Georgia69, myself along with a couple of friends went to Silver Dollar last night.
It was really my first semi-successful 1/4 mile runs since making a few motor upgrades this past winter. I had previously attempted to run this track about a month ago but had fuel delivery issues that apparently have been resolved. ;)
A couple of weeks ago, at a local 1/8 mi track, the car had a best 60' of 1.45, and ran a 6.64 @ 105.42 mph before the posi started slipping.
I had thought the posi issues possibly were due to using Redline synthetic lube so earilier this week we flushed out the rear and replaced it with regular gear oil...hoping all would be well.

Wrong! :(

Last night the best 60' was a miserable 1.745...with the pass wheel spinning real bad and the posi growling.:angry: As the night progressed, I had a hard time getting the driverside wheel to even do a burnout. After the third run (1.866 60', 10.87 @ 130.78), I parked the car.
Made three passes...as typical for this car, the best was the second run...
1.745 60'
6.915 1/8
105.34 mph
10.633
131.77 mph :D

I realize the car is leaving .3 at the line & in the 1/8 mi ET in it's present condition. The Chevelle proved this earlier as mention above.

I guess my question is...
Do I rebuild the posi (Brute Strength, 800lbs springs and carbon fiber clutches) or is there something else that will handle the TQ better?
This posi is one year old...purchased brand new.
A spool is NOT a consideration...too much street driving.

Also, got a chance to weigh the car during tech...3750 with me in the seat and about 10 gals of gas.

Congrats, Bill!!! The car is definitely making some power. I think you're going to have troubles getting a posi to work with 700+ ft lbs of torque. The time has come to make a decision... If you want to realize max ET you'll probably have to use a locker of some sort or a spool. Of course a change like that will affect streetabilty. Even with a spool/locker you may find that you still have a problem with tire spin, thus requiring more work on the suspension. Another option might be a timing control to reduce power off the line, but what fun would that be? The fact that youre running a radial slick is making the tire spin even worse!

Making that kind of power, I'd definately just put a spool in it. I drive mine about once a week with a full spool. As long as you drive with some smarts, you should minimize any problems.

If you wanna keep the posi, the only person I know of who can possibly make it work is Tom from Tom's Differentials. He sells some posi units he custom setup for higher powered cars.

Given your 1/8th & 1/4 MPH, that thing "should" or has the "potential" to run in the 10.20's to 10.30's (or beter) once dialed in assuming the combination is well balanced.

Hi Bill, Several companies sell Detroit Lockers with both 31 and 35 spline axles. This type rear end should handle your power. Is that a Moroso Brute strength posi? My son had a Eaton Heavy Duty Posi in his 481" Truck which seemed to work good. With nitrous this truck ran 10.48 @ 126+ and was running out of juice on that run, with 3.73 gears and weighing 4080 pounds. The posi handled it all. I think he got the the Eaton from Reider Racing.

Detroit Locker.

It'll lock both axles like a spool, but it'll unlock for the street. It's not as nice on the street as a posi, but it's better then a spool in my opinion.

David

How does a locker work? I have heard stories about them not locking both axles then locking them after a car takes off, causing car to pull one way (never used one my self). At the track fri night a car went in to the wall (not posi related). I switched to a spool in my street strip car last winter for this reason. What if that sure grip is not so sure???? I would hate to wreck my car or even worse hirt some one else....some thing to think about. Thats some major torq...
just my 2cents....

Nice Job! Pretty stout mph at that weight. Last I remember you were in the 125mph range. What changed to yield such a big gain?

This is for novaracer. You said you switched to a spool right? If thats so, were talking about something thats full lock all the time, so your not gonna have wheels locking and unlocking on you doing weird things off the line. However, the street is where the problem arises with a spool. When you travel around a bend, the outside tire must travel faster than the inside cause it has to go a further distance(has nothing to do with the differential). The reason is because any car is basically pivoting off the inside wheels around a bend and the outside wheels have to follow a longer arc, so the outside wheels have to spin faster than the inside in order to travel that longer distance in the same amount of time. If you run a locker, that cant happen cause both wheels spin the same speed all the time.

