205 GTI Sprint Car - Way forward

neilc

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I checked the cosmetic website they don’t seem to have a 205 gasket but they have this one
Would it be suitable? Also where could I buy copper gaskets to suit a XU9?





Part #DescriptionBoreMaterialThicknessPack QtyAvailabilityPriceQuantity
C4225-027PEUG P405 M-16 84mm. MLS. .027"84MMMLS.027"1In Stock$161.95
 

Dave

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Just ask Peter for some advice re sealing. I think it's advised to use Threebond around the water galleries. I had one of these on my DFZ/DKZ, tighe cammed combo about 20 years ago and it was epic, but seeped a bit of water (not into the cylinder due to liner protrusion but out the back of the head). I didn't know about the threebond trick back then (I used some sort of VHT copper gasket spray from memory during assembly).

Dave
 

PeterT

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That Mi16 Cometic is the one. If using copper, make sure you have sufficient liner protrusion. On an iron block you have to o-ring, but a liner will dig into the copper nicely, if you have approx. 0.003”. Add ThreeBond 1211 around water & oil galleries. Again, ask for the Mi16 gasket with +0.5mm bore what ever you have.
 

neilc

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Thanks Peter, so if I go down the path of the cosmetic gasket I would want one with a 85 mm for a 1.9 l dfz?

If I go the copper gasket path where would I source them?
 

Dave

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From what Peter Said above you would want 83.5mm gasket if you are using standard liners and pistons. The copper gaskets were from Ridgecrest. https://coppergasket.com.au/
 

PeterT

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If Cometic, it will be the 84mm version.

If Ridgecrest, ask for 83.50mm
 

neilc

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Spoke to Tighe Engineeering with regards reducing lash to .010/.012” I was met with reply about ramp shape, duration and ability to start in cold weather and idling.
Comments please

Another question is lash is it the same thing as the setting for valve clearances, inlet .007” Exhaust .012/.013”?
 

flock

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He bamboozled me too when I was asking those questions. I guess he is confirming if you know what you are getting yourself into with an advertised duration above 300deg?

When he was showing me profiles, I was given cam lift reports which show the duration at different valve lashes from 0.004" up to and beyond 0.050". Looks like he just showed you the cam card reports which only give values at 0.050" and the chosen lash of 0.016". Here's an example of my cam profile after it was ground. Originally he recommended I set the clearances to 0.012" (when hot) but the head guy took it upon himself to set to 0.008/0.010 (cold) which is too tight on the exhaust (Peter recommends 0.012 min).

1655203595209.png
 

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neilc

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Thanks Flock I gather this is for your reground dfz cam with different grinds for your inlet and exhaust lobes
 

flock

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Yeah that first profile B1488c I sent was what I originally showed to Peter but I was advised the shims would be stupidly thick due to how much I would lose on the base circle of the standard DFZ cam. B1454c was basically Tighe's closest profile we could get (hopefully better?) to a 130hp 1.9 cam.
 

neilc

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Hello Flock when I compare your two options the valve lash appears to be the same?
 

PeterT

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I wouldn’t get hung up on Tighe’s comments. If you have enough CR, the difference will be negligible in terms of idle quality and low end torque. I’d rather have a quieter engine. The oem figures are 0.006-0.010” inlet and 0.013”- 0.018” exhaust. In my mind, it’s more important to worry about the 0.050” figure. That’s when the valve/port starts to make measurable flow. The area under the curve from this point has the most significant effect. You also need to be careful with full lift. Anything more than 0.460”ish and you may need double springs.
 

neilc

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Thanks Peter just to recap I should use profile B1783C but request lash of .010 for inlet and .012 for exhaust?
 
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