Mopar Muscle Association UK

[quote="Mossy68"]
No seriously. What I am finding hard to understand is that like you said the bores were not correctly finished to get the correct PTW in the first place.
So why then as Carl says is there not enough left in the bore to hone to achieve correct PTW ?
Assuming that obtaining the correct PTW will remove scoring etc.

There is enough in the bore, thats why I said before he's been given a 2nd chance........so for the last time.......when that Block was bored to .+60 they added, from the sounds of it, (as I have lost track of all the different figures now).......ONLY .015 PTW clearance per side for the piston to expand, that is not enough for a forged piston, it requires a min of .004 per side, thats why they are marked...too tight.

So to put it simply, it was overbored .63 thou when it should've been + .68 to give sufficient clearance for the piston to expand... if the pistons are still ok (they need to be measured), the bores will still only need to go out to .68 thou which they should've been in the first place, thats another 5 thou from whatever the bore is NOW, that 5 thou should be enough to clean up the score marks and cause NO problems to the blocks integrity.....thats what needs to be done, its quite simple and should've been understood before, I cannot see where the problem lies, if your that worried about just another 5 thou being too much for the block then get it sonic checked.

Les

Some days it just best to

Les Szabo wrote:ONLY .015 PTW clearance per side for the piston to expand, that is not enough for a forged piston, it requires a min of .004 per side, thats why they are marked...too tight.

Some of the confusion seems to be with decimal places. 0.015 is 15 thou. 0.004 is only 4 thou. So a lot tighter than 15.

correct, ok so its 0.0015...it was probably still only bored +.063 thou instead of .068 thou finished size as stated. It needs to be all measured properly.

Mossy68 wrote: So in Carl's case the pistons could in reality be too big a diameter to start with hence the reason for the bore having not enough " meat " left in them to obtain correct PTW ?

From the Ross site...

When ROSS manufactures pistons, is the clearance built into the piston, or should I make the bore bigger?

ROSS pistons are manufactured with the clearances built into the pistons. For example, if you want a 4.030 bore, the piston will measure 4.026. Always give us the exact bore your block is honed to, and not the piston diameter you want.

But I imagen all pistons will be the same size.
Meaning you have to make all the bores the same which is the hard bit

Love this thread makes you just want to do a rebore with a tampon in a dremel to show it will work

There is no problem in making the bores the same, its whether they will clean up to the required correct finished size, that is dictated by the actual size of the pistons in their current condition plus .008 thou......so if all your the pistons are NOW 4.095, for example, finish hone your block to 4.103!....I think I typed this before didn't I?.....simple maths and not rocket science to understand by anyone

Forget about in-built clearances of the pistons, irrelevant, you have what you have NOW and it needs correcting in the simple manner described. YOUR BORES NEED TO BE A Minimum of .008 LARGER THAN THE SIZE OF YOUR PISTONS!!!

Les Szabo wrote:YOUR BORES NEED TO BE A Minimum of .008 LARGER THAN THE SIZE OF YOUR PISTONS!!!

Winner, Winnner Chicken Dinner...

Well why didn't anyone say that before?

Les Szabo wrote:There is no problem in making the bores the same, its whether they will clean up to the required correct finished size, that is dictated by the actual size of the pistons in their current condition plus .008 thou......so if all your the pistons are NOW 4.095, for example, finish hone your block to 4.103!....I think I typed this before didn't I?.....simple maths and not rocket science to understand by anyone

Forget about in-built clearances of the pistons, irrelevant, you have what you have NOW and it needs correcting in the simple manner described. YOUR BORES NEED TO BE A Minimum of .008 LARGER THAN THE SIZE OF YOUR PISTONS!!!

Yes Les you did and that is what they will be done to mate . I was just explaining to Gary that the pistons cant be too big because the under size is built into them.

Block is back and he re honed out as much as he could do on the large over bore it already has without going into or getting close to the next 10thou overbore to get all the scratches out he was a bit concerned the block wouldn't take it, but 95% are gone and there is a good hatch over what is left and he says shouldn't be a problem as using total seal rings, I think he put another 4thou into it.

Ive also been thinking, most of the valve train components I have are for oil through pushrods, is it worth me doing the mod to oil through tappets, and if it is what would be the best way, drill and plug the oil way in the block or spin the cam bearings to cover the oil way?

Or will it not hurt to have both systems oiling? Oil pressure issues this way I wonder?

As long as the stock oil feeds are working as they should I really wouldn't bother.

Yes they are but my main concern was having oil through pushrods and rockers oiling as well as the stock system, would this cause an issue?

Carl wrote:Yes they are but my main concern was having oil through pushrods and rockers oiling as well as the stock system, would this cause an issue?

If you introduce another form of gallery into the present oiling system you will lose some pressure and increase volume, that's just plain physics.
How much actual affect it has depends on the quality, type and capacity of the pump, tray, pick up etc.
I assume you're buying a new pump? I wouldn't use the old one.

As a side note if the bores aren't 100% installing top quality rings won't save the job and will be a somewhat wasted excercise, just use some £100 a set file fit rings