Im not sure how much you drive the car but be careful. Driving a spool on the street can put you into a guardrail or something cause sooner or later, yove got to go around a bend while your street driving and you really cant predict for sure how the car will act when you have basically simulated using the brakes, but only on one wheel. So, your basically gonna be dragging one of the wheels around the twisties. Thats hard on the whole rear end as well and can definitely cause premature failure cause theres always opposiing forces arguing with each other with a full spool. Be careful. I would also give a ratcheting type locker a try.

Awesome Bill !!!

have you thoght about using the lockright ? This will be the 7th season on mine.

Will the lock rite fit in a posi carrier?

Will the lock rite fit in a posi carrier?

Nope.

No it will not, just need an open carrier. Some of the companies like Tom's carry them.

Outstanding Bill, closin on 132mph,,, congratulations :beers:

Looks like you got everything going & it appears you are making a wee bit of power :D

Looks to be an honest 700HP in the car under whatever conditions prevailed,,
I see very low tens in your future when you get that "lightweight" hooked ;)

Thanks again for lettin us help a little,,,

Making that kind of power, I'd definately just put a spool in it.
Given your 1/8th & 1/4 MPH, that thing "should" or has the "potential" to run in the 10.20's to 10.30's (or beter) once dialed in assuming the combination is well balanced.
Because we have a wrenching relationship on the 'Velle ( Bill and myself) I agree with Todd......he still has ignition issues( stable timing,needs CRANK TRIGGER! still only running about 35 degrees timing ,WE THINK!...and we feel the carb is a wee small so we will be stepping up to the larger venturi in the 990 B.G. king demon..........I believe if he EVER gets this thing to hook consistantly he will see the 10.20's ......OR?..

Congratulations!! Looks like you've got that dude making some power. Can you give some more details on motor?

That's a bummer on posi going out. I would have thought it would have lasted longer. One tip is to make sure they really put down some water when you are doing burnouts. I often see the box get a little dry and a posi has a hard time when one is on dry pavement and the other is wet.

I've run spools on the street, and it just depends on how far you're going to go. You have to be careful with axles too, cause the side forces on race axles can make it rough on them too if you do a lot of fast cornering...on ramps etc. Just go slow and you can do it. Be real careful in the rain!

When I put together the Dana 60 IRS setup for my Vette, I looked at getting a locker but ended up with a custom posi assy. just for the nice streetabilty of it. So far so good......probably 60 passes (10.0's@141) at 3600 lbs and a stick trans, and so far all is well including lots of highway miles.


JIM

Congratulations!! Looks like you've got that dude making some power. Can you give some more details on motor?
JIM
:D :D :D Looks like you are making more than the orginal 696hp. Bummer on the posi. Once thats fixed LOW tens are comming your way, good luck.

Bill..the awesome..131.7 MPH :thumbups:
I vote for the locker as well

Thanks for all the input guys!! :beers:

I've been thinking about this since yesterday...
Simpliest (and cheapest) solution is to just remove and rebuild this Moroso posi unit. I'll call Tom's Differentials later today and see what they recommend as far as replacement parts. I've kind of developed a theory that I've glazed the clutches by using synthetic oil which lead to their early demise.
I've really tried to keep this car as simple as possible...still running a stock water pump, clutch fan, stock battery location, power steering, full interior including bench seat, ect. Just recently "surrendered" the mechanical fuel pump in favor of an electric one...not without a fight, though.
Heck, I still hate climbing into the car over the roll bar. :(
Anyhow, just to update the upgrades...this past winter we removed the 325cc Dart Pro I heads and replaced them with a new set of AFR 335 CNC ported (THANKS MIKE!) along with a new solid roller Comp cam which came recommended by Chris Padgett. Cam specs are simular in duration to the Lunati it replaced but with more lift to take advantage of the better flowing heads. New heads also raised the CR slightly to 11.0 from a 10.5; DCR remained nearly the same at 8.2

131 is flying in that heavy car. great job.

my chart says your making 670 RWHP with 131.77 and 3750 weight. At 100 % effiency it will run 10.3xxx.

