3.2 to 3.4 upgrade : your advices mates please !!!

[cdrik915]

Hi from France !!!

A technical question for the forum's gurus that i ask for a friend :

- 1- Is it possible to upgrade a 3.2 to 3.4 with a single distributor , JE pistons , and running with a 91 RON ????

- 2 - Will the engine work normally or do i need to down the volumetric rapport ????

- 3 - Or changing the octane value ????

- 4 - Or having a special piston's design ?????

Thanks per advance for all reply ,

Cheersssss !!!

Ced'

[sp_cs]

Hello Ced

You'll be fine with 9.5:1 CR 98mm JE pistons/cylinders, running single plug

But why 91Ron? I thought France had better quality fuel?

Is your engine not RoW spec? Should be 10.3:1 CR, so why go for a lower CR?

FYI - my 3.4 rebuild detailed here: 3.2 > 3.4 top end rebuild

SP

[cdrik915]

Thanks for your input FC-CS , really cool !!!

I asked a question about the 91 RON caus' i tried to be the more understandable as possible , knowing you've got this 91 RON in your country , don't you ???

I'm going to have a look to the link you posted .

Sincerely thanks a lot !!!!

All others input welcomes guy's !!!

[sp_cs]

No problem Ced

I'm sure France (and most of Western Europe) has the same fuel available as the UK, so 95 and 97/99Ron - we don't have 91 Ron in the UK.

If your engine is RoW spec, then 10.3:1 should be standard - mine was increased to 10.45:1 once the cylinder heads were cleaned up. So I try to fill up with 99 Ron to prevent detonation when I can.

SP

[cdrik915]

Yes , we've got 95 , 98 Excellium (with additives) and 98 RON (Octane) in France.

But i thought it was usual to find 91 RON in the States.

Sorry for the mistaken.

For the UK , i knowed that was the same fuel than in France. I didn't notice your location , sorry mate.

Thanks again for your input ,

Ced'

[Steve W]

Cdrik, here in the U.S. we rate fuel octane by AKI or CLC index, while the rest of the world such as in Europe, Australia, Asia, etc is rated by RON. The AKI index is the average of the RON and MON rating of a fuel. Typically the RON rating of a fuel is 4-5 points higher than the AKI rating, so 95 RON is equal to about 90-91 AKI, and 98 RON in Europe is equal to 93 AKI in the U.S.

With a 3.4 conversion, you should be fine with single plug up to about 9.5:1 with a minimum of 95 RON, and 10:1 with 98 RON, possibly just a bit higher, depending on how your ignition timing is set.

[cdrik915]

Sincerely thanks for this explanation Steve , that's clear !!!

[RWebb]

re the displacement increase...

is it worth the $$ to you to add 0.2L of displacement?

I decided it was not worth the $$ when I hotrodded my 3.2L -- it will add approx. 0.2/3.2 = 6% more hp & torque.

[cdrik915]

Yes , you're right Rwebb .

The difference of final cost isn't important for 0.2 more.

You mean 3.6 if i good understand ?

Does my old 915 will resist to the increase of the power and torque ?

Can you please telling me more details concerning your modifications ????

Thankssssssssssssssss !!!!!!

[RWebb]

if it is light enough then a 3.2L will be plenty

a 3.6 is great but is heavier and costs more... but why not go whole hog and shoe horn in a 3.8L RS motor....

mine is a 3.2L with PMO carbs, some valve work, appropriate pistons, not too wild & crazy cams, and SSI exhaust; Monty muffler - this was all done long ago

[m110]

Will a 3.2 to 3.4 conversion and 9.5:1 and single plug with stock ignition, cats and injectors pass smog in California? Let's say stock cams. I was wondering in case I ever have to do a rebuild.