Hi everyone. I'm really feeling down. I put in a bunch of effort to rebuild this motor D16Y7. But I'm hearing engine noise that I think is detonation. I hear a clattering under load, but in neutral, I can vary the engine speed and it sounds fine. I put a timing light on it, and the bottom end is set up to around 12 degrees BTDC. Keep in mind that doesn't say anything about the cam timing. Bore scope reveals the valves are not hitting the pistons.

I had some oil on top of the pistons (leans mixture) plus the block and head have been decked + 1st overbore pistons=bumps compression. So I drained the fuel tank the best I could, put in 4 gallons of 100 octane fuel, and it's still detonating (maybe not as badly).

The car is also stalling sometimes under heavy braking.

I'm really worried because the tach was starting to bounce a little bit. I'm concerned the motor is starting to hurt. I'm​​​​I'm out of ideas. Why is this rebuild detonating so badly?

 

Self help: Laundry list....

 

I would confirm cam timing. How much was the block and head decked exactly? How much was it bored? what pistons were used?

 

A machinist did it for me. The block was barely decked at all. There was still a hint of some oxidation on part of the deck (99% new metal but that one part was barely grazed) So he probably took of the absolute minimum off. And if he did it for the block, Im sure he did the same for the head.

1st standard overbore = 75.5mm bore. +.5mm DNJ standard pistons, rings and pins. New intake valves, all new valve stem seals. MAHLE/Victor Reinz HS54234, standard thickness head gasket.

 

You photo shows the crank pulley at around 10 degrees after TDC... so if your cam gear markings are properly lined up, then the crank gear is one tooth advanced. Recheck your mechanical timing and then see if your symptom still exists.

 

Cam gear timing confirmed correct. Pulley at TDC mark=cam gear marks perfectly level with head. Ignition timing correct.

Confirmed D16Y7 block (originally auto, now backed by 5 speed). Confirmed Y7 head (P2F-HA3) from 5 speed car. P2E pistons.

It's all the right parts. I'm going to redo the timing belt tension, and if that doesn't work, replace these funky spark plugs (pointy electrode/anode). Otherwise, I'm at a loss.....

 

Retensioned the timing belt, its a little tighter than it was. Moved ignition to the most retarded of the 3 marks. Checked valve clearances again while I was in there. Everything looks like it should, but it still detonates. All the injectors measure the correct 13-15 ohms. This is how they are connected:




It still detonates even from a cold start. The only other things I can think to check are EGR system and other Vacuum leaks, try different spark plugs, distributor/coils.

It seems the only progress I made today was to repair a small coolant leak.

 

My statement above assumes that when you took the photo of your crank pulley with the timing cover aligned with the 14' mark (first of the three marks close together), your cam gear markings at the 3 and 9 O'clock position were parallel with the cylinder head. If you took the photo after moving the crank pulley from the previous condition... then maybe you are actually in mechanical time.

Otherwise, when the cam gear is at TDC and the 3 and 9 O'clock marks are parallel with the cylinder head, the crank pulley TDC mark (the one at the far right in your above photo all by itself) should be aligned with the pointer on the timing cover.

The three marks on the crank pulley grouped close together are the 14, 16, and 18 degree advance marks used for setting the DISTRIBUTOR timing only... not the timing belt mechanical timing.

 

Yes. The 1st photo is a photo of the ignition timing, taken with a timing light, with the motor spinning. It was not meant to be mechanical timing, which also appears correct. Sorry for the confusion.

I'm quickly running out of things to check, and at this point, I'm not sure it's an assembly problem. I was really hoping to be back on the road already.

 

Did you use an OEM head gasket?

 

MAHLE/Victor Reinz HS54234, standard thickness.

 

Whose standard?

 

IDK. Honda? It's just a head gasket. It's not marketed as being thicker or thinner. Just a regular head gasket. "Produced to OE standards".

 

I ask because I know Honda used different thicknesses on different motors.

If it's Mahle's standard, how does that translate to Honda's D16Y7 gasket? If you don't know there could be a chance that the head gasket has changed your quench and squish zones to be outside of optimum. And I'm pretty sure Honda relies on that optimum spec in their designs.

