Can't figure out engine noise after rebuild.
 

UPDATE: Fixed. Was an exhaust leak between manifold and cylinder head.

What's up guys. I just rebuilt my D16y7, both the head and the block. It fires up and purrs perfectly at idle but under load, it makes a clattering noise. However, if I hold higher revs, no load(out of gear) the noise cleans up a lot, and basically goes away. It's blowing some oil, but with only 10 miles on the rebuild, I'm hoping the rings just haven't seated yet. Below are some photos of the pistons, and I don't see any evidence of the pistons smacking the valves. Also got a photo of the timing (which I have no idea how to read it adjust). It's idling ariund 800rpm.

Valve clearances were done and double checked after the head was reinstalled, but not since the first heat cycle.

A Honda mechanic I know threw out the idea of spark knock, but he's never seen the car...

​​​​​​What's wrong with my rebuild?

https://cimg0.ibsrv.net/gimg/honda-t...951cdcfafc.jpg
https://cimg1.ibsrv.net/gimg/honda-t...d4e6949336.jpg
https://cimg5.ibsrv.net/gimg/honda-t...a6067e9a1e.jpg
https://cimg7.ibsrv.net/gimg/honda-t...8a4c863117.jpg
https://cimg2.ibsrv.net/gimg/honda-t...c455060ce0.jpg
https://cimg6.ibsrv.net/gimg/honda-t...43100756da.jpg

Re: Can't figure out engine noise after rebuild.
 

that's definitely pulling oil, pools of it on the pistons. either the rings are not even close to seated, or you have some crazy valve seal issues. I would try seating the rings asap, but be careful because the oil can cause detonation, which is probably what you're hearing. how bad is the smoke behind the car when you go full throttle?

Re: Can't figure out engine noise after rebuild.
 

Any suggestions to make that happen? I already did a drive according to what the manual suggests.

Re: Can't figure out engine noise after rebuild.
 

Right now, I'm thinking octane booster + toss in a couple gallons of race fuel and flog it a little bit. Hopefully that will prevent detonation until the rings seat.

Re: Can't figure out engine noise after rebuild.
 

Key words "under load".
I think you're hearing audible detonation.
Reduce base timing a couple degrees and see if it goes away. If it does, I would add little bit of octane somehow and continue seating in the rings.

Re: Can't figure out engine noise after rebuild.
 

I drained the fuel tank and put 4 gallons of 100 octane in. Still detonating. I'm going to check the cam gear timing tomorrow. Only good news is it seems to have stopped blowing oil. I'll have to confirm that with the bore scope. If the cam gear turns out to be correct, what should I do?

Re: Can't figure out engine noise after rebuild.
 

verify valve lash is in spec
then warm it up at idle, and use a timing light to check and adjust ignition timing, aka distributor adjustment.

Re: Can't figure out engine noise after rebuild.
 

See first picture in OP. That's the timing, done with a light.

Re: Can't figure out engine noise after rebuild.
 

So what piston clearance and ring end gap did you use.?

Re: Can't figure out engine noise after rebuild.
 

My machinist suggested that the DNJ ring kit I was using didn't need to be gapped. I did throw a compression ring into one of the bores, and it looked to be about right. Imagine a nylon strap doubled over. Or two credit card thicknesses. IDK. Something like that. Far enough that they're not going to touch.
I left my pistons with him and he honed the bores to the proper clearance for me. He told me I could put any slug into any hole.

Re: Can't figure out engine noise after rebuild.
 

I've never actually assembled a motor on my own, but your post above mine screams red flag. I dont care what ring set it is and who manufactured it, to say that the manufacturer gets the ring gap just right for every application without checking sounds like someone being a lazy ass and not wanting to do the work. Or even worse trying to set you up for failure... How freaking hard is it to check ring gap? I mean I dont get people that skip the simplest steps like this when doing something as important as building the motor in someones form of transportation. Just seems like saving 5 minutes now to end up putting thousands more dollars and days of work in down the line. I would say this is likely the cause of the noise and why you're blowing oil out the exhaust.

To say you can just see that they have enough clearance to not touch is silly, and also for a machinist to say put any piston in any hole is just..... I dont even know. There is a reason most competent shops tell you to bring the pistons with the engine to get the bores honed so they can match the piston diameter to the hole. NO piston manufacturer is good enough to give you 4 pistons absolutely identical unless it was a freak coincidence...

Re: Can't figure out engine noise after rebuild.
 

Gapping rings is a VERY labor intensive job. It probably takes the better part of an hour to do the job on a 4 cyl, and it's possible to damage the bores when doing it. It's also not a highly critical measurement. The book specifically mentions that you can run almost double the "max gap" without issue. The main thing is to have enough gap that it's not going to pinch. A pinch results in instant catastrophic failure, not a minor tick.

