Ive been considering ways to get more power out of my now working 1242cc...

I understand an old trick on Nova's (Fordy, back me up mate) is to use a head from a smaller block on a larger engine to raise the compression ratio- eg: (1.2 head on 1.4 engine)

Ive been thinking whether this'd work on the FIRE series, as according to Pete,the 75 runs a higher comp ratio anyway.

Anyone any ideas on the compression ratios on the following engines?

Punto 75 1242cc MPi
Uno 50 999cc SPi
The GSR 769cc FIRE Unit (SPi)- This I would love to know, just dont know what car this comes from!!(That head on a 1242 could be fun!)

I would just try mix and match, but Im very keen to avoid melting holes thru the pistons and that guff

Tom (AofB)

95 Cinq Sporting - Rattly GrpN Catback Exhaust, <font color="black">Buckets</font id="black"> and 3pt Harnesses,Sexy VW styleé dials (that look great, but dont work!! D)), 10" Sub and 6x9's, ETech Wing. Lots of Dirt!
1242cc Engine in car, not starting, boot delock soon, K+N still in garage!

Punto 75 - 9.8:1 CR
Punto 60 - 9.6:1 CR

Pete.

Links: 1242cc cinq, turbo cinq, Cinqs&Seis forum, Clubcento

The 769cc FIRE unit is a panda 750 engine i beleive

Used to own one




The Man that Can

Just take your own head (no I'd better rephrase that) Take the cylinder head you have and have it skimmed. Take the block.piston measurements to the engineering shop and they will take off enough, but not too much.

Cheers

D

Grumpy old git going fast downhill rather than downhill fast!!

Block-Piston measurements?

Im a little confused D...is that the displacement of the piston relative to the top of the block at TDC?

CR on the 45 Head (999cc) is 9.6:1
CR on the 35 Head (769cc) is 9.4:1

I think I'll start with a high comp one anyway!

Tom (AofB)

95 Cinq Sporting - Rattly GrpN Catback Exhaust, <font color="black">Buckets</font id="black"> and 3pt Harnesses,Sexy VW styleé dials (that look great, but dont work!! D)), 10" Sub and 6x9's, ETech Wing. Lots of Dirt!
1242cc Engine in car, not starting, boot delock soon, K+N still in garage!

You need to accurately measure how far the piston protrudes, if any, from the block at TDC. If the piston does not protrude then you need to know how far down the block it is. There is no point in a huge increase in CR if the valves smack the pistons every turn.

Also be aware that an increase in CR may point you at the Optimax pump every time you go to fill up.

Cheers

D

Grumpy old git going fast downhill rather than downhill fast!!

oh dear...I suppose It may be worth it

Just entered my head, but do yu think the piston-block distances would be the same on the 1108 as the 1242? Especially given the heads are the same on the SPi engines!
Ive got a decapitated 1108 sitting round here somewhere...

Tom (AofB)

95 Cinq Sporting - Rattly GrpN Catback Exhaust, <font color="black">Buckets</font id="black"> and 3pt Harnesses,Sexy VW styleé dials (that look great, but dont work!! D)), 10" Sub and 6x9's, ETech Wing. Lots of Dirt!
1242cc Engine in car, not starting, boot delock soon, K+N still in garage!

given that FIRE engines are non-interference engines, surely the 750 head should have no problems on the 1242 regarding valves smacking pistons?




www.brickfoot.co.uk

I'd think it would be a backward step - surely the bores will be smaller and the valves too in order to match?

Pete.

Links: 1242cc cinq, turbo cinq, Cinqs&Seis forum, Clubcento

Yeah probably.

I think I'll stick to the standard head and play with that!

Tom (AofB)

95 "CinqGTi" 1242cc - GrpN Catback Exhaust, <font color="black">Buckets</font id="black"> and 3pt Harnesses,Sexy VW styleé dials (that look great, but dont work!! D)), 10" Sub and 6x9's, ETech Wing. Lots of Dirt!
boot delock soon, Induction in development!

There is plenty of meat in the head ( No I'd better start that again) the cylinder head has quite a lot of excess metal in the ports that can be got rid of. To be really clever get a scrap head and cut it through a port. This will give an idea where all the waterways are and give you a guide where to grind.

Cheers

D

Grumpy old git going fast downhill rather than downhill fast!!

that´s usefull for porting, i did that when we ported the head on my pandas(999cc fire for both)

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Right another question...

Ive heard from a pro spanner monkey that skimming lots from the head can cause the engine to damage its crankshaft bearings over time...They're going to wear anyway, but id like to limit damage if possible!

The only damage it'll do is from increased compression, so there'll be a little more weight on them. If it's as bad as that though, turbo cinqs would blow the bottom end every few thousand miles...