bore size

[cabrioman 6]

whats the biggest size i can have my block bored out to ie from 2.8 up maybe 3.0 or 3.1 ??

[jims13 6]

ive been told no more than 3.0 litres

as the head design dont allow for much more..

i could be wrong !

jim

[clarkie 1]

i have just orderd 83mm (3 ltr) any bigger then the wall gets a bit 2 thin and can cause probs

[Lizard Racing 0]

Im sure you can go to 85mm, but you need a good seasoned block but as said above walls become very thin. There will be very little gain in capacity increase to be honest. 83 or 83.5 is ok but is only needed if your bores are buggered.

[chazrad 16]

Once you bore out to 3.0 or 3.1 L, you should apparently not be going force induced, because as said the walls of the cylinders get pretty thin. If you are after the biggest NA engine you can, then fine. If you are planning to go 'charger or turbo, then stick with a general rebore to 2.9L.

[jaysVR6 2]

The Americans have been running 3.0 turbod vr's for years but I think rebuilds are common.

I had my VR rebored to 2.9 two years ago and considered 3.0 but the bores become far too thin imo.

You could however do it properly and use a stroker kit, but the VR engine is now an old piece of kit and I'd think long and hard about spending over 2k having a rebore and stroker kit fitted just to get a small amout of NA power out of it.

Certainly not worth it imo unless you are a mechanic and can do the majority of work yourself.

[FishWick 21]

3L doesn't exist. You will get 2.9 and a bit. You need 84mm pistons to get a 'true 3.0' at 3003cc.

83mm gives you 2931cc and 83.5mm gives you 2967cc. The latter size does safely give you 494cc per cylinder, which is quite handy as 500cc per pot is considered the optimum by BMW :-)

85mm.... on a 12V, no way. VW did it with the R32 block, but that is a complete new casting and nothing like the 12V block.

Personally I would stick to 83mm max.

[cabrioman 6]

cool cheers lads looks like ill be goin for 83mm then as i would like to charge it at some point ... any idea of rough cost and where to get it done like stealth or .....

[pops 1]

theres a company in ipswich bit closer than stealth, called scholar engineering, can rebuild bore what ever you want, been around years, and reasonably priced too

[Lizard Racing 0]

For a little more money you can drop an R32 lump in and run it on stand alone!

[cabrioman 6]

really ...... aint that goin to cost ££££`s ????

[Lizard Racing 0]

Yeah its do able for sure. Engines are going for less than a grand Emeralds are going second hand for £350 bit of wiring etc. Use your box and Flywheel also your cooling sytem pipework.

[markiev6 1]

if your gonna be picky 2.9 doesnt exist either

[Lizard Racing 0]

?

[xyber 1]

R32 option is the way to go I think out of the 2, they are getting silly cheap, low milage aswel!!

[craggsy 91]

Markiev6 wrote..... [blockquote]if your gonna be picky 2.9 doesnt exist either [/blockquote]

How can you say this when quite clearly Kev says this.....rather beleive what Kev says to be honest

3L doesn't exist. You will get 2.9 and a bit. You need 84mm pistons to get a 'true 3.0' at 3003cc.

83mm gives you 2931cc and 83.5mm gives you 2967cc. The latter size does safely give you 494cc per cylinder' date=' which is quite handy as 500cc per pot is considered the optimum by BMW :-)

85mm.... on a 12V, no way. VW did it with the R32 block, but that is a complete new casting and nothing like the 12V block.

Personally I would stick to 83mm max.

[/quote']

Now I know nothing about this type of thing but even I know that 2931cc and 2967cc equals 2.9l engine

[Lizard Racing 0]

.....and mine is also 2931cc!

[markiev6 1]

a 2.9 is a 2.861

[Phat VR6 3]

so a 2931 with 83mm bore is a.............2.9!!!!

[FishWick 21]

I know where Mark's coming from.... it's an old 'rounding up' thing they used to do years ago, and still do actually....

2861 is closer to 2.9 than 2.8, so it's classed as a 2.9.

2931 is closer to 2.9 than a 3.0, but people still call it a 3.0? It's still a 2.9 imo.

2967 is closer to 3.0 than a 2.9 and can technically be 'rounded up' to a 3.0 I guess, but in my book, 3 litres is 3 litres, so 84mm pistons required ;-)

Where it gets complicated is if you have exactly 2850cc, what the feck do you size it as then?! 2.85? :-)

[cabrioman 6]

well thanks for all the advise and tech stuff but im not goin R32 route im goin for 83mm pistions which will make it a 2931 cc for thoses who care :-p :-p so i shall keep u all up to date with a step by step guide .. and rough cost etc etc so watch this space

[Phat VR6 3]

What make and compression you going for?

I know you can get 83mm JE forged high compression (10,1) pistons from schimmel performance for $740. I think that works out to about £400 ish which isn't bad, Not sure about postage and import tax....

http://spturbo.com/

Also quick qwestion on the same subject. How do you know if you need a rebore, If your compression is good.... If they just look smooth/polished then wont just homing them do the job, Or is there some kind of messurment you can do with internal vernia gauge, Orr leave the piston and use feeler gauges??

Thanks, should be an intresting tread, Pictures will be nice and if you could post how much it cost you to get your block machined that would be great

[cabrioman 6]

i shall be doin all the above for all the club to see phat vr6, and u measure the bors but u need to know wot ur doin and lookin for i just wanna do it cos the rings have gone on mine and thought id treat my self to a bigger engine lol

as for pistons ill be using wot eva vince at stelth recomends which if i remember was wossner i think ?? cos he said JE are good but a lot more work to ring them and fitt them ....

[jaysVR6 2]

I've got Wiseco forged 83mm ones in mine with standard compression. Before I fitted the charger one thing I noticed was that the induction roar was twice as loud! It sounded bloody mental! To be fair, you wont notice any massive performance increase though if at all.

Rings are always a slut on a vr anyway because of the angle of the bore. The garage did a ring fitting my pistons and had to buy a new set.

Have fun!

[cabrioman 6]

thats y im send it the the experts lol if they balls it up they gota fix it lol