Ran my car yesterday at the drag strip. Best time was 12.283 @ 112.72mph.

Here are my time slips:

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1st Pass - Left line at 1500rpm, engine hesitated badly when I put it to WOT, then launched. No wheel spin. I also had timing less then 35-degrees just being cautious. Shifted from 1-2 and 2-3 at 5500rpm.

I adjusted the squirter pump on the carb to give me a little more squirt. Set timing to all in of 35-degrees (dyno showed this made max hp).

2nd Pass - Left line at 2000rpm, engine did not hesitate, no wheel spin.
Shifted from 1-2 and 2-3 at 5800rpm.

3rd Pass - Left line at 2500rpm, engine did not hesitate, wheels spun and car got a little sideways leaving the line, shifted from 1-2 and 2-3 at 6000rpm.

Here are some engine/tranny info:
468 BBC, Dynoed at 540hp
Holley 850 with mech secondaries, double pump

2800 Stall Converter

3:36 Gears

TH350 Transmission

Mickey Thompson Street Radials

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Looking for any tips, info, that might help my times. I am a rookie at driving so I definitely need seat time.

Thanks,

Roger

 

Very nice times for your first try! Here's some ideas that might help your consistency, and consistency is what it's all about in bracket racing (BTW, you've got some very quick competition on the tree!):

1. Practice on the tree (a practice device helps)
2. Check rear tire pressure - with 275-50-15 MT ET Streets, I run 18 psi.
3. Do a consistent burnout to clean and warm the tires
4. Pre-load the TQ to the same rpm every time - 2,000 rpm appears good; 2,500 rpm does not since you broke traction.
5. Stage at the same engine temperature every time.
6. IMO, I prefer to hold the car in place on the line with a line-lock to the front wheels only (of a C3) rather than pedal braking to all 4 wheels - the resulting rear wheel torque helps pre-load the rear tires for traction.
7. Practice, practice, practice!

 

Very respectable numbers for your first time out.
You should be able to get in the 11s at 112 mph. Your 60 ft times are the key. With your tires, you should be able to leave with very little wheelspin. That 3.36 rear isn't helping but as Larry pointed out, tire pressure, burnout technique and rpm level at launch are important. After another three runs, you might chop off a few more tenths. Your 60 ft should be in the 1.6 to 1.7 range. The rule of thum is for every tenth you take off the 60 ft, you take 2 off the ET.
Good luck and report back on your progress.

 

112 mph seems kind of low for 540hp. I think you need more convertor. What brand convertor are you using?

 

Thanks for the input. Lots of good advice.

Larry- I was running 25psi in rear tires. I didn't heat them up very much during burnout. My brake pedal is too soft. I do have a line lock installed but am trying to figure out why the soft brake pedal (recently installed new master cylinder, 4-new calipers, and new brake shoes. Have bled brakes several times using all methods (gravity, pumping pedal, vacuum pump, and power bleeder pump). Just ordered new rubber brake hoses. If not that I'll check rotor runout.) Hopefully I can get my brakes fixed by this weekend.

BK - Glad to know what 60ft times I am shooting for. I was hoping to run in high 11's.

Airbus - I am running a PTC street strip converter. I think it's a decent converter. But maybe 3500 stall might be better.

If work doesn't get in the way I'll go racing this weekend. Hopefully at least get 3 trial passes before racing starts.its the first race of the year. There was over 200 cars at the track yesterday for test n tune getting ready. Took 5 hours to make 3 passes.

I'll keep posting my times. Thanks for the help.

Roger

 

I would lower the air pressure and do a medium burnout.Leave at as high of an rpm as you can w/o spinning.You need to 60ft better with your gears.
I prefer leaving off idle and flashing the converter but I have no experience in a C3.

 

First..congratulations on a good outing! It ran strong...all the pieces are still where they belong and you had a good time! That's a good day racing!

Tell us more about the motor? What's the combo? Heads, cam compression, intake, headers etc? Do you have a dyno sheet we could see to look at the curve?

JIM

 

A 2800 stall might be keeping your engine out of the powerband too long.

 

96 LT-4
I had planned on trying that (leaving line at lower rpm to flash converter) a couple more times on Saturday, but my carb was working very well that way. The engine stumbled/hesitated leaving the line. It was also so crowded I knew I would only get two or three passes. When I was choosing a converter I had this idea in mind.

427 HotRod,

It was absolutely a great day at the track. 1st day out, wife and kids came, nothing broke. Oh yeah it was good! I had a blood clot earlier this year that was almost lights out for me, so I have a new outlook; stopping to smell the flowers each and every day.

Here's my engine combo:

454 bored .030"
990 Rectangular Port Heads (unpolished)
Reeds Solid Roller Cam 251 duration at 0.05, 0.674 Lift with 1.7 Roller Rockers 108 LSA
CR 10.1
RPM Air Gap Intake
MSD 8362 HEI Distributor
Holley 850 with Mechanical Secondaries (1970's model that I rebuilt)
1 3/4" Headers with Side Pipes and Baffles
2800 PTC Street/Strip Stall Converter
3:36 Gears in Rear End Rebuilt by Tracdogg
TH350C Transmission (updgraded Second Gear Sprag and Added Shift Kit)
Drag Vette Basic Kit (puts half shafts close to level)
Drag Vette Safety Loops on Drive Shaft and Both Half Shafts
Mickey Thompson Street Radials

Here's a couple of Dyno Sheets, I am at work and seem to be missing a couple of them.

