Pistons Rubbing Middle of Cylinders

mach4g63t · 05-11-2008, 02:45 PM

Okay, so I'm building my first engine. Mods are in profile, and everything in the short block is what I will be using. I just got my block back from the machine shop, bored .02 over, and fitted for clearances with my Wiseco 9:1 pistons. I'm using Eagle Connecting rods, ARP everything, and everything plastigaged fine.

HOWEVER, I'm having some issues. With nothing but the crank bolted down by the mains, it spins free, easy, and makes me smile. When I attach even one piston/rod there is a slight "rubbing" sound when the piston reaches the middle of the cylinder. It's not as bad with just one, but when all 4 are in it's a lot harder to turn the crank. A lot harder. When 1&4 are at TDC and 2&3 are at the bottom it is free and has no rubbing. As they traverse down the cylinder bores towards the middle the rubbing and friction begins. As 2&3 reach TDC it goes away.

I can't figure out what this is, and I sure as hell don't want to put it to gether like this. Anyone know if this is normal? Maybe my machining is off? I can't get ahold of my machinist until tomorrow, but this really has me worried.

Thanks

92awddsm · 05-11-2008, 03:15 PM

If machined properly, the tension you are feeling is normal due to the rings doing their job.

redline2k6 · 05-11-2008, 05:41 PM

I understand that. I am just curious as to why it's so hard in the middle. My friend's build with the exact same stuff except 8.5:1's instead of 9:1's was butter smooth top to bottom and around again. Mine drags in the middle and it has me worried. You're saying this is normal? We were thinking it's just because of the angle of the rods during their travel at position of the crank?

<<< Friend's computer - This is mach4g63t >>>

v8s_are_slow · 05-11-2008, 06:30 PM

Did you use a torque plate when it was built? Wondering if the cylinders are straight up and down when the machine work was done.

92awddsm · 05-11-2008, 06:41 PM

Put a little oil in the cylinders and see if it smooths out. The rings should have been drenched in oil before ever installing the pistons.

mach4g63t · 05-12-2008, 02:53 AM

My friend was also asking me about the torque plate. I'm assuming it was, as this was a machine shop referred by a credible guy. Also, I will try using some oil on the rings/pistons when trying to put them back in. I'm going to call my machine shop tonight and double-check everything with him, but I wanted some secondary opinions. Thanks, and I will try and get some more info and use the oil on the rings.

EDIT

Another suggestion I just got from a friend who has built a few engines is that my crank might be warped. How could this happen? I had it polished and anytime that I did not have the crank in the journals of the block, it was standing straight up on the flat end. The crank was good and never had problems with it before. How common is it for something like that to happen?

hostile · 05-12-2008, 10:55 AM

Think about the angle of the rods, top top dead center the rods are all straight up and down. Half way through the stroke all the rods are at an angle. This is why people talk about rod ratio and engine wear.

A torque plate has nothing to do with this.

If you don't trust your machinist, check your piston to wall clearance before you run the motor.

Burnett03 · 05-12-2008, 12:58 PM

Mine did the EXACT same thing when my oil squirters were hitting my pistons.

bastarddsm · 05-12-2008, 01:08 PM

Quote:

Originally Posted by hostile

Think about the angle of the rods, top top dead center the rods are all straight up and down. Half way through the stroke all the rods are at an angle. This is why people talk about rod ratio and engine wear.

A torque plate has nothing to do with this.

If you don't trust your machinist, check your piston to wall clearance before you run the motor.

HEY, ####O. A torque plate could have everything to do with this. This is the exact reason they are used When you torque a head down it pulls the cylinders all around, meaning it changes the shape of them. So If you hone it round without a head on it, it is no longer round when you bolt a head on it. People use torque plates to simulate having a head bolted on it. Now when you take the torque plate off, the cylinder is no longer round. Which is most likly why the OP is having difficulties.

OP: torque a head down and see how it feels. if it feels normal, RUN IT. Otherwise look else-where.

Rob10_99 · 05-12-2008, 01:09 PM

Sounds like its the rod angle hostile is talking about,
The rings are moving their fastest midstroke, and all 4 are on midstroke, meaning they will have the highest static friction when being turned at the crankshaft.

mach4g63t · 05-12-2008, 01:47 PM

Hmm. All good ideas. I will give it a whirl tonight and see what comes of it. Thanks for the input. I'll let you know my findings tomorrow.

Raph · 05-12-2008, 02:16 PM

Thats normal..the 4g63 is a long stoke engine,you will notice a very very very very slight rubbing halfway up .. your ###### just a bit freaked out (if its your first rebuild etc)

You have done everything correctly and you lubed the Rings prior to installation ..right?

Now if theyre seriously dragging.. thats another story.

