubt you can hit 136 with the 4.30's, however you may find yourself hitting that 136 and not much more before the light. 4.10's you likely will hit 136 too! However they give you the chance to hit 140 that the 4.30's wont.

Run your shift loops and see. FWIW a Mustang chassis dyno I was on a few years back you could run a simulated 1/4 mile. If you cant make the track then perhaps some simulated 1/4 mile on a chassis dyno will help you find the best shift rpms.

FWIW I street drove with an 8" convertor originally built for a smallblock. Was supposed to stall 4200-4400. I caught a divorce sale and picked up a $900 (1995 or so) convertor for $300. I had to try it. Behind my 440 it flashed 5200 rpm at launch and I picked up nearly a tenth 60ft and about .25 in the 1/4. On the street normal driving it flared less than my old 3200 street convertor. On the same overpasses at 55mph rpm was 200 rpm less than the street convertor. Water temps stayed cooler on the 45 mile drive to the track as well. My car weighed 3910 with a full tank and myself in it.

[71 Ventura II]

FWIW I show a 4.30 gear @ 140 mph in your combo is +- 7283 rpm's at the stripe and 6944 rpm with a 4.10 gear. JD

[Ron H]

What are the internals of your short block? 7600 is high rpm for a stock block...

[Skip Fix]

I know the dyno showed that rpm as peaks but that sure seems high to me for that combo. Runs good for sure but the rpm seems a little high.

[BruceWilkie]

Originally Posted by Skip Fix

I know the dyno showed that rpm as peaks but that sure seems high to me for that combo. Runs good for sure but the rpm seems a little high.

His chassis dyno curve closely matches desktop's tq peak and power peak curve. Different numbers but very similar curve.

Back when this build was going together either here or PZ I ran the specs just to see. I think I posted something to the effect that the power peak was going to be high. I'll look for the post.

[BruceWilkie]

Well I looked and I didnt post anything and not sure if I might have pm'd or emailed but I have a desktop file dated 3/28/09. I did post my expected chassis dyno hp guesstimate around that time.

[79TA455STROKED]

Originally Posted by 71 Ventura II

FWIW I show a 4.30 gear @ 140 mph in your combo is +- 7283 rpm's at the stripe and 6944 rpm with a 4.10 gear. JD

Thats what my math came out to,so i can hit 140 with the 4.30 gear,just a little higher in the rpm,but if you look at the hp curve,it did not drop off after 7100rpm so i should be good.

Originally Posted by Ron H

What are the internals of your short block? 7600 is high rpm for a stock block...

Its a Butler shortblock,eagle crank,h-beam rods with the better arp bolts,ross pistons,billet caps with arp studs,coated bearings.

Originally Posted by BruceWilkie

Well I looked and I didnt post anything and not sure if I might have pm'd or emailed but I have a desktop file dated 3/28/09. I did post my expected chassis dyno hp guesstimate around that time.

Yes,you posted somewhere or pm'd me.you had the hp rpm peak rite on the money u just guessed a little lower then what i made.I think you said i can make more with a smaller cam but im happy with what it makes,they hit the goal pretty much dead on.
You been a great help,thanks for that Bruce!

So Bruce,looks like i can hit the 140 not at to much of a crazy rpm,what u think about that?
I know i sound like im leaning towards a 4.30 and its true,because i already have a set of 4.30 in a box and i dont have a 4.10 yet! LOL!!

[79TA455STROKED]

And track rental is next mon,trying to get rear susp finished so i can make it.Its fighting me all the way.
Have calvert split mono's,caltracs,afco rear spring slider mounts,movin shocks inboard and mounting afco dbl adj shocks.

[Skip Fix]

I'm in the process of putting the Cal tracs, split leafs Rancho shocks and 12 bolt in my project this week too.Using those factory WS6 rotors and metric calipers like you used also.

And why did that GM engineer put the shackle bolt where you have to drop the tank to get to it!

Hope mine will go as fast too.

[79TA455STROKED]

Originally Posted by Skip Fix

I'm in the process of putting the Cal tracs, split leafs Rancho shocks and 12 bolt in my project this week too.Using those factory WS6 rotors and metric calipers like you used also.

