Decompression Plates?
Turbo Mini Forums

I know alot of people dont like them and I am not a huge fan myself. But I have just bought a 2nd hand supercharger kit and want to stick it on my existing engine and have a play around while the weather is good and do a proper build in the winter. What I want to know is does any one know a good supplier or ones to avoid? Looking at some of the pics I have seen some are stainless and some are just steel. What is best? Does anybody want to sell me one?

Supercharger kit is suck through 8psi

Thanks


Mark

stainless is going to be more heat resistant, doubt it will really make much difference unless the gasket fails,

apart from that there's probably not a lot in it.

alter the combustion chamber shape to the right size and CCs its cheaper and the right way

Edited by BENROSS on 24th Jul, 2008.

I dont want to alter my cylinder head just yet till I have a little play around with the charger setup. My head is a well sorted race job. Not even sure if I will use it on this engine on get another one.

Stainless is better, but I'd happily use mild steel. Thing to watch is that it's been nicely cut - ie no jagged edges on the four large holes to make hot-spots.

So long as you know it's not ideal, and you're willing to accept that, then crack on.

Only other thing to consider is that your valve geometry is all to cock. Longer pushrods, or an insert dropped into your followers will help return matters to a sensible level. Again though if you don't want to do all this - it will work, just not as good as it could be.

All in all - it will make more power than if you leave it with one eadgasket and don't fit the supercharger - even considering all the shortcomings of this less than ideal method of achieving the end result.

Echo what Ben says though - do it right come the winter

Edited by turbodave16v on 24th Jul, 2008.

im running a mild steel spacer plate on my bike ,500cc running 15 psi boost 130 bhp odd ,no problems in 6 years .

i dont undestand why the valve geometry should change , if the rocker post and the valve top are in the same place as they were, then a few turns on the tappet adjuster would put it all back where it was ?

(probably being hopelessly ignorant here )

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Im in the same school of thought as you on this Robert, but someone please feel free to enlighten me further.
Shane

Robert

What you suggest would probably work OK on an overhead cam engine but the A-Series has push-rods which won't get any longer and once you have added a spacer plate the point on which the top of the push-rod has to act is higher up hence a change in geometry.
As TD suggested, longer rods or amending the cam follower would alleviate the problem, but all told it is a less than perfect solution.

Draw out a rocker on a piece of paper and you'll understand. The pivot points are the key - and for a roller rocker they are the axis of the roller, the axis of the rocekr shaft, and the centre of the ball on the adjuster. For non roller nose rockers, the pivot is the wiper pad.

All this makes a difference.

The decompression plate will actually bring my rocker geometry back to normal (oer neear normal) as my block had been decked I was running with spacers under the rocker pedestals.

Thanks for the remnder though! I might have just bolted it back together as it was.

probably being totally fik here ...

so the axis of the roller has stayed the same ,
the axis of the rocker shaft has stayed the same ,
how does moving the contact point of the tappet adjuster 1.5mm
(or whatever the spacer is )
further down, have any effect ?

( unless your all talking about the increase in triangulation between the lifter ,rocker boss where the threaded adjuster goes in ,and the ball on the end of the adjuster ,which would increae rocker ratio on the upstroke then decrease it on the down stroke ,but all minimally .) :$

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM

Edited by turbodave16v on 25th Jul, 2008.

Edited by turbodave16v on 25th Jul, 2008.

yes dave my v8 in the tvr has kenne bell adjustable pushrods .

Medusa + injection = too much torque for the dyno ..https://youtu.be/qg5o0_tJxYM