Mahle 90.5 Pistons sent to John Maher
Posted by Jon on 13 March, 2008
Jon has finally got around to sending his pistons from his 2007cc Beetle engine to John Maher
Yes I know, I think I said I was going to do this a long time ago.
You know how it is; there is always something else to do and eventually such things like posting a set of pistons to the outer Hebrides’s get forgotten.
The aim is to get the engine finished in time for the big day in August but if I run out of time (remember I have the entire car to assemble now and that’s when I get the shell back from the painters) I do have a complete engine I can quickly bolt in.
So what’s the plan with the pistons?
After measuring my deck height on the pistons several time to get an accurate reading we found that there were very slight differences in each height. I’ve been assured this is quite normal.
To get the best out of the engine it is wise to have the compression ratio in each chamber pretty spot on. There are several ways to do this which I won’t go into now.
The way John Maher has suggested is for him to machine the top (ever-so-slightly) of the pistons to match all there deck heights. You can machine the barrels apparently but seeing as mine all seat at the same height I didn’t want to mess that up.
Once the pistons have equal deck heights I can measure the chambers on the heads and get them fly cut appropriately to get my desired compression ratio.
To be honest, the more I think about it, the more my head spins so I will leave you with that while I go and pop some Anadin.
If you need engine work doing or need advice building a performance engine then visit John Mahers website on www.johnmaherracing.co.ukLike VolksWorld? Subscribe to the magazine for more great features.