Head skimming questions

[ArthurH 7]

Hello, I’m looking for some advice.  My son races a Peugeot 205 GTI in the Classic Stock Hatch championship.  Although engine tuning is nominally limited to ‘blueprinting’, one exception is head skimming (and consequent CR increase) which is allowed.  The consensus among the front runners is that we should be targeting a CR of 11:1.   However, we believe the head may have had a light skim in the past.

How can we confirm that?  Is there a datum from which we can measure?  Is the original depth of the combustion chambers known?

 

I understand the CR from the factory was 9.8:1.  If we assume for a moment the head had not been previously skimmed, my calculations based on:

 

CR  = (Swept volume + Unswept volume) / Unswept volume

 

Give me a figure of 0.995mm to be skimmed off to achieve 11:1 – does this sound right?

 

This figure would be reduced by any previous skimming measured as per my first question.

 

All the above assumes the head gasket thickness remains constant.  However, I noticed that it is possible to buy different thickness competition head gaskets.  Has anyone had any experience of these?  Or can recommend a particular gasket?

 

We live in Essex, there are several local engine machinists, but these are not motorsport nor Peugeot specialists.  Is there any reason we should not ask one of these to skim off 0.n mm?  Or is there an advantage traveling further to a Peugeot and/or motorsport specialist?  I’m thinking things like having fixtures to hold the head at the correct angle?  Has anyone any recommendations of machinists?

 

Thank you in advance.

[welshpug 1,661]

the Haynes manual states 141.0mm +/- 0.05mm, Iirc thats from the face to the top of the camshaft journal, though Im struggling to find the documentation for it.

[jackherer 543]

10 hours ago, ArthurH said:

Has anyone any recommendations of machinists?

BGV Engineering in Chelmsford.

[ArthurH 7]

Thanks for both your replies

 

Welshpug, this is exactly what we need - but it would be really good if you can find that missing source. 

 

Jackherer, I can't seem to find any online presence for BGV, so I'm guessing a fairly small business.  Is your recommendation based on Peugeot cylinder head work?

 

 

[petert 588]

You can skim up to 2.0mm from a virgin head. Alternatively, there are copper gaskets available in 0.5, 0.7 and 1.0mm thicknesses. Lots of options to increase the CR.

Edited December 19, 2018 by petert

[jackherer 543]

4 hours ago, ArthurH said:

Jackherer, I can't seem to find any online presence for BGV, so I'm guessing a fairly small business.  Is your recommendation based on Peugeot cylinder head work? 

Yes, he's an old guy that gets all the business he needs through word of mouth so he has never seen the need to figure out the internet!

 

He has done Peugeot cylinder head work for me but he isn't a Peugeot specialist. He does a lot of Subaru and Ford stuff but only because his neighbours are a Ford specialist on one side and a Subaru specialist directly opposite.

[DamirGTI 342]

 

D

[ArthurH 7]

Thanks guys, all really good info ...  that triggers even more questions 

 

Jackherer, so there is a good chance he will have any required fixturing for the 205 head, and so he is now our first choice

 

Petert, I didn't realise it was possible to get gaskets that thin - can you provide a link to any suppliers?  We haven't stripped our engine yet (I thought I'd try to do the research first) but I guess I need to know what the standard factory fitted gasket thickness is to be able to do the necessary calculations.  Anyone know?

 

DamirGTI, being stamped in this prescribed way suggests these heads are being reclaimed during original manufacture; I am aware it can reduce a lot of wastage - perhaps they would then be paired with appropriately thicker head gaskets to maintain the CR.  I am struggling to see where the 'top' arrow is pointing for dimension 'H'.   

 

 

[jackherer 543]

28 minutes ago, ArthurH said:

I am struggling to see where the 'top' arrow is pointing for dimension 'H'

It's the surface that the cam cover (AKA rocker cover) seals onto.

[Thijs_Rallye 87 4 Cars]

Assuming it still is a Jetronic we are talking about, I'd certainly wouldn't omit a distributor overhaul / recurve. More to be gained there then a only a head skim imho.

[ArthurH 7]

Thanks Thijs_Rallye, the championship is open to all makes of pre '92 hatchbacks - https://www.750mc.co.uk/formulae/classic-stock-hatch.htm.  The bulk of the field are XR2s and 205GTIs, but there are some Novas and Swifts.  In order for the different cars to race in a single class, they are ballested to provide a nominal power to weight ratio.  So if, by example, you wish to convert a XR2 into an XR2i, you can, but have to carry an additional n kg of ballast.  In the case of my son's car, it is running an Emerald ECU and carries the appropriate weight penalty.

[petert 588]

Copper gaskets are made here in Australia by Ridgecrest. Normally you'd o-ring an iron block, but if you've got good liner protrusion on an alloy block, the liners push well into the soft copper, creating the necessary seal.

