AP1 S2000 Engine ticking - Stumped!!
 

I am proud owner of a (new to me) 2000 NFR Honda S2000. It's got 120k miles on the body, and a mere 5k miles on the rebuilt engine and clutch. The "oil scroll valve" seal went out and leaked out all the oil on the engine, with the previous owner taking it to a professional rebuild shop outside of Atlanta called Assist Motorsports(anyone have any experience with them?)

Test drove the car, ran perfectly, i just noticed the slightest of occasional, what seemed to be to be a miss or slight vibration at idle. Ran good and made no sounds it shouldn't so it didn't bother me too much, figured it could just use a tune up as the car has had only a couple thousand miles put on it in the past 3-4 years. I got it for 5900(has a lot of dents on one side.. body shop is bringing car back to new for a whopping 1800), but still considering all the work it's had I thought I did alright. Now on to the problem I'm having today:
Drove the car home from Atlanta to Louisville, KY. Somewhere in Tennessee I noticed that if i gave the car any decent amount of gas while in gear on the highway, it would make this odd, mettalic squeaky noise. I assumed it was a dry rotted or wet serpentine belt or something of that nature, I had driven through rain. Long story short, when i parked it it was now ticking at idle and continues ticking all the way through around 2-4k rpm, and it ALWAYS makes this squeaking noise when giving it decent throttle while in gear. When driving a little hard on it(5k+ rpm), it makes absolutely no noises and runs great and pulls hard. Also, when driving it like a granny or broke college student trying to save gas and feathering the throttle, it runs beautifully and make no noises at all. It's the middle(usual daily driving) set up that causes it all the trouble.

What I have done so far:
Sandblasted worm gear and piston(twice..) - seemed to make the sound much quieter and smoothed out the idle a good bit but never came too close to completely fixing it
Replaced all spark plugs - did nothing
Replaced serpentine belt - did nothing, belt on it was not even old due to the engine rebuild
Checked serpentine puileys and tensioners - did nothing
Dumped Seafoam in engine oil to potentially remove oil sludge buildup - also seemed to quiet it out for a bit but didn't last long

I took the car to a local performance shop that has a fully built S2000 and the two workers listened to it for around 30 seconds to decide that one of the cylinders "swallowed a valve" or has cracked retainers. I bought the car from a lady in her 60s who had owned it since 25k miles and I didn't even approach the redline at any point over the journey home, I find their diagnose to be bulls***, that is why I am here today asking for help from the community! Their recommendation to have the motor rebuilt by them and "why not push it to 600hp and build it while you're at it" seemed ridiculous for an engine with 5k on it.

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Thank you in advance! -- Desperate s2k owner

Sounds like a scored cylinder/defective build to me. The frequency is too slow to be TCT related.

If it swallowed a valve it wouldn't be running at all right now.

Broken retainers show 0 symptoms. Yet another clueless lying shop that only cares about selling. Do some real diagnostics for a change instead of random guesswork that is 100% mechanically impossible.

I have yet to see a single "built" engine outlast an all OEM S2000 engine.

Thank you, both the guys said completely different things which led me to be even more hesitant of what they were saying... What are my best options at this point to get the motor running good again?

Find a shop that can pinpoint that noise. With 100% certainty.

Maybe someone can recommend someone near you. Could be as simple as a very loose valve, adjustment wise.

Valve adjustment, comp test, and upper engine inspection is your next move.

I ran a compression test a couple days ago but I know I didn't do a good job of it... the tester i used had been sitting for a bit over 30 years in my garage and the engine was definitely far from completely warmed up... I got numbers all around 150. Terrible numbers, but they were consistent across the board and on top of that my starter has been on its' way out and wasnt cranking very strong. My new starter gets here today and after I install it I plan on warming it all the way up and running another compression test with a new guage i just got from Autozone. My next step is to then take it to another local Import shop who did good work on my Porsche 944 for a second more thorough opinion.

Billman suspects scored cyl. So get that compression test done and get back to us with numbers. In addition to warm motor and good battery, be sure to prop the throttle wide open, and disable the fuel pump fuse. All plugs removed.

If its cranking, but slow, that sounds a lot more like battery than starter to me. What makes you think its starter?

A shotgun diagnostic process is never effective (shooting broadly in every direction swapping out random parts hoping one fixes it). Instead, why not try to focus on discovery. Right now that is getting compression test numbers.

after compression I would grab a boroscope and inspect cylinder walls personally. Id recommend running a leak down as well.

the starter squeals occasionally on startup which I diagnosed as a weak return spring on it hitting the flywheel, and it also just occasionally doesn't start at all when its' warm. Just seemed like it was tired and weak and I found a replacement pretty cheap. I will get the compression test today and try to get ahold of a boroscope

Did it make the noise in the video before you dumped Sea Foam in the oil or just the squealing noise? Doesn't sound good either way, good luck.

the sea foam made no difference, if anything it might've helped a little. I found a similar video here:
listening to those side by side, the noises are very very close. And in his situation, in the comments he said he did fix it by adjusting the valves. I set an appointment with my local Honda dealer tomorrow to take it to them and get their opinion and hopefully get the valves adjusted and see if that doesn't fix it