The V8 Owners Forum -

finished up making the plastic trumpet bases. made two; one is 40mm id for std manifolds (well - actually the OD of the steel trumpets - the idea is you cut them flush) - and a 44mm one which is tvr spec which requires work on the base to sleeve some of the bores.

I tried my hand at grinding a tool from a blank - which cuts the flares in one go - i'm pleased with the results. (amazed the damm thing actually cut rather than just push the plastic round in a molten blob!)



Biggies http://www.mez.co.uk/ms12.html#trumpetbase

Where do I sign

(Looks excellent!)

eliot,
any plans on doing anything for the twin plenum?

Will you be offering these like the 71mm throttle mods?

Looks excellent

Thanks guys.
Ive updated the page with some ideas of cost. If anyone on here buys one - i'll donate some cash to the board.

Elliot very impressed with the nylon trumphetless base addition. However I cannot help questioning that the inner intake tracts will have an overall different length to the valves, the reason why the rover trumphets have a 15mm difference in height.

Looked at your site, very interesting.

adamnreeves wrote:However I cannot help questioning that the inner intake tracts will have an overall different length to the valves, the reason why the rover trumphets have a 15mm difference in height.

As i said before - I dont know what the effect of the uneven inlet tracts will be on the engine. The only way to understand it would be to dyno before after and read the plugs to check for even burn.
Look at the average cast exhaust manifold - not exactly a work of semitry either.
TVR Power remove the trumpets and blend the base (http://www.tvrpower.co.uk/taraka.php) - maybe they know the answer!

the effect of trumpet length will be related to the choice of cam and exhaust (and compression). On an engine producing less than about .8bhp per litre I doubt you will be able to detect any change at all by changing trumpet length by about 2 inches. Get above 1 BHP per litre then your cam/ head/ exhaust combination will mean that you will be trying to ballance all the cylinders in every aspect and the inlet tract length will become significant as will be indexing plugs, matching deck heights, rod lengths, chamber sizes and indexing the crank. With a cam timing below 240 degrees at .05" i would not worry, spend your time on the exhaust and heads.
Hope this is of help
Mike

kiwicar wrote:On an engine producing less than about .8bhp per litre I doubt you will be able to detect any change at all by changing trumpet length by about 2 inches. Get above 1 BHP per litre then your cam/ head/ ......

I take it you mean 80BHP per liter and more than 100BHP per litre?

Just edited to say that a NA 80BHP per litre RV8 will not happen unless it is a full race engine

yes sorry I do
Mike

re your edit
I agree with you if you are using a rover engine it would be full race, however if you are talking SBC or SBF you can easily get 80 per litre on the road and 100bhp/l can be done with the right bits and alot of care, then you need to worry about everything including inlet length.
Best regards
Mike

I kinda of agree what you are saying regarding inlet length but if it is only a concern when exceed 80BHP/litre then why did Rover bother! As you know car manufacturers do things as cheaply as possible usually.

I was just lying in the bath thinking the same everything I have ever read and all the tuners I have spoaken to say it is only worth bothering with inlet tuning when you have done everything else, the returns just ain't worth it until the engine is in a fairly high state of tune. The only thing is that the rover trumpet is basically a simple tube insert, to match the lengths you only need two lengths so it would be dead simple to do, probably add 10p to production costs, if that, so not a really big deal even in the penny-pinching world of rover production.
I supose the exhaust manifolds on the later RR injection engines are designed to be 4:2:1 units and it may be worth a little extra power or smoothness.
Also it may have more to do with ballacing the mixture distribution rather than inlet tract tuning, the center trumpets are closer to the plenum roof than the outer ones, this may lead to the inners feeding from the upper part of the butterfly with the outers from the lower part of the butterfly an low/medeum throttle openings it may reduce charge robbing between the inner and outer cylinders?? .
drying out with a headache
Mike