Garage786

Hi,

I just finished building my engine, got her running and the engine was making a knocking noise. At first I didnt no it was piston slap so I took the head of to see if I put the headgasket the wrong way causing oil starvation. Anyway I noticed there was quite abit of play between piston and bore. I could move pistons forward and backwards quite abit. Pistons are 84.5mm and bore is 84.85mm, what I dont understand is that the 84.5mm I had in before didnt have piston slap. I bought the block of somone of here, thinking it was a good block. But the ring decks were broken and rings were fked. I bought it of slowteg550 I think.

Anyway some people say go 85mm and some say its ok if your going over 500whp. Im so confused I dont no what to do

After putting the head on I let her idle for 45mins, the noise got slightly better. And then i drove her lightly and the noise goes away. So only on idle its there. Start her up the next day and the knocking noise is there as it was the 1st time.

So people, whats the deal

Any help would be appreciated.

Thanks
-Yasir

Garage786

Anyone????

quicksilver1689

so you have .35mm of piston-wall clearance which is like 0.01377952755907" if im correct.

.0030 to .0040 would be a good ball park figure for your setup

quicksilver1689

they will make noise when cold until they expand slightly and take some of the gap up

Syner-G-Racing LLC

piston slap is fine as long as you let her warm up before you put a load on it. what did you gap the rings at?

quicksilver1689

nothing wrong with some piston slap but large clearances can cause excessive piston slap which is just unnecessary wear.

Garage786

Top ring's were 130, I cant remember the middle ones.

Garage786

Started the car up today and there was quite abit of purply/blue smoke. This must mean the rings arnt sealing properly? But it didnt do this when I first started her and drove her...

NJIN BUILDR

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by quicksilver1689 &raquo;</TD></TR><TR><TD CLASS="quote">so you have .35mm of piston-wall clearance which is like 0.01377952755907" if im correct.

.0030 to .0040 would be a good ball park figure for your setup</TD></TR></TABLE>

It's really closer to .017" clearance when you add the .003: or so it would have at 84.5mm.This will rapidly break the skirts off the pistons. It will rock the rings off the cylinder walls at tdc.It will burn oil and have a lot of blowby/power loss.It won't run long like this.

quicksilver1689

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Syner-G-Racing LLC &raquo;</TD></TR><TR><TD CLASS="quote">piston slap is fine as long as you let her warm up before you put a load on it. what did you gap the rings at?</TD></TR></TABLE>

did you see his clearances? dont tell me that is acceptable

Garage786

Yep its definately not sealing properly anymore, ill have to go 85mm which will be on the border line I reckon? 600whp...

I think I might build a spare block on the side, anyone have a sleeved block for sale? Anything up to 83.5mm..