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Date Name Message
20/08/2006 10:23:19   Rob   Hi guys - the supercharged v4 is well on its way but im still a little stuck for which pistons to run
what pistons are interchangable into the ford v4 - i think the pinto ones are but i do not want to reduce the height and greatly weaken them

id like to run a compression ration of approx 8.8:1 which may be still achievable with flat top pistons

what other options are available?

whats the maximum bore an open deck motor can realistically be opened out to?

if i use a 1700 crank in a 1500 motor - all that changes are the pistons - not the rods - is this correct?  
20/08/2006 16:02:06   Alex   Is using an open deck motor not asking for trouble if you want to make a hipo engine? If memory serves me well I read that head gaskets in open deck motors are more prone to blowing up because of the increased friction between the block and the gaskets; open deck blocks are less rigid.

My first impression is that rods will change too, but it depends whether the distance between the pin that connects rod and piston and the top of the piston are the same for both pistons. If stroke increases and rod remains the same you need a piston with less distance between the connecting pin and the top to prevent the piston from coming out of the block at tdc. The increase in the circle that the crank makes must be compensated by the length of the rod in order to keep tdc at the same distance from the centre of the crank.

Hello you engine innard experts, does this laymen's logic make sense?  
21/08/2006 08:19:45   Jon   I would use an open deck block either, for rigidity reasons (although I have no evidence that they are weaker).

I've a 1740cc engine. I changed the crankshaft, bought new conrods for a V6 taunus (same length but stronger), and then bought the appropriate pistons from Burton Power Products (sorry don't have the reference).  
21/08/2006 08:20:19   Jon   I wouldn't use an open deck block...  
22/08/2006 07:52:00   Stefan   as far as I know the only difference is the pistons, the conrod is the same 1500-1700. The Pinto 93mm pistons is usable in the 1700 after boring the block. They will not fit the 1500 due to the piston pin height  
22/08/2006 10:46:52   Rob   would the AE PISTON 2.8 V6 93mm part no. 20319/STD on fit either the 1500 or 1700 crank without modification?
if using the pinto piston on the 1700 do you have to machine the top of the piston?  
23/08/2006 12:48:38   Jon   Is doesn't matter which engine the piston comes from you just have to decide the bore and make sure that the piston top to piston pin axis is correct and then chosse from the list of available pistons. You can always skim a little (1mm max) off the piston if it protudes the block deck. A word on bore: 93mm is a pain as you can't use the std Saab gaskets (and you shouldn't use any after market copies) which can handle a 10.5:1 compression ratio. 90.5mm is really the max bore without having to install copper fire rings.  
23/08/2006 15:29:05   Alex   I bought a set of copper head gaskets from Chip Lamb. He claims that they can be used for hipo engines without O-ringing the block, though using a good sealant is recommended. Very handy, when the block gets bored the gaskets can be done too.  
23/08/2006 19:16:26   Rob   so which pistons will fit a v4 on 90.5 bore without the tops being skimmed off with a 1700 crank?
are the v6 rods the same length as the saab rods?  
24/08/2006 14:02:49   Jon   I'm sorry but I really can't remember the reference for the pistons I bought. All I can tell you is that I got them from Burton Power, they are 1mm oversize from the std bore (so could be 91mm thinking about it), hence my 40cc extra giving 1740cc, the crown height was flush with the block. The only work I did was to balance all piston weights within 1 gram and I dished the piston top to lower the compression ratio as the heads had already been skimmed 1mm.  
24/08/2006 14:03:39   Jon   Yes the Taunus V6 rods are exactly the same length as the V4 1.5 & 1.7 rods, only they are slightly more beefy.  
24/08/2006 22:52:27   Jon   Yippee I've dug out the info for the pistons and rods:
1. Karl Schmidt Piston 91.8mm = 25 each
2. Con Rods 2,9lt V6 Ford Taunus = 33 each
26/08/2006 21:47:39   David   looking forward to reading about the new engine, Rob! Sounds very exciting.  

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