1986 305 timing tab - The 1947 - Present Chevrolet & GMC Truck Message Board Network

Brad_Olson · 04-15-2005, 06:11 PM

My '86 305's timing tab is pretty dirty and all I can see are the "teeth"; the numbers are covered. I think I know what the teeth indicate but want to be sure so I know I'm setting the timing I think I'm setting.

Think of each tooth point as a high spot and the halfway point between 2 teeth as a low spot. There's one low spot that's wider and deeper than the others; I believe this is TDC. The first tooth counterclockwise from TDC is 2 BTDC, the next one is 6 BTDC, and so on. The low spots represent 4 BTDC, 8 BTDC, etc. Currently at idle the mark corresponds with the 2nd low spot, meaning the engine's initial timing is 8 BTDC.

Does this sound right? Thanks!

Brad

Slonaker · 04-15-2005, 07:19 PM

I don't know how much this helps, but I believe the white mark was pointing at TDC when I took this pic.

http://www.slonaker.net/images/truck/TDC.jpg

I will be working on the truck tomorrow, and might be able to answer your question better then.

BTW, mine is an '86 with a 305 also.

Slonaker

Brad_Olson · 04-15-2005, 08:53 PM

Thanks! According to the photo I'm correct about the location of TDC on the tab, so now all that remains is to verify that it's 4 degrees from tooth to tooth. If you could please check that tomorrow (as long as it's not an inconvenience) I'd really appreciate it.

Brad

Prerunner1982 · 04-15-2005, 08:56 PM

i wish i had a timing tab.....

SS79chevy · 04-15-2005, 09:01 PM

Quote:

Originally Posted by Prerunner1982

i wish i had a timing tab.....

join the club

boxrodz · 04-16-2005, 01:22 AM

Brad -

Here's what I got for a timing tab for a 305. Maybe Slonaker will be able to confirm this. Hope this helps.

1986Silverado · 04-16-2005, 03:50 PM

is that 12 at the end?

Brad_Olson · 04-16-2005, 08:42 PM

Quote:

Originally Posted by boxrodz

Here's what I got for a timing tab for a 305. Maybe Slonaker will be able to confirm this. Hope this helps.

Yes, quite a bit - thanks! So it looks like the teeth are 4, 8, 12, etc. and not 2, 6, 10 like I thought, which means I set my initial timing to 10 BTDC and not 8 BTDC. I drove it around a little bit like that today and I didn't hear any detonation w/89 octane so I'll leave it be for awhile.

Brad

1986Silverado · 04-16-2005, 08:58 PM

That is why I asked if that was 12, I to thought that was 10 and it is past that. So my is probably around 14-15 initial!

boxrodz · 04-17-2005, 01:54 AM

You're welcome, Brad. (Sure is it tight where the tab is located.)

1986Silverado -
Yes, the last timing mark is a 12 (ie. 12 - 8 - 4 - 0 - 4).

04-15-2005, 06:11 PM	#1
Brad_Olson Active Member Join Date: Mar 2005 Location: Stoughton, WI Posts: 187	1986 305 timing tab My '86 305's timing tab is pretty dirty and all I can see are the "teeth"; the numbers are covered. I think I know what the teeth indicate but want to be sure so I know I'm setting the timing I think I'm setting. Think of each tooth point as a high spot and the halfway point between 2 teeth as a low spot. There's one low spot that's wider and deeper than the others; I believe this is TDC. The first tooth counterclockwise from TDC is 2 BTDC, the next one is 6 BTDC, and so on. The low spots represent 4 BTDC, 8 BTDC, etc. Currently at idle the mark corresponds with the 2nd low spot, meaning the engine's initial timing is 8 BTDC. Does this sound right? Thanks! Brad

04-15-2005, 07:19 PM	#2
Slonaker Insert Witty Text Here Join Date: Oct 2002 Location: San Antonio, TX Posts: 3,415	I don't know how much this helps, but I believe the white mark was pointing at TDC when I took this pic. http://www.slonaker.net/images/truck/TDC.jpg I will be working on the truck tomorrow, and might be able to answer your question better then. BTW, mine is an '86 with a 305 also. Slonaker __________________ '86 Chevy C10 (Sold 04/19/13 ) Stock '01 Silverado

04-15-2005, 08:56 PM	#4
Prerunner1982 Registered User Join Date: Oct 2002 Location: Edmond, OK Posts: 5,904	i wish i had a timing tab..... __________________ Jon 1982 Chevy Silverado 350/th350.... RETIRED 1993 Jeep XJ 2 door(Cherokee) 4wd 4.0ltr/AX-15 (5spd)/NP231 .... Oklahoma Roll Call

04-16-2005, 01:22 AM	#6
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	Brad - Here's what I got for a timing tab for a 305. Maybe Slonaker will be able to confirm this. Hope this helps. Attached Images __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin... Last edited by boxrodz; 04-16-2005 at 01:23 AM.

04-16-2005, 03:50 PM	#7
1986Silverado What I drive Join Date: Apr 2004 Location: Star, MS Posts: 418	is that 12 at the end? __________________ 1986 Chevy Crew Cab Dually(Choo-Choo Conversion) 2006 Chevy Equinox

04-15-2005, 08:53 PM	#3
Brad_Olson Active Member Join Date: Mar 2005 Location: Stoughton, WI Posts: 187	Thanks! According to the photo I'm correct about the location of TDC on the tab, so now all that remains is to verify that it's 4 degrees from tooth to tooth. If you could please check that tomorrow (as long as it's not an inconvenience) I'd really appreciate it. Brad

04-16-2005, 08:58 PM	#9
1986Silverado What I drive Join Date: Apr 2004 Location: Star, MS Posts: 418	That is why I asked if that was 12, I to thought that was 10 and it is past that. So my is probably around 14-15 initial! __________________ 1986 Chevy Crew Cab Dually(Choo-Choo Conversion) 2006 Chevy Equinox

04-17-2005, 01:54 AM	#10
boxrodz Until Seventy Times Seven Join Date: Feb 2005 Location: Rocky Mountain Front Range Posts: 1,301	You're welcome, Brad. (Sure is it tight where the tab is located.) 1986Silverado - Yes, the last timing mark is a 12 (ie. 12 - 8 - 4 - 0 - 4). __________________ boxRODz 1983 C10 SWB Fleetside When two halves is gone, there's nuthin left. Two nothings is nuthin. That's mathematics son. You can argue with me but you can't argue with figures. Two half nothings is a whole nuthin...



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