knocking in new motor

Mr bayce · tinkerer Joined: 26 May 2002 Posts: 328

Talk about fucking annoying... i just got my motor back and put it in this morning, and when i started it this afternoon, it started first go but it knocks and has noisy valve operation (could be double row timing chain or something) but the knock's whats got me worried, you can feel the knock through the tappet cover..

Is there any way the knock could be caused by something simple that doesnt require the motor to be pulled out again and rebuilt AGAIN????

AND BEFORE YOU ASK,

* yes its worked
* no i havnt tuned it yet but turning the dizzy doesnt change it and it idles pretty smoothly for a 35/70 with massive lift...
* yes theres oil in it
* yes its brand new and was just rebuilt

PS no bullshit plz

MRS_GEMI · backyard mechanic Joined: 16 Dec 2002 Posts: 729

if its a new engine and that was the first start it would normally make lots of noise until the oil seeps through the whole motor. i do not know if this is what is happening to you but it would be best to speak to ur mechanic/engine rebuilder. my timing chain on my twin cam (double row) is making a terrible noise (well thats what we think it is anyway).

Mr bayce · tinkerer Joined: 26 May 2002 Posts: 328

yeah i looked at it and it comes really close to the front of the head, like 1 or 2 mm where the two bolts screw down into the timing case, maybe its rubbing a bit, i can file that down no worries

i had it running for about 5 mins total on and off while trying to set up the fuel pump in the boot, and it hasnt got any quieter hmm..

badboygem · tinkerer Joined: 31 Aug 2002 Posts: 132

um im not too sure about this but.....when u say worked how much do u mean??? i pulled a g200 down once.....had been running a bigvalve 1600 head on it that had been shaved considerably...~12:1 comp.....and it had huge grooves in the inside of the timeing case where the d/r chain had been rubbing because the tensioners couldnt be tightend enough to take the slack, it also rubbed a fair amount on the block aswell. dont know if this is relavent, but id imagine it woulda made sum noise

Mr bayce · tinkerer Joined: 26 May 2002 Posts: 328

ok the chain felt pretty tight and theres heaps left on the head, its only 9.5:1 comp , How could it be excessive bearing clearance when its all new??

but yeah its g180 block, 2l timing case 2l oil pump, 2l crank & rods all ACL bearings, over size intake and exhaust valves in ported big valve head, and the bottom end is balanced also...

Mr bayce · tinkerer Joined: 26 May 2002 Posts: 328

does a double-row timing chain have a different link?, like a joining link that is a bit different shape maybe? ..could it be the timing chain rubbung in the head making the valvey noise and the joining link in the chain making the knocking maybe???

i hope so, im not pulling the motor out again!!!!

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

did u file the bolts near the water outlet for the water pump? is it a dull knock or a loud knock/

ExGem · tinkerer Joined: 10 Feb 2003 Posts: 110

I'd contact the place you got it built and let them have a look at it. If you fuck around with it to much you may break something and then they have an avenue to get out of the warranty.

TXcoupe · petrol head Joined: 05 Oct 2001 Posts: 1675

yeah definetaly

Wagonslut · tinkerer Joined: 11 Apr 2002 Posts: 376

i had a knocking noise in my old 1800 once. several ppl swore it was number 2 main bearing, until we pulled it out and realised the flywheel was loose! worth a look, as for the valve noise, cant help u there buddy, good luck!

Twisted_torque · tinkerer Joined: 26 Feb 2002 Posts: 240

I recently did basic rebuild working with a mechanic assisting in complex bits.. basically just saved him time working on it. The problem we faced when working the head is that when u reseat the valves the spring is no longer under under the same tension because the valve (especially if u have fitted larger valves!!!) sits deeper into the head even if minutely u need to put special shims (they are hardened washers) under the base of the spring. Once the shims are in the spring is back to original compressed length, also under correct tension... otherwise even at idle there is a very slight valve bounce but make a hell of a racquet. Get a mechanic to check the compressed height of the springs (only need to remove the tappet cover) if these are not within original guidelines there is your problem. If that is problem shouldnt be too much to fit.

Gold TX Sleeper · backyard mechanic Joined: 05 Feb 2002 Posts: 509

Maybe having a 'massive lift' cam, oversized valves and a shaved head is causing the valves to kiss the piston crowns... Have you rechecked your valve follower clearances ? But then again, having all that extra shit has prolly made your required clearances a bit out from stock settings - find out what the recommendations are for them and recheck them. The blokes you got to build the motor (if it wasn't you) should have been cluey enough to make sure there was sufficient clearance between the valves and pistons at T.D.C.
From experience most high lift cams will give a noticeably lopey idle so it's a little weird that yours is smooth, but then again i've seen stranger things.
Jasyn...

Gene FJ20DET · Posted: Mon Mar 10, 2003 12:22 pm Post subject: Re: knocking in new motor

yeah i was thinking that. the valves hiting the piston bit.
also how much has the block been decked and the head been shaved?? mine was done so much (the pistons were siting out the block about .5mm at top dead center) that the timing chain was slaping on the timing cover. i had to run a .5mm thick shim inbetween the head and block to make up the differnce.
ie, u have shaved so much of the cam is actually closer to the crank or what ever, meanign the chain cant be fully tensioned, (unless u get adjustable ones)
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Frederick Stienheld · petrol head Joined: 05 Sep 2002 Posts: 2719

Ok this might sound quite stupid but this happened to me. My engine was rebuilt and I had been driving it around for a little while and then all of a sudden it started making a knocking noise. It sounded to me like it was comming from up top of the engine somewhere and I could have sworn it was something to do with cam/valves. It turned out it was the alternator making the noise! Put your hand on the alternator while the engine is running and feel if there is a knock in that. Also since I replaced my standard cam with a racing one the tappets are noisier, you can hear them when idling and lights etc. It's just something that comes with having a lumpier cam. Also after a big day at Queensland Raceway my tappets become quite noisey and require adjusting.

Blue TG · tinkerer Joined: 10 Feb 2003 Posts: 183

Sounds like the chain maybe hitting the timing cover, U dont have to fork out on adjustable chains, you can just buy halflinks, for sinlge and double row, just get em from a chain specialist, my bro had to add a halflink to his chain to make up for the ~5mm decomp plate in his gem