Chevy

Chevrolet Repair Questions? Ask a Chevy Mechanic for Answers ASAP

Ask an Expert,
Get an Answer ASAP!

Chevy

how to set the timing on big block chevy

Customer Question
1973 (454) hei...
1973 (454) hei
Submitted: 9 years ago.Category: Chevy
Ask Your Own Chevy Question
Answered in 1 hour by:
7/22/2008
Chevy Mechanic: Bob, Auto Tech replied 9 years ago
Bob
Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4,087
Experience: Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)
Verified

See Figure 1

Click image to see an enlarged viewFig. 1: The timing marks are located on the vibration damper on this 1977 V8 engine

Timing should be checked at each tune-up and any time the points are adjusted or replaced. It isn't likely to change much with HEI. The timing marks consist of a notch on the rim of the crankshaft pulley or vibration damper and a graduated scale attached to the engine front (timing) cover. A stroboscopic flash (dynamic) timing light must be used, as a static light is too inaccurate for emission controlled engines.

There are three basic types of timing light available. The first is a simple neon bulb with two wire connections. One wire connects to the spark plug terminal and the other plugs into the end of the spark plug wire for the No. 1 cylinder, thus connecting the light in series with the spark plug. This type of light is pretty dim and must be held very closely to the timing marks to be seen. Sometimes a dark corner has to be sought out to see the flash at all. This type of light is very inexpensive. The second type operates from the vehicle battery; two alligator clips connect to the battery terminals, while an adapter enables a third clip to be connected to the No. 1 spark plug and wire. This type is a bit more expensive, but it provides a nice bright flash that you can see even in bright sunlight. It is the type most often seen in professional shops. The third type replaces the battery power source with 110 volt current.

Some timing lights have other features built into them, such as dwell meters or tachometers. These are convenient, in that they reduce the tangle of wires under the hood when you're working, but may duplicate the functions of tools you already have. One worthwhile feature, which is becoming more of a necessity with higher voltage ignition systems, is an inductive pickup. The inductive pickup clamps around the No. 1 spark plug wire, sensing the surges of high voltage electricity as they are sent to the plug. The advantage is that no mechanical connection is inserted between the wire and the plug, which eliminates false signals to the timing light. A timing light with an inductive pickup should be used on HEI systems.

INSPECTION & ADJUSTMENT

See Figure 2

Click image to see an enlarged viewFig. 2: View of the timing marks (on the pulley) and timing indicator - 1975-78 gasoline V8 engines
  1. Warm up the engine to normal operating temperature. Stop the engine and connect the timing light to the No. 1 (left front on V8, front on six) spark plug wire. You can also use the No. 6 wire, if it is more convenient. Numbering is illustrated in this section. Under no circumstances should the spark plug wire be pierced to hook up a timing light. Clean off the timing marks and mark the pulley or damper notch and timing scale with white chalk. The timing notch on the pulley or damper can be elusive. The best way to get it to an accessible position for marking is to bump the engine around using either the ignition key or a remote starter.
  2. Disconnect and plug the vacuum line at the distributor. This is done to prevent any distributor vacuum advance. A short screw, pencil, or a golf tee can be used to plug the line.
  3. Start the engine and adjust the idle speed to that specified in the Tune-Up Specifications chart. With automatic transmission, set the specified idle speed in Park. It will be too high, since it is normally (in most cases) adjusted in Drive. However, it is safer to adjust the timing in Park and to reset the idle speed after all timing work is done. Some trucks require that the timing be set with the transmission in Neutral. Refer to the Tune-Up Specifications chart or the underhood sticker for details. You can disconnect the idle solenoid, if any, to get the speed down. Otherwise, adjust the idle speed screw. This is done to prevent any centrifugal (mechanical) advance.

The tachometer hookup for 1970-74 models is the same as the dwell meter hookup shown in the Tune-Up and Troubleshooting sections. On 1975-77 HEI systems, the tachometer connects to the TACH terminal on the distributor (V8) or on the coil (6-cylinder) and to a ground. For 1978-79 vehicles, all tachometer connections are to the TACH terminal. Some tachometers must connect to the TACH terminal and to the positive battery terminal. Some tachometers won't work with HEI.

WARNING Never ground the HEI TACH terminal; serious system damage will result.
  1. Aim the timing light at the pointer marks. Be careful not to touch the fan, because it may appear to be standing still. Keep the timing light wires clear of the fan, belts, and pulleys. If the pulley or damper notch isn't aligned with the proper timing mark (see the Tune-Up Specifications chart), the timing will have to be adjusted.

TDC or Top Dead Center corresponds to 0 degrees. B, or BTDC, or Before Top Dead Center may be shown as BEFORE. A, or ATDC, or After Top Dead Center may be shown as AFTER.