And why did that GM engineer put the shackle bolt where you have to drop the tank to get to it!

Hope mine will go as fast too.

Lol!! yeah u dont gotta tell me.This time i did away with the shackles and bought the afco sliders for the rear of spring.
Has no bind now back there and sliders dont change the spring rate like shackles do during the range of motion.
Ull love the split leafs and caltacs Skip!!I had them before,just ordered new split leafs to relocate the rear a little and doin the sliders and relocating the shocks at the same time.
I was gonna go with the ranchos but figure ill have alot more adj with the dbl adj afco shocks.

[mysticmissle]

what are you going to do about the roll cage and lisc? have you already taken care of those things, maybe i missed it?
great car and times by the way.

[BruceWilkie]

I use this formula for ball park mph. (rpm x tire diameter) / (Gear ratio x 355) = MPH

(Manual trans use 336 vs 355)

BTW I had less lift on the sim than your signature shows and compression at 10.5. My sim doesnt show a sharp drop in power till after 7500 but 7k is peak.

My 2 cents if you are hitting peak power just before the finish line you used all your power. Up to a few hundred over as your clocked is fine.

I once skipped to 4.56's from 4.10's and later found 4.30's should have been my choice. I improved a tid 60 ft and eighth but no 1/4 et improvement with a loss of about 3 mph. I never got around to trying the 4.30's but did borrow some 9 x 30's but only got 3 runs in. My mph was better than the 4.10's but I didnt get the tires where I was 60 ft'n as good as the 4.10s or 4.56's with a 10 x 28.

[Probird]

That formula is 7.4 mph off for my car. Probably because my convertor isn't the most efficient. I believe it is 10.5% slip.

[70 lucerne lemans]

My votes on the 4.10,I agree with Ron,thats alot of rpm for a factory block with an Eagle crank and rods.I'm thinking of switching from my 3.73 to a 4.10.All the Pontiac guys I see running 4.30s are using 30-32" tall tires.

[Ron H]

4.10's with a 28" tire in my car trapping at 6800, 130 mph.
The 4.10's should keep your converter tight or it will tighten up further on the top end.
It may however lower you launch stall. I dropped 150 rpm off the launch switching from 3.89's to 4.10's.
Your starting line ratio will be going way up with 4.10's from 3.73's as it is. 4.30's will give you fits trying to hook, IMO.

[Skip Fix]

I'm starting with a 3.73 and probably a 28" tire but don't have the rpm peak you do since I have 500", less head flow and a less cam.

[Brent Flynn]

Originally Posted by 79TA455STROKED

Thats what i figuured and i will try movin shift points up but also figured im leavin alot of power out by goin through traps at 6350rpm when my peak hp is at 7100rpm.
So i figured i would change gears to move the rpm up also.
I dont get to go to the track much with it being out of state.

Best shift point is 6-8% abve peak hp.
What is usually best rpm to go through traps in relation to peak hp numbers?
Also,am i lookin for the shifts to drop the rpm into peak tq rpm range?

I would go with 4.30 gear and 9-10x30. The car will think it has more starting line gear...and you will have a better top-end gear. To be honest, i think anything over 6500 rpm with a stock block is just askin for trouble. Why dont you advance cam and try to increase torque at a little lower rpm? If you do that, and it responds, you wont need much more gear anyway. Are you bracket racing this car or tryin to run some sort of heads-up class? Your car is awesome, btw!

[440GP69]

I'm curious to how how this plays out! Ive seen Many hi rpm Pontiacs NOT go faster from shifting past Hp Peak, In fact ive seen more et gains from short shifting these type of Poncho's especially 1-2 shift, But ya never know!

[Brent Flynn]

Originally Posted by 440GP69

I'm curious to how how this plays out! Ive seen Many hi rpm Pontiacs NOT go faster from shifting past Hp Peak, In fact ive seen more et gains from short shifting these type of Poncho's especially 1-2 shift, But ya never know!

i agree with you on the short shifting....most pontiacs like it. Sounds like a wide lobe sep cam in his engine. i would tighten that up with a different cam and bring it back down to 6400-6500 rpms....anything to keep block from splittin up the middle!