Head skimming questions

[ArthurH 7]

Thanks Tom, I thought it was long shot, but worth the ask.

[DamirGTI 342]

Some head porting work would be good to add on the list too .. don't even need to do "much" work to make it better .

 

I can provide some guidance if you want to do the head by yourself .

 

Just finished rebuilding/refreshing my 1.9 8v , standard D6B cam advanced 4deg. , 11.1 CR with an heavy head skim , multi valve seat job along with the head porting on a standard Jetronic management with recurved dizzy (will be fitting soon Mp3.1 management) , mi16 gearbox , 100 RON petrol - cheap to "put together" , and goes like stink !

 

Head/valve seat work along with upping the CR makes an good combination .

 

D

[petert 588]

I agree. Three angle seats and a big skim is the best value for money mod you can do for an 8V.

[petert 588]

Here are the two types of 8V pulleys. You need the one with the pressed in pin, type B as I call it. You can press the pin out and drill the hole oversize. A skilled person with a lathe can turn up a stepped, offset pin. The OD of one end is the oversize hole, the other end fits in the cam. You need to dial in the standard pulley and cam first, then work out how many degrees of advance you need, to achieve the desired lift at TDC. There's a bit of maths involved, but a worthwhile project to get correct.

[ArthurH 7]

13 hours ago, DamirGTI said:

I can provide some guidance if you want to do the head by yourself .

 

DamirGTI thank you for the offer, but sadly the  championship rules forbid head modifications other than skimming

 

5 hours ago, petert said:

Here are the two types of 8V pulleys. You need the one with the pressed in pin, type B as I call it. You can press the pin out and drill the hole oversize.

 

Thanks Petert, really clear photos - exactly the advice we are looking for.

[ArthurH 7]

A quick head related question please.  We are planning to take the head off this weekend with the block remaining in situ.  To save a lot of time and effort accessing difficult bolts, where are the best places to split off the ancillaries?  I.e., the exhaust manifold from the head or split under the car from the exhaust system?  We will be removing the front slam panel and radiator for other reasons anyway, so will do that first.

[ArthurH 7]

On 12/26/2018 at 11:27 AM, petert said:

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.

Although I didn't doubt it, I wanted to get my head around the maths behind this figure.  I started with some very complex formula that included the diameters of both pulleys, to calculate the point at which the belt is tangential, and how that changes as the pulleys are moved closer together by the skim. However, it became clear that most of the maths was adding a completely insignificant value.  The only bit that matters, I think boils down to a the ratio of the dowel offset to skim thickness being the same ratio as the dowel pin radius and the effective overall pulley thickness (as per my crude sketch below).

 

So having scaled from the photos Peter had posted, I get a ratio of approx 4.6:1 for the two diameters.

 

That would imply that to compensate for a head skim of 1.00mm, the dowel would need a 0.22mm offset - does this sound right?

Edited January 4, 2019 by ArthurH
Missing words

[Tom Fenton 1,542]

I've not looked at your maths in enough detail to say if its correct or not.

However the only reliable way in practise to determine your offset dowel requirements is once the head has been skimmed, time up the camshaft and see where it ends up, and what correction is needed. Production tolerances being what they are, means that your theoretical calcs to correct for head skim may not be all that is needed to put the camshaft in the optimum position.

[ArthurH 7]

 

Very good points Tom - indeed that would be the only way to compensate for all the accumulated tolerances.  I had been hoping to get a dowel machined up in advance to prevent the head being off for any longer than necessary.

 

[ArthurH 7]

On 12/19/2018 at 12:24 PM, jackherer said:

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.

Hi Kieran, I have been trying to make contact since the beginning of last week - I can only find one published number for the business (below) - but that goes to 'Number unobtainable' every time I try it.  Any idea?

 

Phone: 01245 362 625

Drakes Lane Industrial Estate, 5 Drakes Lane

BorehamChelmsfordEssexCM3 3BE

 

If BGV is no longer an option, we may try Gosnay's, which are not too far from us - unless anyone advises to the contrary?

 

http://www.gosnays.co.uk/acatalog/History.html

 

[jackherer 543]

That's not a good sign
 

Like I said he's an old guy so maybe he retired since I last went there.

 

I'm actually going to Chelmsford this evening so I'll pass by, it'll be too late to ask any of his neighbouring companies but I'll have a look to see if it looks derelict or not.

[Telf 224 2 Cars]

I had my head skimmed and 3 angle cut here:

http://www.afmracing.co.uk

 

Pretty good service 

[ArthurH 7]

13 hours ago, Telf said:

I had my head skimmed and 3 angle cut here:

http://www.afmracing.co.uk

 

Pretty good service 

Thanks Paul, although that would be a fair trek for us.  Unless anyone warns us of having had a poor experience, I think we will try Gosnays.  They have being going a long time, and claim 'competition' car experience.

 

We took the head off at the weekend so have had our first sight of it.  To our surprise, it looks like it has never been skimmed - but I will do more careful measurements at the weekend.

 

Also, how does a 1.6 cam differ from a 1.9 cam - are there any convenient markings?

 

 

[jackherer 543]

I spoke to Bob's neighbour Rallytec and they told me he retired over a year ago unfortunately. As an aside they are a useful company to know if you are in Essex - http://www.rallytec.co.uk/index.html

[ArthurH 7]

Thanks Kieran for bringing that particular avenue to a close.

 

In my previous post I had asked about camshaft identification; I have been searching this forum and found tangential references.  Is that the difference between B6D & D6B?

