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View Full Version : How To: Check and Adjust Timing


Chicago190
07-05-2008, 08:18 PM
For the future to save people an hour of learning, here is how to check and adjust the timing on Chevy 350 engines. Excuse my laymans descriptions, but it will show that it takes almost no mechanical ability to set the timing correctly.

Tools needed:
Basic Set of wrenches
Timing Light
White out/chalk for marking pulleys

Time: 30 mins. maximum

1. Disconnect lifting shocks on motor box to open it all the way.

2. Start engine and bring to operating temp. Turn off engine and look at the crank pulley (bottom most pulley with the raw water pump attached). Disconnect the safety lanyard and bump the motor over until you can see the timing marks on the pulley. There will be a line in the middle which is Top Dead Center (see picture).

https://mywebspace.wisc.edu/breslin/web/Crank%20Pulley.JPG?uniq=-c58cbq

3. Take white out/chalk and mark the pulley to make it easy to see the Top Dead Center mark when using your timing light.

4. Locate the bracket above the pulley that has the marks for setting the timing. It should have degree readings so you know which to mark. Use the white out/chalk again and mark 10 degrees Below Top Dead Center on the bracket. It will be obvious where to mark when you see it (see picture, yellow mark is 10 degrees BTDC).

https://mywebspace.wisc.edu/breslin/web/Timing%20Marks.JPG?uniq=-c58caw

5. The timing light will have 3 connectors. Connect the first two to the battery, and attach the third to the #1 spark plug wire. The #1 spark plug wire is at the front right.

6. To set the timing, the engine must be put into diagnostic mode. The easiest way to do this is take a paper clip and use it as a jumper to jump pins A and B of the data connector on the back of the engine. This connector is in the main wiring harness by itself and has a gray and black cover on it (see bad picture). The pins are marked so it will be easy to know where to put the paper clip. Stick one end of the paper clip in pin A and the other end in pin B. When you start the engine it should idle at 1000 RPMs.

https://mywebspace.wisc.edu/breslin/web/Data%20Connector.JPG?uniq=-c58cbk

7. Start the engine and then point the timing light at the crank pulley. If the timing is correct the markings will match up with each other.

8. If timing needs to be adjusted, loosen the bolt at the bottom of the distributor to allow the distributor to turn. If the timing is too advanced, turn the distributor counter clockwise and vice versa if the timing needs to be advanced. A little turn does a lot so make small changes.

9. Once the timing is set properly, retighten the bolt on the distributor to lock it in place.

10. Remove the paper clip and you're done.

kah68
07-08-2008, 10:39 PM
Great post, thanks...does anyone have step by step for 351 Indmar/Holley timing?

denverd1
07-09-2008, 12:20 PM
omit step 6. It's pretty much the same.

Gonzo
07-09-2008, 12:28 PM
Boat has a 351 but the truck has a 350 ! Subscribed!!

denverd1
07-09-2008, 12:30 PM
and set at idle, not 1000 rpm.

Chicago190
07-09-2008, 07:18 PM
Great post, thanks...does anyone have step by step for 351 Indmar/Holley timing?

I think the #1 spark plug is different on the Ford motors. I want to say front left spark plug, but do a google search to be sure.

As denverd1 said there won't be an electrical connector on the back to jump since its only for the fuel injected motors.

TMCNo1
07-09-2008, 07:40 PM
I think the #1 spark plug is different on the Ford motors. I want to say front left spark plug, but do a google search to be sure.

As denverd1 said there won't be an electrical connector on the back to jump since its only for the fuel injected motors.


#1 on the 351W is the first plug on the front of the head on the starboard/right side/driver side of the boat.
37396

Chicago190
07-09-2008, 08:15 PM
Just to clarify: when I refered to right and left its when looking at the front of the motor.

Chevy #1 spark plug is at the front of the motor on the port side of the boat/observer's side.

Ford #1 is at the front of the motor on the starboard/driver's side as TMCNo1 said.

kah68
07-10-2008, 09:06 AM
Thanks guys I will set timing this weekend.

Kirk

Hollywood
07-10-2008, 09:56 AM
You forgot to tell them to pull the trigger on the gun! Timing should be checked and adjusted if necessary after installing any EI kit. Shoot for about ~600 rpms at idle. This will drop to ~400 rpm at idle IN gear on the lake.

JimN
10-03-2009, 01:11 PM
and set at idle, not 1000 rpm.

Nope- 1000 RPM for the injected motors.

JimN
10-03-2009, 01:16 PM
You forgot to tell them to pull the trigger on the gun! Timing should be checked and adjusted if necessary after installing any EI kit. Shoot for about ~600 rpms at idle. This will drop to ~400 rpm at idle IN gear on the lake.

The idle for a non-injected motor is supposed to be 600 - 650 RPM and it shouldn't drop that much in gear because there's far less resistance to a prop turning in water than turning against brakes on a car. Most motors won't idle well, if at all, at 400 RPM.

Jesus_Freak
10-14-2009, 12:21 PM
OK, so I tried this yesterday. With the paper clip between the A and B pins, the engine would not even idle. I had to move the throttle forward to hold the engine at 1000 RPM to do my timing test. What does that mean is wrong with my method, computer, or engine?

JimN
10-14-2009, 12:44 PM
OK, so I tried this yesterday. With the paper clip between the A and B pins, the engine would not even idle. I had to move the throttle forward to hold the engine at 1000 RPM to do my timing test. What does that mean is wrong with my method, computer, or engine?

Nothing is wrong. I thought I mentioned that the throttle needs to be advanced for it to idle and then go up to 1000 RPM. Sorry if I didn't. As long as the timing mark is stable, you're OK and able to verify or adjust the base timing advance. I may have omitted it because this happens automatically when a Tech 1 is connected and I have done almost all timing adjustments with that, unless it was my truck, which doesn't quite apply because of the different procedure.

