So heres the low down, cylinder #1 is giving me major troubles. It seems though the piston is hitting the spark plug. (Ie thread name :jamie: ).

 

I have double and tripple checked they are the right plugs. I have double checked the distance from the piston to the start of the spark plug thread (TDC).

 

I have cranked it over, the spark plug does not hit, only when it is fired up does it manage to start chewing on the plug.

 

Totally stumped. I was thinking maybe a lose conrod cap ? But wouldn't that be noisy as hell, there really is no death rattle noise when it is fired up. I'm totally perplexed what to do???

get some shorter plugs and give it a go, something with similar heat range

show us a pic of the plug, this doesnt sound right at all

 

also what engine?

Have you shaved the head? or decked the Block?

 

 

Either way, you should be able to get shorter thread spark plugs, but that also changes the heat range of the spark plug.

 

Maybe try checking the con rod, con rod bearings, gudgeon pin etc.

 

 

Try shorter thread plugs and see how it goes..

For a temp repair add a extra sealing washer off a old plug, Are you sure the thread is factory and not a misaligned helicoil.

strange that its only 1 piston.

are all your clearances in the bearings right?

did you plastigauge everything?

how was the gudgeon pin?

crank isnt a bit bent is it?

I have done a dogie and spaced the spark plug, but I don't like it. All the clearances are right and yes it was plastic gauged. Yes the head has been shaved but its only in cylinder one.

 

 

Its a 4agze (in title :) )

 

Ill get I photo of it when I get some time (dodgy and fixed the clearance back in motor :jamie: ) Crank along with everything else was checked before it was put together.

 

How do I check if it is missalinged, ive check everything with a depth gaige and compared to cylinder 4 everything is identical. Ie, distance from piston to top of head and lenghth of thread. I'm so frustrated, why its so different.

 

I'm temped to pull it down and rebuild the thing.

Edited April 19, 200917 yr by Jason

I have done a dogie and spaced the spark plug, but I don't like it. All the clearances are right and yes it was plastic gauged. Yes the head has been shaved but its only in cylinder one.

 

 

Its a 4agze (in title :) )

 

Ill get I photo of it when I get some time (dodgy and fixed the clearance back in motor :jamie: ) Crank along with everything else was checked before it was put together.

 

How do I check if it is missalinged, ive check everything with a depth gaige and compared to cylinder 4 everything is identical. Ie, distance from piston to top of head and lenghth of thread. I'm so frustrated, why its so different.

 

I'm temped to pull it down and rebuild the thing.

do a depth test with plugs installed from top of plug to the tappet cover see if plug no 1 is sitting in further.

or Unfortunately it may be time to strip down and get to the bottom of the problem

Edited April 19, 200917 yr by KE30_KE35_KE55

missed it in the tittle. The spark plug is a long way from the top of the piston in this engine, sounds like something is majorly wrong here.

maybe theres a bolt lurking in there, or something dropped in there and thats pinging around and damaging everything, would explain why only when running..

got pics of said plugs?

I would to say never to start this thing again til its pulled down. I am guessing its already a lost cause

i did that and regretted it.

 

thrash the f@$ker til it breaks :jamie:

pull the sump off and have a nice little sticky beak inside the bottom of the block that nearly saves havin to pull the head off

just my personal opinion but you wont see anything, you see the diatance from the piston to the head in any stock 4ag (assuming it is) is between 1.15 and 1.2mm, so therfore the piston will always head the head well before the plug.

 

I have to admit the reason I want to see a pic of the spark plug is to see if its detination damage not impact damage. Please don't take it personally Jason

I remember reading somewhere in a Q and A mechanic training manual of a problem that sounded similar - turn the motor over by hand and everything was all nice and rosy but hit the ignition and things went down hill from there.... one cylinder would drop out and its spark plug would get trashed. It was worked out to be that the top of the piston (or the head/dome/whatever) broke free and depending on where it sat it'd either work with the rest of the piston for a little while till it overcame the compression and slammed into the spark plug and rebounded (or was sucked from the vacuum) back down the cylinder... sounds odd ball but it can happen.

 

But all in all it might just be time to take the head off and have a better look at the damage.