85mm pistons

where can they be got, 84 is the max im seeing, thanks.(possibly high compression 85s too)

 

the bore walls will be v.v.v.v.v.v.v.v.v.v.v.v thin unless you plan to offset bore?

accralite in b'ham will make anything you want

 

Audi found some / had them made by Mahle for their Tourers - thread

 

yea i know, i may just go 84s but 85s really tempt me. i know bore flex will be a problem at high rpm, but i intend shaving the block 15mm anyway so i was thinking i could machine ''liner'' type protrusions to stick up say 2mm and recess the head for them like the ferrari 308s are done. that may help flex a bit.

 

better you than me

 

Sounds like you're buying expensive unreliability.

 

Or building a very high spec 16V - which I'd like to see done.

 

Well in theory you could use a deck plate like the turbo Honda guys.

Which you'll need anyway because the deck is only 8-10mm thick (at most) but what are you going to bolt the head bolts to with most of the stud hole machined away...?

Or are you planning on a deck plate and a lower girdle then bolting right through like the Rover K series...?

Could be a little expensive unless you work in / own a machine shop (and a complete waste of time for a road car before you even start thinking about reliability).

As RobT says the bore walls would be very thin, to be honest if your going to all that (machining) effort you may as well loose the stock bores completely and fit some Darton Sleeves.

Cheers

Simon

edit: why do you want to take 15mm off anyway? (and off what, a "tall" or "short" block)

 

there was a engine a while ago the had 84mm pistons, and they struggled to stop it drinking oil due to the bores flexing.

Would it be possible to get a block heat treated or something to stiffen it up.

 

I'd think you'd have to heat treat it before machining - stuff tends to warp in heat treatment.

The overbore and decking the block could sort some of it, but I think you'd end up with a lot of leaky gasket faces.

 

i suppose a short stroke would help too

 

for a start i have all the machines i need, im doing it to pass the time, its going to take me ages, i dont mind, unreliable it wont be, it will possibly need to be rebuilt more often.
its not going to be a daily driver by any means, ive plenty other cars for that, just doing it to see whats possible, getting tired of the usual lark in the line of engines, just want to make something special for me, no-one else.
im going to raise the intake ports approx 15mm(looking at cut heads for months, its the max ill get)as the standard port angle is shocking. i know it can make 200hp but every little helps with a n/a engine, as everyone knows, few hours on the mill and a lot of tig welding should see it done. i can remote feed the oil ways to buckets over the injector cut outs if need be but i dont see a major problem with them.
thats pretty much it, anyone that wants to think otherwise about my choices by all means do, im just passing the time, sure it mightent work at all...

 

sound fantastic, keep us all updated as i'm sure everyone would love to see such a serious engine build

 

If you've got the time and the skills, why not? Go for it, it would be an awesome engine.

 

agreed - sounds like you know whats what - best of luck - it would be nice to see something a bit new

 

thanks guys, and i really mean that, nice to see open minds instead of people saying it wont work or your wasting your time or itll never happen.
im going to be going out on a limb but to hell with it im going to give it a shot.

 

Looks interesting what displacement will it achieve ?

i would go for a stroker crank for the extra capacity, which was the route i was going to take before i got the 92.8mm stroke Eurospec crank off Neal H.

Mike H has gone the Stroker route i think from memory .

 

Have you looked at this thread yet? lots of good info

 

looking at figures on the engine simulator im having trouble getting past i think 1720cc, i dont want a massive throw on the crank, although it will make more torque my rpm output vs work done will be lower due to more swept travel(bigger circumference), bigger journal travel, more friction losses etc , and we all know that hp = torque x rpm/5252, ive a ton of thinking to do yet.
86.5 looks a good throw, but ive alot more number jiggling to do yet..
hp at high revs is all im after, dont care if it has 0 hp low down or if its a pig in town, i just want to hear her scream, and hopefully be interesting in the hp levels up there

edit, i know i should run bigger cc to start with but as 84 is the max ide like to go with the bore, the 85.5 crank suits for the bore stroke ratio in order to get high rpm without it getting too crazy down the bottom end. as i said, ill play round with the simulator tonite another bit, another angle is to keep it at 1600cc and maybe use it in a rally car as 1600 is the biggest your allowed in Ireland if your a first timer.
big hp isent really my goal, but big hp in respect to the cc IS.

 

my 2L valver made 205 psi bmep last time it was measured so thats something to aim at for an efficiency target