Performance Verification - Needle Bounce

[Michael S.]

I need some guidance on the PV testing. What in general is considered acceptable needle bounce for the speedometer and tach? On my 1965 327/350hp, during fast acceleration with the RPMs increasing and then decreasing when shifting, I have noticed the tach needle bouncing. All the gauges were rebuilt over 10 years ago, but there has only been about 3 thousand miles put on the car since then. Any advice would be appreciated.

[Rick A.]

Re: Performance Verification - Needle Bounce

personal experience - any needle bounce is NOT good - ALL gauges should basically be "quiet" - this is especially critical at idle, should be little if any movement in any gauge needle

[Loren L.]

Rick, I would characterize your response

as the ideal example of applying 2007 standards to equipment that is 40 or 50 years old. Yes, I would agree that "at idle" bounce should be virtually unnoticeable BUT in a mechanical gauge driven off a generator or a distributor, bounce may well be present - especially to a thirty year old judge. In the situation described "as going through the gears", I would be surprised if some element of "bounce" did NOT present itself. It's like the PV failure for too much oil pressure - a superlative standard that is b____t. In 1964, if my 300 HP '63 coupe did NOT peg the 60 lb gauge on startup, the only thing it told me was that I was a quart low on oil.

[Dino L.]

Fuel Gage movement

How does a typical midyear Fuel gage react to normal driving, I get a lot of needle movement from my gage, New quanta tank and sending unit.

[Rick A.]

Re: Rick, I would characterize your response

Loren,

agee entirely....was responding based on my TWO failed attempts at PV, and then finally passing this past National....gauge "flutter" played significantly in the failures

[Kirk McHugh]

Re: Fuel Gage movement

My 67 will show some downward drift on hard acceleration, but usually settles out once you are moving. Again, if I stop (say running red lights), it will drift down on acceleration and back up a bit upon stopping. It doesn't "bounce" though, these are gently drifts that I assume are associated with the movement of the gas in the tank as the car accelerates or decelerates.

The needles that bounce for me is my battery gauge. It too will quiet once the car is running, but will initially bounce wildly when I step on the brake, give me a little motion to match the blinker, etc. Always bothered me, but haven't been able to find the reason why.

[Dick W.]

Re: Fuel Gage movement

The needles that bounce for me is my battery gauge. It too will quiet once the car is running, but will initially bounce wildly when I step on the brake, give me a little motion to match the blinker, etc. Always bothered me, but haven't been able to find the reason why. There are capacitors located on the instruments to dampen the movements. Check them out to see that they are installed and are functioning as designed.

[Dino L.]

Re: Fuel Gage movement

there is a capacitor (condensor) that get old dry out and leak DC current, they are meant to filter noise. They are either missing or malfunctioning, there should be one aross your flasher at th efuse block, and one across the brake switch mounte don the brake pedal assembly...check them out, the metallic can is ground and the lead wire is positive.

Anyone have ideas on fuel guages that measure correctly and do not fluctuate at a stop, but fluctuate from 1/4 to 3/4 on turns when the tank is 1/2 full?

[John D.]

Re: Performance Verification - Needle Bounce

Michael, As Rick mentioned you will probably fail your PV with needle bounce. Tach cable problem: See what the fellows here say about the proper lubricant to use as that is typically the problem. My 63 has some tach cable bounce right now and I believe I can fix it with lubrication.
I am sure there are tons of stuff to use but here is what I am going to use. Dow Corning #44 hi-temp medium consistency grease. I have used this for many years on a lot of the fuel injection drive cables with good results. Another good grease is any brand of disc brake wheel bearing grease. Another good grease is Kendall Super Blu Hi-Temp EP L-427 grease. I use this a lot on drive cables too. Don't use the typical speedometer cable grease as this doesn't cut it. Make sure you don't have any kinks in the cable assembly.Your cable and housing is rather easy to get. If necessary but another one. Yes you have to get rid of the bounce or otherwise you will be going for another PV ride.
Make sure you ammeter needle doesn't move around either. If so replace the gauge. 3000 miles and ten years is a lot of time and miles if you haven't lubricated the cable. Don't use the white lithium grease on your cables as the new stuff is very watery. John D

[Gerard F.]

Re: Fuel Gage movement

Dino,

I think your fuel guage is normal and the variation on turns is due to fuel sloshing side to side in the tank. The axis of the float is side to side and you are bound to get fluctuating especially on a hard or tight turn.

Even going up or down a hill, stopping hard, or accellerating, will cause the float to move up and down, and thus the gage to fluctuate. As long as it comes back to a steady reading with steady driving or a stopped position, I don't see a problem.

They are probably not that accurate within 3 or 4 gallons anyway, that is
1 1/2" to 2" in the depth of a 20 gallon tank.

The fuel gage on my 67 fluctates, similar to the above (but slightly less than yours) with it's original sender and tank.

Jerry Fuccillo
#42179

[Dan H.]

Re: Fuel Gage movement

I just completed a PV for my 64 FI. The ammeter was nice and steady, but I had a new 515 voltage regulator on the car. I have since replaced it with a 'restored' 515 with correct dates etc., now the ammeter 'twitches' when the brakes are applied and turn signals are going. For PV you might want to try a new voltage regulator and see if that keeps the 'jitters' way down. Worth a shot!
Regards
Dan

[Paul L.]

Re: Performance Verification - Needle Bounce

Michael,
The tach needle on my 1967 bounces a wee bit at idle but is rock solid at speed. I thought this was normal??

[Michael S.]

Re: Performance Verification - Needle Bounce

Paul -

My tach also has some minor movement at idle but not very much. The problem I have seen with the needle bounce is at the higher RPMs especially when shifting up to the higher gears.

I have decided to lubricate the tach cable per the advice of John DeGregory. Thanks to all for the responses and I will let you know if the lubrication of the tach cable resolves the needle bounce.