VC460 interesting noise, camshaft knock?

scottyk

New member
Hey guys, I have just finished up building a VC460 engine and I have encountered a strange knocking noise which seems to be coming from inside the engine somewhere. So far it is all VC parts that came with the engine camshaft as well. Call me crazy but it sure seems to me like it is camshaft gear backlash, or possibly thrust play. I posted a video of me turning it over with and without the rocker arms installed, video explains it all but it does not make the noise when the rockers are off. I have actually run the engine for a short amount of time and the noise is definitely still there and I wouldnt want to drive around the pits at the drag strip with it sounding this bad. "its a pit golf cart for drag car" The noise is very consistent, 2 distinct clinks from each valve as they are closing, 1 on the way down, and another when the valve is all the way down. So this tells me it probably is not the compression release, and probably not valves hitting the piston.

My thought is the lifter is pushing on the cam and it makes a knock as the gear lash is taken up, then the 2nd knock is when the lifter is on base circle of cam and lash is taken up again.

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Have you guys seen this before and any idea on how would I go about fixing it? I would like to find the problem before just blindly replacing parts like a cam hoping it fixes the problem.

Thanks!
 

flattop1

Dawg 89
That is odd . How much crank end play? It would need to be excessive.
First thought is rod hitting tappet or cam .
Did you use high lift cam or billet rod .
Looks like disassemble time .
 

flattop1

Dawg 89
There should not be that much lash to take up .
Straight gears some , helical gears should be very litte .
Cam end play maybe a possiblity .
 

scottyk

New member
I have taken it apart many times now checking stuff. I will be honest and say I did not check clearances with a cut apart cover on it, since I do not have one. The VC460 block has been machined for rod clearance in multiple places, but I hear ya I really should check that. I even ran the engine for about 10 minutes then took it apart and have inspected everything inside and did not see any signs of contact between the cam and rod. It has a billet rod in it yes, helical cut gears.


I think tonight I am going to take my stock predator 420 apart and measure the cam then install it and see if it still knocks.

How much crank and cam end play would be ideal?
 

flattop1

Dawg 89
On predator the lobe of a high lift cam can nick the top of the crank .you need to relieve the sholder a little .
When its open if you hold the crank up so it does not sag . You get a better picture .
Or lay a straight edge across the case . See how low the cam thrust surface is away from the edge .
 

scottyk

New member
flattop thanks for the reply, after more messing around last night I found the issue is too much thrust play in the cam. I drilled out a washer to use as a temporary shim to test the theory and sound went away. so I need to find some actual shims to use since the washer is too thick.
 

flattop1

Dawg 89
Whatever it is it needs to be hard . I used .010 or .020 shim material on a Triumph crank and it got beat up pretty bad .
Solid brass washer or hardend steel would be best .
 

RDub3

Member
Is the crank end play excessive also? If so then you may be able to machine or surface plate the block and/or side cover at the gasket surface to remove the end play.
 

flattop1

Dawg 89
Is the crank end play excessive also? If so then you may be able to machine or surface plate the block and/or side cover at the gasket surface to remove the end play.
True . Only if the thrust surfaces are below the gasket surface.
 

01ron

Member
Just a thought. Try with no gasket to see if that works. If so and it's legal, just use gasket sealer like they use on the new Briggs 206 side covers. The new stuff seals great and would take the side cover gasket width out of the equation.
 

scottyk

New member
So a little update. I ended up shimming the cam from .029 end play to approx .005, and it did totally silence the noise for about 15 minutes of break in time. then I changed oil and went to go for a rip, first time I revved it up the noise came back. I said screw it and took a couple easy laps up and down the street. The noise goes away as it rev's it up so thats weird. Or its actually getting totally drowned out by other noises Im not 100% certain, but it sure seems to get quieter with higher rpm.

Once I get some more free time and motivation I will tear the engine back out again and open it up. Its a pain in the butt to pull the engine on this golf cart all the time. Im not sure if the case could have worn in a little bit, or the shims might have got ripped out somehow, no clue.
 

flattop1

Dawg 89
So a little update. I ended up shimming the cam from .029 end play to approx .005, and it did totally silence the noise for about 15 minutes of break in time. then I changed oil and went to go for a rip, first time I revved it up the noise came back. I said screw it and took a couple easy laps up and down the street. The noise goes away as it rev's it up so thats weird. Or its actually getting totally drowned out by other noises Im not 100% certain, but it sure seems to get quieter with higher rpm.

Once I get some more free time and motivation I will tear the engine back out again and open it up. Its a pain in the butt to pull the engine on this golf cart all the time. Im not sure if the case could have worn in a little bit, or the shims might have got ripped out somehow, no clue.
Any chance you checked cam length , thrust too thrust surface .
Nothing like shim metal in the oil ?
Insulated engine cover😉.
 

scottyk

New member
To be totally honest, I was measuring the end play in the cam with plastigage. I know its not the most accurate but it did tell me once I hit .008 and lower clearance which SHOULD be enough to get rid of the noise, it that is where its coming from.

and I changed the oil after 15 minutes of running "before the noise came back" and there was some evidence of metallic in there but thats too be expected with a almost new engine. no chunks or anything. I will dump it again and take a look at it, maybe it did eat a shim somehow
 
Check the clearance between the rod and the crankshaft. They tend to get oval quickly. Check the torque on the end cap bolts. Could be loose.
 
I have the same problem as he does. Brand new 460 with a 275 Dyno cams.
It only makes noise when the valve is closing.
‘Take the valve spring pressure off and no noise. He posted this in the golf cart group.
Maybe the cam shaft clearances are very very loose
 
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