6000, 7000 or 8000 rpm tach?

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7milesout

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I'm looking to replace my old tachometer. I like the thoughts of a 6,000 rpm tach because I don't plan on spinning my LA 360 any more than 5,500 rpm at the drag strip.

But I got to thinking that with only 6,000 rpm spread, that needle will be moving quickly at WOT heading toward 5,500 rpm. Which might make it more difficult to hit the 5,500 rpm mark accurately compared to hitting a mark on a slower moving 8,000 rpm tach.

Any opinions? Are there other concerns I need to consider?

I plan on getting either a 3-1/8" or 3-3/8" tach and dash mounting.

Thanks!


7milesout
 
If you arent going to need the extra 500/1000/2000 rpm then why buy one with it? Ive got a 6k since i know its never going over that.

Jake
 
Another thing to consider is that if you go with a lower RPM tach, it will be a bit easier to read, since there will be fewer rev points spread across the 270 degree sweep. If you are planning on using the tach to shift, I'd highly recommend getting one with a shift light like the Autometer 233905 or the 2309.
 
Garry in AZ said:
Another thing to consider is that if you go with a lower RPM tach, it will be a bit easier to read, since there will be fewer rev points spread across the 270 degree sweep. If you are planning on using the tach to shift, I'd highly recommend getting one with a shift light like the Autometer 233905 or the 2309.
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agree, **** lights are for shifting. Tachs are for gathering data.
 
I would get a 7k.

It isn't uncommon to go 250-500rpm over peak through the traps. Now you've maxed out your tach and you also have no room to grow.
 
Whilst I agree with your thinking … at this time, I don't see growth coming in the rpm department. I have the following mods coming.
  • Fuel Line Sheath - to combat and hopefully eliminate vapor lock (that I only get at the dragstrip on the 2nd and subsequent pulls, and only at 6 to 7 seconds into the run).
    • Achieve 13.999 seconds at this level. I've hit 14.128 seconds but shifted a bit early. I think I'm at 13.999 already, but want to see it on a slip.
  • AVS2 - Already procured, not necessarily for WOT but for improved streetability and low / mid range torque. Sitting on the shelf ready to go on.
  • Drop Base Filter Housing, to accomodate the following
  • Air Gap Intake.
Currently I shift at 5,000 rpm. I'm trying to be nice to the LA 360. I'm probably babying it too much, so this season I will shift it at ~5,500 rpm.

I want to hit 13.999 before moving on to the AVS2 and Air Gap Intake. The car is capable of 13.999 … but I'm trying to and wanting to achieve that on the factory 14" wheels, with skinny 215/60 street radials! :D

Once I hit 13.999, I'll move on with the AVS2 and Air Gap Intake and tune that to perfection with the AFR gauge.

I will be happy with the car at that level, because it is a very clean & original, 1972 Scamp. Combine its looks with an easy to drive, reliable street car that can make 13 second quarter mile runs and I'm pretty happy.
 
7milesout said:
Currently I shift at 5,000 rpm. I'm trying to be nice to the LA 360. I'm probably babying it too much, so this season I will shift it at ~5,500 rpm. .
Click to expand...

You should strap it to a dyno and see where it actually makes power and shift it there.
 
I don't even look at my tach. MSD shift light with changeable pill is what works for me.
 
Go with the 8000 RPM Tach. Your engine will probably be running up near the top. You want a 500 rpm cushion
:thumbsup:
 
Done done that, because the tach is too difficult (and freezes) while drag racing.

upload_2019-1-4_8-38-16.png
 
mderoy340 said:
I don't even look at my tach. MSD shift light with changeable pill is what works for me.
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Exactly.

You may use your tach to see what you are trapping at, or launch RPM or double check things, timing the car, etc but you can't beat a shift light for shifting. Not to mention its safer and more efficient because you never look away or down.
 
I would like to have a shift light too, because I agree with what you guys are saying.

But I can't seem to find a shift light in a 6,000 rpm gauge. I may have to go with the 8,000 rpm tach, because I can't find a 7,000 rpm tach with a shift light either. And, a fast moving tach would be more difficult to accurately hit a shift point, than a slightly slower one that has a shift light. However, the tach itself I would use for data, not for racing.

I'm likely going to fabricate my own bracket similar to Valiant1's … since I or others can't seem to contact him.

Up to now, I've used mathematics to determine where I'm trapping. According to my math, I trap between 4,400 and 4,500 rpm at 99 mph.

So I placed those marks on my speedo to be at ~5,000 rpm shift points. Since I had just started putting the love back into the car, I figured I should be somewhat conservative with it and hold it to 5,000 rpm.


7milesout
 
Get a separate shift light.

MSD digital shift light is small and can be set at any RPM. Mine is set at 5800. I go through the traps at 6200.

First picture is the shift light in my car with the new dash. Please escuse the hanging wires and radio missing. It was in progress when I took that pic.

2nd 2 are the car when it had the ever classic trashy autozone/advanced auto tach mounted to the column.

20150430_150841.jpg


1%20small.jpg


20131209_164003.jpg
 
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