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08-16-2015, 07:30 AM | #1 |
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Camshaft jumping forward
I had my engine out to get the main shims adjusted. I have the engine back in and went to check the timing. The timing pin bounces out about 1/4" at the exact same spot in the rotation. I also can feel the indent for the timing mark. I took off the side timing gear cover and noticed the whole camshaft and timing gear jump forward at the same position in it's revolution. I lifted the distributor to see if it was binding at all and got the same results. What else can I look for? I am sure that the spring and plunger are in the front timing gear cover. This engine ran great prior to the mains getting adjusted. It just had a rear main knock that I tightened up with removing shim material.
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08-16-2015, 09:03 AM | #2 |
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Re: Camshaft jumping forward
if the cam is walking , the spring must be to soft . my timing cover has a adjustable cam stop .
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08-16-2015, 09:20 AM | #3 |
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Re: Camshaft jumping forward
An engine that I bought had the plunger placed into the timing gear cover and the spring rubbing the metal timing gear. Don't know if this would let the cam move, but I bet it make lots of noise.
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08-16-2015, 09:39 AM | #4 |
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Re: Camshaft jumping forward
If you didn't do the engine work,who knows what they could of done,cam gear nut loose,cam gear hub cracked,plunger or spring broken or missing,take the front cover off and check.
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08-16-2015, 11:01 AM | #5 |
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Re: Camshaft jumping forward
I've read that the camshaft thrust spring should have 35 lbs pressure. What height is this measured at? Or full compression? Or?
Tnx, Ken
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08-16-2015, 12:39 PM | #6 |
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Re: Camshaft jumping forward
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08-16-2015, 01:12 PM | #7 |
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Re: Camshaft jumping forward
Oil pump,dizzy are driven by the same gear off the cam. Did you by chances removed the oil pump to adjust the bearings? Maybe you didn't get things back together correctly?
Pull the valve cover and timing gear cover and make sure things are happy before start your motor |
08-16-2015, 02:47 PM | #8 |
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Re: Camshaft jumping forward
Worn gear teeth? As the engine rotates, at one point two valves are opening so the cam is pushing against valve spring pressure as the crank gear drives the cam gear. Then, after TDC, two valves are closing so the valve springs are pushing on the camshaft lobes so the cam is trying to run ahead of the engine. Then after BDC it goes back to opening two valves. If the gear teeth are worn, this back and forth action is noticeable, as you saw the cam jump back and forth. It also makes noise as the gear teeth are rattled back and forth.
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08-16-2015, 03:09 PM | #9 |
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Re: Camshaft jumping forward
"MAYBE" you don't have a problem, IF you turn the crankshaft BACKWARDS, the cam will "back out" due to the ANGLE of the gear teeth.
Bill W.
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08-16-2015, 03:11 PM | #10 | |
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Re: Camshaft jumping forward
Quote:
put it together and drive it |
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08-16-2015, 05:41 PM | #11 | |
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Re: Camshaft jumping forward
Quote:
Bill W.
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08-16-2015, 06:19 PM | #12 |
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Re: Camshaft jumping forward
Some movement is normal
if you think it is excessive I find a tight or sticky valve guide can cause this possibly from modern fuel ?? |
08-16-2015, 06:38 PM | #13 | |
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Re: Camshaft jumping forward
Quote:
IMO, It is most likely a good idea to replace, with new, the original 80 some yr old spring if you are working with the cover off, if you do not have a way to ascertain that the original spring is still in good condition. Worn out spring will allow cam to 'walk' forward, particularly if new and/or stronger valve springs put in. I also have the adjustable setup and have found that the cam will walk forward (and make noise with new heavier springs) if not adjusted right. |
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08-16-2015, 07:50 PM | #14 |
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Re: Camshaft jumping forward
Thanks for all the replies!! This engine was rebuilt about 3000 miles ago. The plunger and spring were replaced. I will look more into the drive gear and check with the place that did the main shim adjustments. This engine ran great but had a small main knock that was from the rear main being around .004" Some shim layers were removed to get it back to .001 The other mains and rods were fine. I am still a working stiff so this will have to wait until next weekend.
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08-17-2015, 02:00 AM | #15 | |
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Re: Camshaft jumping forward
Quote:
On my adjustable setup (no spring involved), I used .010 and when cam was forced forward/walked forward all has run well with that adjustment . With stock Ford setup (spring/plunger), if these parts are proper shape, I can see where plunger can/may ride against cam constantly. |
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08-17-2015, 06:38 AM | #16 | |
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Re: Camshaft jumping forward
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08-17-2015, 11:45 AM | #17 | |
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Re: Camshaft jumping forward
Quote:
You're correct ! My bad for 'assuming' that A/B owners had switched to adjustable cam plunger setup . Nevertheless, I think that if a plunger/spring is not as original spec condition, that there maybe/will be problem (noise/wear,etc) and quite possibly excessive clearance that permits cam walking..no ? Last edited by hardtimes; 08-17-2015 at 02:46 PM. Reason: ...... |
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