Did you run this through the mufflers ? If so what set up do you have ?

Mike

Did you run this through the mufflers ? If so what set up do you have ?
Thanks, Mike.
Yes, thru the mufflers. Exhaust system consists of Hooker Super Comps, 2 1/8" primary, 3" pipe (no H or X ) to Ultra Flows with 3" turndowns at rear axle.

I had the pleasure of sitting on the return road near the finish line as Bill went by on the track at full throttle. Awesome! It's like a big white freight train.

131 is flying in that heavy car. great job.

my chart says your making 670 RWHP with 131.77 and 3750 weight. At 100 % effiency it will run 10.3xxx.

Did you run this through the mufflers ? If so what set up do you have ?

Mike
=
Mike,
Don't know what chart you are using but it is wrong, it's giving you engine HP not RWHP.
Most of the on line calculators are not correct, they are using a formula that is for engine HP.
If it were correct that would equate to 800+ at the flywheel,,,

Here is something I have posted before:
Virtual 2000 supposedly gives engine HP I believe, all I can tell you is to do a few calculations & see if it makes sense to you.
If that calculator was right a 204 mph Pro car would be making over 1500 rear wheel HP
Assuming a generous 10% loss we are talking almost 1700 engine HP????

Here is a little formula that has been around since at least the 70's & was used by Chrysler Corp. in their drag racing program & written up in the American Journal of Physics in 1973
HP=(.00426*MPH)cubed * WGT
I add about 50 HP to the number because trap speed is measured differently now than it was in the 70's.

EX:,,,,,,,.00426*97=.41322cubed=.07056*3400=240HP
Add 50 to be nice,,,290HP
I find this formula works pretty fair until you get into some of the very hi end cars like Pro Stock. I find with cars like these it will give you a higher HP number than you usually see, especially adding 50HP.

This formula might be old but I believe most of the laws of physics still apply,,,,,,unless of course you are using that "Good LA air" when you dyno :D

I'm using a spread sheet that a friend of mine sent me. When i chassis dynoed my car it said 292 RWHP and using this formula with MPH and weight i got 316 RWHP. It's been right on with all the other cars we've dynoed and run at the track.


I get 670 RWHP and it says 743 FWHP. right now it's telling me the effiency is 92%.

I believe he derived this from a prostock formula

I'm using a spread sheet that a friend of mine sent me. When i chassis dynoed my car it said 292 RWHP and using this formula with MPH and weight i got 316 RWHP. It's been right on with all the other cars we've dynoed and run at the track.


I get 670 RWHP and it says 743 FWHP. right now it's telling me the effiency is 92%.

I believe he derived this from a prostock formula
=
There is no way you are only going to have an 8% loss in the drivetrain.
Most average accepted numbers are about 15 to 20%.
Pro is undoubtedly less but I don't think you are going to find anything close to 8% ;)
Been wrong before but most of the honest dyno numbers I have seen come reasonably close to the above formula at the crank & have for the last 30 or so years since it was written,,,

Once again..old stuff works! I ran my combo through it and came up with 791HP "without" adding the 50 hp back in. Since it dyno'd at 825.1 hp on a "real verifiable Texas Dyno" on a muggy day with a Moroso street pan and I've since added the "magic Milodon" 15 hp stepped sump drag race pan....looks like I may be in the ballpark with Mikes formula.

Pretty good for 93 octane!!


