Timing chain slack, try this forum
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From: arkadelphia, ar
Timing chain slack, try this forum
This is why I usually come here. I ask this question in the FE forum and haven't gotten a reply, so maybe someone here can help.
I need to know before I tear into it how much slack is acceptable. I took the dist. cap off and rotated the engine until the rotor moved, then backed it off to see how much movement there was on the damper. I moved at least 1" before the rotor moved. Did this several times.
Does this seem like excessive slack?
Have some sort of timing issue and don't know if it is here or dist cam or??????????
I need to know before I tear into it how much slack is acceptable. I took the dist. cap off and rotated the engine until the rotor moved, then backed it off to see how much movement there was on the damper. I moved at least 1" before the rotor moved. Did this several times.
Does this seem like excessive slack?
Have some sort of timing issue and don't know if it is here or dist cam or??????????
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From: arkadelphia, ar
I'm talking about 1" of the circumference of the damper. In other words I had it (the damper and timing marker) on 0 deg. then when I went clockwise, the 0 deg was on the back side of the timing marker. I couldn't read it but think that amounted to about 15-18 deg. (that could be way off)
Could it really move 12", that would be nearly if not 1/2 of the circumference of the damper as it is only about maybe 18" around or less?
Could it really move 12", that would be nearly if not 1/2 of the circumference of the damper as it is only about maybe 18" around or less?
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From: arkadelphia, ar
Whenever I check timing sometimes the line "floats" back and forth about 1/2 inch. I was driving yesterday and decided to floor it, new exhaust and wanted to hear, and it backfired throught the carb. Pinging under a load like a hill, etc. Timing is set at 6 deg adv now.
Honestly grabbing straws. I rebuilt the carb and it runs good at idle, and over all. Just doesn't seem to have the power it should or even sometimes has but then sometimes doesn't. It's backfired twice pretty big in the last week and now I'm quetioning the power valve in the carb.
Honestly grabbing straws. I rebuilt the carb and it runs good at idle, and over all. Just doesn't seem to have the power it should or even sometimes has but then sometimes doesn't. It's backfired twice pretty big in the last week and now I'm quetioning the power valve in the carb.
Post Fiend
Joined: Jan 2004
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From: Elkhart IN
If its blown through the carb, the yeah the p/v is more than likely going to need done. I would get it all fixed before you jump on the carb.
When you timed it, you did it with the advance unhooked at idle speed fully warmed up?
If you did, I would take the guts out of the dizzy and inspect the mechanical advance parts. If all check out there, pull the dizzy out of the block and check the teeth on the gear. A bud of mine had a 78 with a 400 that had a cam with missing timing teeth, and we couldn't get it to hold a steady timing as it would jump around so much.
Just some thoughts, Andrew
When you timed it, you did it with the advance unhooked at idle speed fully warmed up?
If you did, I would take the guts out of the dizzy and inspect the mechanical advance parts. If all check out there, pull the dizzy out of the block and check the teeth on the gear. A bud of mine had a 78 with a 400 that had a cam with missing timing teeth, and we couldn't get it to hold a steady timing as it would jump around so much.
Just some thoughts, Andrew
Laughing Gas
Joined: Apr 2001
Posts: 868
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From: New Glasgow, Nova Scotia
I think the timming is 10 to 12 degrees BTDC, not completely sure. I have always set the timming bear ear or feel. It seems that if I went by the book the truck ran like junk but if I kept advancing the timming till she'd knock whenin drive and I had it floored with the brake on and then back it off 2 or 3 degrees from that , it always seemed to work great , start perfect and had power. As far as the 1" movement you have , I think that is fine, Keep in mind the crank is 2 to 1 in movement. If you have a spare Duraspark ing. module, I'd try that. I had one that would run fine till warm and then backfire and run like junk, but it would also clear itself and run fine for an hour then start acting up again. Swapped the box with my spare, never did it again. The Duraspark box can create a world of headaches because of the symtoms they give never lead you to it, always point to timming or carb trouble. Just a thought.
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Post Fiend
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From: Elkhart IN
Power starts dropping off about anywhere from 10-30 degrees before it starts pinging. Just a fyi.
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Laughing Gas
Joined: Mar 2007
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From: southwest Wisconsin
Are your distributor cap and plug wires up to snuff? If you can see small dark cracks between the terminals on the underside of the cap this will cause a missfire. Backfiring thru the carb could indicate a lean fuel condition. If it backfires when you step on it you might need to adjust the accelorator pump to get bigger shot of fuel. Also if you have added a free flowing exhaust (hedders) this can lean out your fuel mixture.
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One thing to keep in mind is your new exhaust may require a jet change to the carb. I would suggest you take a plug reading. Make sure you have the tools you need to remove a sparkplug and a pair of gloves, than find a nice long stretch of road in the country. Drive around for about 30 minutes and make sure the engine is up to normal temperature. Drive about 2 miles at 50-60 mph than shift to neutral and turn the engine off. Remember you will not have power brakes or power steering which is why I like to use a deserted stretch of road. Coast to a stop well away from traffic and remove a spark plug and check the plug color. You can find plug color pictures on line. See if you may not be running lean.
I also agree with Fast Farmer, check wires, cap & rotor. Another thing to check is distributor drive gear wear and advance springs.
On my 460 the timing chain had about 22 degrees of play when the chain jumped a tooth.
Good luck
I also agree with Fast Farmer, check wires, cap & rotor. Another thing to check is distributor drive gear wear and advance springs.
On my 460 the timing chain had about 22 degrees of play when the chain jumped a tooth.
Good luck
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My measurement is based on the end of the breaker bar that is in ones hand ...because that is easy to keep track off.
12" at the end of the bar would still be 30* (2"-3") at the HB.
what is the diameter of your HB ?
12" at the end of the bar would still be 30* (2"-3") at the HB.
what is the diameter of your HB ?
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From: arkadelphia, ar
Yea Dennis that is what I thought you meant about the breaker bar, but it was early and I'm thinkin' 12" the way I read it would be UNBELIEVABLE! LOL By the way, found a nice wheel locally for $10 with horn button so probably won't need to ship one. Thanks anyway!
Actually rechecked tiiming this morning and it is more like 8-10. Checked the dist cap and had some build up on the contacts so cleaned, re filed/set points, checked power diaphragm and then changed filter on the carb. Drove about 80 miles and ran flawlessly, so think I'll leave it alone for a while and quit worrying. By the way plugs, wires, cap, etc, have about 600 miles. Carb rebuild about 400.
Thanks guys, just concerned about the slack and may change for safety sake soon, but not today!
Actually rechecked tiiming this morning and it is more like 8-10. Checked the dist cap and had some build up on the contacts so cleaned, re filed/set points, checked power diaphragm and then changed filter on the carb. Drove about 80 miles and ran flawlessly, so think I'll leave it alone for a while and quit worrying. By the way plugs, wires, cap, etc, have about 600 miles. Carb rebuild about 400.
Thanks guys, just concerned about the slack and may change for safety sake soon, but not today!
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How is the coil? New, used, old, corroded etc?
The timing jumping at idle would be points or coil. 1 inch of "slack" at the balancer is perfectly fine.
Also check the condition of your resistor wire.
The timing jumping at idle would be points or coil. 1 inch of "slack" at the balancer is perfectly fine.
Also check the condition of your resistor wire.
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