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DanM
Buffalo

80 Posts

Posted - 13 Jul 2017 :  4:28:14 PM  Show Profile  Reply with Quote
After a few years of dreaming and planning and optimizing I took my 71 Lemans to the drag strip.

It's a daily driver, in which I commute 50 minutes each way every day in traffic so I have some driveability limitations: can't overheat in traffic, must idle smoothly, must have decent low rpm at highway cruise speeds.

400 ci, cam is 212 at 0.050" intake, about 0.500" lift, quadrajet, iron intake port matched, #96 heads w/ mild porting (245 cfm max) and 90 cc chambers (8.8:1 ish), Doug's headers, true dual 2 1/2" exhaust. Nothing fancy. 200-4R tranny. 245/60-14 wheels - with wire wheel covers!

I would say my cam is the limiting factor here. I could probably go up to a 218 degrees and still be able to commute in it.

First time to track. 14.6 at 96 mph.
The governor in the 200-4R wasn't letting it shift so I had to "manually" shift by lifting, waiting briefly for it to shift, then WOT.

60 foot time: 2.4

Second time to track: 14.040 at 98 mph
I adjusted the TV cable and got it to shift perfectly at 5500 rpm. After spending several sessions on the chassis dyno I knew exactly where I wanted it to shift, 5500 rpm, based on the power curve. But I couldn't get the tires to dead hook. I let my BF Goodrich Radical TAs down to 20 psi and they did pretty well (that got me from 14.2 to 14.04) but I still was leaving torque untapped.

60 foot time: 2.18

Third time to the track: 13.892 at 98.6 mph !!!
I got a pair of Mickey Thompson ET Street R Bias ply tires, 26-10.5x15, and a used pair of 15x8 rims. With a moderate burnout I could dead hook to all but the most aggressive brake stand. Still, with the aggressive brake stand I could break the tires loose at the green light. I was running the tires at 15 psi

60 foot time: 2.050

I think if I drop the pressure down to 12 or even 10 psi I might get enough traction to dead hook an aggressive launch. Even though my 406 ci engine with the "mild" 212 cam only puts out 290 HP at the chassi dyno, that "mild" cam has my low end torque maxed out so my 400 is creating as much or more torque as a wild 400 or wild 455. Clearly once I get to 3000 things change.

Also I asked around (Jim L) and may need to put an air bag in my right rear coil spring.

So conclusion.

13.892 at 98.6 in a convertible daily driver. Not bad.

And to top it off, when the other racers say "we watched you drive in" I know that my car looks nice to those who truly appreciate such a thing.

71 LeMans Sport Convertible with 310,000 miles driven year round since 1994.

DanM
Buffalo

80 Posts

Posted - 13 Jul 2017 :  4:34:43 PM  Show Profile  Reply with Quote
Another bit of info.

I'm using 3.55 rear gears, posi.

With the 3.55, at 98.6 mph I'm at the top of the HP peak in drive. This means I only have about 5-8 mph left before red-line. This was no accident. When trying to decide what gear I spent some time on Excel calculation and simulating the rpms for various gears at L, S, D, OD at various mph and accounting for torque converter slip.

A shorter rear end would help my 60 foot time assuming I could hook up but eventually I will run out of rpm at the long end. Running this car three full gears down the 1/4 mile I was able to squeeze out every bit the engine can give.

The shift kit is nice too. It snaps from 1-2 and from 2-3.

The time I spent fiddling with my governor was worth about 0.45 seconds. The stock governor shifted at 4800. This left about 50 HP on the table through 2nd and Drive. The top end of the HP curve goes flat from 4500 to 5200 so it didn't matter there as much. The big gain was once I shifted into 2nd from low I was 500 rpm higher up the power curve. That's where I get the 50 HP benefit. Same thing going from 2nd to Drive.
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GtoGuy32
Cochise

USA
842 Posts

Posted - 16 Jul 2017 :  12:16:53 AM  Show Profile  Reply with Quote
Hey Dan, thats what it's all about. Having fun and getting better as you go.

I race my GTO at NED. When I first started going up to NED to race my car, it had a 400 in it, running similar times to yours. I have done work on my car over the years and also improved my driving and now I'm almost in the 10s.

I'd love to connect with you the next time you're up there. I usually race all of the nostalgia races and do a few test and tunes in between.

The next Nostalgia I believe is Sept 27.

Id love to see some pics of your car.

Dave
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