timing jumps with diode out
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Mountain Pass
Joined: Mar 2002
Posts: 190
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timing jumps with diode out
When checking the timing on my 351 (with the diode out then I had stopped/restarted truck) the timing still jumps around. Shouldn't it be stuck on base time (10 deg) and not move at all with that diode out? I'm troubleshooting a sluggish behavior in the truck. Seems to have no low end power but with the pedal down when it gets to high RPM I can feel a surge like someone just turned up the juice. (I have a new timing chain and motor is in otherwise good condition.)
Any ideas? Thanks in advance for your help.
Any ideas? Thanks in advance for your help.
Senior User
Joined: Sep 2003
Posts: 329
Likes: 1
From: Virginia
You got my curiosity up so I went out and hooked up the timing light on my 351. Rock steady at 10 degrees at any RPM.
From past experience (I know you stated that the engine has a new timing chain) but, a worn chain will make the timing jump. Also, the lack of power you are talking about is a direct result of a bad chain (or retarding the cam during installation).
The timing between the cam and crank shafts becomes retarded (cam is behind the crank in terms of rotation) this will kill any lower RPM power and will run like crazy above a certain RPM range. Just the opposite happens if the cam is advanced (or leading the crankshaft) the bottom end power will increase a great deal and then fall on its face usually between 3-4000 rpm for a stock cam.
Obviously, worn distributor parts, gears etc can effect this also but, the lack of power leads me to believe the chain is at fault here. Could you have gotten a bad part? I have seen it happen.
Just my thoughts...Good Luck
From past experience (I know you stated that the engine has a new timing chain) but, a worn chain will make the timing jump. Also, the lack of power you are talking about is a direct result of a bad chain (or retarding the cam during installation).
The timing between the cam and crank shafts becomes retarded (cam is behind the crank in terms of rotation) this will kill any lower RPM power and will run like crazy above a certain RPM range. Just the opposite happens if the cam is advanced (or leading the crankshaft) the bottom end power will increase a great deal and then fall on its face usually between 3-4000 rpm for a stock cam.
Obviously, worn distributor parts, gears etc can effect this also but, the lack of power leads me to believe the chain is at fault here. Could you have gotten a bad part? I have seen it happen.
Just my thoughts...Good Luck
