Engine out and strip down

[Alistair E]

Following the failure of the the clutch I decided to remove the engine rather than the gearbox. I also wanted to do some other work on it, so it seemed like the ideal opportunity.

I've been clicking away with the camera, trying to photograph connectors, pipes etc so that I can remember where they all came from. Engine was actually removed from the car on Christmas eve so I'm glad I took the photo's.

You can see the state of the engine with the oil and pas fluid leaks. These should be sorted on the rebuild. I won't post all the photo's, too many.

[Alistair E]

Some more photo's

I've done some polishing work and a bit of porting i.e. sharpening up the splitters.

Not finished the polishing yet, it's bloody hard work. I bought a dremel type tool from Aldi and used the emery barrels. They were good for the initial smoothing, but way too rough for a final finish. Wet & dry would take too long to take out the scratches. Spent a long time working on the ports by hand with a finer grade of emery. Fingers are killing me. Mind you, some woman is going to be very impressed after all this training.
Then I started on the wet & dry, again by hand. I've been looking round for dremel attachments and splashed out on a few new ones. Revelation, they sell one which has a head made of a similar material to the green abrasive washing up pads. Absolutely brilliant. Takes out the scratches whilst leaving a polished finish. One problem is that the diameter is a bit big for getting well into the bores and it has a tendency to stall the dremel. It's a dremel 511 abrasive buff.

Will post more photo's as I go.

Alistair

[shark_90]

Looking good mate!

[Alistair E]

Just been looking through previous porting & polishing threads. Should the combustion chamber and valve heads be highly polished or slightly rough. I've pinched the attached photo's from Mark Halligan's cylinder head preparation thread (Mark, hope you don't mind).
Is there a reason behind the polishing? I can understand the reasoning for the exhaust ports.

Thanks

Alistair

[Alistair E]

Well, with no answers regarding the combustion chambers I've decided to go ahead and smooth and polish them. Not going to go mad with the finish. Just make them better than they were. I'll post some pics when I'm done.

Alistair

[nemilosu]

nice work.

[Wheeljack]

I would say that you want to smooth things out as much as possible, but you do not want the walls to be polished. Something like a brushed or blasted type finish would be best. The reason is regarding pressure drop and turbulence. Smoothness/shape will minimize pressure drop and get as much gas into the cylinder as possible, while the slightly rough finish will promote turbulent flow and the resulting mixing of air and fuel.

HTH

[Error404]

yes in the intake ports for sure, but AFAIK in the chamber ideally you want a polished finish to help prevent carbon buildup and hotspots

[Wheeljack]

yes, i was considering only between the inlet manifold and the valve seats...

[Knight Rider S4]

Copied from Wikipedia


It is popularly held that enlarging the ports to the maximum possible size and applying a mirror finish is what porting is. However that is not so. Some ports may be enlarged to their maximum possible size (in keeping with the highest level of aerodynamic efficiency) but those engines are highly developed very high speed units where the actual size of the ports has become a restriction. Often the size of the port is reduced to increase power. A mirror finish of the port does not provide the increase that intuition would suggest. In fact, within intake systems, the surface is usually deliberately textured to a degree of uniform roughness to encourage fuel deposited on the port walls to evaporate quickly. A rough surface on selected areas of the port may also alter flow by energizing the boundary layer, which can alter the flow path noticeably, possibly increasing flow. This is similar to what the dimples on a golf ball do. Flow bench testing shows that the difference between a mirror finished intake port and a rough textured port is typically less than 1%. The difference between a smooth to the touch port and an optically mirrored surface is not measurable by ordinary means. Exhaust ports may be smooth finished because of the dry gas flow and in the interest of minimizing exhaust by-product build-up. A 300 - 400 Grit finish followed by a light buff is generally accepted to be representative of a near optimal finish for exhaust gas ports.

The reason that polished ports are not advantageous from a flow standpoint is that at the interface between the metal wall and the air, the air speed is ZERO (see boundary layer and laminar flow). This is due to the wetting action of the air and indeed all fluids. The first layer of molecules adheres to the wall and does not move significantly. The rest of the flow field must shear past which develops a velocity profile (or gradient) across the duct. In order for surface roughness to impact flow appreciably, the high spots must be high enough to protrude into the faster moving air toward the center. Only a very rough surface does this.

[Alistair E]

Well, I've smoothed out most of the rough finish in the combustion chamber. I've not gone too mad with the finish, had enough of all the polishing now. Just starting to grind the valves in. Halfway there with the inlets but won't get chance to do any more until later in the week.

I haven't done any work on the inlet ports. I know some have taken the lines out down the sides, but I thought it probably wouldn't gain much if anything at all.

I'll post some more pics at the end of the week. I'm just glad to be making some headway. So far everything has been taking stuff apart and cleaning. Grinding the valves in seems that it's on its way to being put back together.


Alistair

[Error404]

good stuff
Have you had a decent valve seat job done? That will normally yield the best gains on a "street port" job anyway

[macspring]

Alistair,

Keep the faith, the photos remind me of the struggle of doing what you're doing on the drive as opposed to the facilities of say a dealers workshop.

BTDT, loads of times over the years, but right now I'm just glad mine is OK at present, apart from half a dozen things that are building up.

Keep the photos coming.

Good luck with it and best wishes.

[Alistair E]

good stuff
Have you had a decent valve seat job done? That will normally yield the best gains on a "street port" job anyway

To be honest, the valves and seats weren't in bad condition. I decided to just grind them in.

I know the feeling about the driveway workshop. It was only last week I had the head outside on the brick bbq working away on the ports with the dremel. It was snowing lightly at the time. Mind you, not having a wife anymore has its advantages. It can be quite relaxing grinding the valves in the living room while watching CSI or 24. I drew the line at using the dremel indoors.

Alistair

[Alistair E]

Can anyone tell me which way the step should go on the middle piston ring. Towards the head or towards the sump. Just to check aswell, top ring comletely plain, middle ring stepped, bottom ring is the oil ring.

Any quick replies greatly appreciated.

Alistair