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Lowering compression on visa engine

 
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ealandbob
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Joined: 28 Jan 2009
Posts: 90
Location: France 79 Deux Sevres

PostPosted: Sat Oct 08, 2011 10:50 pm    Post subject: Lowering compression on visa engine Reply with quote

Hi All
This may sound strange as everyone seems to be looking for higher C.R. but for a project I have I want to lower the C.R on my Visa engine from 9:1 down to 7.5:1
Any ideas? Is modifying the pistons the way to go, or is shimming the heads the way to go?
All info greatly appreciated.
Im away til Wednesday so plenty of time to put thinking caps on
Cheers
Boggy
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Jasu
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Joined: 30 Sep 2007
Posts: 211
Location: Finland

PostPosted: Sun Oct 09, 2011 10:31 pm    Post subject: Reply with quote

There is thick gasket between block and cylinder, put two of them, problem solved...

There is made lower compression by that way...
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Pietro
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Joined: 17 Aug 2007
Posts: 13

PostPosted: Mon Oct 10, 2011 8:06 pm    Post subject: Reply with quote

Jasu wrote:

There is made lower compression by that way...

Hi,

I just had a look at the photobucket pictures. Looks very neat work!
This picture puzzles me: on a visa engine I would not expect this extension on the camshaft.
Could you please explain?
Thanks
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Jasu
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Joined: 30 Sep 2007
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Location: Finland

PostPosted: Mon Oct 10, 2011 9:39 pm    Post subject: Reply with quote

There has been made modification to use contact breakers, because in this engine was some serious problems with original Visa ignition system (with previous owner). But after all, this started to leak, quite much, so we took it away...

These parts was taken from 2cv4 camshaft, if I don't remember it wrong..?
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Rusty
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Joined: 19 Jun 2007
Posts: 142
Location: Koudekerk ad rijn Netherlands

PostPosted: Tue Oct 11, 2011 8:57 am    Post subject: Reply with quote

Hi Jasu,

In holland there are several specialists that have a way to put a electronic ignition on a visa engine (on the same place as a 2cv engine) this might be an option, they adapt the engine with an extra oil seal and camshaft as well.

I'm running a visaengine with original computer and had some problems in the past, but all of those were related to broken wires or faulty sensors. it's an ok system, just the computer limits the revs to i think 6500 rpm.

if you need more information let me know!

greetzzzzzzzzzzz

Rusty
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Pietro
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Joined: 17 Aug 2007
Posts: 13

PostPosted: Tue Oct 11, 2011 8:48 pm    Post subject: Reply with quote

Jasu wrote:
There has been made modification to use contact breakers...
But after all, this started to leak, quite much, so we took it away...

I am surprised about the leaking unless the front end was wobbling like this one.
When properly alligned and secured to the camshaft the probability of leaking should not be higher than on a 2cv engine?
I was considering to try a similar adaptation to yours one day.
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Pietro
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Joined: 17 Aug 2007
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PostPosted: Tue Oct 11, 2011 9:17 pm    Post subject: Reply with quote

Rusty wrote:
it's an ok system, just the computer limits the revs to i think 6500 rpm.

Hi,
When the engine is unloaded you may perhaps reach 6500 rpm because you do not need much torque to displace the pistons.
Under load the power of the visa engine drops very quickly after 5500 rpm and on the road you will reach no more than about 6000 rpm.
From what I read the visa electronic system is not able to produce sparks of good quality at these revs.
What about the other electronic systems ?
Do you know if they perform better at high revs or are they also limited?
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