Engine Compression Plates
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Engine Compression Plates
Tried to google this to find out why they are fitted to some engines, when, purpose etc. . but there is not a lot out there. Can someone enlighten me? - I am just curious to know
- Rob Harknett
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Re: Engine Compression Plates
As far as I know they lower compression ratio to give improved fuel consumption. Fuel used needed to be saved in war time in particular.
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Re: Engine Compression Plates
so were they something that was introduced during war time as a cheap alternative to changing machining for war time models and also so they could be retrofitted to existing machines? Also presumably to cope with poorer quality war time fuel?
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Re: Engine Compression Plates
You have answered your own question in that last sentence, Stephen. The low quality fuel situation continued into the early/mid 1950's. This is why the compression plates were used from around 1940 to 1955 and less so after that.Stephen G80 wrote:so were they something that was introduced during war time as a cheap alternative to changing machining for war time models and also so they could be retrofitted to existing machines? Also presumably to cope with poorer quality war time fuel?
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Re: Engine Compression Plates
Interesting letter/announcement/advice issued to owners by the Plumstead factory in Dec 1956 referring to fuel coupons/fuel economy........and referring to a chap who achieved 312.5 mpg with his 350 Matchless.
http://archives.jampot.dk/editorial/Roa ... e_1956.pdf
http://archives.jampot.dk/editorial/Roa ... e_1956.pdf
'There is a tide in the affairs of men
Which taken at the flood............'
Which taken at the flood............'
- GOLDSTAR
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Re: Engine Compression Plates
when I got my Velocette MSS many years ago the original purchaser told me he had the engine rebuilt by a well known Velocette specialist but because of the difficulty in obtaining a MSS piston at the time a Venom [higher compression] had to be fitted, in view of this and to restore the lower compression of the MSS a DECOMPRESSION!!! plate was fitted, why oh why are they always called compression plates is beyond me. kind regards
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Re: Engine Compression Plates
thanks all - I have to agree Goldstar - if they were called decompression plates that would make a lot more sense
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Re: Engine Compression Plates
They are known as compression plates as their presence/absence determines the compression ratio of the engine. It's as simple as that!
- GOLDSTAR
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Re: Engine Compression Plates
tommy rot! if one is not fitted then the compression is as per manufacturers figures when you fit a decompression plate you do exactly that lower the compression ratio therefore you decompress it. kind regardst
- vincentvv
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