4000RPM tach read on an 8000RPM lens - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**Canuckvetter** · 07-28-2021, 07:03 PM

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

HotWheelsFan · 07-28-2021, 07:39 PM

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

**Canuckvetter** · 07-29-2021, 12:22 AM

Quote:

Originally Posted by HotWheelsFan

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

67-72 C50 or C60 Diesel truck

**chewychevy67** · 07-29-2021, 01:42 AM

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.

**Canuckvetter** · 07-29-2021, 10:04 PM

Quote:

Originally Posted by chewychevy67

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.

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

**jabborabbo** · 07-30-2021, 12:15 PM

Quote:

Originally Posted by Canuckvetter

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

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

**Dieselwrencher** · 07-31-2021, 06:23 AM

Quote:

Originally Posted by Canuckvetter

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

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

**Canuckvetter** · 08-01-2021, 12:03 AM

Quote:

Originally Posted by Dieselwrencher

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

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

**Canuckvetter** · 08-20-2021, 11:04 PM

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

**Canuckvetter** · 08-20-2021, 11:10 PM

https://67-72chevytrucks.com/vboard/...1&d=1629515382

**Dieselwrencher** · 08-21-2021, 05:22 AM

It's looking very nice!

**chewychevy67** · 08-21-2021, 12:33 PM

Looks cool. I like it

**Canuckvetter** · 10-16-2021, 09:01 PM

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.

bluek5 · 10-16-2021, 09:06 PM

Flip

**Canuckvetter** · 10-16-2021, 09:16 PM

Quote:

Originally Posted by bluek5

Flip

Thanks!

**chewychevy67** · 10-17-2021, 07:10 AM

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.

**Dieselwrencher** · 10-23-2021, 07:50 AM

Very nice work! It all looks very nice.

07-28-2021, 07:03 PM	#1
Canuckvetter How did I get this OLD! Join Date: Dec 2014 Location: Lamont County, AB, CANADA Posts: 1,047	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 Attached Images __________________ 1967 Oshawa built LWB Fleetside. 327,3 OTT, 515 Vermilion, CST, PS, PB, Shoulder Harness, Tach,Vac, Speed Warning, Choke Delete, Manual Throttle, Fawn interior. Dealer installed A/C 04/2015, N34 Rosewood Wheel 06/2023 Members who I have met personally. Metaldoc, chevnkevin, 62 Longbed, 72LHorn, 72MARIO, YBNORML, TBONE1964, Classic Bowties, Chevemall, Dagnabbitt.

07-28-2021, 07:39 PM	#2
HotWheelsFan Registered User Join Date: Mar 2010 Location: Oregon Posts: 189	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 __________________ 1970 C20 Long Bed Fleetside - Restoration My truck videos - Youtube

07-29-2021, 01:42 AM	#4
chewychevy67 Senior Member Join Date: Jan 2010 Location: Here Posts: 5,557	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.

08-20-2021, 11:04 PM	#9
Canuckvetter How did I get this OLD! Join Date: Dec 2014 Location: Lamont County, AB, CANADA Posts: 1,047	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 Attached Images __________________ 1967 Oshawa built LWB Fleetside. 327,3 OTT, 515 Vermilion, CST, PS, PB, Shoulder Harness, Tach,Vac, Speed Warning, Choke Delete, Manual Throttle, Fawn interior. Dealer installed A/C 04/2015, N34 Rosewood Wheel 06/2023 Members who I have met personally. Metaldoc, chevnkevin, 62 Longbed, 72LHorn, 72MARIO, YBNORML, TBONE1964, Classic Bowties, Chevemall, Dagnabbitt.

08-20-2021, 11:10 PM	#10
Canuckvetter How did I get this OLD! Join Date: Dec 2014 Location: Lamont County, AB, CANADA Posts: 1,047	Re: 4000RPM tach read on an 8000RPM lens https://67-72chevytrucks.com/vboard/...1&d=1629515382 Attached Images __________________ 1967 Oshawa built LWB Fleetside. 327,3 OTT, 515 Vermilion, CST, PS, PB, Shoulder Harness, Tach,Vac, Speed Warning, Choke Delete, Manual Throttle, Fawn interior. Dealer installed A/C 04/2015, N34 Rosewood Wheel 06/2023 Members who I have met personally. Metaldoc, chevnkevin, 62 Longbed, 72LHorn, 72MARIO, YBNORML, TBONE1964, Classic Bowties, Chevemall, Dagnabbitt.

08-21-2021, 05:22 AM	#11
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,142	Re: 4000RPM tach read on an 8000RPM lens It's looking very nice! __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*

08-21-2021, 12:33 PM	#12
chewychevy67 Senior Member Join Date: Jan 2010 Location: Here Posts: 5,557	Re: 4000RPM tach read on an 8000RPM lens Looks cool. I like it

10-16-2021, 09:01 PM	#13
Canuckvetter How did I get this OLD! Join Date: Dec 2014 Location: Lamont County, AB, CANADA Posts: 1,047	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. Attached Images __________________ 1967 Oshawa built LWB Fleetside. 327,3 OTT, 515 Vermilion, CST, PS, PB, Shoulder Harness, Tach,Vac, Speed Warning, Choke Delete, Manual Throttle, Fawn interior. Dealer installed A/C 04/2015, N34 Rosewood Wheel 06/2023 Members who I have met personally. Metaldoc, chevnkevin, 62 Longbed, 72LHorn, 72MARIO, YBNORML, TBONE1964, Classic Bowties, Chevemall, Dagnabbitt.

10-16-2021, 09:06 PM	#14
bluek5 Registered User Join Date: Apr 2012 Location: Lehi,Utah Posts: 1,330	Re: 4000RPM tach read on an 8000RPM lens Flip Attached Images

10-17-2021, 07:10 AM	#16
chewychevy67 Senior Member Join Date: Jan 2010 Location: Here Posts: 5,557	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.

10-23-2021, 07:50 AM	#17
Dieselwrencher 6>8 Plugless........ Join Date: Sep 2007 Location: Prairie City, Ia Posts: 17,142	Re: 4000RPM tach read on an 8000RPM lens Very nice work! It all looks very nice. __________________ Ryan 1972 Chevy Longhorn K30 Cheyenne Super, 359 Inline 6 cylinder, Auto Trans, Tilt, Diesel Tach/Vach, Buckets, Rare Rear 4-link and air ride option Build Thread 1972 GMC Sierra Grande Longhorn 4x4 1972 Chevy Cheyenne Super K20 Long Step side tilt, tach, tow hooks, AC, 350 4 speed 1972 C10 Suburban Custom Deluxe 1969 Chevy milk truck 1971 Camaro RS 5.3 BTR STG3 Cam Super T10 1940 Ford 354 Hemi 46RH Ford 9" on air ride huge project *Tired of spark plugs? Check this out.*



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