I've got a sick feeling I'm going to have to take my 1.8 engine out and completely apart again after rebuilding it.

Cranked it up for the first time after rebuilding it(all new bearings, new rings, head work and gasket set).

The engine has a knock fairly loud at idle but when the engine rpm's are around 1500 it starts to quieten down and at 2000 rpms the knock goes away completely only to come back at idle when rpms are around 800-900. Other than that the engine appears to run very smooth.

Where to I start here. L

Pull the coil to distributor wire. Then crank it. Do you still hear the knocking even tho it's not firing?

what pistons did you use? might be skirt slap. does it go away when engine is warm to FULL operating temp?

Before assuming the worst, take a methodical look at it and go over the basics.

-Valve adjusters; you may have had one or more come loose. I see this often on customer cars.
- Exhaust gaskets; an exhaust leak at the head can have a metallic sound and make you think the motor needs to come apart.
- Hand crank the engine at TDC and rock it back and forth with the plugs out. If you truly have a rod knock, you'll likely be able to make it knock and hear an audible "clunk".

Never assume anything. . . Good Luck!!

you could pull the spark plug wires one at a time while the engine is running. to see if the knock disappears.you can isolate that way.

Update: I followed Mr Bubbleheads advice and pulled one spark plug wire at a time with the engine running.

The knock went away when I pulled #3 wire. So I guess the next thing to do is to check valve adjustment on #3 right?

Bulitt. Couldn't hear it knock when I cranked it with the coil wire disconnected.

Sean. I reused the factory German KolbenScmidt pistons.

Aircooledtechnology. I rocked the car back and forth with the plugs out at TDC on each cylinder and couldn't hear or fill a knock.

With this in mind, did you put the pistons in facing the correct direction?

Are there spacers under the valve rockers?

If so it common for the rockers to tap against the inside of the valve covers. Since you are going to check valves anyway, give the covers a look and make sure there is no indication of impact. If there is just clearance the rocker screw a little.

Zach

i was hoping you WOULDNT hear a change. unfortunately its almost certainly a rod. of course check the valve train. but the valve would continue to make the sound weather the plug was firing or not. but since u pulled the plug and took the pressure off that cylinder and the knock stopped, i think your gonna have to tear it down again. at least you know where to focus your attention now.

I have exactely the same symptoms on my newly rebuilt std 1,7 (all new bearings, new rings, head work and gasket set). Have been running about 2000 miles since the rebuild and it hasn't got any worse.

If it is the rod would it likely be at the small end or..?


/Lars S

So what is it about a rod that will make the knock?

Big end bearing on the crank or little end bushing wobble on the pin, maybe wrist pin movement? As some of you may know, I am starting to RE-assemble my engine for the 2nd time and if there is something I can check while the case is split, I WANT TO CHECK IT.

The large rod ends are just about the only simple place on these engines you can check with plaistgauge.

When I reassembled my engine this last time, I used some rods from the PO and some brand new KB pistons & wrist pins.

I sent in the rods to be rebushed and checked.
The shop complained that I did not send them any wrist pins.
I thought why the hell would they need the wrist pins, arent they all just one size?

Well the shop told me that the rods did not need to be rebushed as they had just been done, BUT they guy said the engine would have probably siezed almost immediately because the wrist pin bushings had not been properly sized after being replaced.

He also straightened one rod for me.

SO.... make sure the wrist pins are not binding in the rod bushing too.

Stu

aircooledtechguy said something very important:
always check the simple stuff before assuming anything. this is good advice worth mentioning again.

If it is a rod can't I take it off the crank without splitting the case after removing the head and both pistons and cylinders?

I just checked the valve adjustment on #3 and it's spot on. No problems appear to be here.

Mark. From what I remember the arrow on each piston top is pointing towards the flywheel.

Zach. No spacers were used under any of the rocker arm assemblies.

No, you can remove a rod without splitting the case. You do have to pull the engine though and remove the cylinder. My question though would be under the circumstances what else is wrong? If you find one smoking gun, maybe just the rod work would be OK, but it may be something really bad in one spot and sort of bad in the rest. That would be my luck.

