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| Europeen style 3800 turbo swap - what do you think ? (Page 4/14) |
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Englishrafe
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MAR 04, 12:33 PM
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I finished one head this week-end.
Here are a few photos:
Intakes, exhausts and combustion chambers nicely poilished up.
Didn't alter the exhaust port shape, just polished the conduit up to a nice finish.
Cutting a 3-angle seat - this top photo is 70° and this one's the 30° cutter.
I will be fitting new valves when they arrive.
So here is one head pretty much ready and waiting for it's hardware:
That's the end of the work for this week-end. Only another 15 hours with the mini-grinder for the other head - my hands are knumb with the vibrations! How do the guys who do this for a living survive?!
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mattwa
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MAR 04, 12:39 PM
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I was about to say, until I saw the last line of text you wrote, you wanna do mine next? 
Looks really good! Keep up the good work.
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Englishrafe
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MAR 04, 01:01 PM
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| quote | Originally posted by mattwa:
I was about to say, until I saw the last line of text you wrote, you wanna do mine next?
Looks really good! Keep up the good work. |
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It might cost a little too much to have them shipped to France!
Thanks for the complement !!
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mattwa
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MAR 04, 01:18 PM
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That is very true, I'm sure those cast iron heads are quite heavy. I do like the idea of drilling those oil holes in the lifter valley, seems like a good idea for better oil drainage, however I'm concerned it would create an area prone to cracking under high stress loads if someone didn't counter-sink to remove the edges.
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Englishrafe
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MAR 04, 02:11 PM
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| quote | Originally posted by mattwa:
I do like the idea of drilling those oil holes in the lifter valley, seems like a good idea for better oil drainage, however I'm concerned it would create an area prone to cracking under high stress loads if someone didn't counter-sink to remove the edges. |
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I just copied what I've seen done by professional engine builders - I'm sure they wouldn't do it if the block became weaker?
By the way, the metal thickness at that point is only about 5 or 6mm and yes the holes are counter sunk. I can't imagine that these holes would set off stress fractures - it's not like you just drilled through a complex part of the casting.
At least I hope not!![This message has been edited by Englishrafe (edited 03-04-2012).]
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mattwa
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MAR 04, 02:27 PM
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| quote | Originally posted by Englishrafe:
I just copied what I've seen done by professional engine builders - I'm sure they wouldn't do it if the block became weaker?
By the way, the metal thickness at that point is only about 5 or 6mm and yes the holes are counter sunk. I can't imagine that these holes would set off stress fractures - it's not like you just drilled through a complex part of the casting.
At least I hope not!!
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Yea, I understand that, guess I'm just paranoid. If I did something like that it would crack and blow-up. But I didn't know it was so thin in that area, thanks.
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Englishrafe
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MAR 11, 07:05 AM
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Yesterday I measured the combustion chambers volume.
I wanted to see if my polishing had altered to a large degree the volume?
I compared the head finished last week with the one I'm working on this week-end.
Here's the technique:
Put a set of valves and a sparkplug back into the finished head, then cut a piece of smooth plastic (old 5 litre can) to cover the chamber in question. Light grease as a sealant between the plastic and the head - the blue colour on the plastic.
A piece of plywood as backing held down lightly with a couple of clamps. There are two small holes drilled near the top - one to inject the water in and one that lets out the air out. Measure the amount of water injected just untill water appears from the second hole.
Do the same as before to an unfinished chamber in order to compare the difference.
My seringe is accurate to the nearest cc.
The results are as follows:
Unpolished chamber volume = 60cc
Polished chamber volume = 61cc
Have you guys ever measured the heads? If so, what are your readings ?
Today, I am going to finish polishing the second head. Then a bit of maths to calculate the static comp ratio.
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30+mpg
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MAR 11, 04:13 PM
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Englishrafe
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MAR 11, 07:10 PM
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Interesting build.
I wasn't surprised to read that his series 1 had "chewed" a piston and pin. I have an ex-minivan S1 motor sitting in my basement with exactly the same symptoms! That's why I'm going S2 - can't beat floating pins for load spreading!
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Englishrafe
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MAR 12, 04:34 AM
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I've just been doing the maths to find out my effective comp ratio.
I ran the numbers with the different pistons available and keeping the standard head gasket thickness.
Since I will be running this car as (nearly) a daily driver I want something that has good performances "off cam/boost".
I also understand that with 95 grade fuel (available here), I don't want an effective comp ratio above 12:1 (13:1 at a pinch  ).
(I can always put 98 grade or some other additive in for the race day.)
I calculated that my polished combustion chambers give a static comp ratio of 9.28:1 when using off the shelf "9.5:1" pistons with 4cc dishes.
So at different boost levels,I get these results:
10psi boost = 11.43:1
12psi boost = 12.28:1
15psi boost = 13.54:1
20psi boost = 15.65:1
This means that I confirm that I'm going to buy the "9.5:1" forged pistons and keep the boost "lowish" for everyday use!! Yes!! [This message has been edited by Englishrafe (edited 03-12-2012).]
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