Seriously, it is worth getting a fair old amount skimmed off the head. The machine shop may charge a little extra for a second cut (tight boogers) but it will help. I got over 1.5mm off the block when I had an engine stripped, and then removed the small raised area off the top of one side of the piston, in an attempt to boost up CR levels. What I did sounds drastic but it still did not get the engine too over 10 : 1. I really like the 1.6 engines, mainly due to motorsport classes.
how does the GU engine make 10:1 ratio if it's got the same head and block? only due to the longer stroke?
The 1.8 (1781cc) engines use the same bore of 81mm, but a longer stroke crank 86mm instead of the 1.6 (1595c) 77mm. The conrods are actually the same length at 144mm in both, but the pistons have different compression heights to compensate for the stroke difference. The stroke difference is approx 9mm but this is halved to 4.5 as the stroke is longer down as well as up on the 1.8. The compression or crown height of the 1.8 piston is therefore approx only about 4mm less than the 1.6 piston. The larger displacement of the 1.8 and later 2.0 engines means that a skim of the head has more effect on the compression ratio as the clearance volume is proportionally smaller to that of the 1.6. swept volume + clearance volume divided by clearance volume.
I would skim the head to a maximum of 1mm if it has not been skimmed before. The std head gasket will be fine with this. Can you put a pic up of the head you plan to use, showing the spark plug hole to gasket face? This will show if the head has been skimmed dramatically already. It is only if skimming the block a lot (more than 1mm) that clearance would become an issue. The raised squish area on a 1595cc piston barely makes it to the top of the bore, never mind the 1mm or so of gasket thickness.
The pic should be trying to show the slight lip where the combustion chamber meets the gasket face, just next to the spark plug hole. As std there is a small lip of about 1mm. This area shows a good indication of previous skimming if any.
will do my best, within reason what sorta increase would you see over the standard 55hp? I know it won't set the world alight but wanna keep it standard trim inside and out but with a little hidden extra
Hi Rich... the best way to look at it might be this. Say you get a 5.5bhp increase on your motor... now on a 220bhp motor, that's a trifling 2.5% increase in power. But on yours it's a 10% increase in power, so in relation quite a substantial amount of difference. No, it won't set the world alight... but yes, you will notice it being a bit more perky. The other thing you "could" consider for the future would be upgrading the ignition to something a bit more efficient. Personally I went down the megajolt route, but I know that some might suggest injection. At least with MJ it's distributor-less ignition and the rest is fairly cheaply acquired, with tunable ignition timing across the rev range. Makes it both more efficient and more perky too. Just a thought to chip in, hehe
Its something to consider I guess, yeah every little helps I guess. This car wasn't bought for power but a car I wanted when I past my test back in 94. Me know I'm old I'm quite happy getting into my 198bhp Dirty Diesel Merc estate lol For me anyway its easy to go down the Gti route, but as a car the Mk2 these days is so retro is gains respect no matter what the model.
The std 1.6 EZ engine is rated at 55kw or 75bhp IIRC. If you can source a digi exhaust manifold and downpipe it will help a little too as the std spring clip type is shocking with regard to performance. It does not isolate the exhaust pulses from each cylinder at all well. As you have the engine and box out the car it is an ideal time to fit the few bits and bobs that will make a difference. GTI box would help too. I know it sounds like a money pit sourcing all these bits and bobs, and folk will say "just put in a 2.0 or 16v", but if your planning on a young lad being able to insure it a couple of years down the line then keeping the original engine will be a good option. My old 1.6 made approx 125 bhp (dyno lottery blah blah blah), and coupled to a low final drive with GTI ratios went very well indeed. It took a bit of sourcing parts here and there when they turned up, it wasn't a terribly large amount of money I spent either, but that was half the fun of it. As it was occasionally in motorsport use, if I had gone with a 2.0 engine I would have got my bum kicked by the mk2 Escorts. No doubt about that, and anyone with a mk1 or mk2 Golf that says differently is in denial.
Going the digi exhuast system what car would I need to look up to source and would I need to changed the exhuast manifold?
I have one off a 2E engine you can have matey, I'm not using it and was gonna just scrap it anyways. If it's a doable option? Not sure if it'd be the right one though.
it a shame you didnt mention exhausts and stuff, i have couple of DP's and a ported manifold, doing nothing 2e is a early mk3 gti 2.0 8v engine, the later ones came with an AGG. the block is 16mm taller than the EZ/PB/GU blocks and they are often refered to as tall blocks.
I believe your main problem was buying an engine off Alan, he is well dodgy you know. That piston will probably be out of a fiat uno or something that he bodged together just to get rid of the engine!
lol @ Nealey, I wasn't aware till lastnight Alan, too many ppl sweet talking me into things lol (I ain't fighting though)
In the pic you put up showing the combustion chamber, it is not that easy to tell how much of a lip there is at the point where it meets the gasket face. There is normally about 1mm of lip around this area. The factory minimum dimension is 132.6mm from the top to the bottom of the head so it maybe worth measuring this to get a ballpark figure first. There is not any serious drama with going over this figure, other than a small affect on cam timing, something that the increased compression benefits outweigh anyway. I use a non protruding tip spark plug as this removes any possibility of electrode damage.
