Thanks Doug and John,
I have studied the cracks again (the head is at the engine builder's in the next town) before reading these messages. The dye penetrant is for finding cracks that can't otherwise be seen - these are clear. They run the 3mm (1/8th inch) from the valve seat (both inlet and exhaust) to the valve hole. I don't think any are as wide as the paper thickness you refer to. If leakage (your pressure test suggestion) was the only issue, it would be no problem. I rang Loctite today - they provide a service for vacuum impregnation of cracked/porous heads in Sydney for only AU$66 (US$40). The engine builder is more concerned about valve seats maintaining their intended tight fit in the head. They are installed with an interference fit that gives a radial pressure on the outside of the valve seat - maybe a crack will relieve some of this pressure, especially with a few heat cycles. Are we paranoid or is this a valid concern? This will be an up to 8500rpm engine - I don't want anything going wrong. The valve seats are standard size. For those people that have fitted larger valve seats in the 16V head, are there any problems? Rick -----Original Message----- From: Doug Curtis [mailto:[email protected]] Yep, I used the wrong word. You can dye test them tho... More than likely they are not a problem. I forget what the exact width is that you need to be concerned with, but if you can't get a piece of paper in, they probably are ok. -----Original Message----- From: John Caldwell [mailto:[email protected]] You can't magnaflux an aluminum head... you can only pressure test it. Magnafluxing uses iron filings and turns the whole head into a magnet, and at any cracks that are large enough it creates a north/south pole, causing the filings to repel each other. ----- Original Message ----- From: "Doug Curtis" <[email protected]> Small fine cracks are somewhat common in any aluminum head. The only way to > know if the fine cracks are deep (which is the real problem) is to have the > head magnafluxed. > > > -----Original Message----- > From: Rick Dathan [mailto:[email protected]] > > I have been studying a 2 liter 16V head that I have just received. > At 2 or 3 of the spark plug holes there are 1 or 2 fine cracks > running from the 'plug hole to an adjacent valve seat. > Is this a normal 16V occurrence? Do they end up causing leaks or are > they benign? > > The head has only just been ported. If I had seen the head before > it got ported I would have knocked it back and picked another one. > Now I don't really want to waste the good work done. > > Rick Dathan, > Australia > _______________________________________________ a2-16v-list mailing list [email protected] http://mail.a2-16v.com/mailman/listinfo/a2-16v-list For list archives, see listinfo link above.
