4000RPM tach read on an 8000RPM lens
 

Making a 4000RPM mechanical tachometer read 8000 RPM with a 50% gear reduction at the distributor. I’m going to re-do the red line to read 5500 RPM

https://67-72chevytrucks.com/vboard/...1&d=1627513183

Re: 4000RPM tach read on an 8000RPM lens
 

Hmm,

Kinda cool thinking there. Sounds logical, like it should work.

Did all 67-72 tachs operate mechanically? Or would that be from heavy duty truck class such as 1 ton and up?


Bob

Re: 4000RPM tach read on an 8000RPM lens
 

67-72 C50 or C60 Diesel truck

Re: 4000RPM tach read on an 8000RPM lens
 

I'm interested to see how it all looks finished in the cluster. Good idea. I never thought of the reduction when I did mine.

Re: 4000RPM tach read on an 8000RPM lens
 

4000 to 8000 was easy 50% reduction
4000 to 5000 is above my pay grade to figure out lol. 12.5% reduction I think.

Re: 4000RPM tach read on an 8000RPM lens
 

20% reduction. My apologies - I’m slightly OCD. :uhmk:

Re: 4000RPM tach read on an 8000RPM lens
 

I'd trade you a nice gas tach cluster if ya wanted. :lol:

Re: 4000RPM tach read on an 8000RPM lens
 

Thanks for the sweet offer lol. I’m looking forward to getting the mechanical one revved up lol!

Re: 4000RPM tach read on an 8000RPM lens
 

A mock up of the lens & mechanical tach in the cluster. I have the vacuum gauge in the truck now. I may convert this cluster to accommodate a clock. The finished cluster likely won’t go in the truck till the winter when I install the L79 intake and tach drive distributor. So far I’m happy with how it has turned out.






https://67-72chevytrucks.com/vboard/...1&d=1629514543
https://67-72chevytrucks.com/vboard/...1&d=1629514565
https://67-72chevytrucks.com/vboard/...1&d=1629514585

Re: 4000RPM tach read on an 8000RPM lens
 

Re: 4000RPM tach read on an 8000RPM lens
 

It's looking very nice!

Re: 4000RPM tach read on an 8000RPM lens
 

Looks cool. I like it

Re: 4000RPM tach read on an 8000RPM lens
 

https://67-72chevytrucks.com/vboard/...1&d=1634431784
https://67-72chevytrucks.com/vboard/...1&d=1634431856
https://67-72chevytrucks.com/vboard/...1&d=1634431925
https://67-72chevytrucks.com/vboard/...1&d=1634431974

I installed the L79 intake yesterday and installed the mechanical tach today. Works flawlessly. I’m very happy with the way everything has turned out. I must say I’m just about done with the personalization of this truck. Now just drive and enjoy!!
Sorry the last pic is upside down. Maybe someone can correct that.

Re: 4000RPM tach read on an 8000RPM lens
 

Flip

Re: 4000RPM tach read on an 8000RPM lens
 

Thanks!

Re: 4000RPM tach read on an 8000RPM lens
 

That is awesome. I can't war to get mine going. A few questions. Can you post a pic of Where you rrouted the cable thru the firewall ad how long was the cable. These are 2 things I need t do till but my cab is at the body shop. Thx.

Re: 4000RPM tach read on an 8000RPM lens
 

Very nice work! It all looks very nice.