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 Post subject: Decompression plates
PostPosted: Sun Jan 16, 2011 6:10 pm 
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Joined: Thu Mar 25, 2010 11:39 am
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Does anyone here have any experience of them?

Looking at cheapish ways of making my turbo project a little safer without going down the forged internal route (that's for later :D)

Currently thinking decompression plate and maybe maching a little off of a set of standard pistons? Not done any research on the piston bit yet though.

Ta :)

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 Post subject: Re: Decompression plates
PostPosted: Sun Jan 16, 2011 6:44 pm 
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On an engine that's renouned for having HG problems I'd steer clear of decompression plates or I'd imagine you'll be in a world of hurt with it :tard:

Removing piston material on stock (weak) NA pistons would also be a bad idea IMO tho I'm no expert on K series Rovers.

Your best bet will be to keep the boost down to 5psi ish to start with & see how it goes :)

Bill

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 Post subject: Re: Decompression plates
PostPosted: Sun Jan 16, 2011 7:41 pm 
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I agree with Bill.
Just keep the boost down to a sensible level. Maybe even less than 5psi if possible..

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 Post subject: Re: Decompression plates
PostPosted: Sun Jan 16, 2011 8:14 pm 
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I think you're probably right. Must not lose track of the original target of just getting it up and running :beatstick: Trouble is it's so easy to get carried away with these things :lol:

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 Post subject: Re: Decompression plates
PostPosted: Sun Jan 16, 2011 9:10 pm 
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Location: Doncaster
For ANY decompression modification the easiest routes in order of simplicity and reliability are;

1) Our indestructable head gaskets which can be made in a range of thicknesses
2) Machine a few mm off the fork end of the conrod and then have the bigend rebored (which effectively shortens it) - this also has the added benefit of ensuring the bigend is perfectly round.
3) Remove metal from the combustion chambers - this also provides the opportunity to match the combustion chamber volumes while you're at it.
4) Avoid removing metal from the pistons at all costs (as they are the most fragile component in the engine) but if you must use that method, remove metal from the central section of the piston rather than the outer section, because a failure at the side of the piston is likely to cause more damage than a failure in the middle and as long as you don't experience detonation it's unlikely that the center will fail.

With regard to a K series engine specifically, it is well know that the head gaskets are a problem and I don't know for certain if our gaskets will be compatable with that arrangement but if it was, it would solve the inhernet problem without question.

On the basis that the head gasket solution is an unknown, that leaves option 2 as you best definite choice.

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 Post subject: Re: Decompression plates
PostPosted: Sun Jan 16, 2011 9:14 pm 
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BTW using a decompression plate on an engine with liners is best achieved by obtaining longer liners and having them fitted through the plate, as that avoids a 2nd combustion seal.

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 Post subject: Re: Decompression plates
PostPosted: Mon Jan 17, 2011 6:05 pm 
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Location: Huntingdon trying to make a Skoda fast.
Hi Dan

On a t3 off a Saab there is an air pipe from the compressor side that goes to the boost control valve (electric valve - black plastic thing with wires) Take this pipe and connect it direct to the wastegate actuator. To start wind the adjuster out until the waste gate is only just closed. Then wind it in a couple of turns until your max boost desired is reached. I found this the only safe way to set up the wastegate on an NA engine as when I started using a t2 of an R5 the boost was 14psi and I had ALL sorts of issues!

As for the HG on a K - they only seem to be bad if the head has been skimmed or the engine has been cooked. I am told by the K experts it is to do with the aluminium grade and the heat treatment of the aluminium head. Skimming the head takes off the heat treated area making the head 'floppy' and soft. Also if the head has been cooked that kills the heat treatment too.

I'm not a K expert but ive spoken to quite a few people who I trust.

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 Post subject: Re: Decompression plates
PostPosted: Mon Jan 17, 2011 8:09 pm 
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I've heard similar stories about the HG but as I've no first hand experience of cause or cure I'll leave it at that.

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 Post subject: Re: Decompression plates
PostPosted: Mon Jan 17, 2011 8:50 pm 
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Never trust an engine that uses one bolt to hold the top and bottom together :beatstick:

I've had a few K engines and they have all been crap... And needed a lot of work done as soon as they hit 50-80K

When I first removed a head bolt on a K I wondered why it was 20" long?? When I was told not to spin the engine with the head off in case the liners popped out I realised just waht a shit desing it was. The coating on the ally is what gets skimmed off when you do a clean up.

The K engine seems to be a bit of a russian roulette engine. I've seen a good few that have made over 90K with no issues. I have seen a lot more that have not even made 50k before head work was needed. I also got involved in a real bargain last year on a T that had all the head work done by a proper engine shop. But the owner gave it away for pennies. Then I looked myself and found the coolant loss was down to the cheap steel coolant lines that run under the car. FFS these should be made out of stainless steel.

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 Post subject: Re: Decompression plates
PostPosted: Thu Aug 02, 2012 7:31 pm 
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Hi man, ive had alot of experience with the old k series lump. Not a bad engine once they have the newer mls head gasket fitted.
The best and safest way to turbo charge one is to get hold of a set of conrods from a factory turbo charged k series as all rover did to lower the comp ratio was fit them with 2mm shorter rods, they even used the same pistons from the na version. Also if you have the engine apart fit a land rover freelander ladder rack which is what the uber long head bolts actually screw into, it is a much much stiffer design and pulls the head down better on the gasket.
Hope this makes sense and helps.


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