Is it possible to make 29cc dome head -> 35cc ???

[Christian_83]

First of all. what is the 29cc a number for, cubic centimeters no.. ?
Then - i got a brand new riva girdle head with non-removalbe domes with 29cc domes. this i too much for me, i would like about 35cc (around 185psi)
Can i get a machinist to remove some material from the domes, making the domes "bigger" ? If yes anything i have to take care of, angle of the chambers or... ?
The reason why im not buying a new head is - thats parts are freakin expencive in Denmark, a new head (ATP with removable domes, like ADA) in DK would cost 690 dollars..
so if i got get my new riva girdle head from 29cc to 35cc that would make my happy ??
Hope you guys can help me

Thanks Christian

 

[Jr.]

Yes, the head can be machined to accomidate that change.
I suggest you contact Chris at Queensford Leasure.
he is more than capable to preform the work for you!

 

[jura]

Maybe I can ship you a 35cc dome. You can mesure it and use it as an example for cutting your head.
Let me know.

 

[godocgo]

is this a flat top dome? i don't remeber riva making a 29 cc domes for round tops, but maybe they did. if it is a flattop dome the compression should be in the 180 range if it is ported. mine runs 178 compression with 29 cc domes on a 85.5 r & d piston.

 

[Christian_83]

i donno if its a flattop ? how do i see that ?
my engine is stock 81mm.

Thanks

 

[Christian_83]

This is what the chambers look like ?
Can anybody tell me if this is for flattop or what ?

 

[Christian_83]

Jura - thanks i will keep that i mind

 

[Shonuff]

Can you go with a thicker head gasket rather than the o-rings?

 

[restosud]

what is the gas octane in denmark,no lead 95 and 98?you can run more than 185psi with european gas you know.with the 98,195 would be ok,that way you don't have to recut your head.

 

[Matt_E]

what is the gas octane in denmark,no lead 95 and 98?you can run more than 185psi with european gas you know.with the 98,195 would be ok,that way you don't have to recut your head.

No no no. :nono:

European Gas octane numbers != American gas octane numbers.

The highest octane pump gas in Denmark will be about equivalent to the highest available in the US.

 

[restosud]

matt,i know your wrong on this.most of western europe has 98 unleaded available at the pump.the low grade is 95.i'm just not sure with sweden,norway or denmark.

 

[#ZERO]

Oh come on guys…..we did a thread on this a while back and it's the same gas. :banghead:

In the United States, pump octane is an average of 2 ratings, Research Octane Number (RON) and Motor Octane Number (MON). If you look at any gas pump in the United States, you will see a yellow sticker that says "octane by R + M / 2" That is the basic formula for an average. These 2 numbers mean different things. The Motor Octane Test employs a higher temperature and RPM and hence is probably a better indicator for today's engines.

In Europe, they only report the RON. You may hear people discussing that in Europe, the octane is higher. Well, that is not exactly true. You see, in Europe, you might find 98 octane at a local gas station. (wow 98, highest we have here is 94). Well, that 98 is equivalent to 94 here in the States. The Research Octane Number is always higher than Motor Octane Number.

The octane value of a fuel can be varied by several different processes. It can be refined to that value (usually more costly) or enhanced with different additives. Different people will argue which method is better.

Of course the Research octane test gives a higher number and that's why the European manufacturers quote it (RON)

http://www.btinternet.com/~madmole/Reference/RONMONPON.html

 

[Matt_E]

EDIT: Beaten. Point is, I do know what I am talking about. :fingersx:

I am right.

Here's the lowdown:
There are two different numbers for octane. One is RON (Research Octane Number). It is based on theoretical stoichiometrical calculations. It is always higher than what you would expect to actually use.
Then there's MON (Motor Octane Number) which is a more practical way to express octane levels.

In the US, octane levels at the pump are quantified using the equation octane = (RON + MON) / 2 (Don't believe me? Check a pump!)

In Europe, the pumps use RON (the higher of the two) exclusively.


So, if you expect real 95 octane gas at a Danish pump, your motor will have a surprise for you.

 

[Christian_83]

Hmm we got 92 ocatne and 95 unlead and super 95 (lead) and some places we still got unlead 98 octane.
I would prefer to run on 95 unlead beacuse we dont got 98 at all gas stations.

Cand anybody tell if this head is for flattop pistons ?