Adrenolin

Last week while driving I noticed a sound from the engine which by the time I got home could easily be heard when at idle. It sounds like the clopping of a horse coming from the drivers rear of the engine. Its steady and increases with RPM. Nothing noticeable performance wise.

Had a question for CompCams so asked them about this while on the phone today. Suggestions were the following starting with taking the car out for a quick drive bring it upto normal operating temperature then..

1. Check the Valve Lash and preload. When I built the engine I adjusted these so there was no vertical movement in the pushrods but could still be rotated. Then I added 1/2 a turn preload per their instructions. Since I have 2500 miles on the engine now he said the lash and preload should be checked again due to heat expansion.
2. Check for a stuck lifter. While checking the VL and preload in #1 ensure that all the roller rockers and pushrods have full travel.
3. Check lifter retainer, 2 cap screws holding it and the lifter guides. Said if the screws had worked loose or if one of the retainer arms wasn't putting enough pressure down on a lifter guide it could generate this type of sound.

I understand suggestions 1 & 3 but I'd think #2 would be making a horrendous banging noise bouncing between the lifter and rocker. Still, what do I know and its easily checked while checking the valve lash.

Question.. When I check the valve lash and preload should I rotate the engine and fully loosen the polylock nuts as I go? I guess thats the only way to check is by redoing each to ensure the correct preload. Correct??

Also with this noise issue is it wise to drive it a bit to bring the temperature up? If the problem is something different I don't want to have it come apart on me. Being my first engine build all this is new to me. My understanding of the different engine sounds (clop, tick, ping, etc) and what causes each is at a novice level.

So you guys with more experience.. any other suggestions? I'm really open to ideas right now.

Thanks

jcoby

valvetrain issues tend to make more of a ticking or tapping sound. they also tend to run at 1/2 engine speed so it's fairly obvious when it's valve related.

as for #2, it's unlikely. my explorer has lifter issues. they leakdown and have trouble pumping back up. they tap like crazy until it's warmed up. it sounds like someone is hitting the engine with a hammer.

a recording would help 1000x here.

you might want to try stepping on the clutch and see if that changes things. it's possible your throwout bearing is going bad. there is a hole in the driver's side of the bellhousing for the lever that could explain it why it's louder on the driver's side.

you can also do the "mechanic's stethoscope" trick and place a large screwdriver against the engine and the handle to your ear. it will transmit the sound to your ear when you've isolated it.

Starfury

Yeah, I'd want to know more about the sound and where exactly it's coming from. I remember my motor made a horrible clacking noise when it chopped a couple lifters/lobes, but I couldn't really call it a clunk or clop.

jcoby

it could also be a header leaking if you have a pair. they love to leak and it can be a lower pitched sound than the valve train.

or it could be a stuck pcv valve. or a sparkplug fell out.

*shrug* it's really hard to diagnose sounds over the internet. i've never heard an engine that sounds like a horse clopping though.

Stepman

If you are talking about a lower pitched, "double knock"....the first thing that comes to mind for me is.....a rod knock.

pinboy122

try to isolate it by pulling 1 plug wire at a time and listening for a difference.This may help narrow it down to a specific cylinder

darkngtz

my 351w in my 84 bronco did the what seems to be the same thing, turned out to be a rod knock...not tryin to scare ya or anything but sound familiar to me

hiboostwoody

+1 to this

jcoby

i was trying to be optimistic. there's a good chance it's rod knock or piston slap but hopefully it's something else. those are the only two things that I know of that would really cause a clap-clap sound. and they're both really bad

a friend's fiero starting to make a weird ticking sound somewhat like what you're describing. he windowed the block 150 miles later driving home. v6 fieros are notorious for dropping a rod.