Any Idea Whats Caused This?
Turbo Mini Forums

Bit of background first

This is a 74mm bore 1399cc engine, Kents 274 cam, 35/29mm valve standard head, running 10.5:1 CR with single point injection and always run on at least 99 octane.

When i pulled the head to fit the Group A head i notice two clean patches, one on #1 and the other on #4 piston. Both exactly in the same place, same shape and mirrored.

You can see from the pics that the injection system has been working nicely with clean chambers on the head and a nice even brown colour on the exhaust valves in all cylinders.









Any one have any idea whats causing it, just out f interest?

MS

i havent got a clue, but the corresponding bit of the head is the area where every thing is flat and there is no shape to it ao i wouldnt of thought it would of been a hot spot or anything

could it possibly be ring blow by or something, which is keeping the area clean?

i havent got a clue really, im just making this all up, did you do a compression test on it recently?

Generally water would clean the pistons...but thats not the same as what you have....

Under what conditions was the engine last run, before it was removed ??

Similarly, under what condition was is stored, before strip down ??

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

LOL

It ran for only minuts to move it on the drive about an hour before the head came off.

Before that it was driven long and hard for two hours week last thursday.

Plugs are the right colour too.

Oh and the engine is still in the car

what deck height/gasket are you running?

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Excess petrol from the inlet manifold dripping through open valves

Metro turbo weekend driver,Mini turbo in the making again!

Definately corresponds to the inlet valves. And it has the pattern of something running down the ports and down that area of the bore.

Ah!

Possability

The car normaly sits on the drivereverse parked, the drive slopes away from the house.

How ever, why is it only the outer cylinders?


Deck hight is 40thou and the gasket used was a BK450. TBH the gasket was the wrong one. The AF460 seems to be a better fit with the 74mm bores.

can inlets 1 and 4 be open at the same time?

I'm surprised no one has come up with bore flex yet -

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."

On 17th of Dec, 2006 at 09:09pm Axel said:
I'm surprised no one has come up with bore flex yet -

Edited by Sprocket on 17th Dec, 2006.

9.85 @ 145mph
202mph standing mile
speed didn't kill me, but taxation probably will

its right below the beak...

"Turbo's make torque, and torque makes fun"

"did you know you can toast potato waffles?"

Thats pretty much as the head came off, other than the wd40 i sprayed on the block as i left the car overnight outside on the drive.

Realy is wierd. Nothing wrong with the engine other than its recently started to loose a little coolant, you can see where its been seeping to the back of the block. Its not getting to the chambers though as where the fire rings seat, its loverly and clean. Wouldnt have thought if it was anything like coolant that it would be identical/symetrical.

Been thinking about it all night and came up with this theory

The fuel mix travels allong the manifold runner. Before it enters the port, there is a projection at the end of the runner, presumebly Rover added this to try and even out distribution? earlier SPI did not have this. The charge then hits the back of the port. Piston very near TDC or ATDC with valve slightly open charge starts to enter the cylinder in a swirling motion, clockwise on #4 and anticlockwise on #1. This effect is greater on these two cylindes and causing the area on the piston to be 'cleaned'.