At least that is the experience I had.

I don't know if the head gasket is your challenge, but I do know it definitely can cause detonation.

You can always retard your ignition timing to 16* or 18* BTDC and see if it helps. Retarding ignition timing from stock is what I had to do when I used a thinner gasket on my motor.

 

Ok. I'll add the headgasket to my list, but I already played with the ignition timing.

 

Replaced the fuel injector nozzle seals. Inspected throttle body-to-intake duct tube and readjusted hose clamps. No change. Sprayed some carb cleaner around the engine. No change in idle, which is normal anyway. Problem sounds like it's cylinder 1 or 2. Leaning to it being 1. Before I took the head to the machinist, I was never able to get the plug out of cylinder 1. Never could figure out why. Machinist said it came out no problem..... I wonder if it's significant...

 

How long has it been sitting? Bad gas still? Maybe you had moisture in the tank?

Oil in the cylinders will cause detonation. All day. Fix this.

Did you do a valve lash adjustment?

 

Fresh 100 octane. Drained the tank before filling it up with race gas. It only sat for 2 months, but I drained it for sake of getting the most octane boost I could.
No more oil in the cylinders. It appears the rings just needed to seat.
Valve lash has been checked and triple checked a million times now.

There is something uncommon going on here.

 

Do you live at sea level? lol

​​​​​​An exhaust leak at the exhaust gasket will make it sound like detonation.

Have you recorded the audio from your knock sensor to verify the sound is indeed detonation and not something else?

Stalling at idle recovery and heavy braking could be idle adjustment screw just needs recalibrated.

 

Close enough. 400 ft. ASL

No knock sensor on the Y7. ECU doesn't look for it. I plugged the hole with a screw before I put the motor back in. Just cause I'm OCD lol.

I did reuse the manifold gasket which was a really thick, crushable one. I have a much thinner sheet metal one I can try. Pretty genius thought.

 

Oh I just saw you said the tach would bounce.

Makes me think bad grounds. Check grounds?

 

I don't really consider it a symptom. If anything, it's the result of the motor hurting. It only did it once. Alternator and starter are grounded. Intake is grounded, block is grounded, trans is grounded.

Literally the only symptom I have is a pinging on the drivers half of the engine, despite every indication the motor is assembled correctly.

I'm down to head gasket not thick enough, exhaust noise, spark plugs or a weird ignition problem I can't figure. Possibly a vacuum leak.

 

Could be the other way around, head gasket could be too thick too.

Researching it's really hard to find what stock OEM D16Y7 head gasket thickness is.

On zeal autowerks calculator, they have a 2 layer D16Y8 option which I believe is a thinner gasket. What I am not sure, is if that is stock and would the Y7 use the same thinner gasket?

Also, it seems strange to be only #1 and #2.

I thought #4 was the hottest cylinder being the farthest from the water pump, I would think it would be that side if there was problems like incorrect temperature spark plugs.....

Yours is a very elusive problem. I'm hoping for all the best and a resolution sooner instead of later, you've put more than enough time into this.

Now that the head is on, you can't exactly inspect the combustion chamber of #1 and #2 to see if there is any flaws that could be causing a hot spot and pre-ignition.....

 

You can confirm detonation though.

Put fresh plugs in, do a pull, then inspect the plugs. Detonation has specific results on plugs.

I found this info awhile back and kept it in the memory banks:

How to read Racing Spark Plugs - Dragstuff

It has good info on detonation/pre-ignition signs.

 

Thanks for the resource. I'm going to switch to some other plugs anyway. To answer your previous post, The noise occurs even from stone cold. Start up, car sounds fine. Bounce the throttle open, and the load induces detonation for one or two cycles, then goes away, even at sustained high revs. Drive the car, and it pings constantly. Whatever is causing this, it isn't a matter of overheating. I can only (and always) induce it with load.

After new plugs, I'm going to have to take it to a pro shop, and tell them straight up not to bother with the wrench monkey and to put their actual engine guy on it.