[Miles 331 1 Cars]

Big minefield here as having started in the series in the late 90's, Back then it was all supposed to be std but far from it when you learn what others where doing at the time, Not sure what it's like now but with Lee etc at the front will take some doing to beat them.

it was well known that some would get a collection of heads and see which one flowed best etc, 12:1 is fine as with the ECU the ignition can be advanced which they do seem to like with good fuel, but it depends as always where you are looking at going

[ArthurH 7]

Thanks Petert, I had seen seen a separate thread on head gaskets that also mentioned the o-ringing of iron blocks, but you have anticipated my thinking.

 

Miles, yes, Lee has secured the '18 championship in his XR2, but it was good to see it was by only a tiny margin over Matt in his 205.  Pip is still competing in his Nova and always does very well.  From this I would suggest the ballesting rules have created as level a playing field as possible - but as you suggest, those with the deeper pockets alway run towards the front 

 

For my son, the last season was a very steep learning curve, but he began to realise that some cars that he had fought past in the corners were re-passing him on the straights - so we are looking for a little more power.  As his engine was running a lower CR than the other 205s, it seems a good place to start.

 

There is a lot on various forums about the 'best' fuel - the consensus seems to be that it is between Shell Vmax or Tesco Momentum, but with little between them.  The MSA have fallen into line with the FIA this year now permitting the use of 102RON.  https://aaoil.co.uk/msa-fuel-regulation-changes/

[petert 588]

I wouldn’t hesitate running 12:1 if you can use 102. Such a massive skim and/or thinner gasket will retard your cam timing however. Thus you either need to use a vernier pulley (legal?) or reposition the dowel/pin in the standard pulley.

[Miles 331 1 Cars]

Fuel again depends on Budget, look at the Sunoco list (100 octane in the day) and I have used it in the past and a few mates of mine still do but it's expensive, Know the feeling of being past on the straights, it's when I found out people where using different gear ratio's and engine mod's but I would hope this has been sorted now but then you had to run the std injection as well which limited things,  

Shame we don;t get the shell 100 Octane here as they do in Germany

Edited December 23, 2018 by Miles

[jimmi 0 1 Cars]

Merry Christmas all. A Long- shot but  here goes.. I need help ASAP ( as all rolling roads near me now closed  until new year).. Anyone have Emerald M3D Ecu maps for a 1.9 8v  running std pistons and a high torque gravel PTS 4078 cam on 97 BP fuel ?  

I've just replaced head gasket and engine is running but detonating 'pinging' under load throughout rev range. I checked ignition map and it seems my son was messing with the maps and has uploaded them to the ecu without saving the good map! 

I'm hoping to use car on a rally later this week...

[ArthurH 7]

Jimmi, I was hoping you would get a response from someone more knowledgeable than me, but in the absence of that...... Are Emerald themselves also closed?  I would have thought them a good bet if open.

 

Petert, I think the use of a vernier pulley would be 'questionable', as it is unashamedly a performance part .  However, I think I could make an argument that an offset dowel was the simplest means available of returning the cam timing to its pre skim factory setting.  Are dowels for the 205 readily available? (I haven't used one since my Ford crossflow days  )

[petert 588]

I've never seen them for sale. I make them to suit the application. Typically 1deg (crank) per 0.010" of skim. Nobody would ever know you've done it, unless they removed the cam pulley for inspection.

[jackherer 543]

3 hours ago, ArthurH said:

Are Emerald themselves also closed?  I would have thought them a good bet if open.

Emerald supplied a base map to Paul ( @Telf on here) recently that is described as "205 1.9 8v with plenum intake installed (modified engine, 160+ bhp)." so I imagine that is what they would send you. I think they put it straight into his ECU when he was there.

[welshpug 1,661]

I wouldnt rely on any map not tailored to your engine if you wish to compete!

[welshpug 1,661]

On 12/19/2018 at 5:04 PM, jackherer said:

It's the surface that the cam cover (AKA rocker cover) seals onto.

no, its to the top of the cam, thats why it states to use 3 caps to hold the cam in and ensure it rotates.

[Telf 224 2 Cars]

On ‎12‎/‎26‎/‎2018 at 12:53 PM, jackherer said:

Emerald supplied a base map to Paul ( @Telf on here) recently that is described as "205 1.9 8v with plenum intake installed (modified engine, 160+ bhp)." so I imagine that is what they would send you. I think they put it straight into his ECU when he was there.

yep they did supply one- uploaded to the ECU when I got it checked over by them

[ArthurH 7]

On 12/27/2018 at 10:53 AM, welshpug said:

no, its to the top of the cam, that's why it states to use 3 caps to hold the cam in and ensure it rotates.

Thanks for the update Welshpug.

 

Our original plan was to replace the shells and rings while the head was off.  However, time will be a bit tight before the first event, so might be preferable to postpone removing the block for now.  If we were to do this a future date, is it possible to avoid replacing the head gasket and bolts? This will be the first wet linered block I will have worked on, is it possible to insert the pistons from the underside of the liners?  Which I guess depends on the there being an appropriate surface for the ring compressor to press against.

[Tom Fenton 1,542]

You can’t remove the pistons from the bottom.