I reported back my time slips from yesterday. Terrible traction out of the hole and the car hits a MPH ceiling of about 97-99 MPH at 5000RPM in top gear. The numbers don't work out right. The converter I have is a reworked TCI 10" Street Fighter - originally 3500 stall (came in the car) I had it serviced and tightened up to 3000 RPM. But my mph is too low for a 5000RPM , 3.73 gear and 28" tire. If I have this right, I have 15% slippage in top gear (or more).

I am thinking I should consider dropping to a good 2200 - 2400 unit. Keep in mind I am planning on installing the XR274R solid roller, so my torque will increase anyway.

What do you guys think?

Joe,what does the convertor flash to? A lesser convertor would cause you to lose ET/60 ft.
The 396 I have ran 12.65 with 4.10's and the same convertor you had,but it was out of the box stock..seemed to flash around 3500 and netted a best of a 1.77 60 ft.
MPH was about 104,and it had an RPM intake.
Eventualy,this combo went a 12.45/105 MPH with another convertor that flashed to 4000
Cam was a Crower flat tappet solid...295/300 advertised,244/246 @ .050 .517/.530 114 LSA
Motor had .180 domes with 215's and 2.06/1.72 valves..very basic and stock other than the cam/intake.

Hard to be exact, but the converter will flash to about 3000. It would flash to 3500 when I got it, the car had 3.31's at the time, needless to say it was sluggish. I had the rear gone over and changed to 3.73's and also had the converter checked out and tightened up to 3000.

Full throttle out of the hole or even a 10 - 15 MPH roll, the car will burn the BFG's sideways. I know that has to be addressed, but I was wondering if I have too much slippage on the top end. Very hard to read the factory tach at that speed, but I am sure I was running 4900 - 5000 through the traps. Actually, I think I hit that at about the 1000' mark. But the info I have says 99 MPH should have been 4400RPM.

What's considered acceptable slippage?

What part of the earlier replies about getting stickier tires did you miss? You are too far down the track before full throttle is really applied - this is keeping your mph AND e.t. slower than it should be. RPM guesses will be no good in computing slip%, and have you had your factory tach checked for accuracy?


You'll get there, just start with the tires and take it one step at a time.

Thomas

Yo Thomas, relax. But seriously, I am aware of the tire change and the front spring changeout. I will probably just put the 30 year old factory Big Block springs back in. Tire wise, just need to decide what tire and size. Currently I run a 275-60/15 on a 10" wheel, fit is good. I assume a drag radial in the same size would be the correct move?

The issue on the converter comes up because I am questioning whether the converter is slipping too much. And no, I have not checked the factory tach for accuracy. I have to pull the driveshaft and take it to get balanced, I have a vibration at top end that is rather severe, didn't notice it before, then again, I have not driven the car over 65 up until last week. If the converter is an issue, I figured I could address it while the car is up in the air and the shaft is out. I don't think it is a problem either, but want to eliminate all of the questions in the process.

Hey GRN69CHV, The torque converter is the most important variable in your cars performance. In my son's car we changed torque converters several times and the trap RPM didn't hardly change at all (about 200-300 RPM) but the speed kept getting better with every converter. The more smaller and more expensive the converter the better the car ran. Larger converters are easier to drive on the street but the smaller ones are faster and generally require some freshening up occasionally. Our car has always had quite a bit of slippage. (About 9%)

Buy an ATI, talk to Charlie Plott.

Mine works very well for me, the 10" ATI treemaster.

Joe,get those 275/60 drag radials.
Your convertor seems to be perfect..especially with the planned cam upgrade.For now,focus on getting the car to hook by using sticky tires.You should see what my car does to street tires ;) smile.gif
BTW,the 396 combo I mentioned originally started off in the 13.20-13.30 zone w/3.73's and an 11" TCI,and the car got quicker with every convertor swap..went from the aforementioned 11",to your convertor,to a full race 10"..each one had more stall than the last.

What drag radials seem to be the best compromise? I want something that I can drive to the track and probably leave on for local cruise nights. BFG's and the Nitto seem to have a little more suitable street tread. What about the Hoosiers?

Also, I probably could stuff a 325-50/15 in there with little effort, just the way the car sits now. Or even a 295-60/15 which would tame the gear just a little. Have to do a search. Even the MT ET Street Radials are available in all the sizes.

Joe,I hear the Nitto's are best for longevity and hook just as good as any other DOT tire.
Personally,I'd stick with the 275/60 size myself.

Thanks for the input. There is a Nitto dealer right down in Claymont, De. (about 3 miles from my shop). I may swing by there at lunchtime and order some in.

I am going to attempt to get the changes made (tires, front springs and driveshaft serviced - up the secondary jetting, more the middle spring back in the carb and maybe give it a little quicker mechanical advance) then get back to the track early Sept..

[For the record, I timed the trip Sunday, backing out the 10 minutes at the gas station on the way, it was exactly a 45 minute drive. Heck I could probably cut that down to 43 minutes if I grab the EZ pass out of my truck).

Joe,I'm jealous..45 minute ride to the track..I'd be in heaven ;) :D
I might go this weekend..3.31's aren't in yet,but I did swap to the RPM intake