Timing Question... - The 1947 - Present Chevrolet & GMC Truck Message Board Network

**COBALT** · 06-09-2002, 11:40 PM

What should the timing be set at for a stock 350 with single-point ignition?

I've been trying to stop this stubborn off-idle stumble I get with hard acceleration, and I thought I'd check the timing. The initial timing at curb idle was set to around 16 degrees left of 0 (according to my indicator). I thought it was supposed to be something like 6 or 8? Since this is a bastard engine I have no idea what it should be.

Anyone help?

**COBALT** · 06-09-2002, 11:58 PM

ttt

Come on, guys...anybody?

Patrick Sullivan · 06-10-2002, 12:01 AM

Stock is 8 BTDC. However, often your engine will run better with more advance - I run mine at 14. Only way to figure out what your engine likes best is trial and error..

*Zkast* · 06-10-2002, 12:17 AM

Most of your GM small blocks run 8-10btc with a 10-15degree vacuum advance and 10degree centrifugal advance. Give it a total of 36 and you are right on top of it. any more on pump gas and your pushing your luck.

If you know your vacuum and centrifugal advance are working right, then do a power time. Power brake it if you can(or get it on the highway in top gear at 45-55mph) then Advance timing until you get just a small amount of spark knock or ping, then back it down 1-2 degree's (this will allow for those hot days and poor fuel quality)

71GMC_3/4T · 06-10-2002, 12:24 AM

Disconnect your vacuum advance line and plug it. Then the timing should be 8 (?) or so. Depends on where you're at (altitude) and how good of gas you can buy.
The hesitation is most likely due to the fuel squirters in the carb. If you're running a Holley, there's several different cams available. I don't know which wire to bend on a Q-Jet though, heh.

**COBALT** · 06-10-2002, 12:41 AM

Ok, thanks guys. I just came in from messing with it, and I know more now:

1. Initial timing (16) turned out to not be enough. I didn't know about disconnecting the vaccuum advance, so I turned the distributor CCW to increase it to 18. That helped considerably. The off-idle stumble is about 95% gone. Power has increased dramatically, however...

2. I couldn't turn it any more because the vaccuum diaphram on the distributor is contacting the intake manifold. Therefore, unless I do a different setup with my vaccuum advance I won't be able to adjust the timing any larger...

...any suggestions?

Oh, BTW: I have a 2bbl Rochester on a 327 manifold (yes, you heard right). The carb is rebuilt by yours truely, and delivering fuel like a champ though, so no worries there. I warned you it was a bastard engine!

Hooter · 06-10-2002, 02:20 AM

One time i tried adjusting my timing on the 74 (some of you already know this story) and i couldn t figure out why my timing was so far off until i discovered that my harmonic damper separated, YIKES!

mikep · 06-10-2002, 03:04 AM

just move your spark plugs wires over one spot each and rotate your distributor over to compensate. You'll have to retime it but you'll have plenty of clearance.

06-09-2002, 11:40 PM	#1
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Timing Question... What should the timing be set at for a stock 350 with single-point ignition? I've been trying to stop this stubborn off-idle stumble I get with hard acceleration, and I thought I'd check the timing. The initial timing at curb idle was set to around 16 degrees left of 0 (according to my indicator). I thought it was supposed to be something like 6 or 8? Since this is a bastard engine I have no idea what it should be. Anyone help? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-09-2002, 11:58 PM	#2
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	ttt Come on, guys...anybody? __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-10-2002, 12:01 AM	#3
Patrick Sullivan Transcendental Trucker Join Date: Dec 2001 Location: Rockaway Beach, OR Posts: 374	Stock is 8 BTDC. However, often your engine will run better with more advance - I run mine at 14. Only way to figure out what your engine likes best is trial and error.. __________________ Patrick Sullivan \| sullivan@oregoncoast.com Rockaway Beach, Oregon 1972 Chevy Cheyenne C-20 1998 Dodge Dakota 4x4 So, fill to me the parting glass And drink a health whate'er befalls... Then gently rise and softly call Goodnight and joy be to you all!

06-10-2002, 12:17 AM	#4
Zkast Account Suspended Join Date: May 2002 Location: Olathe, Kansas Posts: 929	Most of your GM small blocks run 8-10btc with a 10-15degree vacuum advance and 10degree centrifugal advance. Give it a total of 36 and you are right on top of it. any more on pump gas and your pushing your luck. If you know your vacuum and centrifugal advance are working right, then do a power time. Power brake it if you can(or get it on the highway in top gear at 45-55mph) then Advance timing until you get just a small amount of spark knock or ping, then back it down 1-2 degree's (this will allow for those hot days and poor fuel quality) Last edited by Zkast; 06-10-2002 at 12:19 AM.

06-10-2002, 12:24 AM	#5
71GMC_3/4T Weapons Of Construction Join Date: Apr 2000 Location: Colorado, USA Posts: 1,095	Disconnect your vacuum advance line and plug it. Then the timing should be 8 (?) or so. Depends on where you're at (altitude) and how good of gas you can buy. The hesitation is most likely due to the fuel squirters in the carb. If you're running a Holley, there's several different cams available. I don't know which wire to bend on a Q-Jet though, heh. __________________ 1971 GMC 2500, 402/TH400 4.10 Daily Driver Lafayette, CO

06-10-2002, 12:41 AM	#6
COBALT Senior Member Join Date: Sep 2001 Location: Seattle, WA, USA Posts: 5,817	Ok, thanks guys. I just came in from messing with it, and I know more now: 1. Initial timing (16) turned out to not be enough. I didn't know about disconnecting the vaccuum advance, so I turned the distributor CCW to increase it to 18. That helped considerably. The off-idle stumble is about 95% gone. Power has increased dramatically, however... 2. I couldn't turn it any more because the vaccuum diaphram on the distributor is contacting the intake manifold. Therefore, unless I do a different setup with my vaccuum advance I won't be able to adjust the timing any larger... ...any suggestions? Oh, BTW: I have a 2bbl Rochester on a 327 manifold (yes, you heard right). The carb is rebuilt by yours truely, and delivering fuel like a champ though, so no worries there. I warned you it was a bastard engine! __________________ '69 3/4 ton C20 2wd-350ci/TH400 '69 3/4 ton Custom 20 2wd-350ci/4sp Manual '99 2wd 5.7 Chevy Tahoe Seattle, WA.

06-10-2002, 02:20 AM	#7
Hooter My other Love Join Date: Aug 2001 Location: Castlegar B.C. Canada Posts: 4,085	One time i tried adjusting my timing on the 74 (some of you already know this story) and i couldn t figure out why my timing was so far off until i discovered that my harmonic damper separated, YIKES! __________________ Castlegar B.C.The great white North (Canada Eh!) Hooter_5@hotmail.com First generation Monte Carlo club pictures of my life

06-10-2002, 03:04 AM	#8
mikep Used to have a truck Join Date: May 2002 Location: port orchard WA Posts: 1,552	just move your spark plugs wires over one spot each and rotate your distributor over to compensate. You'll have to retime it but you'll have plenty of clearance. __________________ No truck :-(



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