G-tech times and speeds varying

[Flyntgr]

I ran my car 4 times tonight. 1st, ran a 15.67 @96.9; 2nd, 15.61 @94.7; 3rd, 16.66 @ 86.7; 4th, 16.5 @85.7. All shift points were about the same, and the car is a 904 pushbutton 225 slant six 1962 Valiant Signet. The only thing I can think of is that the transmission, toruqe converter or rearend heated up some, causing the times to get worse. The 0-60mph times for the first two runs were about 7.25 seconds, but the last two 0-60mph times were more than 8 seconds. What do you think is going on here? Braking starting with 1950 rpm starts, shifting the same; back to back runs with a little cool down between runs. The engine temp. didn't change at all, and the engine pulled strong all 3 times, though the low end of first gear was obviously the killer in the third and fourth runs. What's going on? Thanks.

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Restored '62 Signet, 229 4bl, Offy intake, auto, Dual Dutra exhausts, shaved head and block, high stall converter, 1.6 roller rockers, etc.

[Joshua Skinner]

For the transmission and rear end to absorb as much energy as the lower ET would indicate would result in a smoking hot trans and diff. Much more likely is that the engine made less power on the later runs. I'd bet a dollar that you are pulling hot underhood air into the engine and that radiant heat from the exhaust is also heating the intake manifold. I'd get cool air to the carb and put a heat shield between the exhaust and intake manifolds.

A few years ago I took my '66 Dart to the Mopar Nationals in Woodburn, Oregon. I did all my practice runs and put a dial-in on the windshield. Well, the time between practice and my 1st elimination run was a lot longer than between practice runs. I was dialed in with a lower ET than my opponent in a 440 powered 4x4 pickup, but I ran him down so fast I hit the brakes. I broke out more than he did and lost. Don't underestimate intake heat on the power you make.

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Joshua Skinner
car nut, telecom tech, tool using mammal
'72 Dart Swinger

[DusterIdiot]

A couple things I have noticed:
Depending on your under hood arrangement-
There is a big pocket of dead hot air close to the fire wall (all the cooler air under the hood is up by the fan).
If you have the heat flapper installed, make sure it still opens/rolls (or wire it open-I've notice in a couple instances on the offy dual and offy 4 barrel the back/last 3 cylinders gets hotter than the front three when using dual duals with the stock heat flap in place), this can also get worse when you shut the engine off and let things heat soak (in one instance I watched the rear carb bowl boil on the dual weber setup).


something to keep in mind

-D.Idiot

[Flyntgr]

My rear exhaust is straight thru like the front one; no flappers. I have a 2" K & N type filter with the free-flow lid like the Extreme Flo K & N filters, too. I do not use a hood scoop or other fresh air intake, but only the stock hood and 14" circumference filters. This is about 1.4 seconds faster than my previous times, and I've yet to receive or install the true 10" converter. I hope my times get much better with the 10" converter, as the first 60 feet is very slow-possibly as slow or even slower than with the stock 1 bl and stock engine. Good things should happen when the new converter arrives.

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Restored '62 Signet, 229 4bl, Offy intake, auto, Dual Dutra exhausts, shaved head and block, high stall converter, 1.6 roller rockers, etc.