worried....... a little

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318willrun

318willrun

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Hey, I installed the summit cam in the LA 318 that's in my thread "Low Dollar 318 project".
I'm a little worried. It slipped in just fine, but once in it "bound" and wouldn't turn. The oil pump/distributor gear shaft is raised up and is not touching the cam. No lifters in yet. I had to wedge it back out about 1/2 inch, then slide it back in by hand. Now it turns by hand, turns easily around the clock except, lets say, 1 1/2 hours (makes sense?) It still turns by hand but a little more resistance. Lets say it turns freely by hand from noon to 10:30 using the nose of the cam, but the last bit of a turn it stiffens up, though I can still turn it by hand using the nose of the cam. Even with the cam sprocket, you can definetly feel the "resistant" spot. I'm worried that the cam could be warped? My 1st time with summit cams, but they have good reviews.
I've installed a lot of cams, never had this issue...... EVER. Any ideas?????
 
I've heard of people taking an old cam, cutting a groove in it, then using it to loosen up the new cam bearings. Then the new cam spins nice and free.

I'll wait for more to chime in that have had experience doing that, but I've heard that it works pretty good.
 
BlueDream said:
Did you mic the new cam journals and compare them to the old ones?
Click to expand...

...and check each journal at a few points to see if there's any out of round condition?

Cam could also be bent, which is tougher to check for, but have seen it on some OHC engines.
 
No, slipped it in out of the box. Maybe I've been lucky, but done it this way for many times over the years. Slipped in nice and easy. Turned very easy on the install. Journals went very easy on the install. I turned it, rotated it on every journal. No issues suspected at that point.
 
out of roundness would affect it at any point. Turns easy for 10 hours of a clock face. then there is a little resistance, not much, but a little.
 
probably, unless it caused a minor "bind" in the tail of the camshaft. I've got the timing chain installed, and I cannot feel it when I turn the assembly by the crank, by hand, using the balancer (heads are off). I could only feel it when I rotated the cam by itself. Just thought it was unusual.....
 
If you can turn it 360* by hand, even if it has a little bit of a hard spot, run it. It will be fine.
 
318willrun said:
probably, unless it caused a minor "bind" in the tail of the camshaft. I've got the timing chain installed, and I cannot feel it when I turn the assembly by the crank, by hand, using the balancer (heads are off). I could only feel it when I rotated the cam by itself. Just thought it was unusual.....
Click to expand...

It is unusual.
Be very careful. Cam bearings wear like any other part. It is likely that the bearings are out of round. You can stick a bearing and spin it in the block. It's not likely, but I have seen them bind up and snap the chain or even snap the nose off the cam.


Or, you could get lucky and nothing will happen. I'd pull the cam and look the bearings over real close.

BTW and FWIW this is one of the things you see when guys run what I consider low oil pressure at idle, and other than OE springs. It will beat the cam bearings out of round. Then add to that at low RPM things tend to drag and you end up with a mess. Once I go over about 280 over the nose I want a minimum of 35 PSI at a hot idle.
 
RustyRatRod said:
If you can turn it 360* by hand, even if it has a little bit of a hard spot, run it. It will be fine.
Click to expand...
This was my thought, it's why I installed the chain.

P.s. yellowrose, the motor was never taken apart, 318 2bbl. cam bearings looked good for the miles, by eye with a light.
 
Possibly the thickness of the bearing journals? Old bearings leave a slight ridge and after sliding in a different cam the ridge may be gone on one spot but not the other so when you turn a bearing surface with a different width you can get a bind... make sense? Your journals are round and true but may have varying width of surface.
 
Your UPS guy probably tossed it across truck and bent it. It could also be due to cheap scummit chinese cam cores cast out of Yugo blocks. Send it back and try again.
 
This sounds like a real puzzle. I've been trying to imagine what scenario could create a bind at only 30' of rotation (10:30 - 12:00).

You've said the lifters were out so they can't be affecting anything.
The distributor/gear is not engaged so it shouldn't be a factor.
The problem exists whether or not the cam sprocket is attached - so it isn't the problem.

The only way I can imagine such a thing is if you've got 2 conditions working together.

You said the cam bearings were used. I'm no expert but I could imagine that the bearings might not wear evenly and have an out of round shape. If that is true and your camshaft does have a bend in it, - it could create a condition where the cam gets tighter at certain positions.

Just a wild guess on my part.
 
magnummopar said:
Your UPS guy probably tossed it across truck and bent it. It could also be due to cheap scummit chinese cam cores cast out of Yugo blocks. Send it back and try again.
Click to expand...

That would mean whomever Crane gets their cores from are cheap, too, since that is who supplies Summit cams. I would certainly like to think that's not the case......but who knows today? Good point.
 
Chances are that you'll be fine but if it worries you, find out what's happening so you'll feel better about putting it back together. It'd be one less thing to weigh on your mind when you fire this thing up.
 
Most flat tappet cores of any make do not have consistent widths on any surface so it could be as simple as them wedging between the ridges on the used bearings..... To find out just mount it with the sprocket and thrust plate then tap on the cam bolt with a dead blow every few degrees of rotation and see if it smooths out....
 
BlueDream said:
But wouldn't a bent cam also make it hard to turn at any point?
Click to expand...

Not always. Nothing is ever perfectly straight, perfectly round, or perfectly aligned. The degree to which they're 'out' increases the more parts are involved.

The bores in the block could be slightly out of alignment, slightly different sizes, and all slightly egg shaped. Same for the cam journals.

There will be a point in rotation where everything aligns, or the opposite and maligns. It could be as simple as journal diameters that are a couple thou larger than the cam it's replacing.

Point being: be careful and take measurements. Guessing does no good, and though chances are that there won't be a catastrophic failure, it's far easier and cheaper to measure parts on hand now than to do it later should an issue arise. Most engine shops would be able to put the cam 'between centers' and check runout on the journals, between that and checking the journal sizes, there's some peace of mind that can be hand.
 
One last thought: if you were assembling a new engine, would you let a cam with a tight spot fly? I wouldn't.

I would look into it and find out why it won't turn like a knob on a poop house door.
 
What changed? The cam. It is not straight. Get another. Put a dial indicator on the bearing journals to verify.
 
The cam HAS to be bent or the cam's journals misaligned to some degree to do this. Binding at just one point is due to the bearings not being in a perfect straight line any more, due to either odd bearing wear or slight block warpage.
 
Did you try sticking the old cam back in there to see if the same thing happens??

treblig
 
I've seen that a time or two, and as stated the used bearing surfaces may not align with the new-cam journals, at every point of revolution.They make a tool for dressing the bearings. I forget what it is called, cuz I haven't seen one in many years.
I kindof agree with Rusty.
The valve springs are gonna drive the cam down, and in no time it will be loosey-goosey.But what if not!?
 
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