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View Full Version : How screwed am I? (unfun motor sounds)



Rian_Colorado
09-08-2025, 12:13 PM
https://www.youtube.com/shorts/M4-hJTo9YUI

So after my big win with the Hydro-boost solve, I was very pleased with myself, and took the now fully functional go cart for a quick trip around the block. Huge smile.... until I started getting some backfires, and then this very unpleasant sound. I quickly put the go-cart back in the shop and shut it off.....

In the clip, I have disconnected the primary to the distributer, so no spark (hence no start) to try and diagnose what the hell this sound is. (that "tick tick" metal on metal sound in the last few seconds of the video)

Motor never got over 2500ish RPM, so I don't think this is a rod or any other internal. My thoughts are a cam lobe smacking a tappet? or probably more likely a valve head contacting the cylinder head.... I've been depressed for 3 days, but it's time to move on to the "find a solution" phase....

I've done nothing to the motor beyond picking it up and placing it in the car (and installing exhaust / electrical etc.) I opened the pro-flow 4 software to connect to it, but just looked around to get a feel - no changing any parameters etc. The motor was built by a pro, and dyno tested for an hour or so, then sent to me. I've had it on and running in the shop for maybe 10-12 total minutes since first start. I HAVE to think it was all good when I got it, but I'm racking my brain trying to think of something I've touched that would have caused whatever this is.

My guess is that it's some kind of timing issue? Some slight or slowly moving timing degradation? Hopefully not a timing chain tooth skip or something? I've never set timing, or really messed with a distributer before - so I'm fully clueless and in full learning mode if that is indeed the issue...

Any thoughts or opinions on what this is/could be? how to test, or better yet remedy the situation?

Help..... https://thefactoryfiveforum.com/images/icons/icon9.png

Rian

tnt_motorsports
09-08-2025, 12:35 PM
Have you contacted the builder? I would start there.

I don't think it jumped time, or the entire engine would be misbehaving not just what appears to be one cylinder. My initial guess is a rocker arm issue. I would pull the valve cover and spark plug to see but again talk to the builder first!

BornWestUSA
09-08-2025, 12:40 PM
Compression test ?

But I agree, call the builder.

gbranham
09-08-2025, 12:42 PM
I'd pull that valve cover and see what's going on under there. Sounds like maybe to rocker came loose.

Greg

Railroad
09-08-2025, 03:50 PM
Pull the distributor cap and see if the rotor is turning, while cranking. You can check to see if it points to #1 plug wire, while the damper timing mark is under the pointer.

Al_C
09-08-2025, 04:24 PM
Have you checked the oil? How much is in the pan and what the pressure is?

Oshkosh Rob
09-08-2025, 04:39 PM
I’m going through something similar and started by pulling valve covers and distributor cap and watched as I turned the motor over. Pulling the spark plugs allows it to spin over easier. Could be a bad lifter, bent valve, bent push rod. Having some idea of what it is or isn’t will help the engine builder understand what path to go.

Rian_Colorado
09-08-2025, 05:04 PM
Yup - first thing I double checked was that it had oil. (not that I hadn't checked the dipstick like 12 times JUST to feel better)

Talked to the builder - next step is pulling valve covers, plugs, and checking things out.....

Cobraman
09-08-2025, 05:09 PM
Sounds like a Rocker Arm is hitting the top of the valve cover this happened to me once had the wrong push rod in one valve.

gbranham
09-08-2025, 05:12 PM
Pull that valve cover! It literally takes 2 minutes. Ill bet a rocker came loose and rotated so a pushrod is hitting the valve cover. Sounds bad, but its not necessarily bad. Had that happen on my MKIII, and the trunion on the rocker got beat up a bit, so I bought a new one and installed it. Pushrod was fine. If that's what it ends up being, PM me and Ill walk you through setting rocker preload and torquing down its fastener properly.

bobl
09-08-2025, 05:20 PM
Hard to tell from the video but it sounds like compression leaking. First thing I would do is pull the plugs and run a compression test. Keep track of what cylinder the plugs come out of. Quite possibly you can tell what's going on from looking at the plugs.

Bob

Rian_Colorado
09-09-2025, 09:41 AM
Winner winner chicken dinner to Gbranham!

Rocker arm had come loose in cylinder 4.

Was worried that it was much worse!

gbranham
09-09-2025, 10:46 AM
Winner winner chicken dinner to Gbranham!

Rocker arm had come loose in cylinder 4.

Was worried that it was much worse!

Sweet! That's an easy fix. Inspect the rocker and pushrod, replace if necessary.

Greg

BornWestUSA
09-09-2025, 01:28 PM
Winner winner chicken dinner to Gbranham!

Rocker arm had come loose in cylinder 4.

Was worried that it was much worse!

Roller rocker arms?

Did you reset the lifter preload on all 16 of them after finding this??