Engine is in. Goes very well. More noise from the forged pistons than I expected but I gather that is par for the course with 4 thou clearance.

John if you are using 0.004 inches piston clearance (4 thou) then it is just tooooo much clearance.
I use JUN cosworth pistons on my engine, despite people telling me that they are regular cosworth pistons, this make for a higher CR (8.5:1).
So here is my story the first time I installed this pistons I did it with a 0.004" as this is what I thought while trying to understand the japaneese instructions that came with the JUN pistons. I ended with a terrible piston slap noise, which ultimately led to some oil comsumption .....
After this experience I asked around, and also got an aswer from JUN (it took them 2 weeks to reply the email) and here is what they said:


Dear Mr. Carlos Hiraoka
Thank for your e-mail.
If you make piston clearance 0.004" for JUN piston, it is big in JUN forged piston.
0.004" = 25.4mm/1inch x 0.004 = 0.1016mm
Right piston clearance 0.04mm
If you have piston noise from engine or oil smog with blue from muffler, you have to make boring process by 0.04mm once more.

Thank you
Junichi Tanaka


Jap english is funny, well ..... I had to source another engine block and now I have 0.04mm (which is 0.0016") piston clearance, with NO piston slap, and have already done 40,000 kms on the engine with no problems and with high boost (just to make it clearer I use 1.5bar max) :D

Carlos H.


[Edited by carlos_hiraoka - 6/30/2003 3:04:10 PM]

But the pistons in John's engine are not Cosworth.

The JE pistons I'm using are supposed to run a 0.035-0.045" clearance. But then I wondered, is that with an alumnium block or an iron block, surely this will have an effect.

Paul

ok fair enough, I have seen and heard a lot of high power (2 bar boost level) DSM engines built with JE / Wiseco pistons that were noisy ..... thought that John had cosworth pistons.

Carlos H.

i use cossie pistons on cdb, with 3 thou clearance there is no piston slap hot or cold.
when i ordered those, i had an option of JE pistons too, but was told that the boring/honing has to be more precise, as if not, would lead to bad piston slap....

ian

sorry to 'hear' it john :)

Ian,

I know in this case the bores are individually honed to match each piston.

i don't think we should speculate just yet.

paul

Paul,

yes mine were matched to each piston too.

sorry, wasnt having a go or anything, was just saying what i was told thats all.
i cant wait to see the results of this engine, good project, good luck jb :)

ian

You should use 1 inch wrap for headers and only overlap them by an 1/8th of an inch. Too much overlap leads to hot spots and fatigue, especially around joints. Also try and avoid wrapping the primarys together, however if the manifold is poorly designed then this becomes a tad tricky.

I also use 92mm Cosworth pistons at just over 3 thou, slappy on start up but sound "normal" once warm. Too much clearance though IMO. Flickers the 2nd light on the KL on cruise, 2 greens and the 1st amber is par for the course from 7k up.

BTW you can get forged pistons which actually have lower rates of thermal expansion than then some cast ones...

We wrapped individually where we could but it got very tight in places.

I now have enough information to be able to give a provisional update to my project :) Mixed feelings, with a very lucky escape and a warning.

Engine was removed just 2 days and 100 miles after it went in because of excessive noise which we thought was piston slap. I can email MVI file of audio/video to those interested if you email me requesting it, but it is 3MB.

In fact the cambelt tensioner is ****ed. Luckily all the valves and pistons have survived the incident and there was no contact evident.

Shame we did not know that cambelt tensioner failure is a great impersonator of piston slap as I have now realised searching old threads. It seems they are notorious on Phase II engines, and none of the cognoscenti thought it was a problem reusing if they are checked (especially since they are £220 each approx). Since it had only done 30000 miles on my original engine it may be time to revise this view even at a routine cambelt change on Phase II engines, even if it does dwarf the cost of the cambelt. The tensioner APPEARED TO BE OK but clearly was not doing its job.

Whilst the engine is out a few other minor issues will be checked before it goes back in, mainly for paranoia's sake to make double certain there are no more potential issues.

Without any prompting I would like to give credit to Lateral Performance and SMG for the way they have handled this issue without prejudice. Until the facts were known I did not want details in the public domain as it would have all been speculation.