 

The general consensus seems to be that you can run a 1.9 cam in a 1.6 engine but it gives no advantage, perhaps even the opposite...?

[ArthurH 7]

I think I have the answer (from 2015) to my question above.  My son's cam has the two brown rings Damir mentions below.

 

On 10/14/2015 at 11:09 PM, DamirGTI said:

My mates car arrived for some repairs , the engine is an 1.9 DKZ but the camshaft is certainly from another engine not the DKZ nor D6B .. so i wonder if it's a 1.6 B6D or maybe 1.9 DFZ , as i do not have any data for the later two engines and nothing to compare to , does anyone recognize this one by the paint markings on the camshaft :

 

 

 

The one fitted on the engine has two white paint rings on the camshaft near the timing pulley end , while the other one which i fitted next to it up top is a 1.9 D6B (two brown ring markings on the flywheel end side of the cam)

 

Is this a 115bhp 1.6 B6D camshaft maybe ?!

 

Thanks !

 

D

[DamirGTI 342]

I remember that one ! was an Motronic 1.3 , 1.9 DKZ engine with the 1.9 405 Sri cam .. it drove relay good , obviously because the management (if comparing to Jetronic) but the cam didn't make much or any if i can remember "lower performing effect" than the 1.9 DKZ cam in the same engine ..  in fact i thought it felt better accelerating faster from mid revs to the limiter with that 1.9 SRi cam .

 

1.9 D6B cam is the highest of a lift/duration of all of the 1.9 8v XU petrol engines .

 

Haven't tried by myself but , by the reports from others who tried that : 1.9 cam in a 1.6 engine makes it kinda "flat" performing so certainly downgrade mod fitting 1.9 cam on 1.6 engine ..

 

D

[ArthurH 7]

It's the only cam we have, so it will have to go back in for now.  However, due to the consensus that it does not provide a performance benefit, the risk of any other competitors formally challenging the eligibility, I would think to be very low.

[petert 588]

I can't recall the 1.6L cams, but 1.9 cams can be identified by measuring lift as follows:

 

DFZ - 0.405" lift on both intake and exhaust

DKZ - 0.445" inlet, 0.405" exhaust

D6B - 0.445" lift on both intake and exhaust

[ArthurH 7]

As always, thanks guys for all your support.  The head is now at Gosnay's being machined.  The Victor Reinz bolts and head gasket are ready to go.  Just the valve shimming, timing and offset dowel to sort out.

 

I know it is not part of this thread, but I would appreciate your thoughts on this question I have asked in a parallel thread:

 

 

 

Edited January 21, 2019 by ArthurH

[ArthurH 7]

Head came back from Gosnay's and I think they have done a great job.  Even stamping the skim depth into the side of the head for future reference.  We have refitted the valves and torqued the head down (spoilt for choice on torquing options, multiple threads on this forum, but in the end went with ARP grease and 60nm, 20nm, 300deg (in stages)).

On 1/4/2019 at 11:50 AM, Tom Fenton said:

... the only reliable way in practise to determine your offset dowel requirements is once the head has been skimmed, time up the camshaft and see where it ends up, and what correction is needed. Production tolerances being what they are, means that your theoretical calcs to correct for head skim may not be all that is needed to put the camshaft in the optimum position.

 

I think we will be OK applying the basic timing as we marked the crank pulley (couldn't find a hole in the block for a pin - but that's another story) and pinned the cam.  However, So I can get an appropriate offset dowel made up, what is the simplest procedure to measure "what correction is needed" as Tom says above?  I have a vernier and a DTI, but the simpler and more foolproof the procedure, the better .  The only spec I have atm for the D6B cam is as Peter provided below:

 

On 1/11/2019 at 10:49 PM, petert said:

D6B - 0.445" lift on both intake and exhaust

[ArthurH 7]

I should really have added that I have already looked at several previous posts about timing cams - but as is often the case, there is a lot of different approaches to choose from.  One suggestion that I thought excellent, was to establish TDC using the Motronics 'teeth' on the flywheel:

 

http://www.taylor-eng.com/xu9j4/finding_tdc.html

 

Unfortunately, we don't have an aluminium (?) flywheel timing marker.  Are they available, or are there any aftermarket ones?

[petert 588]

Every Jetronic 205 had a timing marker. Put up a wanted ad.

 

The maximum lift figure I quoted is not going to help you with timing it. I don't think I've ever seen a lift @ TDC figure for a D6B cam on this forum. I'd be aiming for approx. 0.065" inlet lift at TDC, taking into account a bucket-lobe clearance of 0.010". Alternatively, set it at a lobe centre angle of 112 deg.

[Tom Fenton 1,542]

I'd say that you want to time it to the standard position initially, then if you can, do some rolling road power runs and swing the cam timing to see where you get the best power curve.

[ArthurH 7]

Thanks Peter & Tom,

 

8 minutes ago, Tom Fenton said:

I'd say that you want to time it to the standard position initially, then if you can, do some rolling road power runs and swing the cam timing to see where you get the best power curve.

This would imply using vernier to establish the optimum on a rolling road and then to swap that for a offset dowel for the races.  Although I have to agree this would be ideal, I think it will beyond my son's budget/availability of time.  I think for this coming season at least, we need to stick to the dowel.  Perhaps just the standard dowel, as I'm not sure what the effect of the cam retardation due to a heavy skim will have on power and perhaps more importantly, torque.  Plugging in the actual skim depth and the effective cam pulley diameter, my maths and diagram above suggest this would be about 1.27deg.  I appreciate this unfortunately  ignores Tom's valid previous point around overall tolerance build up.