32 replies to this topic

[Jellevandok]

A new engine shouldn't be having all these problems. After starting the engine I took the car straight to the specialist. He knew it was a brand new engine so he has been running it in slowly on the rolling road with a normal fuel mixture. The spark plugs looked perfect, no signs of overly rich mixtures. The oil consumption started almost straight away as soon as the oil started to get the working temp. The amount of oil that was on the pistons after shutting down was quite something... I'm of to the garage to take it apart. Will follow up on this.

[Artful Dodger]

what oil is being used??

[Jellevandok]

http://www.commaoil....ide/view/6/262/

Comma 20W50 classic oil.

[Jellevandok]

and the gaps should be at 30 degrees to each other when installing. ( so when looking at the piston from a birds eye view the gaps in the piston rings look like an aircraft propeller)

I've laid the engine on the front and we took out piston nr 4. The first thing I noticed was that the gaps of the compression rings were aligned at 11 o'clock and the scraper ring gap was very near at 1 o'clock. So no propeller there. I've let the other pistons in place for the specialist to check out. The bore seems to look normal but I still think the pistons are quite loose in the bore.

Edited by Jellevandok, 08 July 2012 - 02:42 PM.

[Artful Dodger]

then all of the piston rings are aligned then it lets oil though into the combustion chamber.

piston to bore clearance is good, not a worrying point at all!

[Jellevandok]

Let's hope it's as simple as that so it won't have to be a very costly experience. In that case the build up could start by the end of the week and the first track day is in sight. Thanks for the support so far!!

[MiniLuke]

I'm sure this has been covered loads of times. Ring gaps being in line doesn't matter as they rotate freely in use anyway? Is this not right...

[Artful Dodger]

Let's hope it's as simple as that so it won't have to be a very costly experience. In that case the build up could start by the end of the week and the first track day is in sight. Thanks for the support so far!!

hope so! if the bores are at all glazed ( as said by AC dodd, caused by bore wash, thats caused by a poor running in mixture) then it would need re-honing and new rings fitted. the worst case is that the bores are on the limit for that re-bore and it needs to be taken out again, which means new pistons, rings and a rebore and honing...

but heres hoping thats not the case!

get some pictures up of the pistons and the bores:)

I'm sure this has been covered loads of times. Ring gaps being in line doesn't matter as they rotate freely in use anyway? Is this not right...

not really, if they spun in the bores surely they would cause wear:P and in any case its bad practice, as if they are all aligned you get oil leaking into the combustion chamber!

[Jellevandok]

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One said that the hone wasn't 45dgr enough. Too horizontal which would capture the oil as well.

Can't explain the horizontal stripes on the piston. When I got the engine it was very tough to turn by hand. Only doable with a socket on the pulley side. It was on the shelf for a year and a bit but I've lubricated the pistons often and turned the engine every month or so. Before use we lubricated the pistons and turned the engine by hand by turning the wheels in 3rd gear. Then we started without fuel or plugs until the oil pressure was build up nicely. Only then we started the engine for the first time.

[ACDodd]

How course is that honed finish, it looks very rough to me. Have a dial bore gauge put in the bore to verify the wear.

AC

[NED1108]

Jelle

I recently rebuild my 998. Due to other issues i had to remove the engine. I have the same wall damage. According dyno track (cruquis) i could be caused by to small cilinder piston clearance or bore wash. Bore wash is most likely caused by too rich mixture. I posted my pictures recently in this forum.

[Jellevandok]

Also if the heads had porting work done to it, it's worth checking they've not gone too close to the pushrod holes with the inlet ports, this can then suck oil into the engine.....

Another good look at the inlet port showed that there was a very small hole indeed. The maker went through the wall so on cylinders 1 and 2 he must have gotten oil in the mixture when the oil was getting warm.

Turned out that the bore was slightly big for the piston. Also the piston rings didn't close enough. That combine with the ring gaps being aligned made that there was a compression loss on some of the cylinders.

The tuner is getting some new chrome piston rings that seal correctly and the wall will get a proper hone because it was a bit rough. All in all a lot of work and money spent extra.

Bore wash can be excluded. The tuner told me the mixture even was a bit on the pour side.

Edited by Jellevandok, 09 July 2012 - 02:32 PM.

[Artful Dodger]

bad news on the head, but glad you found the problem!

so the pistons are slightly loose in the bore, but he is going to hone it out anyway? if it were me id bore it out and fit new pistons, but it can cost alot:) so if the new rings work,

[Andrew O]

Am I being stupid ? If you payed for a new engine and it is faulty why are you paying to get it fixed ?
The people you bought it off have to sort it by law.

Andrew.

[Jellevandok]

Am I being stupid ? If you payed for a new engine and it is faulty why are you paying to get it fixed ?
The people you bought it off have to sort it by law.

Andrew.

I'm living in the Netherlands. If I lived any closer I would have gone back to the UK. Now it is being done professionally so I know I can use the engine for a while. I'm giving the original builder a chance to compensate my costs. If not I will post again with his name and pictures and all the flaws I discovered.

The bore wasn't that bad that it needed a new hone and piston rings. The 'new' hone is just a light brush up of the current hone. With new rings that seal the problem should be fixed. 1000 euro further all together. :-(

Edited by Jellevandok, 27 July 2012 - 10:41 PM.