Loose tappet?

[jsedivy]

Dear Don,

we bought a rebuilt Atomic 4 from you last year and installed it in our Pearson 30. The engine was shipped from your shop late 2005 and installed before X-mas. Bacuse of a busy work schedule I could not complete the installation until late spring and the engine was not started until June.

Because of a very noticeable "ticking" sound I immediately suspected that I may have a stuck valve, but I don't think this is the case. First, the compression has always been fine. Last time I measured it (today), it was 100-105-90-90 with the engine completely cold and 100-104-106-106 after thoroughly warming up.

We went on a 2 week trip in July and the engine ran flawlessly (except for the ticking noise). I think that after a hard run the noise goes down, and it tends to be less under load. It's most noticeable around 1000-1200 rpm. After the trip all 4 spark plugs looked fine - looks like all 4 cylinders are working and firing just fine.

I don't have a lot of experience with the Atomic 4, but I've done a lot of work on car engines, and this noise sounds for all the world like a loose tappet, especially on engines with mechanical lifters (like the Chrysler slant 6 - I rebuilt a few).

Should I just forget about the noise, since the engine seems to run fine? I don't mind adjusting the tappets, but getting access to them sounds like a real chore. Do I really have to remove the manifods, or is there a way to sneak in there after I remove the carb?

This may sound like fussing over nothing, but we really love the Atomic 4, and since we just invested in a completely rebuilt one, I'd like to be as conscientious and good to it as possible.

Best regards -

John

[Don Moyer]

John,

My guess is that you're hearing a valve tap from a tappet that might be a bit on the loose side. If a valve clearance becomes even a thousandth or two on the high side, a tapping sound can generate. Because of the relatively low RPM at which we operate, these sounds are not usually indicative of a serious problem, but at some point (after 30 hours or so) you may want to check the valve adjustment since you seem to have the ability to do so.

Don

[keithems]

mine makes the same ticking sound but runs fine -- as does a friend's -- i think the ticking may be from the mechanical fuel pump which is driven by a cam also --

[Charles Taylor]

I drove myself crazy trying to find the source of the ticking sound when I first got my Atomic 4 over a year ago. I checked all the lifters, etc. They were all ok. As the engine runs fine, I have come to live with the sound and agree with the others that it's probably the mechanical fuel pump.

[Cellnav]

It's not supposed to tap? If I fixed it I'd have to install a tach so I know it was running...

It's all part of the charm!

[sastanley]

callnav, I do not have a tach on my boat either. Has anyone found a way to easily (cheaply) tell engine RPM? It may help when tuning and troubleshooting since I do not have a good running engine.

I may some day replace the original gauge cluster, since some of the gauges are not reliable, and would add a tach. There are many other pressing matters, so that is a 'wish list' item at this time.

I will say that even when running poorly, the ol' Atomic 4 is like a quiet dream compared to the M-15 in my stepfather's boat.

[Cellnav]

Re Tach

Sastanley,
You can buy a cheap tach at an autoparts store and just run a lead with ailigator clips to dc power and the positive lead of the coil. If you want a semi permanent solution mount the tack inside the engine compartment. I bought a fancy marine tach six months ago and have yet to find the motivation to cut a hole in the boat to mount it.

I hope we haven't gotten too far in the weeds on this thread.

[wlevin]

tachs and taps

Yes, we are a bit off the original topic, but let me put in my vote for installing a tach. I have found lots of benefits to having one, mostly diagnostic. I used it to chart rpms against speed through the water (this curve helped me decide on my best rpm for cruising, since on our boat we get sharply diminishing returns after 1800 rpm). I knew I had the wrong prop when we first got the boat because we could not get more than 1500 rpm then. I even used rpm's to track down rattles in the nav and folded lunch tables and cushion them. etc etc.
Bill and Jeanne
T-34 #453
Otter

[sastanley]

tach hijack

I didn't even think about that! I still have one in a box somewhere that I had installed a few years ago in my Honda Civic, before I 'upgraded' the instrument cluster from a fancier model which includes the tach.

I am having a lot of trouble figuring out the motor and a tach I think would be helpful.
sorry for the continued hijack! - if it helps any, I am pretty sure I have noisy valves tapping away too, but that is low on the priority list right now

[adab1402]

valve adjustment

it,s all about access ,remove the manifold but do not disconnect the carb .three bolts and your there . piece of cake .

[msauntry]

Went through this a little while ago, but it bears repeating...

"Slappy valves are happy valves."

Ancient 20th century proverb explaining that ticking (looser) valves are better than tight valves which if too tight, can lead to a burnt valve with is far worse than a ticking noise.