It unfortunately appears to be a simple component failure (completely unrelated to the engine build or parts or to the guys that kindly helped with building up the supplied long block to go back in) that I have experienced and something for the wary to consider strongly IMHO.

Oh, another thing, as usual T-uk was right if you look back in this thread :rolleyes: :D :p

Good job you did do the investigating. Could have spelt disaster.
IMO the new tensioners are crap. Very easy to swap to the old style, that very rarely give any trouble.

suppose it's good'ish news.

What was the noise then?, due to the tensioner faliure - yes, but was the tensioner itself making the noise or engine parts coming in contact due to tensioner faliure?.

Bit of an off the track story for you(just came into my head).

I replaced the tappetts in my cossie once without a manual for backup. Done the job, then I rang a 'specialist' for cambelt timing setup, fired the old girl up, lots of noise.. thats okay I thought (thinking back to my sisters cvh being noisey for a while when I done the valve stem oil seals), so I took it for a drive (approx 5 miles), got back.. stil bloody noisey, turned it off, rang another specialist, they informed me that out of the two timing marks on the bottom pulley I'd been told the wrong one.

Thanks to someone I had been driving around with the valves nicely making contact with the pistons:rolleyes:, when I re-done it it was fine, kept it for a year or so after, no probs:D

Excellent news.. My heart dropped when I started reading..

I must admit it would be my style to use second hand cambelt tensioner.. but when there is so much money involved..

Glad there was no contact.

David

Nice to hear you sorted it out John.

I was starting to see horror pics of my future rebuild..

Ohh and what a terrible noise the engine made :o
I wouldn't manage to drive it for a yard !!

Hope you have it back in your car and get it running soon :)

Jan

So, what tensioner should I go for guys?

well stevie turbo reckons earlier.. Im watching with interest though..

David

There is no right answer guys, but I need to make a decision. Vote now...

new thread

Old tensioner, definately.
Just count the number of threads on noisy new types, or ones that have jumped teeth.
Then count the threads for the old style...none id guess

Stevie - do I buy a "new" old style part then? Do you know if I need any other brackets to do this?

Hi John,

Those clips sounded awful, glad it was nothing more than the tensioner :)

As you probably know, Steve is building my engine at the moment & insisted that I bought a new tensioner (As I would of probably used the old one too!)
I managed to get a modified Ph2 one new from Subaru for around the £100 mark (this also comes with a new idler wheel) this is apparently modified to alleviate the problems the original Ph2 item can cause.

If you need any more info, let me know ;)

Tim :D

hmm, I think I could do with that info too!

Thanks Tim. Please let me know the details either on here or email.

I would not get to excited about this revised kit i can see no differance to the others, i think thay will have to be chuck away items only to be used the once.
Steve.

Tim K,

I too would be interested in the Tensioner you fitted to a Ph2, if it was £100.

I've been quoted £194 + VAT ??

I want to get mine done when I get the belt changed, as I think mine knock slightly on the occasional start up.

I was pretty convince mine was playing up, but John's sound files have just confirmed this.

Although mine only does it for a 1 or 2 seconds at start up, then seems to have primed up so everything is tight and stops bouncing/flapping.

[Edited by Scott.T - 7/14/2003 4:55:05 PM]

Mine failed at around 12 months old, but was only noticeable when temp was less than 8 degrees, and only for the 1st 20 seconds or so. I initially thought it was slap, but when I talked to dealer he knew immediately.

Still surprised by this issue though - and would like the defintive answer on how to preload (a new ;)) tensioner for a phase 2 and/or phase 1 :)

Richard

Three sound clips:

At idle listening from above front bumper and moving back near to the middle of the block from above (http://www.johnbanks.dsl.pipex.com/109-0924_MVI.wma)
On and off load against handbrake (http://www.johnbanks.dsl.pipex.com/109-0928_MVI.wma)
Revving without load - stationary (http://www.johnbanks.dsl.pipex.com/109-0925_MVI.wma)

Pavlo has "played" his cambelt tensioner down the phone to me and it transmits its horrible sound through his block as well.

BTW ignore the spanner being dropped in the first clip ;)

Since there was no contact, we thing the noise was just from the tensioner. The pistons have been checked and there are no signs of piston slap.

[Edited by john banks - 7/9/2003 11:03:01 PM]

Any news, John? :)

Richard.

Soon, I'll let you know.