I've got a wonky trumpet

[ed_crouch]

Hi all,

well, after pimping my plenum the other month, I refitted the trumpets with Hermetite red, thinking that'd resist attack from engine oil and its semi-setting nature would hold the trumpets in situ in the plenum.

Wrong!!

So, when I removed the plenum top to start investigating a rattle (thinking the worst, naturally. Already priced up a new cam, lifters, springs chain and sprockets) 3 or 4 of my trumpets were on the cock, and one in particular had been rattling in time with the engine speed.

Explains why the rattle was strongest on the plenum top according to the trusty screwdriver stethoscope.

So, what should I use to resecure the trumpets, and should I talk to my mate about machining 10mm off the bottom of them all or is that an old wives tale?

Ta!

Ed.

Edited by ed_crouch on Monday 31st August 19:38

[Campbell]

You can lop off up to 25mm off the trumpets which can help with engine breathing.
If you take any thing off the length use thread lock to glue them back in.

Cambelt

[Earl Grey]

Don't do it!!! it kills your Torque!!

I did this mod on my chim! Before the mod I had 220 bhp 376 nm torque

after ... 226 bhp 335 torque

Keep it standard!!

It's all to do with the gas flows. If you cut them too short, when the valve shuts it does it at such a speed that the velocity / momentum of the flowing gasses bounces back. If this leaves the top of the trumpet before the valve reopens, it messes with the flow of the other cylinders.

[spitfire4v8]

Then again on saturday I did some testing for a company going from trumpets to blended base and the hp trace was identical to the hp! I've yet to see any conclusive proof that any one thing in the plenum is better than anything else ...