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Author: Subject: Crossflow woes/help
Mike Bentley

posted on 20/11/17 at 11:58 AM Reply With Quote
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

posted on 20/11/17 at 12:32 PM Reply With Quote
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

posted on 20/11/17 at 02:33 PM Reply With Quote
if the compression ratio is low, is it worth considering a turbo?
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Mike Bentley

posted on 20/11/17 at 04:28 PM Reply With Quote
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

posted on 20/11/17 at 07:27 PM Reply With Quote
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

posted on 21/11/17 at 07:41 AM Reply With Quote
thanks brian
the list is helpfull

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alfas

posted on 22/11/17 at 09:37 PM Reply With Quote
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

posted on 3/12/17 at 04:21 PM Reply With Quote
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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