Traction Problems/Time slip

[low&slow]

Got a 69 c10 long bed with everything stock except the engine. Truck has been gutted. The rear end is limited slip posi track. I took it to the test n tune this past weekend and could not get the truck to hook very well. My first few passes were on street tires leaving the light at 2200 rpms, spun the tires. One of my buds at the track let me borrow his slicks that are roughly 10 inches wide. Warmed them up and launched at 2200 again, but still spun the tires. Tried again launching at 1800 RPM's, did a lot better, but still spun before it decided to grab.

I'm sure I need to upgrade the drive train, but cash is REALLY low. What can I do to get the truck to hook better?

Also, my time slip info: (not sure if its good or bad)
R/T: .078
60': 1.972
1/8: 8.443
MPH: 83.02
1/4: 13.053
MPH: 100.56

The engine is a 500 Cadillac. Aluminum intake. 750 double pump holley. Headers. Stock heads that have been ported a little. Everything else is stock.
Dyno says the engine is 563 fpt and 477 hp. Not sure what its getting to the rear wheels though. The transmission is a 700R4 with a shift kit. For those that may question me, I have a BOP/Chevy Transmission Adapter Plate.

[69GMC910]

What size tires are you running and what are your gears? That low first gear is gonna be tough to control! I'd recommend a 30" tall tire to help bring the ratio down.
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[low&slow]

I have no clue what the gears are. I got the transmission off of craigslist and the rear end is a stock posi. As for the slicks I ran, I have no idea what size they were. They were on a 15x10 rim. They seemed pretty tall, but I could just be seeing things. The tires I ran myself, I don't know off the top of my head. I will take a look. They are pretty small.

[vin63]

Originally Posted by low&slow

I have no clue what the gears are. I got the transmission off of craigslist and the rear end is a stock posi. As for the slicks I ran, I have no idea what size they were. They were on a 15x10 rim. They seemed pretty tall, but I could just be seeing things. The tires I ran myself, I don't know off the top of my head. I will take a look. They are pretty small.

A couple of things. The 700R4 has a 3.06 first gear, which is a lot for the torque the Caddy makes. Second, that transmission is not going to last much longer (I would strongly recommend a TH400 or a 4L80E). There are a lot of unanswered questions (rear gear ratio, tire diameter, air pressure, etc.) that were asked earlier that we'll need answered before providing any relevant recommendations

I would bet the Caddy is making over 400 ft-lbs off idle, so I would just leave off idle in the meantime. Assuming you were at Firebird, what was the dew point and how was it prepped?

[low&slow]

Originally Posted by vin63

A couple of things. The 700R4 has a 2.52 first gear, which is a lot for the torque the Caddy makes. Second, that transmission is not going to last much longer (I would strongly recommend a TH400 or a 4L80E). There are a lot of unanswered questions (rear gear ratio, tire diameter, air pressure, etc.) that were asked earlier that we'll need answered before providing any relevant recommendations

I would bet the Caddy is making over 400 ft-lbs off idle, so I would just leave off idle in the meantime. Assuming you were at Firebird, what was the dew point and how was it prepped?

The street tires I was running were 295/60R15 on 15x8 rims. The slicks I ran were 27.5X11.5R15 on 15x10 rims. I have no clue what the pressure was on either sets of tires.

If I do end up getting a TH400, would it be best to have a shift kit in it or not?

Also, it was a pretty decent out that weekend and I don't know how they prep it.

Originally Posted by Marv D

Also keep you front street tires out of the water,, they drag water to the starting line,., obviously don't help you cause a bit. Big issue is weight,, you have 80% of it on the nose and nothng on the tailgate. Those big Caddy motors ae a real porker, and make buttloads of torque in a lower rpm range. hell launch from idle and your making more torque that many stout sbc's

If I was to launch at idle, what would be the best way to launch? Pedal to the metal or ease into it?

Also, I'm not so sure about the whole weight thing. These motors weigh less than a 454. With this caddy in my truck, my front end actually sits a tad higher than the rear. But then again, the rear springs could be worn out. I'll try to find some friends that have scales and see if I can get the weight of the front and the rear and compare them.

[chevy72blu]

Keep in mind that if you are able to make this truck hook, it wont be long for life on that stock drive train. The weakest link will pop... Unless you plan on replacing the trans, drive shaft, u joints, rear end, etc in short order, it may be a better idea to simply let it slip a bit. Feathering the throttle out of the holeshot always worked well for me on street tires.

Impressive times, though! I'd love to see pics.

[69GMC910]

Any video of your runs? Pretty decent time/mph!
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[low&slow]

I don't have any vids yet. As soon as I start a build thread, I will get some vids. I only went to the track because my bud paid for me and towed me out there lol. I wasn't really prepared to say the least,

The tires I was running before the slicks are 295/60R15

[low&slow]

Since you mentioned that I should go with a 30'' tire, would a 31/13/15 tire fit a 15x10 rim?

[RexDodge]

Be sure to check your footprint/air pressure. Roll through a wet spot and measure the width of the track left by the tires when you roll out of it. Air em down until you get the width of the tire you are running. You'll be surprised at the difference.

[low&slow]

I'll defiantly give that a try.

Could I also be launching at too high of an RPM? The engine idles at about 800 and all peak hp and torque are between 2300-2700 RPM's.

[Marv D]

Also keep you front street tires out of the water,, they drag water to the starting line,., obviously don't help you cause a bit. Big issue is weight,, you have 80% of it on the nose and nothng on the tailgate. Those big Caddy motors ae a real porker, and make buttloads of torque in a lower rpm range. hell launch from idle and your making more torque that many stout sbc's

[BigDan3131]

I thought first gear in a 700R4 was 3.06?

[vin63]

Originally Posted by BigDan3131

I thought first gear in a 700R4 was 3.06?

You're correct...my typo edited.

[gofastnut]

Sounds like fun! I'd love to see pics. A vid would be even better!