JIM

Great mph - should be a fun ride!

re: Wolf vs. Mike
The 92% efficient is for the torque converter. Even my good stick cars have had twice the total drivetrain efficiency loss+ (~18%), and my non-lockup autos have been twice again as inefficient from the flywheel to the wheels.
The old Chrysler calculation doesn't seem to work very well - even with a 50 hp adjustment for the change in average trap speed calculation. Without the 50 hp correction on my stick car the Chrysler calculation shows close to the flywheel hp, on my auto car it shows close to the rear wheel hp. Wolf, do you remember if the Chrysler calculation was intended for stick cars rather than auto trans?

All that math nonsense aside, Bill is putting some awesome power to the ground.

Thomas

Great mph - should be a fun ride!

re: Wolf vs. Mike
The 92% efficient is for the torque converter. Even my good stick cars have had twice the total drivetrain efficiency loss+ (~18%), and my non-lockup autos have been twice again as inefficient from the flywheel to the wheels.
The old Chrysler calculation doesn't seem to work very well - even with a 50 hp adjustment for the change in average trap speed calculation. Without the 50 hp correction on my stick car the Chrysler calculation shows close to the flywheel hp, on my auto car it shows close to the rear wheel hp. Wolf, do you remember if the Chrysler calculation was intended for stick cars rather than auto trans?

All that math nonsense aside, Bill is putting some awesome power to the ground.

Thomas
=

Hi Jim l :waving:


Thomas,
Gotta agree with your last sentence:beers:

Don't really know but I think it was used with both & as noted is just an estimate.
I have found it to be pretty good & lot closer than most of the online stuff but it's still an uneducated guess ;)

Bottom line, as you said, 132 at 3700+ is pretty damn good power for a real street deal
And you have to remember it is what the power is on that day under those circumstances in the vehicle so if you have 700 corrected on the dyno & run it at 5000' DA the numbers may vary a bit :D

Hey Mike....I sent another Isky lifter customer to you yesterday. Corey...another Vette dude!

Anyone who is getting above 130 mph at full weight is making some power!


JIM

Hey Mike....I sent another Isky lifter customer to you yesterday. Corey...another Vette dude!

Anyone who is getting above 130 mph at full weight is making some power!


JIM
=
Thanks Jim, every little bit helps,, gotta keep the wolves in food so I can get through the yard,,,, or I could just sleep in the dyno room I suppose,, :D

My formula shows about 678 H.P. for 3750 lbs. to run 131.77 which should like Wolfplace says be in the vicinity of 10.3 once the problems are ironed out. Any variation in horsepower calculation could be from the fact that the dyno's always spit out corrected horsepower figures and a day at the track seldom has these ideal standardized weather conditions. The old Mopar formula is pretty close with only a corrected MPH change for the incorrect way the new MPH readings are taken. Meaux Racing Heads says you only need to multiply the new MPH by 1.0072 to obtain a corrected old MPH figure then you could apply the ((.00426 x MPH) cubed x weight) Mopar formula to get a close uncorrected for weather horsepower figure. This figure will generally appear somewhat low but a pretty slick Super/Stock engine builder says that in order for an engine dyno to give exact and accurate figures it must be calibrated prior to testing and takes quite a bit of time therefore most dyno operators just guess, knowing that their dyno is probably from 25 to 50 H.P. high and customers like seeing the higher numbers. If any of you would like to try the formula the average SS/AA Hemi makes about 880 H.P. and the cars total weight is 3170 lbs. David Barton said his best car made 940 H.P. Stick drivetrain losses are about 13-15% and automatics are around 19-20% and i've found Smokemup's MPH calculator to be close but the E.T. calc. is optimistic. My son's Chevelle has chassis dynoed at 924 RWHP with about a 300 flywheel nitrous shot and has run 8.667 at 3610 lbs.

678!........IS THAT ALL?.............Better be RWHP...........Bill ,we gotta get to work on that thing!

Anyone who is getting above 130 mph at full weight is making some power!

True story.