When to shift

[JimNolan]

Guys,
   I've been shifting at 4800 on my 410 FE. It sort of talks to me at that RPM and says "shift dummy".  Should I drop back in rpm for more reasonable outcome in bracket racing. Or, run it till it grunts at 4800. The 410 stock engine had 4600 rpm listed as peak HP. Most of you know my engine so where would you shift. The cam was designed to be shifted at 5000 rpm. Give me some reasoning here.

[427fordman]

If you have a cam rated to 5k and proper valve springs for it, it should be fine at 4800.    I'm kinda new here so don't know what heads you have, I'm guessing stock?   If you're curious to see if it is loosing power at that level, shift it at 44-4500 a pass or two and see how the early numbers compare. 

[JimNolan]

I'll try that. Tomorrow I would like to get a couple runs in anyway after tech. The heads are Edelbrock 428CJ. It's not a wild ass cam by any means 515/540 lift. I idle at 600 rpm smoothly (Cam Research). It breaks loose the 8" Street Pro tires pretty bad. Cast pistons is the reason for the rpm specification. I'll make a couple passes at 4500 rpm and see what happens. Thanks

[jayb]

Your shift point should be set so as to maximize the area under your horsepower curve.  Assuming, of course, that the engine is capable of revving that high; some aren't.  A good rule of thumb is to shift 500 RPM past the horsepower peak.

I would consider trying different shift points at the track, to see how your ETs stack up in comparison.  Fastest ET = best shift point.

[My427stang]

One comment, if looking for the quickest ET, except possibly 1st gear, I wouldn't shift any lower than peak HP RPM, and probably 300-400 over than assuming you didn't have any valve float issues.

Sometimes a torquey engine likes to be short shifted out 1-2, but my WAG would be 5200-5400 shift point for the other gears  if you are peaking 4900-5100

[DEANs427]

you want to pay attention to what rpm level you drop to AFTER the shift, try to keep that point still in your max power band.

[JimNolan]

Thanks guys, I'll try different shift points. I'll take the best of three and see if I can match it. I'll use that for dial. I figure the new "Nostalgia" bracket will be loaded " it's a good payout" and there will be plenty of accomplished drivers there to send me home. Best I can do is "everything the same, every time". I'd like to go farther than my usual three elimination rounds this time.
PS:  I carry 6 - 6 1/2 qts of oil with my windage tray and 5qt oil pan also. I should be ready.   

[bartlett]

when the valves float , SHIFT .....lol 

[JimNolan]

Well, I like to beat my car to death trying to figure out how to drive it Friday. I ended up using 28lbs of air in the rear. Leaving the line with it revved to 2000rpm and shifting at 5000 rpm. By shifting at 5000 I wasn't spending time squealing the tires in second and third. It just went. 14.3 ET @ 98 mph. Everyone was complaining because of the humidity. So, without the humidity I figure I've got a 14.1-14.2 car with street tires. I'm happy. Jim
 PS. The temp was 90 something Friday and I ran 5 times ( about 30 minutes apart ) The first run I pulled all the way through the quarter, Second run the same. Third run it fell on it's nose once, Forth run it fell on it's nose about two times, Fifth time it stumbled all the way through forth gear. Came back Saturday and didn't even run during time trials. Threw a dial-in on it, took it down cold for eliminations and it ran great. I bogged coming off line but it pulled great.  Let it cool down two hours for my second round of eliminations and it went through really strong again. In fact it was so great that I broke out by .3 seconds. And I had dialed in my best time on Friday.

[cjshaker]

Well that's good news. And you know your car needs to be cool to run all the way through if it's hot again.

What I've always found to help me determine what makes my cars quickest is to find at what RPM it pulls hardest. I can find out easily in 3rd gear by flooring it at different RPM levels (not using 1st or 2nd for obvious reasons, like tire smoke control, or even 3rd in my Mach  ), like 3500, 4000, 4500 etc. Then you know that if you shift at the time that will drop the RPMs to that point, the car is going to pull hardest into the next gear. It helps when you don't have ET slips and dyno figures to pin-point exactly what works best.

[Mike Caruso]

Well, I like to beat my car to death trying to figure out how to drive it Friday. I ended up using 28lbs of air in the rear. Leaving the line with it revved to 2000rpm and shifting at 5000 rpm. By shifting at 5000 I wasn't spending time squealing the tires in second and third. It just went. 14.3 ET @ 98 mph. Everyone was complaining because of the humidity. So, without the humidity I figure I've got a 14.1-14.2 car with street tires. I'm happy. Jim
 PS. The temp was 90 something Friday and I ran 5 times ( about 30 minutes apart ) The first run I pulled all the way through the quarter, Second run the same. Third run it fell on it's nose once, Forth run it fell on it's nose about two times, Fifth time it stumbled all the way through forth gear. Came back Saturday and didn't even run during time trials. Threw a dial-in on it, took it down cold for eliminations and it ran great. I bogged coming off line but it pulled great.  Let it cool down two hours for my second round of eliminations and it went through really strong again. In fact it was so great that I broke out by .3 seconds. And I had dialed in my best time on Friday.

