302 Rebuild

[Mando]

HSV300, That motor is a thing of beauty.

Regards.

[07cob]

Had some time today (its the weekend) to do a little more work on the engine.

With the damage to the top of the No.2 piston, I decided to remove the piston and check (a) for damage to the sides of the piston (b) damage to the big end - bearing or journal. Thankfully, the damage appears to be confined to the top of the piston and the mating surface of the head (as in the photos above). Here is the side of the piston:



There was also no visible damage to the bearing or the crankshaft journal for the No.2 big end.

With all this in mind, I am happy to agree with the two earlier conclusions (thanks boxhead and blykins), something has made its way into the combustion chamber and caused the imprints on the piston and head before being exhausted.

So with one piston out, it was little effort to remove the others and the crankshaft.



With all this apart, I measured the crankshaft bearing journals (connecting rod and main), the pistons and the bores and I am very pleased with the results. All were well within specifications for both size and taper.

Before removing the pistons and crankshaft, I also checked the big end bearing play and the crankshaft end play - again, both well within spec. All corresponding measurements were within tenths of thou of each other.

Next, I will be taking the block to be honed and will be replacing the bearings and the rings before it all starts putting itself back together.

Cheers


Geof

[AC-460]

With all this apart, I measured the crankshaft bearing journals (connecting rod and main), the pistons and the bores and I am very pleased with the results. All were well within specifications for both size and taper.

Before removing the pistons and crankshaft, I also checked the big end bearing play and the crankshaft end play - again, both well within spec. All corresponding measurements were within tenths of thou of each other.

Next, I will be taking the block to be honed and will be replacing the bearings and the rings before it all starts putting itself back together.

Cheers


I think while youve got the engine stripped down this far I would be boring it and throwing in a new set of pistons to match those new heads....
Take one of the old rings off and put it in the bottom of the bore measure the end gap....now put the ring in the top of the bore and measure the end gap ....I would bore it....anyway thats my two bobs worth...


Geof[/quote]

[07cob]

Originally Posted by AC-460

I think while youve got the engine stripped down this far I would be boring it and throwing in a new set of pistons to match those new heads....
Take one of the old rings off and put it in the bottom of the bore measure the end gap....now put the ring in the top of the bore and measure the end gap ....I would bore it....anyway thats my two bobs worth...

AC-460

Great idea - I will check this out.

EDIT: What would you expect for a good/bad result for the gap - top and bottom?

Thanks


Geof

[AC-460]

Originally Posted by 07cob

AC-460

Great idea - I will check this out.

EDIT: What would you expect for a good/bad result for the gap - top and bottom?

Thanks


Geof

The bore will always wear the worst right at the top of the stroke where the piston gives a slight rock before it goes back down...when you hone an engine you usually keep honing until youve honed these wear marks out....
By doing this you take more meat out of the top of the bore than the bottom....so when you put your new ring in the bottom of the bore the ring gap will look OK but when you bring it to the top the gap will have probably doubled this cause poor compression and wears the piston ring shoulders because the ring is continuously opening and closing... the oil rings will wear first causing oil usage.....