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Atlaskrukvaxt

camshafts for upgraded XU10J4R

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petert

So 2.1mm is the total distance between valve on the seat and valve resting on the piston at TDC?

 

If so, this is not enough. From this total measurement, you need to subtract clearance. For hydraulic lifters, that size valve, that sort of engine etc., you need 0.080" ( 2.03mm). To this you would add the cam lift at TDC, say 0.040" (1mm). Thus the total you need would be 0.120" (3.0mm).

 

5.2mm on the exhaust would be ok. That's typical 4V Peugeot.

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Atlaskrukvaxt

Thank you PeterT!
Just the information I've been looking for.

 

Yes, 2.1mm distance between the valve touching the piston and being retracted as far as possible in to the valve seat.

In my case that means then 2.1mm-2.03-1.75 =-1.68mm that I need to deepen the valve cutouts. 

 

I took off the head and sump today in preparation for removing the pistons and conrods. It looked kind of disgusting.

No piston cooling jets on this engine though. I was hoping perhaps the channels would have been there so I could have threaded them and put my own but nope. 

 

image0.jpg?width=526&height=702image1.jpg?width=526&height=702unknown.png?width=1246&height=702

 

I'll see if I can find someone local that can do the cutouts for me or I'll have to make a jig and try to do it with the drill press and an old valve with a carbide cutting bit attached to it. 

 

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petert
Posted (edited)

Sorry, it's worse. Your inlet cam needs 1.75mm at TDC. Thus you need a total of 1.75 + 2.0 = 3.75mm at TDC. Additionally, the piston will get closer to the inlet valve approx. 6º ATDC. Thus you really need to add another 0.010" (0.25mm) if taking a "rough" measurement at TDC.

 

ie

1.75 + 2.0 + 0.25 = 4.0mm

 

Nice pics. Now you're down the rabbit hole! Keep in mind that enlarging the pockets will reduce the CR a little bit.

Edited by petert

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Atlaskrukvaxt

I can't say I'm following you now. Your calculation doesn't include the existing piston valve relief? 

 

existing 2.1mm

needed rel. 2mm

valve lift 1.75mm

margin of error 0.25mm

 

0.25+1.75+2=4

minus what I already have 4-2.1=1.9

Or am I completely out for lunch?

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petert

Have the piston at TDC and drop the valve onto the piston. Did you get 2.1mm?

 

 

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Atlaskrukvaxt

Correct. 

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petert

That means there is 2.1mm between the inlet valve and the bottom of the piston pocket. You need 4.0mm

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Atlaskrukvaxt
Posted (edited)

So I'm missing 1.9mm which is the distance I would need to deepen the pocket in the piston, right?

Edited by Atlaskrukvaxt

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petert
Posted (edited)

Correct. Huge!

 

I'm surprised with your inlet measurement of 2.1mm. As that suggests there was insufficient clearance to begin with. Check it again.

Edited by petert

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Atlaskrukvaxt

How does this work with your stage two regrind with 0.065",1.65mm, lift@tdc?

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petert

You would need a valve drop measurement of 3.9mm

 

ie

1.65 + 2.0 + 0.25m = 3.9mm

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welshpug

I doubt you'll be able to make them much deeper than +1mm, depends if they are much more substantial than the rfs piston or not.

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petert

And given they're already dished pistons and you're going to decrease the CR further, it maybe more cost effective to just buy new flat top pistons, rather than pay someone to modify standard pistons.

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Atlaskrukvaxt
On 1/6/2021 at 12:26 AM, petert said:

Correct. Huge!

 

I'm surprised with your inlet measurement of 2.1mm. As that suggests there was insufficient clearance to begin with. Check it again.

Yes, I was very surprised by the measurement as well. 

I tried measuring with zero at both the piston and the valve retracted but got about the same results. 

 

I'll slap it back together and try again right away. 
 

Has anyone got a tried and tested way of pressing out the wristpins from the pistons by the way? 

I read Peugeot recommends changing pistons if you press out the pins. Kind of bad design from a tuning perspective. 

Otherwise I'll just heat the conrod and press over a wooden jig.

22 hours ago, petert said:

And given they're already dished pistons and you're going to decrease the CR further, it maybe more cost effective to just buy new flat top pistons, rather than pay someone to modify standard pistons.

 With deeper valve pockets a thinner gasket could perhaps be used and combat the loss of compression a bit. I'm not sure the loss will be that big though.

But first I'll do the measurement again. 

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Atlaskrukvaxt

I used a dummy spring for this test, 1.4mm gasket and only 4 surrounding bolts tightened to 15Nm.

Result was 0.1mm more than previous measurement. I'd say insignificant considering the circumstances. 

image0.jpg?width=526&height=702image1.jpg?width=526&height=702

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petert
Posted (edited)

Throw the rods and pistons in the bin. Find a set of XU10J4 (S16 or Mi16) rods and buy new pistons. The end result will be better and easier. Perhaps a tad more expensive.

 

https://www.flatlander-ipp.nl/wiseco/wisecoipp-peugeot.shtml

 

Edited by petert

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