Great work and it's fun to go round after round and just drive it not work on it.

[Ratbird]

Quick question gents. I've never drag raced other than as a kid on a remote deadend strip. In other words I've never been a real racer before.
I have a 4 speed top loader. My engine builder told me 6000 rpm was about redline. If I "speed" shift at about 4800 the engine rev will most likely shoot up to the 6k range for a micro second. (of course longer if I miss a gear) Is it super bad for the motor if this happens?
Also, what does valve float feel like while driving?
Still breaking in my motor and clutch until this Spring, but would one day like to take it to the strip in Albuquerque just to see what it will run.
Jim Nolan, I'm curious about your 410 build. I just had one done and I was wondering what hp and torque I might expect from it. Can you tell me what yours has?

thx a ton, Dave J

   

[JimNolan]

Quick question gents. I've never drag raced other than as a kid on a remote deadend strip. In other words I've never been a real racer before.
I have a 4 speed top loader. My engine builder told me 6000 rpm was about redline. If I "speed" shift at about 4800 the engine rev will most likely shoot up to the 6k range for a micro second. (of course longer if I miss a gear) Is it super bad for the motor if this happens?
Also, what does valve float feel like while driving?
Still breaking in my motor and clutch until this Spring, but would one day like to take it to the strip in Albuquerque just to see what it will run.
Jim Nolan, I'm curious about your 410 build. I just had one done and I was wondering what hp and torque I might expect from it. Can you tell me what yours has?

thx a ton, Dave J

   

Dave J,
    It's not speed shift, it's called power shifting. And, you won't be seeing 6K on your tach. Your engine doesn't have that much time between completely disengaged to engaged again to get there. 
   As far as my 410 is concerned I designed it to have a .050 quench, 9.5 CR and 7.5 DCR. It was imperative that my engine take me on a 1000 mile road trip, burn 87 octane gas, not overheat in long periods of traffic congestion, idle at 650rpm and give somewhat decent gas mileage yet make me think I was driving a 60's muscle car. I achieved all that. I estimate the engine to be delivering about 375 horsepower. DesktopDyno5 says I've got 416 HP @5000 rpm and 474 lbs torque at 4000 rpm ( I don't believe it ).  I haven't got tires that will hook up to find out how fast through the quarter mile it really is. It is without doubt a high 13's car if I could break the 2.1 sec 60' mark. If I were you, I'd limit my RPM's to 4800. After everything is said and done you want to be able to use it again. It's still a high torque engine. Not a short stroke chevy that has to wind to 7000 rpm just to get HP out of it. A somewhat stock FE gets it's HP below 5000 rpm. For my engine I like 5000 rpm shifts just because my rpm's don't drop back far enough to overtorque the rear wheels and make them spin so much in 2nd and 3rd. It's a smooth ride once you get past the 60' mark. Good luck.
PS. You asked about valve float. I used to float the valves on my 66 Fairlane GT all the time in high gear. The car will just stop pulling, start maintaining a constant speed and if you look out the back window you won't be able to see behind you because of all the blue smoke. Most performance hydraulic lifters will last to 5000 rpm. You need solid lifters after that. And, don't be misled as to what rpm your engine will go to. A fully blown 650 HP engine is a lot different than a hopped up 375 HP more stock engine. If you look at your manufacture's specifications it'll tell you what to look for in the way of torque and horsepower. The biggest difference between a race engine and a hopped up engine is you can drive farther than a 1/4 mile with a hopped up engine. lol

[XR7]

I have a data recorder that I use occasionally (I would use it all the time if I could, but the class I race does not allow it... so it is disabled). When I ran my old 428 and Toploader, I recorded some runs with it. I "power shifted" it and shifted at 6500 RPM, the engine spiked up to 6800, before coming down to 5100 for the bottom of the next gear. You can see that clearly with the charts. I could shift pretty fast with the "crash box" Toploader and super shifter3, but not as fast as the Jerico with Long verti-gate shifter I run now. I am sure the HP level also matters, as more power will spike higher.. and quicker, than with less power. The 428 had less than 600 HP and at 3580# would run around 10.50@128. My current 427 stroker combo is 7 tenths and 10 MPH faster, but no data as I was in "bracket mode" running for points.

I would drive it like you stole it. Have a working rev limiter, and shift it as high as you dare. If you have a self-imposed 6000 rev limit, shift a few hundred before that. My own engine never sees less than 5100 on a pass from launch to lights, and I know several FE guys that run higher RPM than me, some a lot higher. It all depends on the combo of course, the sum of parts etc. and/or weakest link...

I turned 7700 a couple times last year, not by choice... oops, didn't break anything though... in the engine.

[Mike Caruso]

Combination !!!
I used to help a guy who ran 455 Olds 442 back in 1968 we twisted the snot out of that thing. 25 years later 5400 max and runs quicker and more MPH.
I guess we got smarter along the way LOL.