46 replies to this topic

[Andy500]

before you rip it apart just check the valve clearences on cylinder 4

[Elfin]

ok will do, I guess o double check that it is ok
But this wont explain for the others and the smoke out the breather

[matty...]

Ah my suspicions were right then! The only way to tell what damage has been done is by stripping it down.

I would think new pistons, rings, and rebore would be a minimum. There are a few other parts worth replacing on strip down like oil pump etc.. also.

Are you running a heater with the return to the top of the cylinder head or some kind of feed to the top of the head?

EDIT: missed this page! Yeah check the valve clearances first, but doesn't look good!

Edited by matty..., 11 April 2008 - 02:43 PM.

[Elfin]

Yes
What do you mean a heater with the return to the top, Regarding the oil pump that has already been replaced, anything else?

[matty...]

Some engines didn't have the heater hose returning to the head, I have heard that this can cause excess heat (hotspot)around cylinder 4. IIRC water tends not to circulate aswell here, especially when the thermstat is closed, so by running the heater return to this part of the head it helps with water circulation. I can't talk from personal experience as I always had my return to this part of the head.

Central oil pickup is worth getting if you don't already have one!

[RPMminiman]

matty the ones with the heater missing are generally (Ex)metro engines as there heater runs in a different way on a metro or some people just blank them off with a plate I think for race use.

Central oil pick up pipe works by taking oil from the centre of the box rather then the edge, hence keep oil pressure up whilest under heavey cornering.

As said on other pages I would dish the pistons. Simon at morspeed sorted me a set at reasonable price.

It is personal choice how far you want to go and how much money you want to spend on mods. The pistons will do the job, I would do this only to make sure you have cured your problem before spending more money on goodies.

[Elfin]

I dont think i have a returning heater hose to be honest. Anyway engine is coming out this weekend hopefully and crack her appart bloody thing !!

[matty...]

This is the hose. The one to left of the rocker cover at the front. (opposite end to thermostat)



Have you managed to investigate the low compression problem any further?

Edited by matty..., 14 April 2008 - 08:08 AM.

[Elfin]

owh right, yes i have this it goes off to the heater.
Nope not yet i am sure it was due to running without the decomp plate.
I will be working on it this weekend, so i will keep you posted!

Cheers

[matbmx]

it appears that you have diagnosed the problem to being the rings on cylinder no.4? the compresion test will indicate a loss of pressure but the loss of pressure could be Head/s gasket as that would explain the mayonaise on the rocker cap? it could be the valves not seating propperly? i would sugest to strip the head off and do a good old inspetion of the head gasket/s as piston rings dont just go like that usually. i would try fitting new head gaskets and running another compression test!!!!

[Elfin]

Hi all
right engine is out on the floor, the bores seem fine thank **** i am removing the pistons soon(next couple of days) so i should be able to tell.
When i put the block on the floor on its side water ran from the water vallys(ovcorse) but alot of oil ran under the pistons out onto the floor(as if the bores were empty), so it is defintaly looking like rings.

I have a attached a pic of my box, this looks like a side oil pickup? correct.
Are there any other parts i should look into getting buying before it goes back together?

Cheers

Attached Files

•  DSC03690.JPG   3.3MB   6 downloads

[Elfin]

Right pistons are out,

No.4 is broken around the rings
No.3 is cracked

and so on,
My new question being?

Which choice of piston to go for - Omega or powermax, i originally had powermax 73.5mm and 9cc dished.

Should i go for a bigger dish or not? e.g. 9cc or 11cc. what would i gain from this?

Or go for 9cc dish and either go for 73.5mm powermax or omega, does it matter? would either of them fit stright in?

Cheers

[matty...]

I would buy pistons with a larger dish, this would save the need of using a decompression plate and save you having to get your head chambers enlarged and still bring the CR down to a sensible figure.

The choice is yours, all depends on how much you want to spend really?

It would be worth getting the bores checked to see if they need a slight honing?

[Elfin]

BUT, would going from a 9cc dish to 11cc bring it down enough to not use a decomp plate?

[matty...]

Not pistons with an 11cc dish, I was talking more 18cc dish Accralites! With your head chambers opened to 26cc and NOT using a compression plate you be able to get a CR of Around 8.3:1 this would be good for 15psi +

If you bought 18cc Accralites and kept the head standard 21.4cc it would gve you a CR of about 9.0:1 still a little on the high side but ok for small amounts of boost 7-8psi or so. If you decide to up the boost its an easy enough job to whip the head off and get the chambers enlarged at a later date.