Hmm. I had sealing problems. Unless I get the deck right down to 1.5 I believe I'll make matters worse. I will have to measure the ccs and deck of what I have and report back. Can you see on the piston tops a light circle about where the spark plug is? I wonder what that shows? If it's how far the flame front has got at TDC it's small?
Jonathan at AA Performance says 70cc With 3cc(?) pockets and 1.5mm deck, 8:1. I think that's pushing it both CR and chamber size. And I don't have 1.5 deck so would need new barrels to turn down so new rings. What a faff. I could though, then save 3cc by going 102mm but still the barrel turning down if still needed is a hassle. Tomorrow I'll try to measure the effective length of my existing barrels.
I’ve just read the Samba thread and agree with ‘Get a good efficient deck height’. I do not agree with using head gaskets, especially if they’re aluminium – all it does is add another joint face, aluminium head to aluminium gasket to iron cylinder. And the slightest leak will soon burn the aluminium gasket, as VW discovered and deleted them. 70cc combustion chambers, 3cc valve pockets, 1.5mm deck for 8.0:1 CR sounds good to me, a good deck and an acceptable CR. IMO 8.0:1 is not too high, even with a standard cam. Machine your 104’s to length and hone, new rings and you should be good to go. The head/cylinder sealing face must be perfect and although lhu1281 doesn’t agree I’d lightly lap the cylinders to the heads. Upping the head stud torque would help clamp the bigger surface area of the 104’s.
It appears to be doable. I've ordered a cheap burette to cc the heads I have. I can't see a way to reuse the barrels but maybe I'm being too cautious about the milage already on them and honing would sort any top ring wear step. Would I need new rings? Copper gaskets not aluminium and I do take heart that Wreck uses them successfully. One to dwell on. So...maybe it's worth a go adjusting my heads to 70cc, turning barrels down and hone, copper gaskets, up the head torque. Almost zero new parts is attractive.
Meanwhile oil is dripping from the lowest follower hole, I didn't think it would be so high up. Grr. I'll have to let a litre out I think. Looking for a good way to de-carbon the heads...any tips or just scrape at it?
...is something I have, I'm doubtful though, it's mild stuff. BBQ cleaner maybe but I dont have any. I'm just getting set up to clean it now.
Caustic soda works - if you can still buy it legally ?? Soak overnight and rinse off . Sent from my SM-G960F using Tapatalk
Blimey.. you go fishing for day and there's an engine out!.. that reflection on the cylinder bore threw me for a while on the pistons! Those valve pockets on AA heads are definitely down the low side 3cc sounds about right from mine (bit smaller bore but pockes probably similar).. citric acid from your local multi-cultural food shop cleans lots up and relatively easy to dispose of after.. don't know why but alays easiest to get from there.. and a soft wire brush works for me. Watch out with caustic soda and alumnium it can eat it quite quickly.. Sent from my SM-G930F using Tapatalk
The engine is still firmly in the van. I just ripped into it until I could get the head off. Possibly unwise, getting it back together will be more difficult, I may have to hinge it down on the front of the gearbox. Meanwhile brake cleaner is not the answer, I'll clean it mechanically somehow.
Good to know about brake cleaner being no good Citric acid sounds interesting, if you can source a cheap supply.
I'm going to scrape, I don't want to soak them really. Right now I just want to cc one head. If I'm going to have to do this every 15,000 miles it would pay me to have a spare pair ready to go so current thinking is see if these would open out to 70cc in which case the plan would be to sort the deck height situation, get the AA heads and adjust/skim these ones at my leisure.
Yes, it would be silly not to. You go with Wreck, I’ll go with Alstrup ‘resurface the heads, clean the cylinders and lap the to the heads in the respective positions, clean again and assemble, with 27 28 lbs.’ I smiled at his ‘Resurface it and put it together, then start on a new and proper build. - You have 15000 miles worth of time to do it.’ That’s odd, the oil level should be well below the follower bores.
seems crazy anyone would mix and match pistons ….. If everything was machined square and to the correct length super accurately they should seal no problem you can`t expect to lap two barrels in to one head and hope its all square and true … On my SC project i had to make the copper sealing rings as i couldn`t find type 4 ones …..it just goes to show if you DIY you know exactly what you have ….
I'll go cheap and cheerful I think. Get the heads skimmed, slap it back together. Sod the copper rings in a special groove...for now. Up the torque to 27-28ft/lb. Just need to find a machine shop, post them off and cross my fingers.
If you can get down to Warrington, The Head Shop in Birchwood skimmed mine.. you'll like him he's proper miserable about VW's most of the time.. https://www.head-shop-uk.co.uk/contact Not sure who @GARRICK CLARK uses but he's at Bamber Bridge so he might know someone local Sent from my SM-G930F using Tapatalk
