Guys,
I'm going to be doing my first full engine build in the next few days, 2 actually a 1V and a 1Z TDi. The motors are fully taken down. Obviously all the bearing caps are with the rods they came with, the right way round etc....
Basically what I'm saying is - the crank is a new area. Dont want to get it wrong, so I thought it would be best to ask the pro's.
1/ I've heard of crank polishing. How important is this ? The cranks show no wear, both engines had very good oil pressure, oil lights out almost instantly. I gave the journals a quick clean up with Scotchbrite, I rather like this stuff, it makes everything look clean, but should I not use it ? I know on Alu. plate it can cause an uneven surface, but on the crank journals, would there be cause for concern ? I'm just talking about a quick clean, not standing rubbing for ages.
2/ The main bearing caps where hard enough to get out, i'm just wondering about how hard they will be to get in correctly and true. Any tips here ?
3/ A good engine builder I know always cleans the crowns of pistons hes using again with a wire wheel on a bench grinder. I took an old piston the other day and gave it a shot on the same wheel he used when at my place one day. It had quite an effect on the piston, I dont know if I like the idea of using it to be honest, it radius'd the valve reliefs of a TDi piston quite a bit. Any ideas ? I'd rather dip them in a solution of some type to remove the carbon.
4/ Piston rings - spacing the gaps. Last time I done this I simply spaced them as far apart as possible. Top ring gap (clock face reference) at 12, second ring gap at 6 and the oil control ring gap back up to 12 again. Is this correct ?
5/ Assembly lube - Some guys I know simply use a 15w40, some others use a dark grey paste called graphogen during assembly. I'd rather use an oil if possible. What is best ? Would a heavy gear oil be the best ? Maybe it would stay there longer if the engine was sitting for a while.
6/ I've seen some people have shot blasted there engine blocks before painting. There are obvious risks - would anyone say shot blasting is a big risk to take just to get a nice paint finish ? I could fit an old scrap head, sump, vac. pump etc... blast it and then clean everything down afterwards. But I dont have any scrap oil seal carriers front and back. Is it impossible to get all the media out ?
I know there are a lot of questions here, but I know you guys are the people to ask, theres a lot of knowledge here.
Look forward to learning somthing.
Regards, Matt
1 - For a complete engine rebuild, you'd want to micrometer-measure the diameter of the crank journals. But you can first plastigage check the bearing clearances. If the journals check out as too badly worn or need major surface reconditioning, you'll want to send the crank to a professional polisher to have it turned and/or polished down undersized and restore it to a perfectly round shape.
I have heard of nicks, burrs, etc being removed from crank main and rod bearing surfaces by mechanics using fine strips of emery cloth. The strips are wrapped completely around one of the crank main or rod bearing journals, and then a string wrapped a few times around it, with ends of string held in each hand and being moved in while other moves out and back until the a good looking surface is restored.
I can't imagine you doing any damage to the hardened crankshaft bearing surfaces by cleaning off residues by hand using a scotchbrite pad, of the type you'd use to scrub baking residue off of a dish.
2. The VW main bearing caps are locked in place by machined steps. Just try and go on squarely keeping the engagement of both bolts fairly even, and tighten according to service manual procedure. It is recommended to position the 3rd bearing cap which has the thrust bearing surface but while the bolts still loose, to press the crank towards one side and then the other (levering it with a bar or use soft hammer on the ends) to center the 3rd main bearing thrust surface. If the thrust bearing shells aren't perfectly aligned, you can get premature thrust bearing wear.
3. I found scotchbrite by hand with solvent works well to clean up carbon-caked pistons and cylinder head surfaces. Bench wire brushing aluminum pistons sounds extremely risky! If you lean into it with a stiff wire brush, the aluminum will get chewed up badly. If you are unlucky enough to catches an your piston will go flying. A very light touch may be OK but I would use extreme caution.
4. I'd follow whatever recommendation is made by instructions coming with your piston rings (if any), or from your engine's service manual.
5. Assembly lube is good, but prelubing the engine (which pressurizes the oil before you even crank the motor over) is best. I think you can prelube a 1Z TDI like you can an older IDI VW Diesel or 8v motor... using a drill with slotted shaft on the oil pump through the vacuum pump/distributor hole. An unbroken camshaft needs something special, assembly lube might work but I have seen some kind of grey moly-type grease/coatings used for unbroken in cams. ...probably less important if you prelube the engine right before starting it up.
6. Shot blasting is spraying heavy steel balls (steel shot) at a surface to impart compressive forces in and slightly below the surface of the material, which strengthens it if it's cast iron or steel. You would want to be careful on what surfaces get the heavy steel balls sprayed with, IE: avoid precision machined surfaces unless you are planning on maching them afterwards. It would be overkill to use for painting surface prep.
Other gentler abraisive media suitable for painting prep such as glass bead blasting can definitely be left behind and is not good to have floating around in your motor. Bead blasted parts should ideally be thoroughly cleaned (I often hear recommendation they be scrubed with soap and water, but if you do this, be sure to dry and spray with WD-40 or similar product to protect against corrosion afterwards).
Hope this helps.
I don't know what kind of wirewheel you have but I clean everything under the sun with mine including piston tops and it doesn't even affect the stampings on it let alone dish it out and I lean on it pretty hard at times. Yours must be extremely course or stiff something on those lines or the pistons are getting soft
. My biggest concern though is not getting the wheel in the ring gooves or something like that but it has never dished something out. Just an everyday 8 in. wire wheel from Lowes on my bench grinder.
I have soaked my pistons over night with the crowns face down in solvent and gone at them like a madman with the heavy duty scotch brite and that carbon is not coming off. I'm curious what people do, I keep reading not to brush or sand them, but I don't know what else is going to work.
I use a very fine wire wheel on the bench grinder... as per a previous poster it gently removes the carbon to the point that you can see the original piston sizing marks.
Also as has been stated I *don't * use it on the ring lands... those are a sealing surface and a carbide-tipped ring land cleaner works a treat.
I use a very fine wire wheel on the bench grinder... as per a previous poster it gently removes the carbon to the point that you can see the original piston sizing marks.
Also as has been stated I *don't * use it on the ring lands... those are a sealing surface and a carbide-tipped ring land cleaner works a treat.
I've got one of those ring groove cleaners too and I've used it a few times but the thing I don't like about them is that they don't have a cutter for every size ring groove and if the fit isn't real close it can either not get enough carbon out or worse yet it can increase the groove space causing the ring to be able to flutter. I've actualy seen people use hack-saw blades before. I use one of the cutters that is a little smaller than the groove itself then finish it up with a broken peice of the old ring. I don't know what else would be easier or safer and like was said earlier there doesn't seem to be a cleaner that will cut carbon very well if at all. I'd be scared as hell to get the wire wheel down in there, might as well use the hack saw blades as seen before