As it happens I am pretty sure that I made a compression ratio error on my 2.0 build just completed. Pinks/pings under load with 93 octane. So as Joe Walsh put it: welcome to the club
http://youtu.be/OA6Qa3z0igM

But you can be sure I am looking for other causes of the sound...

Worn, please splain the "no, you can" thing to me. Just don't want to assume something.

You can pull the cylinders off, then the pistons, and work around the rods to reach in and remove the conrod bolts. You reach in through the spigots where the pistons go.

It doesn't look like much fun, but it's probably less work than tearing the entire thing down. But you won't get to check as many things.

--DD

Whenever I need to pull the cylinders, I pull them with the pistons still inside. It saves wear & tear on the rings.
Slide the cylinder out over the piston until the wrist pin is exposed, then pull the pin.
You have to install/remove them in a certain order to have enough room.

Yes you can remove the rods without splitting the case.
But you pretty much need to have the opposing cylinder off too. SO you pretty much need to pull them all.

Worn,


What was your deck height?

Stu

Exactly what I meant to say. Thanks Dave.

Nominal answer. 0.045". True answer: I am not sure. I made up several jigs using dial indicators etc, and I got different answers with different methods. To some extent this was due to the rocking of the piston without the rings installed.

Symptoms: As break in progressed cranking the engine became slower with the plugs in. Pinging under load with an AF reading of 11. High cylinder head temps - over 400 if I let it with freeway driving on a cool day. Pinging slightly reduced with octane booster.

I am going to try a lot of things, and perhaps even try race gas. One problem has been the adjustments of A/F at the MPS and knowing exactly what timing to run. Lots of tuning has not solved the problem, but the car drives fantastic! Close your ears, don't look at the gauges.

Also though, I do not believe a number just because a gauge says it. In the end I think I would do what is in the manual - use a straight rod and a feeler gauge. You can use the micrometer to check the feeler gauge. I built an analog to the pieces for sale, but was never able to easily maneuver the dial indicator, and besides the measurements had variations between set ups. In my world, at least three experiments independently conducted give you numbers.

sure, thats what i would do. i would also check the rings on #3 also. im not sure if you can measure the journal while the crank is still in the case tho. also if the journal is scratched galled your gonna be slitting it. so be prepared.

post pics when you pull the rod....

See if you installed a con rod flipped in the wrong direction. It will still install (either way), just another something that needs to be marked upon removal to avoid installing wrong.
I did this on a Vw engine in high school auto shop and got to take it apart again....yes it knocked

And how can you tell?
I did not install mine in any particular direction.
The were identical either way....no distinguishing marks.

Stu

Stock rods have #s stamped on the rod and cap. The #s must go on the same side.

I got that part and made sure to keep the caps oriented the same, but Maltese Falcon seems to be saying you can put the whole rod in backwards.

Stu

I rebuilt my first VW engine (40-horse) in 1970 and installed the pistons with the arrows pointing toward the front pulley

Marking face the sky

T4 rods are straight but stock pistons have a pin offset which smooths the motion around tdc.
If the offset is reversed the piston will rock before tdc is reached and the knock may be noticeable.

Ok Everybody here is what I know.

I just lowered the engine down and removed the right side head and #3 p/c and rod assembly.

The arrow on the piston face is pointed towards the flwheel

The numbers on the edge of the rod and rod end cap are mated together on the same side.

The small rod end bushing appears to be good. I can't feel any play or wobble with the piston wrist pin installed.

Is it possible that I put the rod on upside down? I didn't have the presence of mind to pay attention earlier today when I took it off the crank to see if the numbers were on top of the crank or the bottom.

I guess I'll have to pull off the #4 p/c and rod and see how the #4 rod was put on.

Should the rod end cap numbers be installed on the top or bottom of the crank?

If I put the #3 rod it on upside down will the engine knock? So far I don't see any really big obvious problems but I'm sure something is wrong. Any help appreciated. L

Numbers face the sky, as in UP.

End play shims done properly?
Oil pump new? Type 4 or modified type 1?
Flywheel stock or resurfaced?
Flywheel bolt head show any signs of hitting?


Foley explained the answer to your piston and cylinder questions already....read all the answers, slowly.


Rich

dont the rods a a tab or tange on one side of the rod? on the narrow face lengthwise between the big end and small end?

