What could cause a motor to make a mechanical high pitched knock
for the first few revs at the startup cycle?

My engine revs to 2K with this knicka knicka knock when it starts and when the oil pressure light goes off after about a second and a half, the sound clears and no performance issues at all. I am suspecting that I have a loose cam cap bolt or uneven tq spec across the cams. I also have changed them out twice since I have had this engine to replace retainers and before that when we assembled the motor. It developed each time about 1500 mi into installing the cams. We did not, I repeat DID not replace the o-ring on the dowel pin in the center of the head. Some guys are sticklers about this. The engine does build oil pressure in about 2 seconds, it is very consistent the light goes out each time when BONE COLD in about 1.5-2sec. I bought the GSR head used and mated it with a R-DOT ITR shortblock from the factory bought NEW. I am going to try taking out the cam bolts, cleaning the holes to make sure there is no oil in them and re-torquing them to 20/7.2 in sequence like the helms said. thats just my idea, I also think I will re-install my stock cam gears and set her at 16BTDC just to be sure. There are no drivability issues with the motor. I also think I will install a oil pressure guage to monitor this if there are any changes to note. I am searching for ideas, guys please advise. The motor has 16500 on it and has been doing this at startup from 1500 miles to 12000 when I changed retainers and from 13500 until now. It runs very strong, just concerned that this may be a problem down the road.

thanks,
mike

 

Mikesarr_GSR.......Well i was having the Same problem with mine.. It could only be Two things.. To thick of Oil or Your oil pump is going out.. I had a 94 Gsr pump on mine So i put a 2000 ITR pump on and its Kinda still there..Not as bad as it was with the Old pump... But that might be because i dont drive my car every day..( I have a Beater).....But what i was going to do is Take a 12V switch and tap into the distributer wire and turn the Spark off and Bump it over until i see oil pressure on my gauge and then start it.. Thats what i was going to do...So Just get a Oil Pressure gauge and hook up that wire to the distubuter and try that...

-Ross

 

I get a knock on cold startup. i beat the **** out of this motor but its kind of annoying. The oil pressure light goes right off after its started up. no drivability issues here either.

 

good ideas, I run a 10-40w amsoil by the way. Its pretty thick when its cold, however I have a friend of mine with an ITR that rund the same oil. does not have this issue. I will look into running an ignition kill off a coil fuse or something also. I have a guage I just need to install it.

Thanks,
Mike

 

worn main bearings?

ive seen that on ol' chevys not sure about honda's though......

 

Mine does it as well.

I always attributed it to the bore taper, which is really the only thing I didn't correct.

Even before rebuilding the engine, it had that rattling/knocking sound on cold starts...sometimes worse in intensity and duration, with no real pattern...like it happening more while cold or parking the car on an incline.

After the rebuild, the sound became more noticeable, with random variations as to how bad or long it happened on cold starts.

My bore taper came out to .0019" after ball honing it; with a service limit of .002".

 

yea, I unplugged my coil and fuel pump fuses and cranked her until the light went out, then started it cold, no sound. I'll investigate it at some point at length... for now I got people coming over for bbq and bowling later:

ITRChris, ILUVTEC, RealTypeR, EleanoR... and some chics, so gotta get the place cleaned up

 

probably just a little rattle until oil fills in the gaps.
i would assume this only happens when the car sits for an extended period of time.

 

you are correct bro, only after it sits for 1-2hours or more

 

I know this is 7 years after the last post on the subject but my 2.3 CL does the same thing (it has 252,000 on it but I replaced the oil pump while doing the timing belt & water pump figuring it might be the culprit). After doing this to no avail, and until I have time to pull the oil pan and plastic-gauge the bearings, I decided to try something to nurse it. I bought a non-chip key and I crank the engine until the oil light goes out (usually about 15-20 seconds). Then I put my chip key in and start it. No knocking at all now at cold startup. And I still run it to 5,000 rpm sometimes and it's relatively quiet. Shame no-one has come up with a definitive solution to the problem but I really believe it's a rod bearing. After a month or so of doing this I decided to change from regular synthetic to Shell Rotella synthetic 5 w 40 (yes it's diesel oil). Now I only have to crank it for 10 seconds in the morning or after it sits for a couple hours. Hope the non-chip key idea helps someone.

 

A simple compression test will tell you if you have rod knock.

 

Thanks, I'll get a chance to run a compression test Saturday and I'll post my results.

 

So here are the results:
#1 208
#2 203
#3 206
#4 211

If it helps to figure this out, here are my oil pressures with 5w40 synthetic.
Cold it runs 80 psi at 1000 rpm and 60 at 700 when it warms up for a minute or so.
Now for the hot numbers (after 30 minutes or more on a 90 degree day):
700 8
1000 11
1500 20
2000 28
2500 38
3000 42
3500 52
4000 58
4500 62

 

There's nothing wrong with your engine or oil pump. I would take a look around the valve train for anything out of the ordinary. You could have a bad tensioner.

 

I don't think a compression test will tell you if you have rod knock. You can have good compression with a shot rod bearing. Compression tests tell you if you have either a bad head gasket, bad ring seal, or bad valve seal, but not bad bearings.

 

Thanks for your help. I'll pull the cover & check the rockers. Pullies are all good. Just replaced the head Oct 2015 & oil pump 3 months ago. Noise started about 4 months ago. Just strange that I've seen other threads for this problem & no one has posted a solution. If I figure it out, I will post the fix.Thanks

 

You seriously don't think having rod knock will have an effect on the ability for the piston to seal the cylinder ? So if the rod has plenty of play that would still allow the piston to seal perfectly and not have any compression loss ?

 

Sorry but I have to agree with m4xwell, I didn't think a compression test would unveil a rod knock but I'm open to any suggestions. I was just hoping someone had a trick I didn't know about before I spent time pulling the oil pan and plastigauge-ing the bearings. This is my daily driver and I can't be without it other than over the weekend and from what I've heard, the best place to get the bearings for this engine is the dealer but I will need to know the journal dimensions before doing so. Just had a master-tech verify that the sound is definitely in the bottom end, not in the valve-train or outside the block. Maybe just a few more weeks and I'll have some time to get to it.