  1. Loosen the distributor base clamp locknut. You can buy a special wrench which makes this task a lot easier on V8s. Turn the distributor slowly to adjust the timing, holding it by the body and not the cap. Turn the distributor in the direction of rotor rotation (found in the Firing Order illustration in this section) to retard, and against the direction of rotation to advance.
  2. Tighten the locknut. Check the timing again, in case the distributor moved slightly as you tighten it.
  3. Replace the distributor vacuum line. Correct the idle speed.
  4. Stop the engine and disconnect the timing light.

 

Ask Your Own Chevy Question
Ask Bob Your Own Question
Bob
Bob
Bob, Auto Tech
Category: Chevy
Satisfied Customers: 4,087
4,087 Satisfied Customers
Experience: Plus 40 years GM, over 30 certified with Chevrolet, ASE certified Master Tech. (Expired, Retired)

Bob is online now

A new question is answered every 9 seconds

How JustAnswer works:

  • Ask an ExpertExperts are full of valuable knowledge and are ready to help with any question. Credentials confirmed by a Fortune 500 verification firm.
  • Get a Professional AnswerVia email, text message, or notification as you wait on our site. Ask follow up questions if you need to.
  • 100% Satisfaction GuaranteeRate the answer you receive.

JustAnswer in the News:

Ask-a-doc Web sites: If you've got a quick question, you can try to get an answer from sites that say they have various specialists on hand to give quick answers... Justanswer.com.
JustAnswer.com...has seen a spike since October in legal questions from readers about layoffs, unemployment and severance.
Web sites like justanswer.com/legal
...leave nothing to chance.
Traffic on JustAnswer rose 14 percent...and had nearly 400,000 page views in 30 days...inquiries related to stress, high blood pressure, drinking and heart pain jumped 33 percent.
Tory Johnson, GMA Workplace Contributor, discusses work-from-home jobs, such as JustAnswer in which verified Experts answer people’s questions.
I will tell you that...the things you have to go through to be an Expert are quite rigorous.

What Customers are Saying:

I was having a terrible problem with the wheel bearings on my 98 Chevy Cavalier and I suspect that using this website saved me plenty of time and money.

Todd LRochester NY

Wonderful service, prompt, efficient, and accurate. Couldn't have asked for more. I cannot thank you enough for your help.

Mary C.Freshfield, Liverpool, UK

This expert is wonderful. They truly know what they are talking about, and they actually care about you. They really helped put my nerves at ease. Thank you so much!!!!

AlexLos Angeles, CA

Thank you for all your help. It is nice to know that this service is here for people like myself, who need answers fast and are not sure who to consult.

GPHesperia, CA

I couldn't be more satisfied! This is the site I will always come to when I need a second opinion.

JustinKernersville, NC

Just let me say that this encounter has been entirely professional and most helpful. I liked that I could ask additional questions and get answered in a very short turn around.

EstherWoodstock, NY

Thank you so much for taking your time and knowledge to support my concerns. Not only did you answer my questions, you even took it a step further with replying with more pertinent information I needed to know.

RobinElkton, Maryland

< Previous | Next >

Meet the Experts:

GM Tech (Cam)

GM Tech (Cam)

Chevy Technician

15,289 satisfied customers

GM Grand Master Technician 2007. 14 years experience.

Gary

Gary

Chevy Technician

9,357 satisfied customers

15 years GM master tech

Tim&#039;s Auto Repair

Tim's Auto Repair

mechanic

8,866 satisfied customers

Have owned a repair shop for 25 yrs.

Dave Nova

Dave Nova

Chevrolet Technician

7,092 satisfied customers

ASE Master Certification. GM World Class Certification

John

John

Master A.S.E Automotive technician

4,071 satisfied customers

A.S.E MasterTechnician A1-A8 w/L1,38 years experience General Motors Master Technician

Don - Mo Lurch

Don - Mo Lurch

Auto Mech / Electronics

2,918 satisfied customers

Chevrolet Cert., Heavy Line Mech, Race Shop Owner, Mobile Electronics.

Ron Z.

Ron Z.

