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-   -   1986 305 timing tab (https://67-72chevytrucks.com/vboard/showthread.php?t=151464)

Brad_Olson 04-15-2005 06:11 PM

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

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.....:lol:

SS79chevy 04-15-2005 09:01 PM

Quote:

Originally Posted by Prerunner1982
i wish i had a timing tab.....:lol:

join the club :lol: :whine:

boxrodz 04-16-2005 01:22 AM

1 Attachment(s)
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).


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