I'm going to have my transmission guy tweak my governor in my TH350 to raise my shift points. It's currently way low at about 3800rpm at WOT. Any suggestions on a good shift rpm? Engine and drivetrain specs. 1966 Skylark true 9.5:1 71 455 Stock iron heads Stock exhaust manifolds 2.5" dual exhaust Dynomax Super turbo with x-pipe TA288-94 cam Dave's Smallbody HEI B4B with 800 QuadrajetPower built carb 3.08 71 8.5 posi rear 235/60-15 tires TH350 w/about a 2000 stall conv. Thanks for any info.
youre gonna have to experiment with shifting manually, but if it's set up correctly that engine should be good for 5200-5500 RPM.
First off I would strongly suggest a chassis dyno session be done on your car to find out at what rpm it makes its peak TQ and HP, other wise your just polishing your sword! In general you want the rpm after a shift to fall back into the middle of the torque cradle rpm range! For example if the motor makes peak torque at 3800 rpm then you want your shift to be whatever rpm it takes to get the motor back into the 3800 rpm range given 200 rpm on either side of that 3800. The only time for a car like yours in a 1/4 mile run when rev's above 4500 rpm matter is for your mph you attain , not ET numbers. The more you rely on the torque band of your car to power you down the track the more consistent it will be also! Also a TB350 Trans behind a 455 unless rebuilt for such usage will not last too long before going south once you start beating on it!! If you do not have a HD sprag in the Trans already and a seperate cooler in the nose of the car then you had better start saving up for towing bill you will eventually need to pay!
Probably around 4800 to 5k to be honest, you may not even have to click 3rd in a 1/4 if you put some 255 DR's on it
The best way (other than trial and error at a track) is as follows. Measure torue (or hp, gives the same answer) in every gear, and plot all on the same graph. Where the tq (or hp) falls below (actually crosses) that of the next higher gear, that is the optimum shift point which will maximize acceleration going down the track. Where the curves do not cross, shift point is engine redli ne.
Those rpm drop calculators don't really work well for mild Buick engine builds because they can never make decent power close to "red line" or even much above where they make peak HP. Those calculators work great for free revving engines like a SBC or LS. Once a BBB makes peak power around 5200-5400 they barely rev freely past that point and usually you can just feel the power dropping off fast. It is lucky to rev a few hundred rpm past peak HP. That being said set it up for the usual 5300-5500 and you'll be fine. Maybe on the low end of that range because you basically have a stock engine with a cam in it. I never once had a non-stock cam Buick that ran the quarter faster by shifting at 5200 or less. From my experience with stock cam Buick engines they even like right around 49-5000 rpm shift points. Maybe a little more. Generally speaking because you can never rev high enough a few hundred rpm past peak power will probably be good enough. Most BBB's with mild cams will be in the 52-5500 rpm range for peak HP even with a decent sized cam. Also the idea that shifting at lower RPM because "the Buick is a torque engine" mystifies me. When somebody says that to me I have to ask then why did you put a bigger cam in the engine? All that does is move the peak torque rpm up to a higher range. If you want to shift at a lower rpm than the cam makes peak power at then why not put a milder cam in it and make more power(torque) at a lower rpm. About the only reason I can find that makes sense for a lower shift rpm on some setups is because of a looser converter which doesn't allow the engine rpm to drop as much as a tight converter. But you're talking a pretty loose converter, not your typical tight street converter. If you have had a setup that actually runs faster at the track by shifting at a lower rpm than the rpm the engine should be making peak HP rpm at then I'd be looking at other problems, restrictive exhaust, weak valvesprings, too much lifter preload, poor ignition, tach's off, or inadequate fuel delivery. http://www.wallaceracing.com/calc-rpm-drop-shift.php If you won't be going to a track to test what rpm works for lowest ET I'd take it out on some back road and try different rpm shift points from 2nd to 3rd. Try manually shifting maybe starting at 5200 and then going up 100 rpm each try. You'll feel it if the car doesn't like that rpm because when you drop it into the next gear the car will feel like it is accelerating faster which means you shifted too late. Take about 100 rpm off that and you'll be good. If it makes it to 5500 and still is pulling then just leave it at that. Trying to figure it out with a 1-2 shift point is tougher because the car is accelerating faster at the slower speeds. The higher speeds and slower acceleration at 2-3 will make it easier to spot. Maybe because of the 3.08's 1-2 might be possible to do it at.
