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BAD WB Offline
#1 Posted : Saturday, 16 May 2009 12:45:22 AM(UTC)
BAD WB

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building a 383 vr engined holden. How high can you safely go with the vn heads, heard of most peolpe run around 10.5:1. Whats ther safe limit with the cast heads???
HK1837 Offline
#2 Posted : Saturday, 16 May 2009 2:56:29 AM(UTC)
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It depends heavily upon the cam. COME might be your best help on this.

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Dr Terry Offline
#3 Posted : Saturday, 16 May 2009 3:38:55 AM(UTC)
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quote:
Originally posted by BAD WB
Whats ther safe limit with the cast heads???


Arent all production heads cast ?? They can be made of cast alloy or cast iron, but theyre still cast.

Dr Terry
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adam PERTH Offline
#4 Posted : Saturday, 16 May 2009 5:28:58 AM(UTC)
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brendon, the heads arent the limiting factor with hi compression.
its the head Gaskets and piston side skirts(pinging) which will limit you as you increase compression.

Good thing you live near the airport, you could bump it upto 11:1 and run Av gas.?

look into Copper shim head gaskets,
or, O - ring gaskets to run with a hi quality felpro gasket.

If you do go for hi comp like 10.5, try and keep the piston as close as possible to Zero deck height, and take less off your heads.
This will create greater turbulance in the chamber, particularly around the valves.
Not only that, your inlet manifold has a much better change of sealing because it is bedding onto the original V shape it was designed for between inlet manifold and head ports.

WANTED:
-2 14 x 9.25 CSA style Centrelines.
-2 x 15 x 8 Dragway centrelines

Edited by user Saturday, 16 May 2009 5:37:41 AM(UTC)  | Reason: Not specified

Old holdens brought on the spot, quick decision, cash paid.
BAD WB Offline
#5 Posted : Saturday, 16 May 2009 9:09:47 AM(UTC)
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Like the av gas idea just need a bloody long hose. by taking less off heads are you talking less decking??
cheers

Edited by user Saturday, 16 May 2009 9:11:41 AM(UTC)  | Reason: Not specified

Mr Void Offline
#6 Posted : Saturday, 16 May 2009 8:04:19 PM(UTC)
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Deck height is on the block - it can be machined down as well as facing the heads. This will bump up the c/r but remember the intake manifold will have to also be machined to suit.

Cometic make great mls head gaskets too.


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