when i took the knackered barrels off my engine, they seemed to have some sort of spacer (like a big washer, same diameter as the barrel) but when i took the barrels off my old engine, ithere wasnt any.. what are they for? and are they essential to put back on when i rebuild it? cheers
It's to do with whether your case has been spot faced or the halves refaced before line boring, but yes, it's to correct the deck height
It is the distance between the top of the piston, and the top of the barrel when that piston is at TDC... Ideally it should be no less than 1.20mm
It's the distance between the top of the the barrel and the top of the piston at the top of it's stroke. When you get the first barrel on, clamp it down to the block and check the deck height. You want 1-2 mm and aim for 1.5mm.
Nah give it 3 mm to drop the compression and then turbocharge it Konadude you need a copy of one of the aircooled rebuild dvds as that will show you step by step how to go about it Actually in all honesty i wouldent mind a copy myself Even though i understand it all in theory ive never rebuilt an aircooled engine and i learn a lot better when shown instead of reading about it Ive rebuilt and tuned plenty of watercooled engines but aircooled even though a simple design have there own strange needs
thanks a lot guys, quite a bit of the aircooled terms are new to me, so your help is endlessly appreciated. in that case the deck heights on cylinders 1 & 2 were definitely bigger than on 3 & 4 on this one, im going to assume thats not normal... and yeah para, ive built countless watercooled engines, including the 394.6 brake (dyno proven ) RB in my 180sx, so i never imagined i wouldnt be able to just bosh together an engine for my bus! haha a dvd or some literature on the subject would certainly be useful, does anyone have any recommendations?
It's pretty easy to measure the deck height once you've got your barrels installed on the engine. You'll need to tighten them down: the studs are too long without the heads on, so either put a stack of sockets on the studs or (better idea), cut some 15mm copper pipe to the right length and use that to take up the excess length on the studs. Once everything's tightened down, turn the engine on the crank pulley nut until the piston in each cylinder comes up to top dead centre (that is, right to the top of the cylinder, before it starts going down again). This is quite easy to see if the heads are off, maybe with a wiggle each side of TDC. For each cylinder in turn, put a small steel ruler across the top of each cylinder in turn and measure the gap between the top of the piston and the bottom edge of the ruler with a feeler gauge, in several places. This is the "deck height" - the amount of space between the top of the piston and the "top" of the cylinder at TDC. If it's too little, you'll need to shim at the base of the cylinder to bring the barrel up a bit. Very bad (but unlikely) is if the pistons protrude slightly - they may clout the head when the engine's running. If it's too little, remove any barrel shims until it's right. Paper shims might do, unless the case has been machined, in which case thicker ones. Tis quite easy peasy: go for it. PS You should have Tom Wilson's red engine book, if you haven't already.
I think you can also use the rings to change the compression ratio and cc I was told its also a idea to check the cc of the head chamber and us the ring to correct a new head i bought was total different to a old vw one there was a online video showing you how to do it with a old CD
