The Stovebolt Site Forums The Shop Area Engine Shop Replace my new head gasket?

Was starting to put my newly machined 235 back together and discovered one of my pistons sits backwards. Now for all you guys that have never made a mistake putting an engine back together perfectly, I have kicked myself sufficiently for not being more patient and double checking things before torquing down the head bolts. Should I replace that beautiful new copper-lined head gasket or can I reuse it?

If it hasn't been through a heat-cool cycle or a retorque, bolt it back together with the same gasket. Just be sure to do a hot retorque after the engine warms up.
Jerry

If you had the head installed, how did you determine the piston was backwards?

If the rod is simply on the crankshaft journal backwards, just unbolt it, push it up past the crankshaft counterweights, turn it half a turn, and bolt it back together. No need to remove the head. If the piston is installed backwards on the rod, no joy! Gotta pull the head!
Jerry

Thanks. Sorry for the delay in writing back. Had some health problems I needed to take care of. I've pulled the crank thinking I will change the rear gasket to the neoprene type. The wick made it almost impossible to hand crank. But I can't turn the piston because that will make the rod opposite in direction. I think I put the piston on the rod backward. The head is going to have to come off. The engine has not been fired up so I think I will reuse the gasket

Back in the early 1960's, I watched my boss change rods on a 216 from the bottom side. There was enough room to pull the piston down in the block far enough to slide the wrist pin out of the piston from the crankcase side. I think the 235 is just enough bigger on the bore size to make that procedure impossible, but it won't hurt to try. The rope seal will form itself to the crankshaft flange pretty quickly, so it might not be necessary to go to the lip seal. A rope seal is a lot more forgiving of slight roughness on the crank hub that a lip seal won't tolerate, also.
Jerry

Back in the early 60's, one of my sources of income in college was repairing jalopies in the parking lot. Putting in rebuilt babbit rods was a common thing. I never pulled a head. On passenger cars, it was more trouble dropping the pan than replacing the rod. I never had reason to try to replace a 235 rod. As Hotrod says, try it. The pan has to come off anyway. And on a pickup, dropping the pan is no big deal. If you do have to pull the head, I think the gasket would be reusable and I have done it before. But you might want to buy a new gasket just for peace of mind.

Will the wick seal relax a little if I just leave it there for a while? Right after I torqued down the bearing caps, I tried to turn the crank. It was very hard. Perhaps if I left it for a while it might relax more. Just looked at my pistons from the bottom of the engine (it is on a stand upside down). My rods are oriented right. I'm struggling to remember why I thought the one piston is backwards. It was several months ago that I noticed it. Is there a correct orientation for the piston. I seem to remember a notch on the top of the piston that was supposed to be toward the front of the engine. Is this orientation absolutely critical. Looking at the bottoms of the pistons I do not see a difference. I might have to scope the cylinder heads through the spark plug holes to see if the notches are all oriented right. Otherwise I guess I will have to pull the head. From your responses I feel comfortable reusing the head gasket.

If the piston has a "front" notch, it's because the wrist pin is offset slightly. This allows the piston skirt to preload itself against the cylinder wall during the compression stroke. Putting one in backwards will cause the piston to be in a "floating" situation as the spark plug fires, and it will slap the cylinder wall. It's hard to see the offset, it's usually less than 1/8", but it's vitally important to a quiet-running engine.
Jerry

Back the torque off the main bearings one at a time, and see if it's just the rear cap that's making things tighten up. Did you go through the shim-checking procedure one at a time on the mains as you assembled things?
Jerry

I checked the bearing clearances very carefully. They are all great. I actually replaced the wick filter with the neoprene one and the crank turns easily, so I assumed it was the wick seal. I have heard that the neoprene seals like to leak alot. I've got the crank out now and am preparing to put it back in as soon as I figure out if that piston is in backwards. I would like a good seal and a crank that is not so hard to turn but worry about leaks. Wonder if most people use Neoprene or stay with the wick. Thanks for the info on the notch. I remember now. I just am not sure which way the notch is oriented now. Hope to tell with a scope. If not, I will have to unbolt the head. Sheeeesh! I am a slow learner.

I'm very partial to the rope seal, as they don't concentrate the sealing to one very narrow area of the crankshaft hub. I've seen far too many crank hubs with a deep groove where the lip seal has been contacting the crank. As long as the rope seal is installed correctly, it's very reliable, and easier on the crankshaft. Most of the leak problems with rope seals come from people not knowing how to install them correctly. I hope you didn't install the seal dry- - - -it's supposed to be soaked in oil before it goes into the groove.
Jerry

The seal came with oil on it. It wasn't dripping wet. My fingers were smudged after touching it. Does it need more oil. Can I use any oil or is something better? Do you put anything on the ends of the wick as you are mating the bearing halves? I'm going to give it another try. Just seems like the Neoprene seal is too susceptible to leaking. Thanks for the ideas.Rod

I usually immerse the rope seals in 30 weight oil, let them soak for a while, and install them wet. There used to be a driver tool the same diameter as the crankshaft flange that was used to pack the seal into the groove, but if you're careful, the crankshaft itself can serve the same purpose. Pack the rope seal as tightly as possible into the groove, then use the crankshaft to roll it into the proper shape. Do the same thing with the rear main bearing cap; install the soaking-wet rope, and form it to shape by rolling the cap over the rear flange on the crank. Use a single-edge razor blade or a box cutter blade to cut the rope ends off exactly flush with the block and cap. A tiny dab of RTV sealer could be used between the seal ends as the cap is installed, but I've installed hundreds of them without using any sealer at all on the ends. Make sure none of the rope gets trapped between the block and the cap as the bolts are torqued- - - -it can mess up beazring clearance if seal material gets sandwiched between the mating parts. A rope seal that's properly installed should last as long as a lip seal, be virtually leak-free, and cause less wear because there's a much wider point of contact with the crankshaft flange.
Jerry

I brought home a flexible fiberoptic scope from work (I'm an anesthetist) and peaked into the cylinder that I believed had the backward piston. Come to find out it was so I removed the head and turned it around. Tried to pull the piston down into the bottom of the engine like Hotrod suggested. The main bearing seats get in the way so you can pull the piston down far enough to get the wrist pin out. Anyway, I'm back to the beginning of assembly again and excited to get going again. Wow, the fiberoptic scope easily saw the notch. HF now has some scopes for that purpose but I have my own resource. Now I have to hope that I can get that wick seal to work. I'm planning to soak it. The head gasket looks pristine so I feel good about reusing it

My wife really loves anesthetists! Due to her having a tiny, crooked airway, she has to undergo awake intubation anytime she has general anesthesia! Some guys can do it without a problem, while others have nearly choked her to death! Since she's a respiratory therapist with 30+ years' experience, she knows exactly what's involved in the process! We discovered her problem during a gall bladder operation when they put her under, then couldn't get the breathing tube in! After nearly 2 hours of CPR, she started breathing on her own again!
Jerry

There are fortunately few people with tough airways like your wife. But fiberoptic scopes are the best way to deal with them. They also are great for looking down into little places in engines. Just too expensive.