Mike Bentley
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posted on 20/11/17 at 11:58 AM |
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Crossflow woes/help
Hi guys and Girls
Here goes.
I bought this engine a 1600 681F with unknown history it had been standing for 2 years and started straight away without a single Knock or rattle
I opened it up and found it to be bored out to +090 with no bore ridge and still nice honing marks, plus the shells are almost like new.
At first I thought happy days but +090 on a 681!! on further inspection it has a chambered head but "711m" pistons. (Low Compression??)
I was hoping to fit a very big valve and ported head I bought at a good price years back ( After measuring and comparing chamber sizes) along with a
BCF2 cam and twin 40s.
But I think the comp ratio will be to LOW.
I have a 1300 engine in the shed (Which should have a flat head on it) so could just fit that.
QUESTIONS
1. IS IT WORTH FITTING THE BCF2 CAM WITH THE STANDARD 1300 HEAD.
2. OR WILL THE FACT THAT A LOT OF GASES WILL BE GOING IN AND OUT OF THE RACE HEAD WITH CAM AND CARBS THAT THE LOWER COMPRESION WONT MATTER MUCH.
I KNOWN I AM PROBABLY DREAMING
Please photos in my Achive
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Brian R
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posted on 20/11/17 at 12:32 PM |
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Check the bowl size on the pistons. You may have pistons from a smaller capacity engine. It's the easiest way to raise the compression on a
crossflow. I've done it myself.
https://www.google.co.uk/search?source=hp&ei=V8kSWvWQOYf1aOrfhtgG&sjs=3&q=ford+crossflow+piston+bowl+size&oq=&gs_l=mobile-gws-hp.1
.1.41l3.0.0.0.273662.1.0.0.1.1.0.0.0..0.0....0...1..64.mobile-gws-hp..0.1.42.3...0.7w53seMZCLA#imgrc=B69aaqot3NoqMM:
The 1600 is on the left.
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gremlin1234
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posted on 20/11/17 at 02:33 PM |
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if the compression ratio is low, is it worth considering a turbo?
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Mike Bentley
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posted on 20/11/17 at 04:28 PM |
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Thanks Brian and gremlin
The piston on the left is a 1300 which you put in a 1600 to raise compression
My are deffo 1600 ones.
As for a turbo that should be great but I think the old thin block of the 681 would self distuct
Plus I am on a tight budget so will probably fit the 1300 head and just one 40 on an lynx manifold I have.
And sell the race head etc
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Brian R
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posted on 20/11/17 at 07:27 PM |
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Sorry. The image I tried to copy was the pic in post no. #11 in this forum thread.
http://www.turbosport.co.uk/showthread.php?t=313551
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Mike Bentley
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posted on 21/11/17 at 07:41 AM |
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thanks brian
the list is helpfull
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alfas
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posted on 22/11/17 at 09:37 PM |
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first of all:
the 681 block isnt THAT bad
and THE 711 block isnt THE miracle.
a well balanced 681 might restain more revs or abuse than a badly (or standard ford) balanced 711
in theory the 711 are supposed to have thicker walls, but we're talking about 30-40 year old castings that might have seen 100000+ miles, that
were never that accurate in the first place... for a road car your unlikely to stress it more than it can cope , even with a max overbore and some
other tuning items fitted.
original 1600 pistons for that engine are rare. the pistons are differtn due to those engine-models having a chambered head
later 1300 pistons will give you around 10/1 ratio
this said...it also depends on the chamber....heads from that age exist with small and bigger chamber.
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Mike Bentley
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posted on 3/12/17 at 04:21 PM |
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SORTED
Bought a big vale ported flat top from ebay with unknown garage clearance history, just pope it has not hidden cracks.
paid £93.00 so its a gamble.
photo in my Archive
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