Joined: Thu Feb 24 2011, 12:55PM
Location: London, UK
Posts: 152
Hi, I'm trying to figure out if my car is running close to optimal or if there is something amiss. I took it down the track a couple of times yesterday to see how it did and it was not quite as quick as I was expecting, so I just wanted to compare results and thoughts with you on this. Now, I'll be clear....I'm not looking for it to be a race car, it's a daily driver street car...but I just want to make sure it's running as would be expected.
Here's some spec:
66 Polara 2dr hardtop 727 Torqueflite /1500 stall converter 440 with approx 9:1 compression (built about a year ago) Lunati Voodoo 10230702 cam (262/268 advertised duration, 220/226 @ 0.50) 3.23 gears with Detroit TrueTrac locker diff 235/70 15 tires.
I'm not sure of the car's weight but I tried some of the online calculators using a weight of 4200 lb (including 200 lb for me) and when combined with MPH it says 283.84 HP and then with ET it says 236.38 HP.
What do you think....or is it just my poor track driving?!?
The first thing that jumps out at me is you left it in D to shift.What rpm did it actually shift at(assuming you have a tachometer)? I would wager a guess that it is shifting early and that will slow you down quite a bit.Your 1/4 time of 15.2 bears that out as it is quite fast for a 10.0 1/8. Granted you are on skinny street tires so I can see where traction could be a problem.Your stall speed is rather low but without sticky tires it is fine for street driving just wouldn't E.T. as well in race conditions.
I see no reason you couldn't run some low 14's as is.Try shifting it yourself and I would guess 5300-5500 is a good place to start and see what happens.
Joined: Thu Feb 24 2011, 12:55PM
Location: London, UK
Posts: 152
Hi dacuda, that's kind of what I'm getting at......the track times probably are about right for a 250 HP car, but this is a rebuilt 440 with 915 heads and a mid level cam (that 'feels' strong) so would have thought it was more in the region of 350 HP. Hence me being a little surprised at not getting into the 14's.
Joined: Wed Nov 17 2010, 03:28PM
Location: florida
Posts: 1311
you say approx 9 :1 comp,could be lower .prob should check as a starting point. maybe a dyno tune to dial it in.you made no mention of fuel system or ignition.
Joined: Fri Mar 13 2009, 11:21AM
Location: San Marcos, CA
Posts: 713
Are you running the stock valve springs? if so, 5000 RPM is about as high as you should spin it. I ran 94 MPH with my Roadrunner with similar stats (3.23 sure grip and a very heavy B body) it ran 14.5s. Are you spinning off the line? if so, try to find the throttle application where you don't spin. I usually test brake torquing it between the water and the starting line to find the point that it hooks without wheel spin then launch at that RPM... My $.02
Joined: Mon Oct 10 2005, 10:24AM
Location: The Netherlands
Posts: 160
Gearratio is holding you down a bit. Heavy cars need torque or deeper gears to get moving.
As for self-shifting, I would just put the translever in 2nd and let the trans do the 1-2 shift. Then manually shift to 3rd when you feel it's right. There's no use to rev it to moon if you just have grandpa large tires, a mild cam and bone stock castiron manifolds.
Try a pair of 60-height series tires on the rear. That should help favor your gearratio.
I would try shifting it manually myself.Going to 5000 rpm on the 1-2 shift (and trying that on the 2-3 shift as well.It may like more but I doubt it will respond well to less.
As for valve springs if they were the ones recommended with the cam then they will handle rpm just fine.
I would experiment raising the shift rpm 200 rpm at a time until it stops improving.
One area that will make an improvement is tire pressure. When you get to the track,bump your pressure up to around 50 lbs air pressure front and rear. If the rear tires spin, just a little,leave it there. If it spins a lot,lower it to 40 then 30 or lower at the rear. Write all your adjustments down and its something to go on. A heavy car such as this and the gears can probably use more converter.