VC460 valvetrain noise

[Shepard]

Did any of you do a clearance check before you assembled your engines. Not every cam comes all ground and clearanced for all applications. This is necessary with any parts.

[raydhd]

I did that even on my long rod conversion to be safe. The balance shaft needed some material removed to clear the long billet rod. There was some work done on the balance shaft done by VC but it was too close for comfort for me.So I gave it some more clearance. I think Sho found the same situation on his long rod conversion lifan 420.

[KRAZYMATT]

Originally Posted by Shepard

Did any of you do a clearance check before you assembled your engines. Not every cam comes all ground and clearanced for all applications. This is necessary with any parts.

Yes everything rotated and cleared fine by hand with the side cover off which I know the shafts might not been perfectly lighted sitting without the side cover but no apparent physical or visual contact was noted. Appeared to ok clearance on all lobes/weights of the rotating assembly. Again checked with side cover on and fine. Noise only comes into play with push rods installed and valves/springs on. Basically as soon as the cam gets any kind of load from the lifters it makes the noise.

[scottykify]

I tried putting the stock predator 420 cam in the VC460 and it still made the same noise, but of course that stock cam in the stock 420 engine and it did NOT make the noise.

So to me, that narrows it down to the crank, or the case. The 2 cases measured the same between crank and cam bosses "using a dial caliper" within a thou.

I agree this loud of noise sure doesnt seem likely to be caused by gear lash. but I have no other explanation. I just wish someone would make a replacement gear for the crank so we could try simply replacing the gear. I know you can get a keyed gear for those aftermarket billet cranks, maybe a guy could put press one of those on the crank and weld it on or pin it or something. Assuming its the same diameter

[KRAZYMATT]

I have a genuine Honda gx390 camshaft ordered maybe the gear will be a little larger and mesh tighter? Either way we will see if the noise is there with that camshaft. Could it be something with the lifters? Maybe hitting that tab on the compression release of these cams?

[KRAZYMATT]

Has anyone looked into the lifters? And or the compression release on the cam?

[KRAZYMATT]

Originally Posted by KRAZYMATT

Has anyone looked into the lifters? And or the compression release on the cam?

OK GUYS, I THINK I HAVE FOUND THE CULPRIT! I was away this weekend relaxing and a couple of times this issue would cross my mind as i am trying to get my carryall put together for a camping trip in 2 weeks. As i questioned above about the compression release, i was away and not able to investigate this mechanism until today. First i opened the motor and removed the balance shaft, still made the noise. I also ordered a OEM Genuine Honda GX390 Camshaft which came today. Second thing i tried it with the OEM Honda cam- still made the noise. I started looking at the 2 cams side by side and i noticed a couple deep gouges in my 460 cam on the tab that makes contact with the lifter to operate the compression release, the Honda cam had more of a bevel and was smooth in this area however remember it still made the noise with this cam. The gouge surly cant be normal i thought so i took it into the machine shop and buffed the gouge out of the tab. Cleaned the cam and re-installed it. Put the cover on and rockers back on. Pulled it through the cycle a couple of times by hand- It was much quieter- Im getting somewhere now i thought so i opened it back up and removed the cam and did more polishing on the compression release tab. Cleaned it again and reinstalled it in the motor. Cycling it again now and it is nice and smooth, all i hear now is normal valve noise!!! NO CLUNKS!!!!! AGAIN NO CLUNKS! I will try to post a couple photos... So to you guys having these noises- TAKE A LOOK AT THE COMPRESSION RELEASE TAB WHERE IT MAKES CONTACT WITH YOUR LIFTER!!! I polished the gouge out of mine buffed it smooth and made a gradual ramp into it and it seemed to do the trick!!!

[KRAZYMATT]

I don’t know if the angle of the lifter bore is off just a little or what causes it to jam into that tab. But it **** sure cleared the noise in the motor polishing it. When I got the Honda cam it was smooth, I put it in the motor and a couple rotations and removing it it had slight gouging on the same spot. Also made noise with this cam.

I did not take a photo when I first pulled the 460 cam out of the motor. I didn’t realize this would be the issue or I would have. Here are a couple pictures of the cam after I just knocked down most of the rough stuff and tried it- this was when I realized polishing that would quiet it down some. So after these pictures I took it in the shop and polished it smooth and put slight bevel/lead in to it. When I put it back in the motor at this point is when I determined the clunking was gone and that was my issue. I did not take it back apart to take picture of it.

Again these photos are of the cam when I just first started to polish the gouging out of the compression release tab.







The next 2 photos are of the Honda cam which also made the noise. When I looked at the cam before installing it was smooth on this tab and even had some polishing marks but did still make noise.

Honda Cam pre-install:


This is the Honda Cam after I removed it- only had a couple revolutions by hand. As soon as I noticed it still did it with this cam I removed it and went back to work on the 460 cam. You can notice slight gouging starting.

[scottykify]

Nice! Nothing feels better than battling a problem like this and actually finding the problem.

Must be a different than the noise with my engine, because it would happen as both intake and exhaust valves were either opening or closing, and at high rpm when the compression release is no longer pushing the lifter.

Just goes to show you every engine is different, every part is different

[Yamahama]

On this topic, has anyone tried completely removing the compression release tab from their cam? I would imagine doing so would prevent this noise and maybe reduce wear in the lifter.

Would a starter/generator or stock clone starter be able to turn the motor I over? I imagine emergency pull starts would be next to impossible.

This is question is part of a larger idea if mine where I get a billet cam with no compression release