Engine Rebuild Machining Questions

[aspekt9]

I'm in the process of building a new engine with forged internals I just had a few questions first about the machining process.

I got the bare block with the front case, mains, and crankshaft. I was told the engine spun a bearing. My question is assuming the crank is garbage, which I'll have the machine shop look at it, can any other 6bolt crank be swapped in with no issues? Will I need to bring the new crank with me when I get all the machine work done? (align bore and hone for ARP mains, cylinder bore & hone, deck and hot tank) If I get a new crank is there a chance that the engine could end up spinning another bearing? From what I understand it's the cranks fault that the bearing spins, which means the block I got from the guy should be fine assuming I get a new crank and rebuild everything with new parts correct? Thanks

 

[Clutch GSX]

If you have a 6 bolt block then you can drop in any 6 bolt crank. Just make sure its in good condition. Are you buying a new one or using an old crank laying around? Any good machine shop will need the crank to take measurements to build the engine. So, yes you will need to leave the crank at the machine shop if they are putting it together for you. Spinning a bearing happens usually due to loss of oil pressure, too little clearance or contaminants in your oil. If the engine is put together right then you should be fine. Just make sure the person building you block knows what they are doing. Clean the block and look around. If there are no holes, cracks, or gashes/scratches then it should be fine. You may not even need to aline bore if the crank spins freely when the mains are torqued down all the way. Obviously the bearings need to me in and the clearances set and lots of lube used when you check for the free spin. Just take it to a reputable machine shop and let them do what they recommend.

 

[lacroixdp]

Don't count your crankshaft out of the fight just yet. I've seen 6bolt cranks survive some nasty situations, such as complete loss of oil pressure and spun bearings. They're tough. Take it to your machinist and let him or her make that call. It may need as little as a micropolish, depending on if it got gouged or not. If you do end up needing to replace it, get a crank that has NOT been turned, and for the good Lord's sake make sure it was stored properly, which would be standing upright on the flywheel side... the last thing you need is a bent crankshaft. You will need to give the crank to your machinist, along with the main/rod bolts, rods and pistons you intend to run. If you don't have the measurement tools or the know-how to do it, ask your machinist to spec and assemble the bottom end for you too. It will save you a lot of potential trouble and money later on. Make sure you tell your machinist what rings you are using so you can get the proper hone. For your cylinder bore, give your machinist the ARP studs you intend to use, and make sure they use a torque plate. Lastly, make sure you clean those oil galleys again after you get the block and head back from the machinist.

 

[aspekt9]

Good to know, thanks guys. I'm assembling the bottom end myself, I'm going to bring them my pistons and rings, crank and main caps so they can properly bore and hone for the correct piston to wall clearance. Is PTW clearance measured with the rings on? Most likely if I'm running stock mains they'll probably just have to align hone the main caps, correct? Do I need to bring my bearings with me as well for them to check the crank? I have plastigauge so measuring bearing clearance is not an issue.

 

[Clutch GSX]

Based on your posts thus far, you should not be building your bottom end. Don't use plastiguage to measure such tight clearances as your main journal oil clearance. If you dont even know why engines spin bearings or how to measure piston to wall clearance then it is doubtful that you will build a successful engine. Do you have a set of micrometers and a bore guage? Do you have feeler guages and a ring filer? Are you going to plateau hone your bores? If you are not familiar with all of these things then you should not build your engine. I'm just trying to make sure you dont waste your time and money.

To answer your questions: Piston to wall clearance is measured without the rings. You measure just above the lowest point of your piston skirt. You'll have to check the meaurements of your main journals to see if line honing is needed. It certainly may not be needed. Yes bring your bearings in if you want them to measure your oil clearance. You also need to measure correct rod journal oil clearance.

 

[aspekt9]

Based on your posts thus far, you should not be building your bottom end.

This is a learning experience and I feel it is one that with enough research I can accomplish successfully. I do not plan on rushing this, I am in no hurry and wish to drag the build out over the course of a year.

Don't use plastiguage to measure such tight clearances as your main journal oil clearance.

Which method do you advise I use to measure said tight clearances?

If you dont even know why engines spin bearings or how to measure piston to wall clearance then it is doubtful that you will build a successful engine.

Again, this is a learning experience.

Do you have a set of micrometers and a bore guage? Do you have feeler guages and a ring filer? Are you going to plateau hone your bores? If you are not familiar with all of these things then you should not build your engine. I'm just trying to make sure you dont waste your time and money.

Yes, yes, yes and yes. The honing and boring will be done by my machine shop. I will have them check clearances at the shop and double check them when I receive the block back. I know what all of these things are and how to properly use them.

To answer your questions: Piston to wall clearance is measured without the rings. You measure just above the lowest point of your piston skirt. You'll have to check the meaurements of your main journals to see if line honing is needed. It certainly may not be needed. Yes bring your bearings in if you want them to measure your oil clearance. You also need to measure correct rod journal oil clearance.

Thank you for the help and explanations.

 

[Clutch GSX]

For piston to wall, main and rod oil journal clearances use a bore guage and a micrometer and then subtract the bore diameter from the journal diameter. You need to make sure you really know how to measure using a bore guage and micrometer though or you could be off by a decent amount. The clearances in these areas need to be very precise and plastiguage just wont be very accurate. You need to measure with the bore guage at different angles in the bores and you must have the bearings you are going to use installed when you are measuring. Make sure you don't mix up the bearings once you have measured! The machine shop will need to know the diameter of your piston just above the bottom of your piston skirt in order to bore your cylinders to the perfect diameter.