timing question - The 1947 - Present Chevrolet & GMC Truck Message Board Network

76bonanza · 09-20-2005, 10:12 PM

My new truck is set at about 12-13 intial timing seems high to me run and starts great. It is midly hot 350 roller rockers and such about 9-1 compression I am guessing about 330 hp and 387 lbs not sure if any of that helps?

thanks

Fred T · 09-20-2005, 10:41 PM

As long as it runs good and doesn't ping.

68haywagon · 09-20-2005, 11:35 PM

Quote:

Originally Posted by 76bonanza

I am guessing about 330 hp and 387 lbs

Pretty precise guess

Fred T

Mike

76bonanza · 09-21-2005, 07:55 AM

well it was desktop dynoed so it is an educated guess

68C15 · 09-21-2005, 08:15 AM

I have about the same set-up. I run mine at 16* initial with the vacuum coming from timed instead of ported. & I use 87 octane. I know, I know, it is on the ragged edge of detonation but the mileage is cool & I drive it sensible

76bonanza · 09-21-2005, 09:24 AM

when you say timed you mean intake vaccum or contstant vaccumm?

68C15 · 09-21-2005, 09:32 PM

by "timed" I mean it is dead until the throttle is opened. "ported" is straight from the manifold & has the same vacuum as the engine.

jhow66 · 09-22-2005, 12:31 AM

Quote:

Originally Posted by 68C15

by "timed" I mean it is dead until the throttle is opened. "ported" is straight from the manifold & has the same vacuum as the engine.

Have't you got that backward?

68C15 · 09-22-2005, 07:23 AM

I could be wrong. but I always thought since it waits until the TIME the throttle is opened it was correct. and since a manifold is simply a set of PORTS this was fiting.

jhow66 · 09-22-2005, 03:23 PM

Ported -any port that has a opening above throttle blades.
manifold (fulltime)- any port on manifold or below throttle blades.

68C15 · 09-22-2005, 10:18 PM

OK, so I'm wrong. not the first time & probably wont be the last.

what was the original question? oh yeah, the 12-13* initial. its fine, some engines qill take more than others. it has to do with the cylinder pressure. some cams will bleed off at lower speeds. also the combustion chamber plays a roll as for how the flame front travels.

in short, if it works then all is fine.

PS. is it possible the balancer ring has moved?

09-20-2005, 10:12 PM	#1
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	timing question My new truck is set at about 12-13 intial timing seems high to me run and starts great. It is midly hot 350 roller rockers and such about 9-1 compression I am guessing about 330 hp and 387 lbs not sure if any of that helps? thanks __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

09-20-2005, 10:41 PM	#2
Fred T Cantankerous Geezer Join Date: Aug 2002 Location: Bel Aire, KS Posts: 6,264	As long as it runs good and doesn't ping. __________________ Fred There is no such thing as too much cam...just not enough engine.

09-21-2005, 07:55 AM	#4
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	well it was desktop dynoed so it is an educated guess __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

09-21-2005, 08:15 AM	#5
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	I have about the same set-up. I run mine at 16* initial with the vacuum coming from timed instead of ported. & I use 87 octane. I know, I know, it is on the ragged edge of detonation but the mileage is cool & I drive it sensible __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

09-21-2005, 09:24 AM	#6
76bonanza Senior Member Join Date: Mar 2003 Location: St robert Mo Posts: 2,001	when you say timed you mean intake vaccum or contstant vaccumm? __________________ 1968 c10 lowered 3" 4" 355/Th400 built by Hatfield racing in joplin MO

09-21-2005, 09:32 PM	#7
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	by "timed" I mean it is dead until the throttle is opened. "ported" is straight from the manifold & has the same vacuum as the engine. __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

09-22-2005, 07:23 AM	#9
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	I could be wrong. but I always thought since it waits until the TIME the throttle is opened it was correct. and since a manifold is simply a set of PORTS this was fiting. __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

09-22-2005, 03:23 PM	#10
jhow66 Registered User Join Date: Jun 2002 Location: Knoxville Tenn. Posts: 3,058	Ported -any port that has a opening above throttle blades. manifold (fulltime)- any port on manifold or below throttle blades. __________________ 56 Chevy Bel-Air 2dr. HT (purchased new) 71 Chevy Cheyenne SWB PU (502HO) 65 GMC short bed step--work in progress and my gofer

09-22-2005, 10:18 PM	#11
68C15 blood type; Retumbo Join Date: Jan 2004 Location: next to my reloading bench Posts: 10,269	OK, so I'm wrong. not the first time & probably wont be the last. what was the original question? oh yeah, the 12-13* initial. its fine, some engines qill take more than others. it has to do with the cylinder pressure. some cams will bleed off at lower speeds. also the combustion chamber plays a roll as for how the flame front travels. in short, if it works then all is fine. PS. is it possible the balancer ring has moved? __________________ Man rule #77...if you own a 67 stepside with a caddy 472 you will never be in danger of loosing you man card

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