I decided to use these people as there were a few bits that they could help with. http://www.formhalls.com/ Relatively local and look great when I went to see them. Waiting for the case to be ready.
Is 2g difference good? 2g = a tad over 1/16oz in old money. I remember weighing my H-beam rods and they were all bang on 498g. Genuine question, I don't know the answer.
2 gram difference is pretty good, from memory VW accepted 10 gram difference for the reciprocating mass, Porsche a bit better. My H-beams were 595.6 to 596.8 and with pistons and pins 1085.6 to 1086.
RAtwell suggests to match them with the pistons weight wise, but I don't know if my pistons have a weight difference.
According to Volksbolts - ‘Standard production pistons in a 2.0 litre Type 4 engine have been found to vary by as much ss 10 grammes. Con-rods by as much as 5 grammes.’ http://www.volksbolts.com/faq/T4lightening.htm
A couple of grams is insignificant, especially at the revs we use but I wouldn’t want 30 grams difference which, if Volkbolts are correct, is possible if heavy rods are matched with heavy pistons and light rods with light pistons.
I got lucky on the type-4, not that I built it, but I did weigh pistons and conrods which all came balanced to the gram (new). Again on the type-1 wasser, conrods and pistons all weighed in to the gram. I suspect modern manufacturers, knowing their customers will weigh them and comment on the internet , try harder than VW did.
Are you going to file/machine the oil spray grooves in the rods per VW Technical Bulletin 10-90 T01? You should IMO.
Thanks for that info. I really appreciate it. I've just read the notice and I'm not clear if the area to grind out is just the con rod big end or the shell as well? The diagram suggests the shell as well.
The shell doesn’t reach the edge of the rod so it’s just both sides of the rod that gets the groove. The bulletin says a V shaped groove but I make mine U to minimise stress risers.
Good idea about the shape. The other part of the bulletin talks about the adding shims and removing the seals. (https://ratwell.com/mirror/www.dolphinsci.com/techbull.html) My little bundle of joy had both shims and the seal. As I have AMC heads with the lip, should I remove the seal as suggested?
Definitely remove the head gaskets and check the deck height and CR to calculate how thick the cylinder base shim needs to be.
@Chrisd With AMC heads you might not need cylinder base shims, but do some measuring to make sure, if pistons get intimate with heads it will spoil your day. And having read your post again – AMC heads with head gaskets and base shims - the compression ratio was probably very low. I can’t remember if you did a compression test before you stripped the engine, did you?
Yes both leak down and compression were OK, compression below after a good run. No 1 = 160 No 2 = 158 No 3 = 147 No 4= 160 I don't know how to link threads, but it was in my other one called Compression Puzzle.
