[engine_work] 88mm Crank Conversion

[Paul_13 212 1 Cars]

I thought I'd start a new thread

 

I will be using a GTI 6 block and a diesel crank in this conversion, unsure about pistons as I will probably buy some forged/custom ones.

Just a project to do over time really and then drop the engine in and sell the old one

 

Recently bought this off a member the 306gti6 forum:

 

 

Includes:

Exhaust/inlet gasket

Valve stem seals

Thermostat gasket

Headgasket three layer (the layers seem to be separate and not joined apart from around the piston, is this right?)

Headbolts

Exhaust fitting kit (with two sets of bolts?? Bit generous of Peugeot)

And a circular rubber seal which I am unsure what it is for

 

Bit of a bargain at £130

 

And my diesel crank I will be using. Going to take it to an engine shop and see if it needs a regrind or could do with a polish.

 

 

Going to be picking up the block, head and sump this weekend or next.

 

Any advice/support is welcomed

[Anthony 1,003]

You're definately going to need different pistons in my opinion, as valve clearance is tight at TDC on GTi-6's with a standard 86mm crank, and moving the piston a further 1mm up the bore is going to leave you almost no clearance, and given how thin the pistons are I'm not sure that I'd be wanting to cut deeper pockets either.

 

If you're not going to overbore the block, you'll need to find an unworn one, as any wear lip is going to ruin the rings in no time at all as the piston repeatedly goes back and forth over it.

 

Also, whilst I've not worked it out, I suspect that you're going to be looking at very (too?) high compression - over 12:1 I'd guess.

 

I've done a 2045cc (86x88) S16 before now, which feels very strong, but that's got the advantage of different pistons without the valve clearance issues, and the head has a 4cc larger chamber which kept compression at a sensible(ish) figure - something around 11.5:1 from memory.

[Paul_13 212 1 Cars]

I was expecting to get new pistons to be honest, I've heard the clearance is bugger all and I may install cams at some point later on in the build. Money permitting lol

 

I was planning on boreing the block, not sure wether to go for the full whack of 88mm or 87.5mm. 88mm has problems of the cylinder breaking through to the water jacket I believe.

 

I understand what you were saying about the wear lip near the top of the bore, my old S16 engine had a humungous lip.

 

I haven't a clue about compression ratios, but i'll learn at some point

 

 

 

Oh yeah Anthony, my mates says a big thankyou for the engine. He's enjoying it... i'm not I need to get mine on the road

Edited July 30, 2009 by paul_xiii

[welshpug 1,657]

yup, definitely different pistons required, standard gti6 pistons are dished and come up to deck.

 

what you could use is S16/2.0 MI16 pistons, they are flat-topped and sit about 1mm below deck, drop them straight in and you'd have about 13-1 compression they'd still have a decent valve cutout too, maybe a bit too much compression though, skim them down a touch?

 

of course, you have the big bore option and custom pistons, though they're not cheap.

 

 

looooads of maths and figures here, though "disclaimer" please check them to be sure!

 

 

http://forum.205gtidrivers.com/index.php?s...=105736&hl=

Edited July 30, 2009 by welshpug

[Paul_13 212 1 Cars]

I just sent a set of S16 pistons to a bloke in Portugal who's on here.

But i'd rather get the block rebored = new pistons

 

I had a look at that thread ^

What do the figure mean with compression ratio, getting a bit confused with it all

Edited July 30, 2009 by paul_xiii

[welshpug 1,657]

not sure what's ideal but you need to work out what cams you're going to use too, I think for a road car between 11 and 12-1 is good.

 

speak to an engine builder I think, as they'll be able to assist with choosing cams and the design of the pistons.

 

edit, plenty of reading on the internet

 

 

http://en.wikipedia.org/wiki/Compression_ratio

Edited July 30, 2009 by welshpug

[James_R 3]

I'd have a look at 16v205's engine build he got wossner pistons for his engine on an 88 crane, mighty nice items aswell

[richsmells 2]

Gti6 / 88mm crank build: http://forum.205gtidrivers.com/index.php?showtopic=90889

[Cameron 16]

Don't take this the wrong way, but I think its probably a good idea for you to get a grasp of the basics before you go any further with this. Learn what a compression ratio is and how to calculate it, and learn how to calculate how far up the bores your pistons will need to sit in order to get the compression you want. Otherwise you're going to seriously piss off whoever makes your custom pistons, and probably have them come back wrong. If you put all your faith in somebody else doing the work for you, and just bolting it together and hoping it works, you're going to end up with a bunch of expensive swarf.

[Paul_13 212 1 Cars]

Don't take this the wrong way, but I think its probably a good idea for you to get a grasp of the basics before you go any further with this. Learn what a compression ratio is and how to calculate it, and learn how to calculate how far up the bores your pistons will need to sit in order to get the compression you want. Otherwise you're going to seriously piss off whoever makes your custom pistons, and probably have them come back wrong. If you put all your faith in somebody else doing the work for you, and just bolting it together and hoping it works, you're going to end up with a bunch of expensive swarf.

 

I see what you mean Cameron, was going to sit down and have a read through and try and suss it out.

I did engineering at college 2 years ago but it went in one ear and out the other...

 

Just got to learn maths again

[welshpug 1,657]

this might help

 

http://www.pumaracing.co.uk/CAPACITY.htm

[Paul_13 212 1 Cars]

Cheers, thats put it in simpleton terms for me

 

I'm going to have a go at doing a few sample calculations to get the knack of it

[Paul_13 212 1 Cars]

Got this and the roll again, going to start checking things over/mocking things and do a few calculations.

 

Of course i'll keep you posted

 

Got the:

Block

Crank

Pistons

 

Need:

Gti6 sump

Oil pump

Possibly a head... Or rebuild old one

 

Only bit i'm unsure of is the thrust bearing. Spoke to Miles and he believed this would the main problem.

I'm trying to find the topic where Sandy modifies one!?

[ryan_stdt 2]

I see what you mean Cameron, was going to sit down and have a read through and try and suss it out.

I did engineering at college 2 years ago but it went in one ear and out the other...

 

Just got to learn maths again

 

 

i wonder why lol