For the bores, you got to remember there's a tolerance +/-. If the slugs are close enough to each other, your machinist can pick a size that will allow all your slugs to fall within that tolerance regardless of bore. I did measure the bores after the overboring was done, and they were all within .0005 of each other. That's a really good tolerance. Also, I did leave my pistons with the machinist...

Also, the car doesn't blow oil anymore. It just needed to drive it a little bit and seat the rings. I'm actually getting back on this project this weekend to investigate further.

Re: Can't figure out engine noise after rebuild.
 

Bad pcv valve is about the only thing that will cause oil consumption, other than ring wash. Leakdown test will find your culprit. Valve seals usually only leak alot of oil at startup. Most v8 race engines I build dont get valve seals. A proper plateau hone requires no "break in" of piston rings. They are broke in immediately. That break in garble went away after plateau honing, and the use of chrome rings. I see smooth cylinders? There should be a reflection of a crosshatch.

Re: Can't figure out engine noise after rebuild.
 

Gapping rings is labor intensive? Like I said Ive never done it but ive seen it multiple times and if thats labor intensive then you and I have different definitions for intensive. Checking the ring in the bore with a piston to square it off and sticking a feeler guage in the gap is no bog deal. Yes then you go back to the ring gap filer and cut it down to fit. Wash, rinse, repeat. To save yourself that one hour (that's a real stretch but let's just go with your number for arguments sake..) is it really worth risking your engine? Im sorry but even double the accepted ring gap is what 40, 50 thousandths? To say you can easily eyeball that it looks ok and just run it is pretty shadetree if you ask me. But to each his own I guess

Re: Can't figure out engine noise after rebuild.
 

Considering that I'm making 175-180psi across all cyclinders, and it's not blown up, I'd say the ring gap is fine. Thanks for your concern.

Re: Can't figure out engine noise after rebuild.
 

You fixed it! It's magic! I had a yamaha motorcycle do that. Built the thing, and it puked oil like hell. Then I figured, since it's not mine, I might as well blow it up before I tear it down again. Pounded the snot out of it. Mosquito patrol all the way, then it ran beautiful. To this day, I don't know what the hell that was all about.

Re: Can't figure out engine noise after rebuild.
 

Well, it's not fixed. It's healthy in in every metric I've tested so far, but it still makes a noise I'm not thrilled about. At this point, I'm seriously considering doing just what you say. Find out one way or another...

Re: Can't figure out engine noise after rebuild.
 

Is the noise only present under load or is it mildly present at idle?

I ask as I wonder if you could probe around with a mechanics stethoscope to isolate where the noise is at.

Re: Can't figure out engine noise after rebuild.
 

my last biuld sounded exactly like that from a cracked exhaust manifold. Only under load from exhaust pressure. Just fixed a broken exhaust stud on an f22 about a week ago too. Exhaust leak made it sound like there was something seriously wrong with it. Horrible knock.

Re: Can't figure out engine noise after rebuild.
 

Only load. But it's also super sensitive to that load. If I open the throttle aggressively I'll hear the noise for a single cycle. The inertia of the motor is enough load to induce the noise. But I can also hold it near redline and it will sound perfectly fine.

Someone else made that suggestion to me. I'll add it to the list.

Re: Can't figure out engine noise after rebuild.
 

If it is in fact a mechanical knock, you can also use a wood dowel, a broomstick, or a big screwdriver if you dont have a stethascope. Just put it on your ear, and wherever you think you hear the noise. If it goes away when the engine is spinning faster, it could be a loose bolt on something that rotates, like the cam gear.

Re: Can't figure out engine noise after rebuild.
 

I spent a few minutes with the car today. I can 100% say that the noise is coming from the front of the engine, and the driver side half of the block. Doesn't sound like top or bottom sounds more medial. It's not a knock, it's a tap, a clatter. Might be an undertone of a puff of air, not sure. So I crawled under and looked at manifold. Didn't see anything. But I did get this photo. Notice the freshly machined surface. The head overhangs the block. You can also see a little corner of head gasket in the top right... Is that normal? Always seemed odd to me, but it literally only goes together one way....https://cimg6.ibsrv.net/gimg/honda-t...d677fdb37a.jpg

Re: Can't figure out engine noise after rebuild.
 

For the 20 bucks, I would recommend picking up the Lisle stethoscope. I have done the snap on long screwdriver trick and the wood dowel trick and the difference to the stethoscope is night and day.

If your findings keep to the top of the engine block and not the head or the bottom of the block, you could have piston slap.

If the taper or out of round of the cylinders were borderline on service limit spec and the engine was honed it could push it just beyond service limits and cause the piston slap.

Re: Can't figure out engine noise after rebuild.
 

IDK. This block was overbored, not just honed. I have a bore gauge micrometer, and the work looked good to me. I'm going to leave that low on the list since it's a full teardown to fix....

Re: Can't figure out engine noise after rebuild.
 

Some cars drive a very long time with piston slap so really, I suspect it's the least evil out of them all when it comes to knocking like sounds.