Jesus_Freak
10-14-2009, 07:38 PM
Nothing is wrong. I thought I mentioned that the throttle needs to be advanced for it to idle and then go up to 1000 RPM. Sorry if I didn't. As long as the timing mark is stable, you're OK and able to verify or adjust the base timing advance. I may have omitted it because this happens automatically when a Tech 1 is connected and I have done almost all timing adjustments with that, unless it was my truck, which doesn't quite apply because of the different procedure.

Cool. Thanks. Yes, I have done this in various makes and models of automobiles but never had to sustain throttle advance to keep the engine running. Now I know....

Kummer
05-18-2011, 11:44 PM
This is a great post and should be a sticky - Problem is the pictures are no longer being shown. Can Chicago190 post images?

Chicago190
05-21-2011, 09:36 PM
This is a great post and should be a sticky - Problem is the pictures are no longer being shown. Can Chicago190 post images?

I don't have them on my current computer, but I will be at the lake next weekend and I can take new pictures and add them. If you have any questions in the interim I (or someone else here) can respond.

Engine Nut
05-21-2011, 10:34 PM
Here is a link to the ignition/adjustment procedures for Indmar/GM engines 1993 and newer.

ftp://ftp2.indmar.us/Service%20Information/Ignition%20Specs%20and%20Adjustment.pdf

wtrskr
05-23-2011, 06:29 PM
I'll comment on my experience since I recently adjusted the timing on my 1994 tbi.

After I put the paper clip in A & B the RPMs dropped a little. I did have to manually increased the RPMs to 1000.

After pulling the paperclip, the computer increased the RPMs to aproximately 2200 for a little while before settling back down into the normal range. I did the adjustment in my driveway and during my first attempt my hose-in-the-bucket bucket started to run out of water. I had to shut the engine off before the process was complete.

The other thing to be aware of is that the timing light may need to be powered by the battery. In my case, the cords did not reach the battery which is located in the rear by the gas tank. I pulled a car right next to the boat for my first attempt and used its battery for power. The second time, after suggestions from team talk, I put the positive clip where the juice goes to the starter, and the negative on the engine block.

Overall it was a pretty easy process.

1redTA
05-23-2011, 07:58 PM
Wtrskr, you could hook the light to the alt for power

46Chief
05-21-2015, 08:16 PM
Don't hook your light to the alternator, I don't think you'll get consistent voltage

JimN
05-21-2015, 09:36 PM
Don't hook your light to the alternator, I don't think you'll get consistent voltage

Don't really need constant voltage, just around 10VDC-15VDC, to make it operate.

mikeg205
05-21-2015, 09:58 PM
holy thread revival ;)

thatsmrmastercraft
05-21-2015, 11:36 PM
holy thread revival ;)

No kidding. Lots of forgotten good stuff here.

ahhudgins
05-26-2015, 08:22 AM
I'll comment on my experience since I recently adjusted the timing on my 1994 tbi.

After I put the paper clip in A & B the RPMs dropped a little. I did have to manually increased the RPMs to 1000.

After pulling the paperclip, the computer increased the RPMs to aproximately 2200 for a little while before settling back down into the normal range. I did the adjustment in my driveway and during my first attempt my hose-in-the-bucket bucket started to run out of water. I had to shut the engine off before the process was complete.

The other thing to be aware of is that the timing light may need to be powered by the battery. In my case, the cords did not reach the battery which is located in the rear by the gas tank. I pulled a car right next to the boat for my first attempt and used its battery for power. The second time, after suggestions from team talk, I put the positive clip where the juice goes to the starter, and the negative on the engine block.

Overall it was a pretty easy process.

I’m glad that this thread was reborn. I had just asked about checking the timing on my 95 TBI a week ago. The Indmar manual states that my timing should be 10 degrees BTDC at 1000 rpms and the engine should automatically go to 1000 rpms when put in service mode. I checked my timing before going to service mode and it was bouncing around between 12 and over 14 degrees while idling around 750. When I put it in service mode the engine rpms dropped to around 500 and I saw no difference in the timing mark. Now I know to manually set it to 1000 rpms next weekend. My rpms also jumped to 2000 when I took it out of service mode (for about 10 seconds) and settled back to normal idle speed…just like yours.

My question is: How much (if any) timing fluctuation is normal?
The manual states that the timing will be “at idle in base timing mode” but then the tips state that the rpms should automatically raise to 1000 for EFI, which mine did not.

This is the manual I used.
https://www.m2omarine.com/resources/IndmarIgnitionTiming.pdf

catamount
05-26-2015, 02:52 PM
I can't speak to your '95 TBI, but your timing lights should not jump around. This indicates either advance weights in your distributor that are sticking, or cylinders that are not firing for whatever reason (weak spark, too rich, too lean, weak compression, etc).

How is the boat running, generally?

ahhudgins
05-26-2015, 06:10 PM
I can't speak to your '95 TBI, but your timing lights should not jump around. This indicates either advance weights in your distributor that are sticking, or cylinders that are not firing for whatever reason (weak spark, too rich, too lean, weak compression, etc).

How is the boat running, generally?

Boat runs great, it just idles a little ruff and all of the plugs are showing a rich mixture. It has been like this since I purchased it a few years ago. The distributor is electronic so no weights. I replaced both injectors last week.
After a little research today I will start doing some more tests next weekend. Check for one cylinder not firing and compression test. The MAP sensor regulates mixture and timing so I will check that. I already replaced the vacuum line to the MAP sensor.