Camshaft jumping forward

[Ken B]

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.

 

[V4F]

if the cam is walking , the spring must be to soft . my timing cover has a adjustable cam stop .

 

[Jwilli]

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.

 

[rocket1]

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.

 

[katy]

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

 

[Mark in MT]

Try looking at the distributor/ oil pump drive gear, you can pull it out and see if the cam still wants to walk forward. I found one combination that was not happy together, changed the drive and the cam stayed where is was supposed to be.

 

[Big hammer]

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

 

[40 Deluxe]

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.

 

[BILL WILLIAMSON]

"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.

 

[Mitch//pa]

"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.

i dont think he has a problem either.. thats why a spring is used and not a solid spacer for some give..
put it together and drive it

 

[BILL WILLIAMSON]

How and why are you turning the crankshaft backwards?

See 40 Deluxe post for correct answer.

LOL, he probably ran PAST the dimple & turnin' it backwards, using the FAN or one of them re-bent, multi-curved crank pulley wrenches the suppliers sell! AND, don't lecture me about turnin' it with the FAN, most have done it at times & just don't have the BALLS to admit it. IF you don't know how to turn an engine, SAFELY, by using the fan, you're not much uf a MEKANIC Being a MEKANIC takes a lot of IMAGINATION & CURIOUSITY & lurnin' how NOT to BLEED or BURN yourself
Bill W.

 

[colin1928]

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 ??

 

[hardtimes]

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

Actually, there should be a small clearance between the front of cam/plunger...010"(?).
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.

 

[Ken B]

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.

 

[hardtimes]

Rich,
I am not aware of any clearance between the plunger and the cam. The whole point is to exert a force o the cam??

Cam Plunger and Spring on Ford Garage

Ok, that was the adjustment that I used when installing my adjustable setup Thanks for your reply, as it makes sense when using a stock setup/equipment.
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.

 

[James Rogers]

Ok, that was the adjustment that I used when installing my adjustable setup Thanks for your reply, as it makes sense when using a stock setup/equipment.
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.

This is why it is advisable to investigate your answer when giving advice. Bad advice is worse than no advice.

 

[hardtimes]

This is why it is advisable to investigate your answer when giving advice. Bad advice is worse than no advice.

Hey James,
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 ?