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Engine building questions
Just can't stay away
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2015/10/19 0:47
From Lyngby, Denmark
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Hey dattoheads

I'm building my A12 as a start, as engine swaps is a bit of a hazzle to get approved here in Denmark.

I just wanted to port match, with the intake that I designede, but ended up going to town and doing a full porting

It's going to be supercharged, using a Rotrex Supercharger and might go turbo down the road.

I know that I need APR studs, but should I also get a metal headgasket? The only one availeble is for 79 mm pistons but i have not bored the cylinders out(std 73 mm). And when I'm alredy making and order from Japan, so I'm also buing double valve springs and some other small bits.
Lots of good things came out of the A12 turbo thread that was on a little time back, thats where some inspiration came from :D

Will post pictures of what I have done below.

Thoughts and advise is appreciated ❤️

Posted on: 8/28 18:28
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Re: Engine building questions
Just can't stay away
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Here the images go:
(PS. I also cleaned up the bowl a little, sharp edges ect...)

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And what is this on my exhaust valves ????

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Cleaned up tho... With a lot of effort...

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Posted on: 8/28 19:10
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Re: Engine building questions
No life (a.k.a. DattoMaster)
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Correct me if I'm wrong but I don't think you can bore out 6mm. That's a quarter inch Usually the head gasket will and can be a half to 1.5mm bigger bore than the cylinder.
Depending on your boost, Stock gasket will work fine. I boosted a A15 to 8 psi on a stock gasket and it was fine.

Porting is great but not so much needed with force induction. It will find its way in there when pushed hard enough.
Enjoy.

Posted on: 8/28 19:20
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Re: Engine building questions
Just can't stay away
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Think I read it here?
http://datsun1200.com/modules/mediawi ... p?title=Bored_And_Stroked

And this is the gasket I'm thinking of:
http://www.datsun1200.asia/category/select/pid/8790

I don't know how much you can bore/stroke the A12, but that's not in the question either :)
Should I use the stronger gasket even though the gasket is that much bigger?
I'm thinking about running 10-18 psi of boost depending on what my tuner says, and how happy the engine is.

I know that the porting wasn't necessary, just got carried away... ups...

Posted on: 8/28 21:15
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Re: Engine building questions
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Quote:
I also get a metal headgasket? The only one availeble is for 79 mm pistons but i have not bored the cylinders out(std 73 mm)
If you are planning to keep the 73mm bore, I would not use a 79mm gasket

The stock head gasket is good for 14.7 psi (1 bar) boost, no need for a metal gasket -- both types of metal gasket (copper gasket and multi-layer steel gasket) are overkill unless you are boosting more. And then special prep is needed to use those gaskets

Posted on: 8/28 21:25
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Re: Engine building questions
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Quote:
what is this on my exhaust valves ?

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That is normal combustion. The valve has been making good contact with the seat if the bright line is continuous

Attach file:



jpg  exhaust valve.jpg (59.39 KB)
174_5b85b30ee7f2c.jpg 500X350 px

Posted on: 8/28 21:30
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Re: Engine building questions
Just can't stay away
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Quote:
The stock head gasket is good for 14.7 psi (1 bar) boost, no need for a metal gasket --


So Stock head gasket and ARP head studs will be fine for 10-18 psi? or is 14.7 psi the hard-limit for the stock gasket even with stronger head studs?

And that valve looks like that after 5min on a power drill with a round of 240grid removing the worst and outer most layer... It were some kind of mineral build-up? Like calc or something else don't know...

Posted on: 8/31 10:19
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Re: Engine building questions
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No need for ARP head studs. Just make sure you have chrome-moly factory bolts (marked '13'). These are strong enough for Nissan's 2.4 liter engines

Is 14.7 psi a hard limit? No, but many have reported zero failures at under 15 psi boost, so 14.7 is conservatively safe
Quote:
Datsun100ATurbo: I have boosted my A15 to 14-25psi with standard gasket and bolts, and I haven´t blown a head gasket in ten years
* The particular composition of gasket may also matter -- sikyne used a non-factory $18 Durapro brand gasket and got 22 psi but later it failed at 16 psi
* Keep temperatures down (inlet air temps, coolant temps, and exhaust temps)
* Allow zero detonation
* Prep the block deck surface and head surface better than factory, for example with no boost the factory specs are up to 0.004" head surface warp. If that is reduced to less less 0.001" it may hold more boost


Quote:
It were some kind of mineral build-up? Like calc or something else
normal combustion product, very common. Gasoline and oil products burning -- that's how mine looked (the ones that were not oil-soaked)

Posted on: 8/31 21:54
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