Forget him Dennis...

We all know who the "man" is.

You have been on here and the older HPI forums helping us all out with correct and usefull information for years. Your engine mod skill and knowlege speaks for its self.

And whilst it may be true that no question about engines is directed at anyone in particulay, most of us hope to see a reply from Dennis. Accurate and informed responses!

TG777 your posts while interesting do not constitute an answer to the persons question. You have special pistons and sleeves, rods etc etc that none of us have so using any of your tuning teqniques or advice is pointless to 99.99999% of the forum users, and as Dennis quite rightly pointed out using your advice may actually damage peoples equipment.

I am happy to read your posts but please remember that most of us will never buy your engines or equipment so keep your "experimental" posts in the "experimental" engine war thread.

I think my question is getting lost in this soap opra.

Can anybody please answer my question about boost bottles being the same concept as expanding the chamber by adding shimms?

Why don't we just take the "experts" to the sideline and let us mortals state our experiences with what works and what not

As I stated earlier, I run my Nova Rossi based engines (Mugen, RB, Nova Mega and Top, most modified and ugly fast) in very hot weather.

I use 30% O'Donnell fuel with 0.3mm shims under the head.

For plugs I use either MC 59 or CT5F which are the hottest plugs of their kind.

I have never had a problem with pre-detonation, neither has any of my engines developed a hunger for plugs (I actually ran a CT5F turbo plugs for over 3 month, racing every Sunday)

Usually I run them between 240 and 265 F.

So, all theoretical knowledge aside, these are real world experiences that are prooven to work.

Next opinion please!

Slammed,
A boost bottle has nothing to do with the combustion chamber. A boost bottle theoretically evens out the pressure pulses in the crank case and improves low end response and smoothness.

So, to answer your question, a boost bottle is not the same concept as expanding the chamber with shims.

Stefan I heard that somewhere before?

Rapid Roy

Maybe an echo?

Maybe just a way to keep you two lovers from cutting each others throat.

Better real information twice than y'alls catfights

Motorman - all respect to your knowledge. I missed it when you took your sabbatical from this forum.

Can you give a General principle for shimming and a starting point for, say, an MT12.

What I mean to say is - at a given % Nitro- increasing the gap generally does X (and you need to do Y to your plug). . .

Also - I've heard that you can use a piece of Solder to measure the gap. . .is that an okay method?

I used the solder method. It worked OK. just bend a piece at a small right angle and insert into the head and tun over the engine then mic the flat piece.

It came out the same as measuring the depth of piston and thickness of head button so but it did confirm the measurement

boomer have PM

Hai Motorman...
I need your input, do you always add xtra shim, let says .5mm in total when you break in a new engine ?
Im talking about high end one.

For your reference.. im a newbie but im done a lot of engine break in the hudy bench.

no not usually, I usually run it like I expect it to be. Usually I rarely change the head shimming to start with unless its off from the recommendations I have posted.

Help! I am running a Rossi Pixi 5pt. on 40% Byrons. I want the most out of my engine. I have 2 shims under the cooling head now. Should i take both of them out. I really don't know the thickness, but they are stock. Please help ASAP

yess loose them and install one of the thinnest ones you can find or see if it will seal without any. Use an odonnel 77 plug in that setup. you need the extra heat This is only a recommendation for the PIXY.