Dave,Dave,Dave,Dave,Dave
If i read your last thread right you used an arc welder to weld up an aluminium manifold?????
Arc is for steel only thats why a piece came adrift and entered your engine.
At least its not to bad and i hope you get it going without to much expence.GREG

The one that i was sent by Greg (vixen) was an A15 polution manifold and had those two ports in the back of the manifold for some vaccuum crap im guessing. As i did not have the 'bit' that went on there, what better way than to cover it up...

Dave

Oh one question, is TIG welding that hard as it looks? It uses tungston yeah? Why is this better on alloy than MIG etc..?

Why did the manifold need welding repairs in the first place?

Finally some good news! Took the head & a picture of the piston into Merv Gray today (guys who built my engine) and they said that a forgein object is the result of this, and sure enough we filed a bit off the no. 4 head swirl & put it under the microscope. Does turn out it was the slag from my sh*tty arc welding!
Must have had such a suck & poor penetration from the job that it sucked a bit off and into the chamber.
There is no damage to the head apart from the chunk, no valve/seat damage or notching in the ports thank god!

Its a relief that it is the weld and not so much detonation, & also i can get just 1 piston & the head is salvageable. They are going to run a weld in the notch and grind it down. Im going to pull the engine tommrow arvo & if im lucky mite even get it going by thursday/friday...

This time i am going to live by the rule 'do it right, do it once'

Dave

Post a pic of the spark plug electrodes. Any have broken porcelein? Is the porcelein tan (it should be) or white (bad sign). Are the electrodes burned down?

I posted some comments here:


Cracked Piston & Head

No the manifold was off the car, in my garage completley away from the car.

Im not sure about a washer, my cat was roaming around in the engine bay so that could be the culprit!!!

Some pics of the carnage










I need answers please, if i dont get this car moving in the next 3 weeks my parents are going to get rid of it. Their sick of it sitting in the garage not 'doing' anything, and frankly - so am I. They have no Datsun faith and im sorry at the moment neither do I, or it could just be my lack of skills at a mechanic!

What im really looking for is some answers into how and why this could happen so quickly. It ran fine(ish) on the way home. Parked it started it, rev'd it to about 4500RPM then try to let it idle - it did not as it hadnt been doing it all morning then tried to start it again and the piston seized and couldnt crank it by hand either. Suggestions?

There looks to be a bit of detonation on the pistons surface, what causes this? Is it bad mixtures and gas pulsing?

Help
Dave

I'm guessing that you did the welding repairs while the manifold was still on the engine. Not such a good idea.

The 'quick, easy & cheap' method isn't always the way to go as you are finding out.
Is it possible that a small child could have put a couple of nuts or washers down the carb when the air filter was off?
This happened to a friend & his Big Block Dodge engine many many years ago.

Ok update on what happened...

I pulled the head last nite and found a nice dirty crack along the crown & dish of no. 2 piston and a large chunk taken out of the dish (about 2mm by 2mm)
Also there is little chips take out of no. 4 piston about 10 of them, this is the same on the head. Little chips on no.4 swirl & a large indentation or 'bluge' in the swirl of no. 2.

I have no idea how this could have appened!!but my guess is something got inside my engine when i had the air cleaner off to adjust my choke.
On that note, i did weld up 2 holes on the back of the manifold with an arc welder - not a great job & didnt completeley fix up the vaccum but ill get it done with a TIG tommrow. Could some of the slag or splatter have broken off (or some that was lying in the manifold) caused my engine to do this?

I will post some pics of the carnage tonite.

Soooooooo how much will a new set of pistons cost & i hope the head is salvagable by surfacing the head.... otherwise more money needed for a A15 head.

God dammit
Dave

Any clues on what happened to your motor,hope its not to serious.GREG