Strange sounds

[Tanman]

Hello all,

I finally found some time to put the 12/2 together. I have the bottom and top end all together, just no fuel lines, flywheels, or cooling hooked up. I oiled it up good while assembling, but when I turn it over there is a 2x metallic clank. It seems to occur almost exactly when the number 2 cylinder vales are in their exhaust then intake cycle. It sounds like it may be coming from the camshaft? Any ideas? Is there a normal click clack that I should be hearing when turning it over? I never really turned it over when I got it because there was a little rust in cylinder 1. So I don't really know what is "normal" for sounds.

[32 coupe]

My 25/2 does that....
Somewhere I read it is the way the valve overlap works on these.
I'm sure someone will chime in with a better explanation.

[Tanman]

What’s interesting is it’s seemingly only the number two side valves. I’m concerned it may be touching the piston ever so slightly. One thing I noticed putting it together was that one of the valves was really tightened down and it actually stopped the rotation when I was turning it over. I was doing it very slow with no flywheels so I don’t think there’s any damage, but after gapping the valves correctly it didn’t bind at all….. just those two metallic sounds that seem like they are happening as the exhaust then intake valve are opened.

[32 coupe]

When this came up in the past I remember someone said it is the "slop" in the entire
valve train.
When the cam rotates the pressure on the lifters forces the cam to "slam" over to the
next cam lobe. That and the "slop" between the cam, idler and crank gear.
When I put mine together I used an offset ider bolt and the bronze gear.
The offset bolt takes the guess work out of the idler gear bolt hole being in the wrong
place as many seem to be. My bronze gear shows no wear after running for 50 hours or so.

Look in the posts here about the idler gear problems. Some are not round creating the problem
of the gear train being tight then loose......others blow up after a few hours running.
I would encourage you to read as much as you can about the idler gear problems and gear
train problems before you run the engine.

Here again, I'm sure someone will chime in with much more knowledge than myself.

If you need an offset bolt I can make you one if you know about how much offset you need. Someone
here (I think it was John) made and sold them at one time.  My machine work is not as perfect as his but
they do work and I have good feedback from people that have used them.

At this point read, read, read. Learn as much as you can about the gear train and idler gear. It may
save you headaches down the road.

[38ac]

The intake valve can't hit the piston unless the cam timing is really out of whack. The exhaust is a different story. Late cam timing will cause it to hit, as will a combination of tight squish and tight valve lash the exhaust  valve decompression lifter can cause it to hit when everything else is OK. Not knowing where you are at putting it together here are a few steps to eliminate guess work.
1. remove the injectors so you can turn the engine freely without the decomp in use.
2. turn it over two revolutions
3. If it clicks but doesn't bind loosen the exhaust valve lash a about two turn s and try again.
4. If it quits clicking its the valve hitting. If it still clicks Its the gear lash. It would not be odd that the gear lash changes throughout rotation of the gears causing
one cylinder to click more than tbe other.
5 lastly engage the decomps one at a time to check for binding or return of clicks. The last 12/2 kit engine I put together I had to grind the pads of both decomps as they made the valves hit the piston.
Another often messed up deal that causes ckicks and binding of the fuel pump lifter(s) when set too high.
Do these things and that will thin down the possibilities and corrective actions can be suggested.

[Tanman]

Thank you 32 coupe and 38 ac! I will dig in this weekend and see what I can find, you guys are great!

[Tanman]

I found it! So looking inside the engine I slowly turned it over to exactly when it clicks, and I could actually see the camshaft clicking the idler gear. What I mean is the camshaft is basically spring loaded from the valves and at a certain point the pressure on the camshaft was causing it to jump forward and make a click sound against the idler gear. So I think my gear lash is a bit too loose. I attempted to measure it with my feeler gauge and I think it’s around a .018 gap.

[32 coupe]

Yep, that's what I thought.....they all do it.

You want to measure the backlash at different points as you rotate the entire assembly.

[Tanman]

32, are you still up for making an offset bolt?

[32 coupe]

PM me with info.