If you're torn down this far, probably a good idea to check all of them

The way I read what Chris said above is that there is not "right-side up" for the rods.

Only the pistons (if they are stock).
Am I still misunderstanding?

Stu

That's right.
Type 1 rods have an orientation IIRC. T4 rods don't.

The stock piston offset is primarily for quieting the piston slap. They can be reversed for a slight hp gain.
The aftermarket pistons I use have no pin offset, therefore can be installed either way.
That is until I cut eyebrows for valve clearance.

I guess I'm a little confused now. Am I getting conflicting answers on the rods orientation on the crank?

Anyway these are stock type 4 rods and the factory Kolbensmidt pistons and cylinders

-the end play appeared to be set properly with no excess in movement
- I reused the stock type 4 oil pump
-stock flywheel used and not resurfaced. No evidence of the flywheel bolts hitting.-

Don't worry about the rod orientation.
Just make sure the arrows on all the pistons are going the correct direction.

Update. Chris I pulled #4 p/c and rod off and compared rods

#3 rod is 3mm SHORTER than #4 rod. Coudl this cause the knock in #3

I also checked and #4 rod was installed on the crank with numbers on the end caps both pointing down.

So when you checked the deck height you didnt notice that one was different from the rest by .118?

(3mm is 118 thousandths when the deck is only 40 thousandths...)

It is possible that the piston with the longer rod is actually hitting the head.

Did you measure from the bushings, or the overall length of the rod?

Stu

stu. I measured the rod end to end and the shorter one from #3 is 1/8" shorter than #4.

I don't think #4 is hitting the head but I'll check. As I said earlier the knock is coming from #3 which is the "shorter" rod

I checked closely and don't see any evidence of either #3 or #4 piston hitting the head.

I do have another stock 1.7/1.8 rod that is the same length as the longer one #4. Would it be an option to use this one if the deck height checks out?

How are you measuring rod length? I would expect that it should be measured from the center of the big hole to the center of the little hole. I would also expect that a variation in length would also mean a variation in weight and your knocking, maybe?

If you have this thing torn apart, get you some matching rods.

Someone has to have a set and you could re-bush and be right as rain. Or buy these... $120

RIMCO RODS for TIV

Pull the rods, measure them, and weigh them all too. It's actually best to have the whole rotating assembly balanced, but then you'd need to split the case again

If you don't want to go that far, you can do this:

Weigh each piston (including the wrist pins) and each rod and write down your findings.

Then mate the light pistons with the heavy rods and see if you can achieve equal weights. If they're 'off', you can grind some meat off of each heavy rod until the total weights of all four piston/rod assemblies are equal. Ideally, each piston should weigh the same, and each rod should weigh the same. (An Ohaus triple beam scale comes in real handy for doing this)

Click to view attachment

Mark. I've looked closer at both rods.

It appears that the end square tit on the very edge of the small end of the of the #3 rod has been grinded down about 3mm.

This is probably why it measured shorter. When I line both rods up where both large and small openings are even then both rods appear to be the same length internally.

I will try to get them weighed tomorrow. Any advice appreciated. L

That makes sense. I didnt think you could put in a rod that was 3mm longer than the others from bushing to bushing without seeing that when you decked the cyls.

The guys that balance engines will also verify that the rods all match weights on both the small & large ends.

Stu

stu. so they weigh both sides of each rod individually? If so I'm sure #3 rod will be lighter on the small end where 3mm of metal has been grinded down.

Could this throw off the balance of the rod and cause a knock?

Click to view attachmentHere is a picture of the rods. #3 is on the right side.

The retangular end looks to be possibly grinded down on #3. Not sure if this was done to lighten/balance the rod.

It appears that they measure the same distance from the center of each hole but I guess I need to have a machine shop possibly check this.

That's highly unlikely.
The knock sound is more likely to come from something out of dimensional specification such as a con rod big end loose on the crankshaft, or a piston loose in the cylinder, or a valve out of adjustment.
A balance issue may cause a vibration which will become more pronounced at higher rpm, but not a knocking sound.

If you are really anal about your balancing:

https://www.youtube.com/watch?v=QLpiF0E0EJU

Stu