CorvetteForum - Chevrolet Corvette Forum Discussion

C3 Tech/Performance V8 Technical Info, Internal Engine, External Engine, Basic Tech and Maintenance for the C3 Corvette
Sponsored by:
Sponsored by:

RPM readings

Thread Tools
 
Search this Thread
 
Old Oct 21, 2012 | 10:33 AM
Share
  #1  
Iron_dog's Avatar
Iron_dog
Thread Starter
Racer
10 Year Member
Conversation Starter
All Eyes On Me
Liked
 
Joined: Apr 2011
Posts: 471
Likes: 3
Default RPM readings
Hi guys,
while checking for idle RPM I've found that the gauge reading is different from timing light reading... which is about 400 RPM lower... what's wrong??
Reply
0
Old Oct 21, 2012 | 12:15 PM
Share
  #2  
Easy Mike's Avatar
Easy Mike
Team Owner
Supporting Lifetime
20 Year Member
 
Joined: Jun 2000
Posts: 38,923
Likes: 1,482
From: Southbound
Cruise-In II Veteran
Default
What gauge is "reading different"?

My timing light does not show rpm. I use my dwell/tach for that.

At idle, what rpm shows on your tachometer?

Reply
0
Old Oct 22, 2012 | 03:23 AM
Share
  #3  
Iron_dog's Avatar
Iron_dog
Thread Starter
Racer
10 Year Member
Conversation Starter
All Eyes On Me
Liked
 
Joined: Apr 2011
Posts: 471
Likes: 3
Default
I've a timing light with dwell/tach functions. At idle instr gauge is 1000 while timing light shows 600... I dont know which is the right one...
This is my timing light:

http://www.lawson-his.co.uk/assets/d...ns/TL93_V2.pdf

thanks!
Reply
0
Old Oct 22, 2012 | 03:29 AM
Share
  #4  
marshal135's Avatar
marshal135
Safety Car
10 Year Member
Veteran: Marine Corps
Conversation Starter
Liked
 
Joined: Sep 2011
Posts: 4,118
Likes: 1,230
From: Madeira Beach, FL
2024 C8 of the Year Finalist - Unmodified
2024 C2 of the Year Finalist - Unmodified
2023 C2 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
Default
My mechanical tach remains un rebuilt on my 68 BB.
My timing light and dwell meter both show 710 RPMS.
My tach guage shows 700.I'm not worried about that small margin.
400 RPMS seems like allot to be off.
Not trying to be smart but was the light defaulted to 4 cycle?
Marshal
Reply
0
Old Oct 22, 2012 | 04:44 AM
Share
  #5  
Iron_dog's Avatar
Iron_dog
Thread Starter
Racer
10 Year Member
Conversation Starter
All Eyes On Me
Liked
 
Joined: Apr 2011
Posts: 471
Likes: 3
Default
Originally Posted by marshal135
My mechanical tach remains un rebuilt on my 68 BB.
My timing light and dwell meter both show 710 RPMS.
My tach guage shows 700.I'm not worried about that small margin.
400 RPMS seems like allot to be off.
Not trying to be smart but was the light defaulted to 4 cycle?
Marshal
Marshal... I think you are right! I've realized the unit has two different modes: 2 strokes and 4 strokes! I think I set it wrong... thank you!
Reply
0
Old Oct 22, 2012 | 05:00 AM
Share
  #6  
marshal135's Avatar
marshal135
Safety Car
10 Year Member
Veteran: Marine Corps
Conversation Starter
Liked
 
Joined: Sep 2011
Posts: 4,118
Likes: 1,230
From: Madeira Beach, FL
2024 C8 of the Year Finalist - Unmodified
2024 C2 of the Year Finalist - Unmodified
2023 C2 of the Year Finalist - Unmodified
2020 C3 of the Year Finalist - Unmodified
Default
You are most welcome.
This forum has been such a wealth of help to me as well.Now its time for me to pay it forward.
Don't forget to disconnect the distributor vac advance if you are timing.'Its easy to forget.
Marshal
Reply
0

Get notified of new replies

To RPM readings

Back to Subforum
C3 Tech/Performance
View Next Unread
Timing for performance with 22* Vacuum 22* Mechanical




Click for Advanced Search
Reply Closed Thread Share
Forum Jump
Trending Topics

All times are GMT -4. The time now is 07:29 AM.

story-0
10 Ugly Corvettes That We Still Kinda Love

Slideshow: 10 ugly Corvettes that we still kinda love.

By Joe Kucinski | 2026-06-03 10:34:17


VIEW MORE
story-1
Top 10 Most Expensive Corvettes Ever Sold on Bring A Trailer

A lot of money has changed hands at the online auction house over the years.

By Brett Foote | 2026-06-03 10:21:50


VIEW MORE
story-2
10 Things Every Corvette Owner Needs (2026 Edition)

Slideshow: 10 great gifts Corvette enthusiasts actually want for Father's Day!

By Michael S. Palmer | 2026-06-03 15:43:40


VIEW MORE
story-3
8 Most "Only Corvette Owners Understand" Quirks and Problems

Slideshow: These are the quirks, annoyances, and oddly lovable problems that every Corvette owner eventually learns to live with.

By Pouria Savadkouei | 2026-05-28 09:31:39


VIEW MORE
story-4
10 Reasons the C6 Z06 is Still A Performance Benchmark After 20 Years

Slideshow: 10 reasons why the C6 Z06 is still a performance benchmark after 20 years.

By Joe Kucinski | 2026-05-27 17:20:09


VIEW MORE
story-5
How Much Horsepower Every Corvette Engine "LOST" in 1972

Slideshow: How much horsepower every Corvette engine lost in 1972.

By Joe Kucinski | 2026-05-27 16:54:53


VIEW MORE
story-6
Top 10 DOs and DON'Ts for Protecting Your Convertible Top!

Slideshow: How to Protect A Convertible Top: 10 DOs & DON'Ts

By Michael S. Palmer | 2026-04-03 00:00:00


VIEW MORE
story-7
Top 10 Most Explosive Corvettes Ever Made: Power-to-Weight Ratio Ranked!

Slideshow: The 10 most explosive Corvettes ever built based on power-to-weight ratio.

By Joe Kucinski | 2026-05-20 07:23:03


VIEW MORE
story-8
150 hp to 1,250 hp: Every Corvette Generation Compared by the Specs That Matter

Slideshow: From C1 to C8 we compare every Corvette generation by the numbers.

By Joe Kucinski | 2026-05-12 16:54:12


VIEW MORE
story-9
8 Coolest Corvette Pace Cars (and Replicas) of All Time

Slideshow: Some Corvette pace cars became collectible legends, while others perfectly captured the look and attitude of their era.

By Verdad Gallardo | 2026-05-11 09:50:51


VIEW MORE