General 1108 NA tuning?

[Renrut]

Conventional wisdom seems to be that you can take it down to the max skim measurements (the little dimples on the face of the head). After that you'll no longer have a "safe" engine. So you might want to look at an adjustable cam pulley, too.There are different thicknesses of HG available, also.

So many factors are important regarding detonation. Most obvious ones are fuelling and ignition timing. (Which is why I suggest an aftermarket ECU.) You also want to use the hardest plug you can without fouling (maybe an 8 or even 9 in the NGK range).

NA tuning to the limit is probably at least as expensive as going turbo.

"DIY flowbench" in Google throws up some stuff which might be of interest. Some good general ideas about porting here.

Thanks for that. Any idea what the approx thickness of the standard HG is once fitted? If it works out right is it possible to get rid of it and in its place either use a super thin metal HG or something like Hylomar Blue?

Just seems like a fairly cheap upgrade without too much extra messing if I'm gonna pull the head off to do some manifold to head porting work anyway.

 

[fingers99]

I'd not use blue unless you prepare the block first -- even so it'll be marginal. But the later metal gaskets are said to fit fine. While the head is off, recut the valves, new valve stem oil seals, and re-shim the tappets.

 

[Renrut]

How much thinner are the new metal gaskets compared to the old ones?

 

[fingers99]

Never had one in my hands -- I think 0.5mm or more.

 

[GoBe]

Is that 0.5mm thinner before or after torquing down?

 

[fingers99]

After. The different CRs the later ones run will give some idea. Of course, the early ones come in two thicknesses anyway, so don't treat it as gospel.

 

[timeless]

Hi,
the 1242 8v rod weight is:505g
the 1242 16v (punto mk1 or mk2) or new 500 1200 8v rod weight is:380gr

So A lightening of 500g on the unit (4 rods)

It is difficult to replace the 8v rods by 16v rods, keeping the 8v pistons?
Which are the modifications to be carried out (crankshaft, piston…)?

 

[craigb244]

Hi,
the 1242 8v rod weight is:505g
the 1242 16v (punto mk1 or mk2) or new 500 1200 8v rod weight is:380gr

So A lightening of 500g on the unit (4 rods)

It is difficult to replace the 8v rods by 16v rods, keeping the 8v pistons?
Which are the modifications to be carried out (crankshaft, piston…)?

the gudgeon pin is larger (iirc) on the 16valve then the 8valve so it would not be possible to fit them onto 8valve pistons

also not sure if the rods on the 1.2 are the same length as the 1.1

 

[fingers99]

I think the gudgeons are the same, 1242 16 and 8v. (After all, one of the turbo tricks is to use 16v pistons.)

1108 rods will be completely different to the 1242.

Personally, unless I knew that the material/heat treatment of the 16v rod was significantly better, I'd not use the lighter rod, as a hole in the block does not aid progress. In any event, get the lot re-balanced.

 

[timeless]

Hi my engine isn't a 1108 but a 1242 8v.
So my standard rods are from the 1242 8v.

 

[craigb244]

I think the gudgeons are the same, 1242 16 and 8v. (After all, one of the turbo tricks is to use 16v pistons.)

1108 rods will be completely different to the 1242.

Personally, unless I knew that the material/heat treatment of the 16v rod was significantly better, I'd not use the lighter rod, as a hole in the block does not aid progress. In any event, get the lot re-balanced.

the pins ARE different. i have 16valve rods/pistons in my turbo. same as Tricker.
the rods wont be any weaker and most likely stronger as they are a much better design and material this is used on all new cars.

 

[fingers99]

But do you know this?

It really depends how far you're going. That the rods are thinner and lighter (but is the rest of the assembly?) helps the engine rev, but were you to build a real screamer you'd use I or H beam rods, which are heavier.

Note that the longer stroke engines were never designed for high revs (by FIAT or by physics) and carry a broom and dustpan in the boot to sweep up the bits.

 

[craigb244]

i know this cos i measured them... at first i thought you needed to keep the 8valve rods and seen that it was not possible due to the wrong size pin

iirc the pin is a few mm larger but much thinner so should be a lot lighter

 

[fingers99]

I mean about the strength. Easy enough to lighten gudgeons a little by Ving the i/d where it doesn't bear substantial load.

 

[timeless]

Ok so 16v rods don't match 1242 8v pistons.