http://www.pumaracing.co.uk/pug2058v.htm
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Let's compare the 1.9 Gti engine with the Golf 8 valve and see how Peugeot got so much power. The 1.9 has a claimed 130 PS (128 bhp) compared to the Golf's 112/115 PS (110/113 bhp) in 1.8 or 2.0 litre form. Firstly Peugeot made the bore larger at 83mm and this allowed them to fit larger valves - 41.6mm compared to the Golf GTi's 40mm items. This 8% increase in valve area is worth about 10 bhp. The head was given large ports and a decent shape and flows very well for a standard item. The induction system was carefully designed to flow well and flows enough to allow even well modified engines to breathe ok. Peugeot got the exhaust system bang on - it flows well, has good tuned lengths and an excellent manifold design - whatever you do, don't waste money on an aftermarket system - you won't get more power - you'll probably get a fair bit less. When it rusts away go and buy a genuine Peugeot item - not a pattern part. Finally Peugeot topped the engine off with a really good camshaft. Most 8 valve engines of this size have about 400 thou valve lift as standard and a fast road cam from Piper or Kent etc will add another perhaps 30 to 40 thou to that. The Pug 1.9 has 445 thou lift as standard and fairly long duration as well. It's already more than a match for an aftermarket fast road cam for most other engines. The good exhaust and big cam add the other 5 or so bhp that similar engines lack.

So in effect the Peugeot engine is already the equivalent of a fast road tuned Golf. Given that the exhaust and induction system are so good what can we do to improve the power further? Well the main area left to improve is the cylinder head but it takes really well developed port shapes to give more flow and that takes flowbench time. There is also some power available from even higher lift/longer duration cams but at the expense of some tractability. We'll look at both areas later.

BLOCKS AND CRANKS
Both the 1.6 and 1.9 share the same 83mm bore and the capacity comes from different crank strokes - 73mm and 88mm respectively. The wet liner engine is strong and reliable with a few idiosyncrasies to watch out for. The liners have no shims underneath and must protrude above the top of the block by the right amount to seal properly. This relies on accurate machining at the factory as the clearance is not adjustable. 4 to 5 thou is the figure to look for - too much lower than this and leaking head gaskets and/or water in the sump can result. Over time the liners tend to distort to a slightly oval shape because of the constant piston thrust in one direction. However, if you remove the liners and leave them on a shelf for a while they seem to go back round again - weird but true. A good tip when rebuilding an engine that is still in good enough condition to not warrant new liners is to refit them turned 180 degrees round in the block. Most of the wear takes place on the thrust side of the engine and rotating the liners lets the relatively unworn side seal against the rings better.

Beware when removing and refitting the cylinder head not to turn the crank until the head bolts are done back up or the pistons will move the liners. The liners just sit on machined recesses at the base of the block and are sealed with thin rubber O rings. Move them and they are unlikely to seal again without new O rings and the consequence will be water leaking from the block into the sump oil.

Peugeot did a huge amount of messing about over the years with the number and arrangement of plain and grooved main bearing shells, the reasons for which have always eluded me. The Haynes manual comments on the complexity of it all and states that when they stripped their own test engine it didn't even have one of the bearing combinations listed in the official Peugeot charts. Other engines nearly always have 5 grooved bearings in the block and 5 plain in the caps for very good reasons of oil supply to the crank. That's the way I build the Peugeots too, regardless of year, and they run perfectly happily like this of course. Peugeot actually finally settled on this combination anyway for later 8 valve engines and the 16 valve engine.

The rods are very sturdy and survive race use happily enough so road use is no problem for them even on tuned engines. Standard pistons rarely cause problems either except for sustained use over 7,500 rpm.

Early engines had an oil pump drive which relied only on the friction of the tightened crank pulley nut to turn it - no woodruff key or other locking system. This strikes me as one of the worst bits of engine design I have ever seen and the first time I rebuilt one of these engines I was convinced for ages that I'd lost a part somewhere. I know someone whose Mi16 engine grenaded because of not tightening that bolt up properly and after a few miles with no oil pressure everything came to a very expensive halt. You have been warned.

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