I've found vertical scoring on cylinders 2 and 3 on an engine that has about 500 miles on it. The scoring is on the 'drivers side' of the cylinders and only goes up as high as the rings travel. It is not really deep; the engine was running and seemed to have good power, but I want to address this while the engine is out of the car. The scoring feels about like the ridges you can feel on a fingernail.
Is this something I can take to my local (competent) machine shop to have cleaned up? Right now it's at +.030; it should clean up at .040; if not then I guess it goes to +.060. I know if I was to get a crank ground the person doing the work needs to be aware of the journal radius; Are there any particular concerns specific to a 4 cylinder model T block?
The owner of the shop that did the work passed away a few years ago so I can't discuss it with him.
you're talking about boring and rebuilding an engine that has 500 miles on it and (is not smoking?) and has good power, why?
I put in a new rod for Tim, the Englishman driving coast to coast...that rod bearing had disintegrated and the wrist pin gouged the cylinder wall. This damage made #2 cylinder match #3 cylinder gouges, which had the same thing happen 3000 miles prior. Put it all together and it did not smoke (!) and ran fine.
Model Ts are pretty forgiving creatures. You might want to pull the piston to see if it is scuffed, and if so, dress it up/clean it up, but I sure wouldn't put $$ into something that did not have some sort of performance shortcoming associated with this.
Probably need to assertain what oversize pistons are available first.
With only 500 miles on the engine, it is possible that the bore was a little tight for the piston. When the engine gets hot the aluminum pistons expand at a greater rate than the steel block causing the piston to bind. If you continue to drive it can cause the engine to seize. You need about 6 thousandths (.006) clearance from the piston to the cylinder wall for proper running. Do you know whether the scoring is in the same position as the ends of one of the rings? it could just be the rings seating in and no problem at all. If it were mine, I would leave as is. Otherwise you should replace the rings and hone the cylinders because once you remove the pistons, the rings will not be in exactly the same position and will not seat properly. Even so it would probably run fine by using the same rings, but might use a little oil.
I concur with Norman - pistons might have been a "tad tight". A competent engine machine shop can hone out the scoring and check your bores with a bore gauge and verify the piston to wall clearance.
I have a couple new sets of good old JAHNS pistons - .040 over, if need be.
I guess I should have mentioned why I have this engine open.... that's what I get for posting in a hurry.
This is on my late 1911 engine (I have a fresh, spare, engine in the car while I work on this one).
I used to run an aluminum Reeder head. I replaced that with the original early (pre made-in-USA) low head. The work I am doing now is installing domed pistons, so I will already be buying pistons and rings. I was surprised to find any scoring at all on an engine with this few of miles and I figured while I am replacing the pistons already I should address the cylinders.
I am open to suggestions / recommendations.
If it was set up too tight to run aluminum pistons, there's a good chance they can hone out enough to clean up the scoring and get you the clearance you need without having to go to the next oversize. Good measurements will tell the tale.
Edit to add: Also check your ring gap. You could have something going on there if no corresponding scoring / scuffing appears on the pistons.
(Message edited by Wmh on September 14, 2017)
(Message edited by Wmh on September 14, 2017)
Regardless your changing the pistons. The cause of the scoring is important, but likely not serious.
Aluminum pistons too tight are a major cause of scoring, and scoring extends to near the top of the cylinder. If that is the case, the fit should be rechecked. If the damage is minor (usually is unless the motor seriously seized), pistons can usually be cleaned up with light use of emery tape. The bore can be cleaned up with simple honing. .006 fit is ideal, .007 should work fine (I have seen .010 work fine however that is extreme and not recommended).
Another common cause of cylinder scoring is the wrist pin. The score will usually be on either the front or back of the cylinder, but I have seen wrist pins that floated and scored both. The score will end more than an inch below the top of the cylinder, and must be in line with the wrist pin's place of travel. Wrist pin scores can be caused by several things. Improper pins, too long, offset notch for the locking bolt, or improperly installed pins where the locking bolt allows the pin to move beyond its normal position. Another cause for wrist pin scores is a bent connecting rod. If the rod is bent to one side a bit, it can force the wrist pin forward or back in the piston enough that some pins are long enough to cut the cylinder wall (seen that one a few times). This is one of the reasons why connecting rods should be checked for how straight they are, and straightened if they need it.
I have seen several engines with wrist pin scores put together and run for many years with no apparent problems, even though the score was left in the cylinder wall. That becomes a judgement call. How bad is too bad. Model T engines are quite forgiving.
Since you said "only goes up as high as the rings travel", I would guess the pistons were too tight, and a simple clean and check the fit of the new pistons is what you need.
Gary, check your scoring closely. You may find that it is not really scored at all. It may be deposited aluminium from the sides of the piston. That was the case when my engine siezed. The root cause was a set of replacement aluminium pistons with no expansion slots in the skirts.
Either way, just fit and forget. Way deeper wrist pin scores seem to have no effect on T engine's performance.
Allan from down under.
You should use kevlar piston rings too...
I can only think of the countless T engines that were fired up at the factory when they were going down the assembly line and run in.
Was there some minor scouring here and there on the cylinder walls?
Of course there was.
And those engines ran for years after they were put in a Model T.
What was the ring gap? Maybe too tight?
Just get a dark good determination of what caused the damage before you spend any $.