The dreaded knock. Options

[atmadsen914]

I recently rebuilt a 2.0/4 motor and installed it in my 914. After getting many fuel system issues sorted out I finally was able to drive it a few times but after about 150 miles of driving. It developed a knock. I readjusted the valves and the knock seems to get better but never goes away. The knock is audible from idle to about 1500 rpm then smoothes out. When I roll the motor over by hand I can hear a knock on every cylinder.

The motor is basically stock with the exception of a web cam (73 grind).

I am about to pull the motor and start disassembling as the sound does not seem good. However after many hours of tinkering has not gotten worse.

Ideas? or do I just get to do it all over again?

[McMark]

Slight valve/piston contact is a possibility.

[Jake Raby]

Sounds like a worn lifter bore... OR the camshaft thrust bearings are zapped.

Or a couple hundred other possibilities. Get a video of the sounds and post it, I can probably diagnose over the net.

[Cevan]

Get a video of the sounds and post it, I can probably diagnose over the net.

Well, you can't beat that for a response.

[2-OH!]

Same problem here until I realized...A. I used a 1.7 distributor and, B. Once you go to the Webcam 73, you can no longer use the book timing...

Make certain you have a 2.0 distributor and experiment with the timing until you loose the knock...Timing is a tricky thing so watch your temps...

2-OH!

[Brett W]

If it is a mechanical noise, could be contact between the cam gear bolts and the oil pump.

[PeeGreen 914]

(IMG:style_emoticons/default/blink.gif) Glad we have people like these to help with this (IMG:style_emoticons/default/beerchug.gif) Hope between the powers that be you will get this licked (IMG:style_emoticons/default/drunk.gif)

[atmadsen914]

Thanks for all the responces!

Jake I might take you up on sending over the sound. I will pay for the service of cource. But before I do that. I did use a 1.7 distributor. Is that an issue? And and I set it at the stock timing. Should I adjust that?

I relize this is like diganosing cancer over the phone.. in the dark.. with a bad conection.

Thanks for your help everyone.

[atmadsen914]

Here are two clips of the idle. 2nd has two revs in it. (they are the quiet spots) Notice as I shut it down it seems to be very loud.
Timing seems to not effect the sound.

Thanks again.

[brant]

Ouch...

if that diesel sound is your knock then I think you had better not start it again.

I however am no expert what so ever...
still that sounds bad..

bump for Jake's expert ears

[atmadsen914]

My thoughts exactly! I assume it needs to be disassembled. I figured I would ask before I started over. Practice makes perfect.

As an FYI. I am using a mega squirt system and adjusting the idle mixture seems to make some difference. I assume at this point that this is a coincidence.

[Brett W]

Pull the valve covers off and look at the rocker arms before you drop the motor. Look for anything out of the ordinary. Otherwise it is time to pull it apart and see what you see inside the case.

The dizzy won't make any difference in this case.

[Cap'n Krusty]

You put the pistons in right side up? The Cap'n

[SGB]

exhaust is tight? Those valves are RIGHT THERE at the exit from the head. They actually do go "tapitty-tap" in a distinct metal to metal way that is essentially muted by the rest of the exhast-
BUT-
If it does this on rotation by hand, there is something mechanical going on.
Did the rockers go back on OK? Sure those pushrods were seated when you set the valve adjusty?

[atmadsen914]

exhaust is tight? Those valves are RIGHT THERE at the exit from the head. They actually do go "tapitty-tap" in a distinct metal to metal way that is essentially muted by the rest of the exhast-

I wondered about this. As part of the project I installed a set of headers. They are very dificult to get tight. (angle of the bolts) So I am not 100% that they are tight as the need to be. Will that give you a for lack of a better description a dieseling at idle?

Because at speed the motor sounds perfect an builds good power.

[atmadsen914]

Pull the valve covers off and look at the rocker arms before you drop the motor. Look for anything out of the ordinary. Otherwise it is time to pull it apart and see what you see inside the case.

The dizzy won't make any difference in this case.

Rockers look perfect and have been holding adjustment perfectly.

[Mark Henry]

What was the end play?
Keep rolling it over as you take it out and tear into it, just in case you get lucky.

[atmadsen914]

You put the pistons in right side up? The Cap'n

I sure hope so.

[atmadsen914]

What was the end play?
Keep rolling it over as you take it out and tear into it, just in case you get lucky.

My current theory is actually endplay. I fear the flywheel bolts have loosened. (I was not the one who installed them). As the sound seems to be very similar to when you roll the motor over on the bench without the fly wheel attached.

I have no play however on the front side but it is difficult to test with the motor in the car.

Just a theory at this point.

[brant]

What was the end play?
Keep rolling it over as you take it out and tear into it, just in case you get lucky.

My current theory is actually endplay. I fear the flywheel bolts have loosened. (I was not the one who installed them). As the sound seems to be very similar to when you roll the motor over on the bench without the fly wheel attached.

I have no play however on the front side but it is difficult to test with the motor in the car.

Just a theory at this point.

not questioning your abilities at all
but how was the end play when you first built it?

I had one with loose end play that I decided would be "good enough"
it was on the outside edge of the specifications
it broke the crank shaft in two
had a horrible knock at idle and deceleration
but under load the crank halfs would catch each other on the angled split and the noise would go away...

I hope thats not your situation but how was your end play specs when you did your build?

brant