3.2L to 3.5L machining

[quint22cp]

I'm 1/2 way through the engine rebuild of my Euro 3.2L

I want to keep costs down so I'm planning to undertake as much work as possible. I have access to a machine shop so I'm considering DIY twin plugging and boring the crankcase for 100mm cylinders.

Questions:

On this forum I have seen references to chamfering the heads, is this a 45deg bevel to match the 95mm head to 100mm cyl'd ?

Does the mating surface between the head and cyl'd need enlarging to match the 100mm cyl'd ?

As there is no gasket at this joint what sort of surface finish should I be aiming for ?

Has anyone got an old head to practice on I am prepared to pay for it and the shipping to the UK.

To all you UK readers has anyone found a quality machine shop in the UK who can undertake valve guide replacement and valve seat cutting ?

thanks for all the help you guys give, it's a great site.

[cnavarro]

The head register is the same going to the 100mm 3.5 cylinders from the 95mm 3.2 cylinders, just the case register goes from 103.00mm to 105.00mm, just as you already know :-)

I can't comment on the degree of the chamfer, but it's not a bad idea to put it in there, just take out as little material as is humanly possible.

If normally aspirated, don't worry about a sealing ring, unless this is a racing engine with tons of compression. I'd rather leave more meat in the cylinder than cut a groove into it.

[MBEngineering]

HI quint22cp just where are you and I can point you in the direction of a head man to sort the guides for you if you are south , if not you can send them to me , I can also get the twin plug work sorted, I have 3.2 heads twin plugged on the shelf?. which pistons are you using and have you had the crank stroked.

regards mike

[quint22cp]

Hi MBEngineering,

It's like a Porsche vacuum in the UK. The US appears to be awash with parts and quality machining.

I'm in the West Midlands but shipping stuff around the UK is no probe as I can use the shipping dept' of the company I work at.

I was looking to use pistons and cyl'ds from 'Nickies' (LN Engineering), from reading this forum the Mahle Motorsport here on Pelican appear to deviate from the advertised compression ratio and I want around 10.5:1

No I haven't had the crank stroked.

Is ROB WALKER PERFORMANCE ENGINEERING LTD any good ?

[cnavarro]

To be perfectly honest, there can be some variation with the JE's since they are usually supplied 'off-the-shelf' and have been based off someone elses chamber volume. The only way to have it perfect is to take your actual cc's and then size the dome properly, which isn't a big deal, but something to keep in mind when ordering.

[BReyes]

I have heard said the 3.5 is too much, a 3.4 is better. I guess it is related to this chamfer issue? Were talking new P&Cs twin plug with a flame ring. Heard lots of 3.5 around too.

Who has the lightest pistons? What are the piston to cylinder tolerances?

Regards,

[cnavarro]

The mindset of the 3.5 being too much stems from the fact that the walls are thinner and that it is questionable that flame ringing should be done to a 3.5 cylinder just for that same reason, but if the boost is reasonable (under a bar) and good head studs are used, I wouldn't be concerned. Normally aspirated, it's a mute point. I've done quite a few 102mm '3.7' sets N/A for both street and track.