knocking sound... need some help

[downest]

I don't post on here much... my little SOHC is hardly considered "All Motor", but I'm having some issues I think the engine building guys can help me out with. Here's my build thread on CRX Community, I don't want to copy all the posts over. So I'lll summarize: Setup: D16A6 block, not decked ACL bearings stock rods PM7 pistons OEM seals, 3 layer HG, belts pumps etc D16Y8 head, ported and rebuilt Crower Stage 2 NA cam AEM Cam Gear Z6 intake mani DC 4-2-1 header AEM CAI from 99-00 Si Compression (static) should be about 12.6:1. I've run this before on a stock Y8 cam, I ended up taking it apart because I thought it was having a motor issue with a weird misfire, it turned out to be some loose metal in the dizzy. I know it can run and not ping on 93, but it seems everyone is quick to say the compression is too high. It should be even better now with the cam, since dynamic compression will be lower. Anyway, I finally got it started this past weekend, and my friend who tunes it for me (Crome Pro) just made me a really quick safe map to move it around on. My AFRs are conservative, it's eating quite a bit of fuel. He's coming this weekend to tune it correctly for normal use. Anyway I put a few miles on it, and it started to knock/clatter really inconsistently just as I was getting close to home the other day. I assumed it was rod knock, though my experience with that is limited to my A6 that knocked for a few minutes before it blew a hole in the block. A few hours later, I started it up to show a friend and the knock was gone. Once it warmed up, the knock was intermittent again. I tried pulling plug wires to locate it, but it didn't seem to make a difference. I did some reading around here and found that the LMAs can be noisy, so today I went back to the shop to check them out. I thought it would be likely because the head sat for a long time, and I didn't know to soak them in oil. I checked the LMAs and they sprung back fine, but I took them out and let them sit in oil for a few hours, and pumped them in and out while they were submerged. Reassembled, checked the valve lash again. A couple of the intake valves were a little tight, so I got everything the same, 006 intake and 008 exhaust as per the Crower specs for the cam. Retorques all the bolts in the head, but nothing was really off anyway. Set the timing to 12BTDC. Then when it was warm I changed the oil. I used a clean pan to check for metal flakes or anything that would indicate a bad bearing, didn't see anything. I even took the filter apart to see what was in there, what a pain in the ass. I didn't want to hacksaw it because that would put more metal flakes in there, so I mangled it in the vise and used a hammer and chisel/screwdriver. Nothing. There was a little piece of RTV, on one of the circumferential holes that's visible on the filter when you hold it normally. I did a compression test after that, 200-220-220-200. I think the middle two had a little oil in them still, as it was on the plugs. I regapped the plugs from 025 up to 035. Started it back up and it ran smooth, the knock is again intermittent, now it's quieter and at higher RPM only when it does appear. I'm stumped! I'm going to borrow a laptop later if I can and see what my AFRs look like, but it's louder than what I've heard detonation to be with my old motor (more of a clatter than a metallic buzzing). Any ideas?

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[downest]

No ideas anyone? Anything else I should check?

[downest]

I tried a stethoscope on the motor, it seems the noise is coming from cylinder #4. It's still inconsistent, but it seems to be loudest just above the engine code plaque. It's also pretty loud in the left-most valve cover bolt (passenger side).

[Runnerdown]

do you have good oil pressure? Before it gets any worse, take the oil pan off and pop the rod caps off. Seems weird that there is no trace of bearing material though.

[downest]

Yes, oil pressure is fine... I thought that was weird too not seeing bearing material in there. I mean, I don't expect to spin one so quickly, but I have no other explaination for the noise.

[downest]

I just realised you're in Albany, where at?

[Runnerdown]

I actually live in scotia, and work at synapse. Also a fellow ef owner

[downest]

Originally Posted by Runnerdown

I actually live in scotia, and work at synapse. Also a fellow ef owner

Were you at either of the JVG meets? If you're not too busy this weekend... I'm sure I can find some beer...

[Runnerdown]

I didnt go to the meets, been working on the car and its out getting paint at the moment. I'd like to check out the setup and maybe help find out what the noise is. not sure exactly whats going on this weekend just yet. I'll pm you.

[downest]

That would be great, I was half joking but I'd really appreciate someone else taking a look too. I'm going to pull the pan and take a look at the #4 rod bearing today. Tuning is put back a little, so I have some time, but I want to get it straightened out... it's really hard to not have the CRX on a beautiful day like today!

[downest]

Pulled the oil pan... looks like the #4 rod bearing is cooked. It's not welded to the crank yet, but I have a spare crank so I'll be pulling the motor again soon.

[Scott_Tucker]

I know you already figured it out but I wanted to write about a good method to determine what is causing a knock.

If the engine is making a knock, pull each spark plug wire and ground it. If the knock decreases in intensity it most likely has excessive rod bearing clearance. If the noise is a high frequency rattling sound, and it decreases intensity when pulling a plug wire it is most likely pin noise. If the noise is a deep metallic thud, mostly under load, it is probably excessive main bearing clearance.

[downest]

I was all set to order my rod bearings through Honda tonight, but I can't figure out the colour codes. I got the letters/numbers off my crank and rods, and I found how to figure out what "colour" bearings I need. The problem is, Honda's online thing only lists the letters, A-G. Do I just order the letter of the bearing I need? Does it not matter? The differences between the colour codes for each letter is 0.0002"-0.0003", and the tolerance in the manual is 0.0007". I know I should know this, but I've always used ACL bearings, which are one size, and until now they've always worked. I want to get the proper bearings because the OEM ones SHOULD be better if they are matched, since the ACL are not.

For what it's worth, my rods are all "3", and the crank is C3, B3, B3, C3. I really want to get this stuff ASAP, it would be great if someone could help me out.

I re-read that and I think it might be a little confusing (not the main problem about sizing, but what I meant about the tolerances).

To clarify:

Each combination has a letter and number, together they correspond to a colour/size. For example:

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote &raquo;</TD></TR><TR><TD CLASS="quote">
"A"
1= red
2= pink
3= yellow
4= green

"B"
1= pink
2= yellow
3= green
4= brown

"C"
1=yellow
2= green
3= brown
4= black

"D"
1= green
2= brown
3= black
4= blue
</TD></TR></TABLE>

What I meant was that the differences between all the numbers in each letter is a total of 0.0003" or 0.0004" (ie, blue to green, black to yellow etc); I didn't mean between each different colour. The total difference between the largest and smallest (blue and red) is 0.0007", which happens to be the tolerance in the manual.