approx 4k been done !

 

looks like the compression ring isnt doin its job properly!

 

looks to me like the engine has been driven like a pussy for the 1st 1k miles, not given any load to bed the rings in properly and create a good seal as you can clearly see the blow by (burnt marks) after the compression ring.

IMO of course lol

 

solution ? new rings only ?

 

what do the bores look and feel like??

were the ring gaps ok in the bore?

 

Thats exacly the problem

 

lol at these replies

defo had some blowby issues, some may say its because your running to high compression by the 'pf' rules you have to be less than 7.0:1

but on a serious not, i would check the ring gap in the bores pal, looks very big there, but that could well just be the close up, measure the bores tolerance and check it against the piston size pal.

 

mark, the gap does look fairly large but as said, ould be the pic

BUT

it looks black all around the edge of the piston, and the ring looks 'burnt' all around the edge too, unless it oil maybe?

its brown see

of course, i am NOT an engine builder, or with any mechanic qualifications at all (still reckon i know more than most tho )

so i could of course be talking arse

 

i rechecked the rings they are smooth and shiney no "brown marks"! ?
the pussy running seems to hold true as when i got this engine running i did in deed run it very lightly no load no high revs for a couple of hundred miles.
know what to do next time

 

seriously mate, i know peeps dont usually want to, but giving it a bit from the off is not usually a bad thing.

take it easy for like 50 miles, then give it some.

if something was to break, it would have done it by then.

 

ok if the rings / bores have not mated! whats the action needed to sort it ?
new rings only or rebore and new rings/pistons ?

 

you need to check everything over mate sizes of rigs bores and pistons to be sure you got al the right bits, should not have them burn marks down past the first comp ring not to that degree

 

as said, if it all measures up ok, a hone and new rings should be all it needs

and then run in properly lol

 

Also looks like its run a bit lean with too much ignition advance to me...

Did you get any det?

 

What was the piston to bore clearance?

Given that it anything it seems it may have been loose to start with i should think a rehone on new rings is out of the question.

 

i've got a spare block std block so i think i'll just get that bored and honed to the pistons and new rings ? best bet ?

 

well it depends on what the cleraance is on your current one, but yeah that sounds like its probably the best option.

what was your piston to bore clearance?

 

got to measure it. but when it was built it was 6thou

 

6 seems a little generous TBH mate.

About half that would be more normal.


Ive gone for 4.5 on my engine, but only cause im specifically building it to take a lot of heat and im not expecting it to do tens of thousands of miles anyway.

 

PS

How accurately was it 6 thou?


My experience of most peoples work is pretty shocking TBH, ive only acutally got one person i REALLY trust to get this right to within a tenth all the way up.

most places trying for 6 would end up with 9 in places based on what ive seen!

 

why is there a second compression ring? to catch what gets past the first ring ?
so why is it such a problem that theres a bit of blow by?
my piston only has blow by marks on thrust face and not at the sides or back of the piston? any comments

 

possibly that the bores have ovaled if its only on the front face.

how old was the block you used?

 

second ring should ideally only be seeing a moderate amount of gas, the way your piston is discoloured looks like its more.
If its on the thrust face i should have thought that implies it means the piston was rocking excessively in the bore and exposing a lot of the ring at that point, but TBH its not very easy to make guesses based on a not very good picture and a vauge description!

 

well same as all 11years etc. but it was not a 16v or turbo and had been in my family since new and i knew that it had not been thrashed!
thats why i picked it, i had a good look at the bores now and its apparent that the cross hatching is smoothed off respectively. i.e
no1 had good compression and the cross hatch is still very evident.
no2 had less good compression and the C/H was a bit less than above
no3 had even less good compression and the C/H was less than no2
no4 had bad compression and the C/H was almost not there!

 

Certainly sounds like it was bored by a wanker then

But could equally be fuel has washed the bore clean and increased friction by removing the oil

 

what do you reckon for block No2. 3-4 thou ?

 

Are you going to be running nitrous?

What do the piston manufacturers say as it does vary a little.

4 thou seems very generous to me though, even if you are using a little nitrous on it.

3 thou if you arent sounds more than enough, i really cant see that being too tight, its still double standard clearance!

 

PS

you will obviously be better off with new pistons as invariabley with excessive bore clearance it resluts in lots of wear to the skirts as they tip.