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Head Skimming


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2 replies to this topic

#1
Kartman205

Kartman205
  • Drivers
  • 57 posts
Joined: 20 Dec 2008
  • Location:Jacksdale, Nottinghamshire
Hi everyone, I`m new to the forum and am looking for advice.
I`m in the process of building the engine for our new racer, my son races in the 750 M/C Stock Hatch series.
The regulations regarding the engine are very tight, basically we can`t do anything apart from blue printing but ignition, compression and injection is free.
How much can be taken off the head face to get a sensible compression ratio?I don`t think the head has ever been touched so is the original thickness, does anyone know the standard measurement?
We tried 1.9 injectors this year and the car ran worse, no top end power and snow white plugs indicating a very lean mixture, an adjustable pressure regulator was fitted and showed ample pressure, swapped the airflow meter,throttle body then blew it up at Snetterton at the season finale. B)
The new car is a phase 2 and I`m using the later engine. All the bottom end will be balanced.
We do have the option of a homologated Kent cam profile for the series which I gues is the blue printed standard cam, has anyone any experience of this cam and is it a worthwhile option?
The exhaust is Grp A spec with standard manifold.
I`m open to suggestions on this topic welcome any advice so long as its legal :blush:

Many thanks, Paul

#2
mattbenselin

mattbenselin
  • Drivers
  • 489 posts
Joined: 19 Oct 2008
  • Location:Coventry, England
Hi mate,

I was told by Neil at DES Developments that as standard the depth of the combustion chamber from the head face is 7.5mm. When I had my head measured it was 7.3mm which would indicate a skim or 2 which is normal. I had my head skimmed down to 6.5mm which on a D6B 1.9 engine would bring the CR up to 10.5. If you speak with Neil he has a program which will calculate how much you need taking off to get a desired CR. I'm not sure how much can be taken off depends on valve lift and piston clearance I suppose, sure someone will know on here how much for standard components.

Not sure about the cam, if it's just a Kent version of the standard cam you might as well use the standard 1.9 one, if it has longer duration and/or higher lift then it will be of benefit but there are limits with standard ECU and the CR needs to upped to match.

The standard manifold will flow enough for 150-160 bhp, but I would think you can't change that anyway. Just get a downpipe with the split in it cause it helps with torque.

Good luck with it all...

#3
Kartman205

Kartman205
  • Drivers
  • 57 posts
Joined: 20 Dec 2008
  • Location:Jacksdale, Nottinghamshire

Hi mate,

I was told by Neil at DES Developments that as standard the depth of the combustion chamber from the head face is 7.5mm. When I had my head measured it was 7.3mm which would indicate a skim or 2 which is normal. I had my head skimmed down to 6.5mm which on a D6B 1.9 engine would bring the CR up to 10.5. If you speak with Neil he has a program which will calculate how much you need taking off to get a desired CR. I'm not sure how much can be taken off depends on valve lift and piston clearance I suppose, sure someone will know on here how much for standard components.

Not sure about the cam, if it's just a Kent version of the standard cam you might as well use the standard 1.9 one, if it has longer duration and/or higher lift then it will be of benefit but there are limits with standard ECU and the CR needs to upped to match.

The standard manifold will flow enough for 150-160 bhp, but I would think you can't change that anyway. Just get a downpipe with the split in it cause it helps with torque.

Good luck with it all...



Hi Matt, thanks for the reply.
The class is for 1.6 engines 8v or 1.4-- 16v.
I will measure the chamber depth and take it from there.
I will speak to Kent about the cam, they came up with a profile as an alternative to the standard cam, you can use either but nothing else,so I imagine theres not a lot between them, the real art is in the timing/positioning of it, which I can do.
The down pipe is the proper split one, but extended and gives more torque :P (so I`m reliably informed)
Once its up and running again we will set it up on a rolling road.

Rgds Paul