decompression plate are they any good what else is needed
Turbo Mini Forums

i've seen around things called decompression plates that go between the block and head are these any good is it as simple as that or is it a lot of work are new pistons needed etc.

cheers sean

Generally they're not liked on this forum and are considered to be a bodge.

more places to have problems with imo

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

sorry i'll leave now taxi for one please.

lol

It's generally considered better to machine the head to decrease the compression ratio.

no point in leaving, most people on here prefer to go the hole 9 yars instead of cutting a few corners which you do with a decomp plate, use the search button and have a gander about decomp plates and what evere else it is you have queries on its very helpful mate

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

isnt having low compression a good thing to have.

is machining the head expensive

http://turbominis.co.uk/forums/index.php?p=search

Drives
-Ford S-max Mk2 Ecoboost
-Rover 100 VVC #2 - track project

Searching is all you need on TurboMinis

http://www.twin-turbo.co.uk
http://www.hillclimbandsprint.co.uk/default.asp

A man without a project is like a like a woman without a shopping list.

think i'll stick it out and get a machined head
seems to be a sore point
this is why i'm hear to learn new things

Hi,
We're all still learning here, but something like compression ratio has been covered many times before.
There's also enough different permutations to fill a large book.
This is why people are pointing you to the search button, so you can gain more knowledge to ask a better question, so you can get a better answer. :)
For example you haven't given any details about what you want to use your car for, what power you're expecting or what you want to achieve...
Cheers,
Gavin :)

Edited by Bat on 19th Aug, 2008.

VEMs Authorised Installer / Re-seller. K head kits now available!

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Visit www.doyouneedabrain.co.uk

My Mini build diary

at the mo my engine isnt in yet was just looking at my options before it goes in havent got a lot of money when it comes to what i want from an engine i suppose i want speed in 2second and third gear not worried about top end

i've used a decompression plate and i think they are shite, mine leaked oil out. i took my head to my local engineering shop and he chamberd the head and re cut the vavles and fitted new oils seals for 140 quid,. the CR is in the 8's he got the ratio out of a vizard manual(the yellow one) and he reckons it will take 14psi, whether it does we will see......

Hi,
If your budget is tight, time spent doing some research could save you making an expensive mistake
There's turbo choice, cam choice and CR to consider...
Cheers,
Gavin :)

VEMs Authorised Installer / Re-seller. K head kits now available!

WB/EGT gauges. Click here for customers write-up

Visit www.doyouneedabrain.co.uk

My Mini build diary

I'm going to put a point in for decompression plates.

I like circular chambers myself. With the squish left.

Snag is that (I assume) that people just make a steel head gasket which you seal with 2 head gaskets. So, in order to maintain the squish, you match the piston dish widths with the bore holes in the plate. This makes absolutely no difference at all to squish and assuming there are no HG reliability issues arising from 2 HG's, I can't see a problem. Not only is it a good way of getting the extra capacity, it allows you to keep the original chamber shape and even get an over skimmed race head back to a normal level. I don't like the way that the bit of steel is non cooled though. But unless people find that reliability is compromised, there is no snag.

It is a bodge though.

I prefer the idea of setting it up in a mill and just whacking the chambers out circular. It beats pissing around with a die grinder for hours doing a piece of art.

Bugger off, I'm getting there.

I think that coolant and oil flow through a compression reducing plate will help to stabilise/reduce its temperature by no means active cooling but much more than nothing at all!
However, the area around the edge of the piston and the corresponding area of the cylinder head within the combustion chamber ( known as squish) will completely dissapear, it will not reduce, because squish by its very name means an area where charge (fuel and air) are purged (squished) from the sircumference of the chamber into the centre of the combustion chamber closely around the spark plug for most efficient combustion. Even new 4-valve chamber heads manage to have areas around the edge where squish can be achieved in the strive for more economy, and we are talking a multi-billion pound industry here.
So Mr. Engineering Joe who thinks he has invented the ultimate solution to CR reduction for amatuer engine builders should be shot!¬
I dont mean to rant but ive read many books on building engines for reasons ranging from horsepower to economy to ultimate forced induction, chemical forced induction (N2O), torque and not forgetting pure enjoyment...

didnt realise hedgemonkey you said it was a plate that goes into the cahmber past the edges of the bore and mimics the combustion chamber shape of the head just making it deeper, sorry i didnt realise thats what type of plate you were talking about,
Still a shit idea though.. lol