scutter
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| posted on 13/11/06 at 06:17 PM |
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Crossflow mods
A quick question for you all.
I want to raise the compression ratio of the engine from its current 9:1 to a more respectable 10.5:1, the engine is a 1698cc Crossflow.
The main question is is this achiveable with a block skim? and I've heard talk of fitting modified 1300 pistons, what modifications are
required?
The engines coming out over winter to have the main bearings replaced as one picked up some dirty during rebuild
ATB Dan.
The less I worked, the more i liked it.
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Marcus
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| posted on 13/11/06 at 06:40 PM |
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The 1300 pistons are a direct fit.
You may need to cut out pockets in the crowns for the valves though.
Marcus
Because kits are for girls!!
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thunderace
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| posted on 13/11/06 at 07:27 PM |
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i have done this just swaped for 1300cc +90 pistons ,got them on ebay for £15 (new boxed).
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UncleFista
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| posted on 13/11/06 at 08:18 PM |
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quote:
Originally posted by Marcus
The 1300 pistons are a direct fit.
You may need to cut out pockets in the crowns for the valves though.
They should be fine with a standard lift cam though... 
Tony Bond / UncleFista
Love is like a snowmobile, speeding across the frozen tundra.
Which suddenly flips, pinning you underneath.
At night the ice-weasels come...
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lotustwincam
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| posted on 13/11/06 at 08:33 PM |
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quote:
The main question is is this achiveable with a block skim? and I've heard talk of fitting modified 1300 pistons, what modifications are
required?
The engines coming out over winter to have the main bearings replaced ...
Since the combustion chamber on a crossflow is in the piston, skimming the head will make no difference to CR whatsoever. And since the pistons come
vitually to the top of the block, there isn't a lot to be gained from skimming the block.
Changing the pistons to 1300 ones is the solution. Might need valve pockets deepened, depending on what type of camshaft you're using. IIRC
valve to piston clearance should be at least 1mm.
When replacing the main bearings, as well as checking the journal diameter, be carefull to measure the diameter of the bearing housing. Brand new
engines, direct from Ford where sometimes supplied with bearings that were oversize on the outside diameter.
Even professional engine builders have been caught out by this. I speak from experience. The result was an oil pressure of around 5 PSI, and a lot of
head scratching!!!!
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MikeR
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| posted on 13/11/06 at 09:01 PM |
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also, the 1300 pistons whilst increasing compression aren't really designed for running at high rpm all day. If you want to race then you should
invest in some proper forged pistons.
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paulf
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| posted on 13/11/06 at 09:09 PM |
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My 1600 crossflow is fitted with 1300 pistons and has been ok so far , I use a rev limit of 6500 which may be to high but havent managed to break it
yet.
Paul.
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viatron
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| posted on 13/11/06 at 09:09 PM |
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On the oversize main bearing housing issue, most good ae stockists should have an AE go / no go gauge for excatly this use. If they are oversize do
not pay the exhorbitaqnt money some suppliers want for "rare" oversize housing bearing, just call FW Thorntons on 01743 357081 to find
that they are only pennies more than standard and available off the shelf, 2 reasonably well known crossflow performance parts suppliers tried to
charge be over 3 times what Thorntons charge and they were buying them from there!!
They are also excellent for single replacement piston rings check them out at:
http://www.nbcgroup.co.uk/page_general2.php?id=25&nav=1
Mac
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scutter
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| posted on 13/11/06 at 09:26 PM |
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Cheers folks, Looks like i'm watching the Fleebay for the next few months.
I'm running a Kent BCF 2 cam, nice power from 3000 to 6500, hardly every rev over 6000 anyway well oly if i fluff the changes.
ATB Dan.
The less I worked, the more i liked it.
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rusty nuts
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| posted on 13/11/06 at 09:42 PM |
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Just picked up my block, crank, rods etc from machine shop this evening. The pistons supplied are 1300 and the cam I'm using is a BCF2 .
According to the machine shop there won't be any clearance problems even with a big valve head . Using a cam with more lift the valve pockets
need machining .
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gazza285
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| posted on 14/11/06 at 07:17 AM |
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Don't skim the block as the pistons are then in danger of hitting the head.
DO NOT PUT ON KNOB OR BOLLOCKS!
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Ham
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| posted on 14/11/06 at 01:35 PM |
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Just a note, correct practise when fitting 1300cc pistons, is to "deck" the block, this eliminates early detonation created by the higher
compression.Left un checked can result in piston meltdown!
Fit crank,rods and pistons into the block and measure distance from the block surface to the top of all the pistons, now machine the block down to
level with the "lowest" piston, the remaining three pistons will be slightly proud (Ford engineering) Measure how far each piston
protrudes from the block, strip and machine pistons to suit, this should create equal compression across all the bores. On my motor my pistons sit
slightly proud by 1mm, the head gasket gives me another 1mm clearance,
It is tight, but it's right!
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