Trap speed 106 MPH.
Rear gears, 3.42.
27" tall tires.
Engine RPM 5800-6100 ?
Something doesn't add up.
I trap at 108 with 3.73 and a 26" tire and have less engine speed than that.
Your gearing and trap speed works out to about 4500 RPM. Toss in 10% converter slippage and your still less than 5000.
What's up with that?

 

i will go again wednesday night and i am starting to see where i am at the more i run.
i also think wheelspin is a problem at off the line and into second..possibly more...the gearbox is real good and reliable and my mate has built over 4000 GM automatic boxes since the 1960,s with zero come back...

i will get back wednesday our time as thing dont add up here either....i will say i am running against a lot of hot LS1,s and they aint smokin me completely..i beat a few allready

 

Nothing you say makes sense and it has been that way since post #1.

 

i bought a full set of NVU 1960,s retro style gauge set...tach,speedo in mph,,oil,fuel,volts,temp gauges and i dont think these gauges are any good...have ran out of fuel while showing 1/4 tank and ohms are adjusted correctly for my car,,oil pressure is up and down + - 20lbs some days, the temp was saying car was boiling at traffic lights and i was paniking,, fitted a VDO temp gauge and car sits on 180 all day...
i did buy a cheap rev limit light and set it for 5800 gear changes and when the light comes on tach is at 6000+.
NVU are apparently made in america and i will sell the set and put VDO in it..its german and work...
the whole thing is all over the place ..

you maybe confirm my thoughts...
last night i was thinking
if this car was reading over 6000 in top gear and only managed 106mph...its hopeless....the car should on an open road run 140+ mph at them engine speeds on a country road for instance..lets just
see how we go this week

 

I would not say hopeless. If you really are turning those RPMs with that size tire and gear ratio you need to go through the trans and or swap the torque converter. Something is slipping and causing the higher rpm. To help control your wheelspin, I would run a larger purpose built converter with less stall speed. Something like a 10.5" 2,500 rpm stall with decent quality (not a restalled stock rebuild with the impellor fin angle changed aka cheap junk) would work well with the torque of a 400 small block with a milder cam. Look at the 3rd gear clutches for signs of heat from slippage.

I ran a 4,600 lbs race weight (250 lbs me in it) 4 door luxury sports sedan making 408 RWHP and 420 RWTQ on a 275/40R20 street tire a few weeks ago and went 12.40 @ 112 mph on a 1.92s 60' in 2,500 DA. 1/8 mile was 7.99 @ 91. On street tires I run the front tires close to 40 psi at the front and run about 26 psi in the rear. Car calls for 32 psi all around and the max inflation is 44 psi. So you can make a street tire get a decent bite. I drive around the water box and back up to the area in front of it and give the tires a quick dry spin to clean them off. Too much of a burnout will only make them greasy and hurt their grip. The track crew let some idiot in a diesel truck on mud terrain tires burnout in the water box and drag water into the stagging area before my second run. I spun pretty bad and ran a 13.00 @ 110 on a 2.10s 60' and went 8.40 @ 88 in the 1/8. Biggest performance change I made in the car other than the Intake/Exhaust/Tune was the rear-end center section swap from the M56S 2.62:1 final gear to the M37S 3.36:1 final. With the stock rear end gear shifting at 6,500 rpm I was running through the traps at 4,800 rpm in 4th. Now I run through the traps at 6,200 rpm in 4th. I still have 3 gears to go. 4th gear is 1.40:1 and 5th is 1:1. My engine carries good power beyond 6,500 rpm on its way to the 6,950 rpm fuel shut-off. My next tires will be P305/35R20 in the rear. I should be able to trap 122 mph without hitting the fuel shut-off which gives me a good bit of growth power and MPH wise before I have to hit 5th gear in the 1/4. I habe some goals for this car and I want it to be a MONSTER.

I have been talking with American Racing headers to build a set of long tube headers but that would require them having my car for 2 weeks or so on the north east coast of the US. I have also found the weakness in the stock trans which is only rated for 440 ft/lbs input torque. Trans needs to go to Level10 in New Jersey for a $5000 build to hold more power. Level10 will custom build me a converter amd revise the transmission tuning to work for my intended power level. I also talked with Jim Wolf Technologies out in California and they are intending on creating exhaust cams for my engine which should give me another 40-50 hp up near redline. With nothing more than a spring change the stock heads flow enough and stock intake cams have enough duration/lift to turn 7,500 rpm and make more than 600 hp as the car sits. The factory bottem end can actually take the abuse with no exotic changes. It is very LS like with 6-bolt cross bolted main caps, a forged factory crank, and forged rods that are over 6" long. The restriction is the tiny exhaust cams and factory exhaust manifolds. The factory heads have 2" exhaust ports on a 338 CID engine.

 

The gearbox was built by an old friend who has been building HI PERformance GM gearboxes and TorqueFlights since the 1960,s and never had 1 failure EVER,,lots of 10 and 9 second cars since day 1
the torque converter is 2500 stall and its hand made not an old reco or re jigged junk thing.
its a dominator torque converter made here since 1970 with premium results.


The gearbox has the big GMPP high volume pump and extra clutches.
its not the box.


I feel the tacho is out and although brand new NVU unit its unreliable and my shift points need to be more accurate.
i did fit a budget shift light and set it at 5600rpm and it working ok.
Wednesday night will tell as its on again.
Hope to run a 13.00 on street tires.

 

Something is out. The numbers don't add up.
Can you borrow some slicks? It will make a huge difference and help to narrow down whatever other problems there might be. At least they will provide an accurate 60' time.

 

i can buy a set of mickey thompson street ET tyres
and more track time will also help i think..

i have to sort out 1 thing after another and its allmost there...car was off the road over 10 years and its going ok at this point...i just need that 1/2 second better time

 

Thanks Gary
i ran again last wednesday and ran 13.3 @ 107mph
tachometer is definately a problem,,and shift light is not comming on as i think its wired into the "brand new NVU brand instruments i bought for $800.
tacho is telling me 7500rpm when its more like 4700.
i will try get onto them to sort out this rotten thing and the fuel gauge is 1/4 tank out!! walked home 2 times allready...


anyway i will run a local aussie made tacho while the NVU unit goes to check Callibration.


I am still on BFG T/A street tires and its really going good.
Steve in Australia

 

Hello Gary


Got a second Tacho and its reading a lot lower than the NVU unit in my instrument cluster,,drove from the auto electrician and got a chence to nail it and it seems to make power aroung 3500 to 4600,,its movin allright and this wednesday i will run it again and see where i am at.
i would assume i was in fact crossing the line at around 5200,,maybee less

 

It's starting to make sense now.
The performance of the car notwithstanding, at least now you have accurate instrumentation.

 

Check the back of the tach and make sure the small dial is set to 8cyl, not 6cyl or 4cyl. This will make a difference in RPM.

 

i paid $780 for an auto electrician to install all my new NVU instruments and it all appeared to work..
then i started getting eradic readings on all gauges and the battery went flat...took car to another electrician and it was found the gauge instal had small diameter wires to power and it was the culprit all along.

tach was giving false readings,,and others also...1/2 my problem fixed in 1 go..fitted a second tacho just to see where we are and NVU unit is out by 300rpm accross the whole range.

ran car and managed 13.22 @ 107 mph with wheelspin.

cant get car off the line on the gas hard. too much wheel spin
next move...
rear end suspension and M/T slicks this next week and up the strip again.