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AirBusPilot,
You may be right. A higher stall may be in my distant future. I already spent more on this car then I had planned so I'm gonna ride this one for a while. I can't wait to get a full day of test n tune with only a few cars so I can make lots of passes trying different rpms at the line. Especially after I get the carb adjusted so it doesn't fall on its face at the line.

I'm also going to add a rev limiter this week. It won't make the car any faster, but will give me a little piece of mind. I'm always worried i'm gonna accidentally shift from 2nd gear to neutral and over rev. I have plans to weld some stops on my shift plate, but not for a couple of weeks or more. I wish someone made an automatic rachet shifter or similar that will fit under the console. I bought a stock corvette shifter and have been looking at ways to modify it. If I come up with something smart i'll post it. considering making a shift plate to bolt or weld on the side of the existing shift plate. Haven't had time to try it yet.

Thanks,

Roger

 

I have the joy of running a dyno. The first printout tells me a few things. One is that valid testing needs real life water temps like 180.

To chase big numbers I can use cold water...... I would not be happy with the tester. I'm also surprised at no oil temp column

I don't know your compression, so I can't comment on your timing. But with the 100 degree water your correct timing is also a guess when you are at normal temps.

I was also surprised at the side to side A/F ratio. I'd install a thermal 4 hole carb spacer if you have room. I've run motors with staggered jetting to get better A/F ratios to all the cylinders.

Line locks are actually kind of fun. Soft brakes are not something I would want to be doing 112 mph with. If you believe that you have no air and the MC is good. Maybe it is time to replace the the short rubber flex lines with steel braided.

 

Gkull,

Thanks for response.

I'm running 10:1 compression ratio.

Glad to get your perspective on duno results. I'll keep checking my plugs at 35 degrees and 36 degrees.

Do you think the different air ratio readings are do to carb or intake manifold? Reason I'm asking is its a new air gap intake and my ratios were pretty close on my previous dyno.

I ordered new rubber brake lines. Will put them on this weekend.

Is it normal for my brake light in dash to come on when I try to use line lock? Mine flashed on for a brief second.

Thanks

Roger

 

My brake light on the dash does not come on when I use my line lock. I don't think it should.

 

Some old brake lines get pretty rusted in place. I've rounded the end nuts even with a brake line 3/8th box end wrench. So have a good vise grips with you. You are going to throw them away anyway.


On the dyno sheet you have 12.4 left and 14.00 right A/f ratio. You have several things to look at. One of them is the dyno machine it's self. What if one sensor is out of whack? For a carb to do that it would have to have a partial plugged air bleed, internal flow path.......... or jets a few sizes different from side to side. Idle mixture screws many turns different. Or even a simple vacuum leak on one side. I had a manifold that had a vacuum leak from the cam valley to the cylinder head.


I would get a magnifying glass and compare your inner 4 cylinders spark plugs from side to side. 4&6 compared to 3&5 If they look the same the dyno might be wrong.

Line lock should not cause a brake low pressure light to come on. Line lock is just stomp on the brake, push the line lock switch and let off the pedal. I would put my tranny in second gear in the water box and and let it do an auto shift 1-2 then just run my speedometer to about 90 mph turn off the line lock and the car would move forward out of the water. Then just let of the gas and drive up to the pre-stage

 

BKBroiler,

I didn't think my brake light should come on when using the line lock either. It only did it once, but that's enough to make me think there could be air in proportioning block (or whatever it is). I am certain there's no air in the master cylinder, and pretty sure there's no air in the callipers. I bench bled the master cylinder on several angles to make sure I got the air out of it. Also bled callipers with them unbolted from the car so I could use different angles to help air come out. Probably pushed 2 gallons of brake fluid through the system.


Gkull,

I'll use your advise changing the brake lines.

I do believe the dyno A/F ratio sensors had an issue. The first few pulls only one side was working. At some point the bad sensor (or wiring) started working but as you pointed out the readings are not very close. I dynoed a previous motor with this carb and cam a few months ago and the A/F numbers from side to side were close, but I was using a different intake manifold (gm aluminum dual plane), pistons, and block (I had a cracked block). I rebuilt the carb before the 1st dyno and the A/F ratios were pretty close from side to side. I don't remember the jet sizes but i'm sure they were not mismatched. I'll check the plugs real close this weekend if we don't get rained out. It's supposed to rain all week and weekend(no fun at all).


I'm just learning about big block chevy's. What's ya'lls opinion on solid roller lifters. That's what I have in my engine, but recently I have seen several posts saying they don't last very long (less then 1000 miles). I have a Reed's solid roller cam, and Comp Cam standard roller lifters. Would using a hydraulic roller with enough lift/duration to make 500hp (similar to what I have now) last longer, mile wise? Or is there a good set of solid roller lifters that would last several thousand miles? My cam has 0.375 lift (0.624" with 1.7 rockers), not really extreme. I want to drive my car on the street on weekends, pretty day's, etc.

Thanks,

Roger

 

I have two roller motors with more lift and rpm than you. My lifters and rockers last and I have just reused them after engine refreshes. I think my one SR motor has @20,000 miles on the valve train.

I do run the tighter lash cams

 

I use billet steel sleeved distributer cams, both of my motors have Crane Ultro pro lifters, steel RR's