Need help with 2.7 conversion about shave piston 3 mm ?????

[jojoejoez]

Hi everybody I Need some advice because I'm going to made 2.7 with my engine but I don't know how to made it exactly so could anybody told me hotw to build it



This is the way to make 2.7

1. use 325e crank (81) + 325e piston + 325e con rods (130 mm) + 325i head = I think this will give me a low compression but suitable for turbo the compression is about 7.9



2. Use 325e crank (81) + 325e con rods (130mm) + 325 i piston + 325 i head = But i have heard that If I'm using 325e con rods which are 130 mm The piston will lower about 2 mm so I have to shave the bottom end for 2 mm and I think this is not a good way

3. Use 325e crank + 325 i con rods [ 135 mm ] + 325i piston + 325i head = I have read that This will give piston up from the block for 3 mm so I have to shave piston for 3 mm and do you have the picture of the piston that shave head for 3 mm ? and how much compression do i have if i shave 325i piston


Is this right ?? I don't sure about how to make 2.7 correctly


and which is the best way for you To make 2.7 With N/A I'm not plan to turbo I decide the Shave the piston for 3 mm. Can anybody confirm me that it's correctly to shave the piston 3 mm. And How much compression do I have If I using the 325i piston with Shave head of the piston
I can't find super eta piston in my country I'm living in Thailand Thanks

[Widge]

I have never heard of anyone machining the pistons as it would be very expensive to keep the shape for the power.

If you want to keep the setup in the photo email Mike at FERRIDAY ENGINEERING and ask about bonding an ali plate to the bottom of the head.

If you use 320 rods with the 2.5 pistons and head you will need to deck the block approx 3mm and machine the pistons to clear the crank counterweights.

After all this you will need a vernier cam pulley as the timing will be out - avalible in the zone shop soon.[/url]

[jojoejoez]

First, I think about shave the block for 2 mm if I using 320i rods with 325i piston but It will have a problem with the temperature of the engine. The engine will be more hotter if shave the block

I have reading many people are shave the piston like this


But I can't remember Where I save this picture from
So could anybody confirm me that I shold shave the piston for 3 mm from the top of piston[/img]

[jojoejoez]

First, I think about shave the block for 2 mm if I using 320i rods with 325i piston but It will have a problem with the temperature of the engine. The engine will be more hotter if shave the block

I have reading many people are shave the piston like this


But I can't remember Where I save this picture from
So could anybody confirm me that I shold shave the piston for 3 mm from the top of piston

[Jimbob]

I shaved my piston skirts..

[jojoejoez]

After that I tried to put the M50 piston in the block with 325e crank and 325e con rods the result is the pistons is lower than the block for 1.5 mm

[Widge]

Wow wow wow - hold the horses

Why would shaving the block make the engine hotter????

And those pistons look bloody aweful - BMW designed the pistons as they were for a reason, and that is very rarely done for a reason, I should think that picture was from someone experimenting. I think the valves will hit those pistons too as there are no cutouts - and no hump which aids the mixing of the mixture for an even burn giving more power and torque. Also they will enlarge the combustion chamber. You will sacrafice power and possibly compression by shaving the pistons like that. It would work out better to have custom pistons made, and probably cheaper in the end.

[jojoejoez]

So you wouldn't recommend to shave 3 mm of 325i piston ?. buy the custom piston is better right ?


I think shave the block will have some effect and made the engine hot. I'm living in Thailand and the Average temperature is about 35 cencious

[Widge]

Shaving the block will not make any differance to the water jacket or water circulation so as long as your cooling system is up to cooling a 2.5 it will cope with a 2.7.

As for custom pistons, yes if you can afford them go for it!
I am afraid I think M50 pistons would be pointless too as they are designed for a 24v head and so are the wrong shape............. everything is about the shape

[jojoejoez]

I'm going to sent my m20 325i piston to shave for 3 mm tommorow This is my piston

[Widge]

Well it's your project mate - good luck