302 knocking

I rebuilt a 302 for my cobra and fitted it just before xmas. It ran beautifully 'till 300 miles when I noticed a knock at start up that went away when hot. by 400 miles, it was knocking even when stinking hot. I pulled the car off the road and dropped the sump, thinking it may be a big end. They were in perfect condition, but I replaced them anyway. Started it up and it still knocked!! tore it down (still in the car)and fitted a new cam and lifters. Started it, it still knocks!!!
What the hell is it??? It was rebored, crank reground, new pistons rings, no mechanical fuel pump. The sound doesn't go away when any of the leads are taken off, it doesn't sound like the mains (they'd rumble rather than knock..right?)
At the moment the only thing I can think of is piston/wrist pin problems, that means the whole thing'll have to come out and be sorted, but before I do, does anyone have any other ideas? I'm using a 15w40 oil surely that wouldn't cause any harm?
Any advice appreciated.
Thanks guys
Simon

I had a V-8 Pinto eat me alive like that! Even went so far as to think it might be a piston slapping around! Put the engine in another car & it went away. Next car in the Pinto... same thing... it was a bad converter... not saying it is[img]/phpBB/images/smiles/icon_biggrin.gif[/img] Something to think about[img]/phpBB/images/smiles/icon_confused.gif[/img]
[addsig]

Something hitting in pan? do ya have a crank scraper or windage ledge built on the pan?

Simon
Give us a breakdown on what aftermarket parts used (ie. pistons, cam, lifters, oilpump,distributor,etc) or what was re-used. Are you EFI or carb'd, original or aftermarket oilpan, oil-pump drive.
Then, we should be able to point some fingers in the right direction.
Do you hear the knock at idle? Did you find any metal in pan or oilfilter? Have you read your plugs?
Sorry, there are a lot of questions before you can get an answer.
[addsig]

There's no windage tray and its a manual gearbox! I rebuilt it myself with a +30 rebore with new standard (but plus 30 of course) pistons and rings, the crank was reground for +10 big ends and mains, new oil and water pumps, SVO oil pump shaft, standard dizzy, standard (but ported) heads. New double roller timing chain, standard sump, edelbrock intake manifold, holley carb. Edelbrock performer plus cam and hydraulic lifters, standard rocker arms (although I've just put in a Crane Cams adjustment set when I put in the second cam)
The knock is at idle and now as I rev the engine as well, plugs look fine. I did find a small amount of metal in the pan but couldn't see where it could have come from. What do I look for with piston problems?

<font size=-1>[ This Message was edited by: simonjrwinter on 3/1/03 2:24pm ]</font>

This may sound a little funny, but this knock, is it possible it could be the water pump?
Another thing, can you feel the knock in your steering wheel? Reason I am saying this is the rest of the package sounds right, it is just hard to diagnose without actually being there.
My advice is to hit the local autoparts house and get yourself a stethescope, and slowly move it around the engine til you locate the noise.

[addsig]

A good way to narrow it down is to pull one plug wire at a time and go for a quick ride.
When you hit the cylinder that has a bad bearing, the knock will disappear or get quieter. If the knock gets quiet or goes away on opposite cylinders, like #4 and #8, you may have a bad main bearing.

Hope this helps.

Did you align hone with new main studs or bolts? or use seasoned bolts. Clamping force of new bolts/studs requires align hone.

Did the engine sit a long time from when the pistons were put on the rods to when it was finally started up? If a wrist pin runs dry on initial start-up it can seize or partially seize and force the piston skirt into the cylinder wall hard enough to collapse the skirt and lead to a piston knock. The pins are splash oiled from what the crank slings around and are the last thing to get any oil when first started.

Did the engine sit a long time from when the pistons were put on the rods to when it was finally started up? If a wrist pin runs dry on initial start-up it can seize or partially seize and force the piston skirt into the cylinder wall hard enough to collapse the skirt and lead to a piston knock. The pins are splash oiled from what the crank slings around and are the last thing to get any oil when first started.