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about this Blocks,

does any of you make your original ones bigger, they are 32mm inside and 41,5mm outside

i like to bore out mine, how big could i go do you guys think,
i guess every one that have ported heads have bored out blocks?
but it seams to big to bore out to 38mm in the blocks as it is 41,5 out side
there for i thinking not to go with 38 inlets in heads, maybe 36 would go?

what is you experience?
Old 02-03-2009, 02:11 AM
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ok, i was wrong I didn't bore mine out to 31.5mm by memory.


I actually ended up boring mine out to 37.5mm. I just measured an extra one I did this morning.

Hope this helps.
Old 02-03-2009, 05:51 AM
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Originally Posted by nocarrier View Post
ok, i was wrong I didn't bore mine out to 31.5mm by memory.


I actually ended up boring mine out to 37.5mm. I just measured an extra one I did this morning.

Hope this helps.

is hard to see, was this the factory bakelite ones?
Old 02-03-2009, 07:51 AM
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Quote:
Originally Posted by nocarrier View Post
I actually ended up boring mine out to 37.5mm. I just measured an extra one I did this morning.
Nice. The bravest I got was to 36mm. Mine measured OD 40.5, so I'm at 2.25mm wall. At 37.5mm that's 1.5mm wall thickness. Are you running 1bar of boost through them? How long have they been back in? Did you use new ones? I bought a new one to do test cutting on, and then when I cut my old ones they were NOT in great condition. If I were planning to run my CIS for much longer I'd order 5 more new ones to mod.
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Old 02-03-2009, 08:09 AM
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Phenolic block walls are pretty thin as is - the aluminum blocks with some manifold work + SC heads are a great idea.

I have yet to do a thing to my phenolic blocks or manifold.......
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Old 02-03-2009, 08:35 AM
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Originally Posted by jpnovak View Post
Those injector holders are the $hit!!! I can see so many new applications for such a product.

Thanks for the link. I will be waiting...
Thought you'd like those
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Old 02-03-2009, 07:32 PM
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Yes, they are the genuine bakelite injector blocks from Porsche.

They were brand new from Porsche and machined really well with an amazing surface finish.

I have only run .8 bar through them controlled via a Tial 46mm waste gate.

They have been on the car for about a year or so.

There was an interesting observation I made when I removed and inspected the old ones that were also bored out. I found that the ones that had cracked were cracked at the bottom flange area of the block. The thin area of the walls were all intact.

It's my understanding that the stock ones crack in this area also. I am not really sure how much of the life I have "bored" out of them. Only time will tell.

-Adam
Old 02-03-2009, 07:49 PM
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I'm running the OEM injector blocks bored to 38mm with 1 bar boost and k27 turbo. After 7 years i'm looking to replace at least 3 of them due to cracking of the thin sidewalls. The next set I'm going to bore to 37mm. Hopefully they will last longer.
Old 02-24-2010, 07:08 PM
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If the exhaust is 34mm it would seem something in the 34-36mm would be a fit looking at what Porsche did on there NA motors.

How do we come up with an ideal intake or exhaust port size?

I am guessing we do not want to go any larger than needed to try to keep intake port velocity up which seems to be relevant with CIS looking at what Porsche did with the SC reducing its intake port size half way through production.

As a point of reference I have one friend that made 425+ rwhp through stock intake ports and SC cams. He did however have an extrude honed intake manifold with tapered injector blocks down to the stock ports.

I wonder if we can use the relative difference between intake and exhaust valve sizes and a valid point of reference.

The exhaust valves are 41.5mm diameter and or intake valves are 49mm. Thus, the intake valve has an 18% larger curtain area under its valve seat.

It would seem we would want an 18% larger intake port cross section to support the 18% larger area under the intake valve seat.

A 34mm exhaust port has 1.42 sq inch volume. If we want the intake to have 18% larger cross section it would need to be 1.68 sq inch. A 37mm intake port has an 18% larger cross section than the 34mm exhaust port.

However, the intake valve is also open longer than the exhaust with most cams so 37mm might be larger than needed.

Thus, it might be that unless the exhaust ports are opened further anything larger than 37mm for the intake is probably not going to be much of a benefit.

Of course there are more variables than this.

I think if I was doing a motor today I would look at something in the 34-36mm range with the right cam.
Old 02-25-2010, 08:42 AM
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I have the set pictured for sale, they have been opened up for the large port SC heads.
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Old 02-25-2010, 05:02 PM
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