- Chevy Tech -

2,734 satisfied customers

18+yrs experience. State Inspector and Chevy Diagnostics

< Previous | Next >

Related Chevy Questions
My chevy impala is cutting off while driving...but it only
My chevy impala is cutting off while driving...but it only does it every so often. It just started on Friday and it has done it about 4 or 5 times since. It starts back up after it turns off but im co… read more
Eric
Eric
Retired
N/A
14,436 satisfied customers
Chevy express 2500: cyl..wont start..chassis..fuse box
Chevy express 2500 2006 4.8L 8 cyl with gas in the tank will crank-won't start. Pulled a spark plug wire and cranked with plug wire to chassis- it sparked. Every fuse in the fuse box has been checked … read more
GM Tech (Cam)
GM Tech (Cam)
Chevy Technician
Vocational, Technical or Trade Scho
15,289 satisfied customers
Spark plug firing order for Vortec V8 5.7L engine.
I need to know the spark plug firing order for a vortec V8 5.7L engine. form the cap to each plug...… read more
ttiger79
ttiger79
Auto Mechanic
High School or GED
880 satisfied customers
I change the spark plugs I change the wires I change all
I change the spark plugs I change the wires I change all three coils I changed the gas card and I still getting the same code po300 lot of people is telling me that he could be the ignition module at … read more
David Craig
David Craig
OWNER/MECHANIC
Associates
4,414 satisfied customers
I already change the spark plugs and wires on a Malibu 2003
I already change the spark plugs and wires on a Malibu 2003 Chevy it won't start … read more
kalamykid
kalamykid
Pactor automotive
Vocational, Technical or Trade Scho
97 satisfied customers
Won't start, get spark from the spark plugs, have put gas in
won't start, get spark from the spark plugs, have put gas in the intact still won't start. Starter is turning all the belts … read more
heavy_chevy_396
heavy_chevy_396
Vocational, Technical or Trade Scho
2,518 satisfied customers
2014 Chevy Silverado 4.3 cylinder two misfire a spark plug
2014 Chevy Silverado 4.3 cylinder two misfire a spark plug is looks like it's wet with gasolineAlso engine code P0106… read more
fordguy4u
fordguy4u
Automotive Tech
Vocational, Technical or Trade Scho
70 satisfied customers
Pulled spark plug out and fuel came out with the plug.
pulled spark plug out and fuel came out with the plug. … read more
Dan
Dan
Automotive Technician
Vocational, Technical or Trade Scho
25 satisfied customers
Misfire code p0306 I️ changer distributor cap spark plug and
Misfire code p0306 I️ changer distributor cap spark plug and wires new fuel pump don't understand why code is appearing … read more
Gary
Gary
Senior Technician
Vocational, Technical or Trade School
59 satisfied customers
Misfire in cylinder #1 replaced coil and spark plugs, engine
misfire in cylinder #1 replaced coil and spark plugs, engine light on and flashing. Put in injector cleaner also. … read more
eauto
eauto
self employed
High School or GED
74 satisfied customers
Crank ok but won't start when hot, fuel 55psi,spark plug
when it cold start up no problem,i even replace coolant temp sensor… read more
Michael Solis
Michael Solis
363 satisfied customers
1 cylinder Spark Plugs crack and misfire. Random at first
1 cylinder Spark Plugs crack and misfire JA: How many miles are on the car? Is it a steady misfire? Or random? Customer: Random at first 79000 mjiles JA: What is the model/year of your Chevy? Customer… read more
Pete
Pete
Independent Auto Technician
Vocational, Technical or Trade Scho
138 satisfied customers
Crank, no start. fuel pump is working. spark plugs (I think)
crank, no start. fuel pump is working. spark plugs (I think) are firing. … read more
eric remington
eric remington
FORMER SHOP OWNER/TECHNICIAN/INSPECTOR
associates degree
293 satisfied customers
I'm trying to change the spark-plugs on my 2006 chevy
Hi,I'm trying to change the spark-plugs on my 2006 chevy Malibu,3.5 But I ran into a problem,a couple of the spark-plugs seem to be froze.they don't turn one bit.how can I get them out with out Breaki… read more
Eric
Eric
Auto Technician
589 satisfied customers
Second opinion] I'm trying to change the spark-plugs on my
Second opinion] Hi,I'm trying to change the spark-plugs on my 2006 chevy Malibu,3.5 But I ran into a problem,a couple of the spark-plugs seem to be froze.they don't turn one bit.how can I get them out… read more
Jerry Newton
Jerry Newton
Vocational, Technical or Trade Scho
2,066 satisfied customers
P0300 and P0480, 09 Chevy cobalt, Coil pack, spark plugs,
P0300 and P0480 JA: What is the model/year of your Chevy? Customer: 09 Chevy cobalt JA: Are you fixing your Cobalt yourself? What have you tried so far? Customer: Coil pack, spark plugs JA: How many m… read more
roy
roy
Associate Degree
3 satisfied customers
The check engine is on. I have changed all the spark plugs
Hi the check engine is on. I have changed all the spark plugs and core and ignition core. … read more
GM Tech (Cam)
GM Tech (Cam)
Chevy Technician
Vocational, Technical or Trade Scho
15,289 satisfied customers
2009 spark plugs wet engine run rough loss of power. 41k
2009 spark plugs wet engine run rough loss of power. … read more
GM Bob
GM Bob
Automobile Technician
High School or GED
1,003 satisfied customers
Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Disclaimer: Information in questions, answers, and other posts on this site ("Posts") comes from individual users, not JustAnswer; JustAnswer is not responsible for Posts. Posts are for general information, are not intended to substitute for informed professional advice (medical, legal, veterinary, financial, etc.), or to establish a professional-client relationship. The site and services are provided "as is" with no warranty or representations by JustAnswer regarding the qualifications of Experts. To see what credentials have been verified by a third-party service, please click on the "Verified" symbol in some Experts' profiles. JustAnswer is not intended or designed for EMERGENCY questions which should be directed immediately by telephone or in-person to qualified professionals.

Show MoreShow Less

Ask Your Question

x