Hi All,
First time to post on the XK-Engine forum but have been active on the E-Type one. Just got my engine back front the machine shop and about to start assembling it with new bearings. First engine rebuild so questions follow.
Core Plugs - I have seen sealant used when installing Core Plugs. Is there a preference for which type to use i.e. soft/hard setting, high temp etc ?
When using plasti-gauge to check the main bearing clearance should it be done dry and bolts torque to full spec, or should assembly lube be added ?
I am going to use all new standard bearings as determined by the machine shop. I plan to use assembly lube for the bearing surface that touches the crankshaft. I have seen some use it on the block side of the bearing also but not sure if this is good practice ?
I don’t have the Jaguar tool for sizing the rope seal. Can I size it with the crankshaft and main bearings bolts torqued or should this be avoided ?
Plasti-gauge goes on dry with NO lube, torque the bolts to spec. then unbolt, do not rotate crank.
Machine shop will tell what size [oversize] bearings you will require. I doubt very much you have a Standard size crank.
When re installing the con rods make sure the numbers on the caps are facing the EXhaust side.
When re installing the Thrust washers, make sure the grooved side faces the moving part [the crank]. and a 4 to 6 thou end play is required ,no more.
Everyone says put the numbers on the rods on the exhaust side. Has anyone ever wondered why? The early XK engines used split skirt pistons and the rods had a very small hole that squirted oil through this slit to help cool and keep the exhaust or thrust side lubricated. These holes were done away with on the later engines. In fact, the rods stopped being through drilled in the early 70’s. The rods will technically go either way unless you are reusing the early pistons and rods.
Thanks Dick for that explanation, l can now not bother wondering why , but can you tell me why pistons have Front stamped on top, my last set l purchased did not indicate which way, can l install pistons with no marks any direction?
My guess is yes.
Morris
Unlike the rods, pistons are directional on most all engines, not just Jaguar. The wrist pin is offset so that the piston goes down under compression with the thrust on the side skirts evenly distributed. Without being offset, there would be a lot of wear on one side of the piston .
If the seal is to tight on the crank, it will burn and leak. If to loose, it will leak. Using the crank to size it will leave it to tight. Highly recommend using the factory sizing tool if using a rope seal. Properly done, it should last the life of the engine.
All, good thoughts, also keep in mind, that JCNA has a great tool loan program. You can borrow the correct tool to size the rear seal. Its really the only way to do it correctly. Jeff Smith Atlanta, GA
re special Jaguar tools…is the tool loan now thru Coventry Foundation ? thought I read that in JCNA Journal? It is likely, that a lot of forum members may have special tools, or shim sets, or the like, that they may be willing to loan…it’d be nice to have a way of having a list of such, somehow in this website.
Nick
Hi All,
Decided to check the piston ring gaps in the bore this afternoon. As machine shop said it needed only light honing and I am using the original pistons
I purchased Hastings Standard Size piston rings (pn: R39520*) from SNG.
I checked the clearance with these rings for the upper and lower compression rings and they are out of spec by 10 thou.
Compression (top) → 0.015 in to 0.020 in
#1 0.029 in #2 0.028 in #3 0.029 in #4 0.029 in #5 0.027 in #6 0.029 in
Compression (lower) → 0.010 in to 0.015 in
#1 0.025 in #2 0.025 in #3 0.025 in #4 0.025 in #5 0.025 in #6 0.025 in
So I believe I need to change the rings to 10 thou oversize to bring it within range ?
Or would it be better to purchase 20 thou oversize and file them to the correct gap as per spec ?
Others will chime in here I’m sure but I would be more inclined to check what clearances you have on the pistons first if standard rings have that large a gap then I would expect its time for a rebore. Also I don’t think an oversized ring gapped down would seal very well?
There is properly rebuilding an engine and there is slapping some new parts at it and hoping it runs without blowing up. And with the quality of aftermarket parts out there, it is getting harder and more expensive to do a quality rebuild. With any substantial mileage on an engine, the bores are not round as they have wear on the thrust sides. Honing the cylinder out hones the whole cylinder making the piston to cylinder clearance even greater. This is why the ring gaps are greater than normal. Rebore is not necessary if currently stock size. Oversize pistons fitted to properly bored out cylinders is the answer. They come with new rings that should have real close to proper gap out of the box. The crank also should be machined. Only way to tell if it is straight. Polishing does not tell. How about line boring the block to make sure it is straight. Replacing the connecting rod bolts or reusing them? The bolts are designed to stretch when torqued. They can only stretch but so many times before they do not hold the proper torque and you see a rod exit through the side of the block. Then there is the rear seal discussion on this thread. Everyone complains that the rope seals do not work yet so many keep trying to install without using the proper tool to set it up to work properly. If you are not going to do the job properly, then when the engine takes a dump, knocks, burns or leaks oil, it is not because of a design flaw. Every factory tool all the way back to the prewar cars are available for free loan to JCNA members and Coventry Foundation members. If people here have a problem with being a member of one of these fine organizations, then maybe Jag-Lovers can start a tool loan program. All you need are a lot of tools, insurance, somewhere to store them and someone to ship them out and check them back in after doing the paperwork on both ends. Piece of Cake!
I recall always checking line bore on an XK engine, but it seemed rare to actually have to do it, and then–IMS–only if the mains had gotten badly trashed.
The boring machines got so bad that by the mid 80’s, Jaguar was replacing engines very frequently. I had one replaced with less than 50,000 miles. I have seen them come in the shop so bad that they leave a stream of oil on the floor. Could be the crank, could be the line bore. Fix both or do it over.
