Tach install and RPM's

[No8Easy2]

hey guys i need some help figuring this out, i just pulled a 3 hole cluster out and installed a 7 hole with tach (all factory). and i have taking the truck out twice since the swap
and i cant figure out why my RPM's are reading so high on the tach
on the way home i was going 35 MPH and the tach was around 3k in 3rd gear??
specs on the truck are...
350 / th350
stock converter
275/60/15 or 28" diameter
i'm not 100% on rear gears but when i used a gear ratio calculator (here) even at 4.11 and 35 MPH it should be 1783 rpm
any ideas and thanks for any help
Chris

[69SCSS]

Was the cluster out of a truck with a 6? If so then it's a 6 cylinder tach, and will read high.

[No8Easy2]

i got the whole cluster from a another board member who rebuilds them
and it should be a 8 but maybe its not
i can pull the tach and check for any markings but are there any numbers to look for?

[69SCSS]

Doing the math, look slike at 35mph with 4.11's you'd be at 1780ish like you said (not compensating for converter slip), but if the tach is a 6 cyl tach it would read 2310ish. Unless your converter is slipping a lot at 35mph, that doesn't sound right. Not sure what the issue would be if that's the case, the 6 cyl tach was the first thing that came to mind.

[TBONE1964]

Chris,

I got your PM and I will be more than willing to take care of the tach issue for you.

I agree that the RPM's you see are high even for a 6 cylinder.

You will not see any markings on it that will tell you if it is for a 6 or 8. The original part number comes off when I glass bead the tach tin. I know this tach is for an 8 cylinder. Not sure exactly what the problem is but would like you to send the tach back or even the whole cluster, what ever is easiest for you. I will cover your shipping and get this corrected for you.

I sent you a PM also.

Thank you for bringing it to my attention.

Take care,
Tom

[No8Easy2]

thanks Tom that more than generous and speaks to the quality of your clusters so thanks again
I'm going to upload a video here is a bit maybe it will help also Tom is there any way to
check the tach on the beach i might be able to generate pulsating DC voltage at work
or do i need something else?

[TBONE1964]

Originally Posted by No8Easy2

thanks Tom that more than generous and speaks to the quality of your clusters so thanks again
I'm going to upload a video here is a bit maybe it will help also Tom is there any way to
check the tach on the beach i might be able to generate pulsating DC voltage at work
or do i need something else?

I have a tool by Kent Moore that is a tach calibrator and you hook the tach up to it and it will tell you where the tach should read as oppose to where it actually reads. I use this on every tach cluster I sell and it should get the tach very close to right on. Your tach obviously did not like the cal.

I also have a NOS tach hear that I use to compare. I use my 72 Cheyenne and a tach harness to check and make sure I don't have needle stick and the RPM looks good.

Another thing you can do if possible is find some one that has a timing light that has an RPM read out. Snap On makes one and I know they are very expensive but it will give you an accurate RPM reading. Not sure if that is something you could borrow from someone. If you have a correct baseline, you can turn the calibration screw that is in the back of the tach and dial it in that way.

Like I said, I have no problem taking care of this for you but my time has some limitations for the next month.

Let me know,
Tom

[No8Easy2]

here is the vid sorry not the best but you get the idea! lol

started from a stop light and got to around 40MPH and 3rd gear

http://youtu.be/dU_nwOYhGNg

[TBONE1964]

Originally Posted by No8Easy2

here is the vid sorry not the best but you get the idea! lol

started from a stop light and got to around 40MPH and 3rd gear

http://youtu.be/dU_nwOYhGNg

Yes, I got the idea OK. That is not good. I can hear the engine RPM's and they don't sound to be over 2000. Where is the tach reading at idle Chris?

It should depending on your cam between 800 and 1200 roughly.

Let me know what you want to do with it and I will take care of this. I really appreciate your patients.

By the way, the interior from what I can see of it looks very nice. Not often I get to see one of my clusters after installation

Take care,
Tom

[FRENCHBLUE72]

Been awhile since I have been on here but looks like we have another great vendor...

[No8Easy2]

thanks Tom the idle seems to be fine around 800 or so
if you think this is just a tach issue i can wait Tom until you let me know when its good for you
and i will just send you the tach or is it easier with the whole cluster ?
i'm in no rush Tom at our convenience
thanks again for this!

[TBONE1964]

Originally Posted by FRENCHBLUE72

Been awhile since I have been on here but looks like we have another great vendor...

Thank you. I see you are from Grants Pass. I am moving to Junction City, OR in September to do the cluster business full time. Maybe I will meet up with you sometime.

I appreciate the comment. I do not want any un happy customers.

Take care,
Tom

[TBONE1964]

Originally Posted by No8Easy2

thanks Tom the idle seems to be fine around 800 or so
if you think this is just a tach issue i can wait Tom until you let me know when its good for you
and i will just send you the tach or is it easier with the whole cluster ?
i'm in no rush Tom at our convenience
thanks again for this!

Here is what I will do for you Chris. I will get one that I have here ready and ship it to you and you can send the one you have back. There is no need to send the complete cluster to me and chance shipping damage. That way you can just swap it and send me the bad one back. I will test the one I send on my truck and make sure it is OK.

I will get one ready and need you to PM me your address again.

Thanks again for your understanding.

Take care,
Tom

[No8Easy2]

that sounds great Tom and once again thanks for your help and standing behind
the cluster
it speaks volumes to you and your work!
pm sent with address

[PanelDeland]

That folks is why using BB vendors is preferred over LMC.You get someone who actually knows about these trucks and customer service. Not only that but you can see how the vendor solves problems. And me,McD's can't even get my order right.

[No8Easy2]

Just wanted to update Tom and pass on that the replacement tach he sent me works 100%
thanks again Tom for all your help and standing behind your clusters
great vendor!

[TBONE1964]

Originally Posted by No8Easy2

Just wanted to update Tom and pass on that the replacement tach he sent me works 100%
thanks again Tom for all your help and standing behind your clusters
great vendor!

Thank you Chris. I appreciate the kind words and most of all, I am happy the tach is working good for you now.

Have a great weekend,
Take care,
Tom

[72MARIO]

What is involved in adjusting a factory tach. Mine reads 800rpm fast. Its a 8cyl tach

[TBONE1964]

Originally Posted by 72MARIO

What is involved in adjusting a factory tach. Mine reads 800rpm fast. Its a 8cyl tach

What you really need is a reference. There is an adjustment on the back side (top/middle) that will tune it in. 800 is a lot. Is it 800 PM at idle or what RPM range?

I use a tachometer calibrator made by Kent Moore tools. I also use my 72 Cheyenne with a NOS tach to make sure everything is correct. These tachs may be correct at idle (800 RPM) but be way off at 2000 RPM's.

If you are going to adjust it, be careful not to over adjust. It only takes a slight movement to get a big RPM change.

[72MARIO]

Its very close at idle. I think the engine is turning 2200 but tach shows 2700-²80ⁿ. I bought a 90 dollar tach from amazon that shows a digital display of rpm I can use to adjust it.

Thanks for the advice I never would have known there tunable.