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Author Topic: AS21 case?  (Read 5488 times)

Offline ArcticDave

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AS21 case?
« on: May 18, 2017, 11:12:02 AM »
Anybody use one in their build? 
I found one with a huge pile of new parts for $500 locally. It has never been machined from stock and supposedly in excellent shape. The guy used a type 4 instead in his sand rail and has all this left over. 
 A set of 041 heads, 94mm pistons and cylinders(I don't think I can use these as they are for a 69mm crank)rods, crank, 2 different cams, 009 distibutor and coil, and numerous other parts come with it. My main interest is the case and the heads. Price seems fair...what do you think? 
Yeah or nay on the AS21?

Offline flyover1974

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Re: AS21 case?
« Reply #1 on: May 31, 2017, 12:35:15 AM »
First of all: Take it !!
I try to explain it with my poor english:
The as21 is the best solution in therms of loose bolts because the as21 was developed to prevent the pressure marks from the bolt washer on heads caused by thermal bruise when the cylinders and heads extend and studs not or less. They tested it over a long period (dont remember exactly but think 2 monts) and the result on as21 cases where 50% less loose of pressure on the head bolts because the as21 material resists more on pressure. This was even the cause because VW decided in 71 to mount 8mm studs instead of 10mm because they ar more flexible in length.

Offline flyover1974

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Re: AS21 case?
« Reply #2 on: May 31, 2017, 12:41:18 AM »
You can use the 94 cylinder, need only change the pistons. There is made the change for stroker cranks, it means the bore for the rod attachment axle inside the piston is higer near the top of the piston and probably the pistons are shorter because the stock ones maybe strike the stroker crank when on the bottom.
Edit:
Anyway if you decide to build a big bore with stroker over 82 mm (like mine, its 86 with chevy rods) with less compression rate about 8:1 you need big spacer rings under the cylinder seat to enable more head volume. I made a biiig work on heads, extractig 20ccm of material from heads to get the right  compression in addition to a 4,5mm ring under the cylinder.
Next time i safe the head work and put a larger spacer under the cylinder. The result probably is the same

Offline ArcticDave

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Re: AS21 case?
« Reply #3 on: May 31, 2017, 06:32:31 AM »
Thanks for the input. 
I passed on the deal because I couldn't get any solid info. I had heard that it was a superior alloy and resisted thermal distortion much better than the AS41 case, but I couldn't find an example of anyone actually using one.

Offline flyover1974

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Re: AS21 case?
« Reply #4 on: June 05, 2017, 02:31:32 PM »
Myself asking why nobody use it...
In german tuning scene they dont use it because on extreme tuning seems the case crack easier than the as41.
But airplane use never is extreme tuning, so i see no problems for using. And this kind of case is much younger than the most as 41 ones.

Offline Maxray

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Re: AS21 case?
« Reply #5 on: May 20, 2018, 03:40:02 AM »
I have an AS21 case machined and line bored for 94mm with case savers. I was wondering also if
it would make a good engine. However, I bought a Mosler 1/2 VW so I will probably sell the AS21
in case anyone is looking for one.
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