Ive got a 1.8 abs single point injection engine in the garage and a spare 1.6 driver engine. Im looking to put the 1.8 crank into the 1.6 block as the 1.8 doesnt have hole in the block for a mechanical fuel pump. I will be running with the 1.8 cam and head so i can still run my carb and save me messing about with wiring up the SPI unit. Im thinking that if i use the 1.6 pistons which have less of a cut out in the top of the pistons it will have slightly higher compression and run a bit better. Have i got this right or would it be better to run the 1.8 pistons with new piston rings? Cheers for your help in advance guys and girls
GTI pistons are the same as the 1.8 driver pistons out of the ABS engine i already have. If I use the 1.6 driver pistons the compression should be slightly higher and therefor the power should also be slightly higher although i will lose a very small amount of capacity. The advantage of the 1.8 crank is that it will have a longer stroke which makes the engine more torquey. At least i think that is right, i was hoping someone could confirm this for me as im trying to make the best of the bits i have lying round in the garage.
Hi Adam, i'm afraid I can't really help with which pistons fit what but if you do decide to use the 1.8 Gti pistons i've got a brand new set of total seal piston rings which you can have, delivered for the price of a set of standard ones. Sorry for hijacking your thread a bit, but if you're interested perhaps you could PM me or you can get me on 07859 069818 Anyway good luck with finding out what goes where - there's plenty of people on here with loads of useful knowledge so you should be ok!
I know both pistons fit, just wondering which would be best when i pull the engines apart i will check the rings and if they need changing i will pm you. anyone have any opinions?
there isnt much point pushing the CR to high unless the rest of the engine is up to it. it will only lead to pinking.
I think the bottom end with the 1.8 pistons in has a comp ratio of 10:1. I wouldnt have thought that the 1.6 pistons cutout would push the comp ratio too high. I will measure the difference in capacity between the two pistons and see if i can work out what the comp ratio will be. Roughly what sort of ratio could i push it too before it starts pinking, ive been told it should be fine upto about 12:1 with a higher spec head gasket.
You'll need a lairy cam to run at that, and it'll probably still tend to overheat, unless you upgrade the cooling. If it's a road car, I'd stick at around 11:1, with a 270-ish duration cam.
Im not one for changing things just because im in there, if they are in spec then i see no point in messing with something that works. I have found over the years you can cause more problems than solve besides its no a massivley difficult job to do even when the engine is fitted (I know a man with a ramp, makes it real easy).
Ive only got a 1.8 driver cam in at the minute would a gti cam do till i can get a performance cam, and do you have any suggestions for manufacturers, Kent cams seem popular. Cheers for you help so far folks
