The Ford Barn

wga · 08-07-2011, 09:24 AM

Ref: 8BA stock - with Pertonix ignition and coil. NGK B 4L plugs
stock ignition wires. Warmed up to 160 - 170 degrees.
Checked the timing at 550 RPM, vacuum line plugged, vacuum gauge connected at base of carb. At idle the timing consistently jumps a few degrees advance beyond the setting of TDC. Watching the vac gauge, it is at 18 in. vac., however the needle moves from 17 to 18 continuously.
(plug gaps set tight ?)
Compression checked at it is
1 - 140 5 - 145
2 - 140 6 - 135
3 - 140 7- 140
4 - 150 8 - 145

What causes the timing to fluctuate as it does?

thanks

Ol' Ron · 08-07-2011, 09:33 AM

I never saw a stock engine with this much compression?? A variation in timing could be caused by a bad distributor. But valves come to mind??

wga · 08-07-2011, 09:47 AM

Ron - the heads were cleaned up about .010" after a bad head gasket.

gerrald meacham · 08-07-2011, 10:08 AM

one degree is not much it could be set on 17.5 that means it is varing .1

gerrald meacham · 08-07-2011, 10:09 AM

we are talking about a light that is digidal and rounds off at 1. degrees

jdl · 08-07-2011, 10:10 AM

Sponsored Links (Register now to hide all advertisements)

That is a lot of compression for only .010" off the heads, they might have been milled sometime in the past. as for the flicking of the needle on your vacumm that indicates a valve problem. see senario 5 and 7 in the link below, scroll down...

http://www.secondchancegarage.com/public/186.cfm

JWL · 08-07-2011, 10:36 AM

I described the timing fluctuation in my book and explained how to measure and to correct it. The basic problem is usually excessive camshaft thrust clearance. The nervous gauge needle is probably showing a slight intake valve leak.

wga · 08-07-2011, 02:10 PM

Thanks, the vac gauge site is a big help.

JWL's book:http://www.flatheadv8.org/jwl.htm

BUBBAS IGNITION · 08-07-2011, 05:14 PM

Quote:

Originally Posted by wga

Ref: 8BA stock - with Pertonix ignition and coil. NGK B 4L plugs
stock ignition wires. Warmed up to 160 - 170 degrees.
Checked the timing at 550 RPM, vacuum line plugged, vacuum gauge connected at base of carb. At idle the timing consistently jumps a few degrees advance beyond the setting of TDC. Watching the vac gauge, it is at 18 in. vac., however the needle moves from 17 to 18 continuously.
(plug gaps set tight ?)
Compression checked at it is
1 - 140 5 - 145
2 - 140 6 - 135
3 - 140 7- 140
4 - 150 8 - 145

What causes the timing to fluctuate as it does?

thanks

Pretty normal for a stock distributor with some wear. The spring tension is a bit weak and the vacuum diaphram is somewhat loose.
Plug the vacuum and tighten the spring tension up a bit by turning the eccentric pins and retest....

08-07-2011, 09:24 AM	#1
wga Senior Member Join Date: Jul 2010 Location: Yorba Linda, CA Posts: 897	Erratic timing Ref: 8BA stock - with Pertonix ignition and coil. NGK B 4L plugs stock ignition wires. Warmed up to 160 - 170 degrees. Checked the timing at 550 RPM, vacuum line plugged, vacuum gauge connected at base of carb. At idle the timing consistently jumps a few degrees advance beyond the setting of TDC. Watching the vac gauge, it is at 18 in. vac., however the needle moves from 17 to 18 continuously. (plug gaps set tight ?) Compression checked at it is 1 - 140 5 - 145 2 - 140 6 - 135 3 - 140 7- 140 4 - 150 8 - 145 What causes the timing to fluctuate as it does? thanks __________________ Henry Ford designed the flathead without the aid of a computer.

08-07-2011, 09:33 AM	#2
Ol' Ron Senior Member Join Date: May 2010 Location: Chester Vt Posts: 8,857	Re: Erratic timing I never saw a stock engine with this much compression?? A variation in timing could be caused by a bad distributor. But valves come to mind??

08-07-2011, 09:47 AM	#3
wga Senior Member Join Date: Jul 2010 Location: Yorba Linda, CA Posts: 897	Re: Erratic timing Ron - the heads were cleaned up about .010" after a bad head gasket. __________________ Henry Ford designed the flathead without the aid of a computer.

08-07-2011, 10:08 AM	#4
gerrald meacham Senior Member Join Date: May 2010 Location: FRANKLIN GEORGIA Posts: 158	Re: Erratic timing one degree is not much it could be set on 17.5 that means it is varing .1

08-07-2011, 10:09 AM	#5
gerrald meacham Senior Member Join Date: May 2010 Location: FRANKLIN GEORGIA Posts: 158	Re: Erratic timing we are talking about a light that is digidal and rounds off at 1. degrees

08-07-2011, 10:10 AM	#6
jdl Senior Member Join Date: May 2010 Location: California Central Coast Posts: 931	Re: Erratic timing Sponsored Links (Register now to hide all advertisements) That is a lot of compression for only .010" off the heads, they might have been milled sometime in the past. as for the flicking of the needle on your vacumm that indicates a valve problem. see senario 5 and 7 in the link below, scroll down... http://www.secondchancegarage.com/public/186.cfm

08-07-2011, 10:36 AM	#7
JWL Member Emeritus Join Date: May 2010 Location: Fitzgerald, Georgia Posts: 2,204	Re: Erratic timing I described the timing fluctuation in my book and explained how to measure and to correct it. The basic problem is usually excessive camshaft thrust clearance. The nervous gauge needle is probably showing a slight intake valve leak.

08-07-2011, 02:10 PM	#8
wga Senior Member Join Date: Jul 2010 Location: Yorba Linda, CA Posts: 897	Re: Erratic timing Thanks, the vac gauge site is a big help. JWL's book:http://www.flatheadv8.org/jwl.htm __________________ Henry Ford designed the flathead without the aid of a computer.