B6E Machining advice. - Compression ratios.

[ALEX 101 1 Cars]

I have A B6E engine block and I believe it to be the original matching head (1.6 XU5Ja).

the head was in need of welding before skimming see below pic of bad pitting.

They have done a fairly decent job, but long story short I'm going to need to skim a total of 1mm off to get it right.

 

The compression ratio book figure is 9.25:1 due to the deeper dished pistons than the earlier B6D's at 9.8:1.

 

I'm hoping to run a mix of 95 and 98ron fuel. Due to availably near me. I'm also changing the fuel lines to accept E10. so Knocking is a concern.

All standard 1.6  Jetronic injection system. (F plate) B6E Engine isn't original to car.

 

My options are Std Gasket 1.3mm to give a  10.31 : 1 ratio

Or 10.07 : 1 ratio with a 1.5mm gasket.

 

I'd love the experts thought on this! 

 

Regards

Alex

 

  

[welshpug 1,721]

you wont need to change any fuel hoses, the pressure side in the engine bay is a nylon line, the return is normal rubber but unless its perishing I'd leave it alone,     fuel has had some quantity of ethanol in it for over 40 years.

 

the pitting pictured isnt of any concern as its not where the steel insert of the gasket is squashed between the head and the liner.

 

ignition can be easily pulled back slightly if it pinks.

[ALEX 101 1 Cars]

I've added pictures of where I am with the head. It's come back from welding with a 0.6mm skim (took 2 attempts). They've fixed the cavity but a pin hole has appeared at the top right that im a bit concerned about as its on the gasket ring.

So weighing my options.

1mm skim might sort it (additional 0.4mm) And with it having  low compression pistons than the B6D I might be fine with just a Std gasket. 

I already have an adjustable timing pulley to compensate the retard on the timing belt.

I also need the exhaust guides changing, so it's going to the machine shop again Either way. 

Or I could maybe fill the pin hole with some metal putty.?

 

Edited December 5, 2025 by ALEX

[DamirGTI 358]

Similar happened to me while ago with 2.0 T head .. welded twice , and flattened down way too much for turbo engine making it unusable .

 

Also theres a few of those dimples on mine but smaller and on other areas ..

Impurities bubble up during welding (wrong gas could be too , thicker alu. needs helium gas not argon) , welder sadi was hard to weld even after good cleaning and preheat .. they're not easy for "general purpose" alu. welders .

 

This one looks tricky because craters are on the fire ring area .. standard epoxy will not work id say , propper high temp epoxy like Belzona stuff would but costs quite a bit .

 

Honesty id try to find another good head , that's if you can find some in UK at reasonable price ? 

Non GTi head will be cheaper for sure , like from the 406/Xantia 1.6 and 1.8 .. just swap the cam .

 

D

[ALEX 101 1 Cars]

You're right the head was welded by a general ally welder.

 

New head wasn't what I was hoping to hear.  These are getting less common to find than they used to be, 2nd hand ones are a gamble and could be worse than mine. There's a recond one going for £600, but it doesn't say how much has been machined from it. (Also my options increase if I'm willing to budget that emount). TBH I'm not.

I thought I'd struck lucky finding out it's a low comp 9.25:1 B6E after reading up on here about 9.8:1 is too low anyway with the more common B6D. Saying talk of 2mm skim is OK. 

 

I'll take it to my local enginine builder for advice, they'll know about what is needed for a good lasting seal,  though i thought best advice about compression ratios woubd be here.

 

 

 

 

Edited December 5, 2025 by ALEX

[DamirGTI 358]

I see , 600 here buys entire engine  ..

But such head was fitted on various other models making them "less GTI" marked up price . Only real difference is the cam .

If you'd like i know an place where you can find them for around 80-100EU + shipping (around 50EU) .

 

Mine had till now 2mm skim , chambers where just 24cc (on 1.9 engine) , still high over 11.1 one period even 12.3 CR .

Timing needs correcting both cam and ignition .

Will likely need 98/100 RON petrol period , mine does ..

 

If i was to start over Id build lower CR engine but with as much squish as possible , and plug it on Motronic management .

 

D