If you still have SERIOUS doubts, show it to the machinist.

v8s_are_slow · 05-12-2008, 02:30 PM

Quote:

Originally Posted by Burnett03

Mine did the EXACT same thing when my oil squirters were hitting my pistons.

If they were hitting the oil squiters, it shouldn't make it harder at the halfway point of the piston travel. Only at BDC.

Rob10_99 · 05-12-2008, 03:45 PM

Where did you check your ring gaps? at the very top or bottom? middle? all three?
And what were they set at?

One more thing, have you fitted a piston in the bore and checked for tightness?
Does it scrape(or a lot of friction) mid-stroke?
Do this with no rings in it, to narrow it down.

Did your machinist have the pistons when the block was being machined?

mach4g63t · 05-13-2008, 02:54 AM

Quote:

Originally Posted by Rob10_99

Where did you check your ring gaps? at the very top or bottom? middle? all three?
And what were they set at?

One more thing, have you fitted a piston in the bore and checked for tightness?
Does it scrape(or a lot of friction) mid-stroke?
Do this with no rings in it, to narrow it down.

Did your machinist have the pistons when the block was being machined?

Yea, I checked the gaps for my rings at top, middle, and towards the bottom. It all came out pretty good and within specs. I didn't try the pistons with no rings, and yes my machinist did have my pistons while doing the work.

And I had read something about someone having problems with their pistons and oil squirters hitting. I removed them and then tried to move the crank by hand again and it was the same results, so I reinstalled it.

I'm gonna get with my machinist tonight and see what's up. Overall, people think I might just be paranoid because I've never done this before. Everything checks out. Rings, plastigaging, etc. It's just not something I want to rush considering the amount of money that's potentially at risk, and how long I've been living in the poor house check-to-check to get it all. It's just dragging to make me double-check everything before I start full assembling it and cranking it. I can still spin the crank by the throws, or if I even had the crank pulleys attached. But my buddy's we built was easy to move by the crank with nothing attached and just spinning on the smooth end rod. That's the only reason why I have my doubts.

Again, thanks for all the info so far.

RipperXX · 05-13-2008, 05:41 AM

Have you tried oiling the cyl walls, and then bolting the head on and see how it turns over?

mach4g63t · 05-13-2008, 06:47 AM

I did not get to it yet. Yesterday I helped my buddy finish up the wiring into his Talon. One of the questions I had about doing this was whether or not I needed to use a HG when I did this. I have a Cometic, so I don't want to bolt that down and then have to remove it later.

Can I do this without using a headgasket? We have a stock felpro just laying around from my buddy's gasket rebuild kit, but I was wondering if I needed one at all just to test this theory. Any input? Push comes to shove, I'll use the stocker to get it tested out, but I didn't want to waste my cometic.

---EDIT---

Got ahold of my Machinist just now. He says when he bored/honed my cylinders he did NOT use a Torque plate.

This has me worried. I've been told this guy has built quite a few 4banger motors for my buddy (mostly hondas) and has never had a problem out of any of them. Most ran 11 and 10 seconds on boost.

Now, I understand how a torque plate works (simulates the variations of distortion that bolting the head down will create). How BAD is it if he DID NOT use the Torque plate on my motor and I go to slap this all together? I'm really concerned now because this is a pricey build for me and my income level, and I don't want to have to scrap the block and the 200 it took to get the work done and start with a fresh one. He says the drag in the center is the actual force of all 4 rods being in the middle of their stroke and creating their normal resistance due to opposing forces.

Any input?

RipperXX · 05-13-2008, 10:55 AM

I would think it depends on how distorted it is.

Rob10_99 · 05-13-2008, 05:17 PM

No torque plate? wtf.
Hondas are open deck and aluminum, might as well be talking about a rotary.
Cast iron blocks need to be torqued plated!

92awddsm · 05-13-2008, 08:19 PM

No 4g63 ever came from the factory with a plate bore and hone and they have all worked great. Why does everyone think that it is required when rebuilding.

Now, lets question those that are using arp studs and torquing higher than apr specs. Did any of you have a plate hone? If not, you have more distortion in your cylinders than if you stuck to arp torque specs. Those that did have a plate hone and are over torquing their studs, you wasted your $ on the plate hone. The machine shop torques the studs to spec when honing and if you increase that torque, you are just distorting the cylinders and defeating the purpose of the plate hone.

For the majority of everyone, there will be no performance or reliability difference between using or not using a torque plate.

Rob10_99 · 05-13-2008, 08:41 PM

Just for reference,
Lets use nascar, they will machine the block torque plated, at operating temp, with oil and water in the jackets.
Why? because the block will deform with each additional variance.
Only less than 1% leakdown for those guys. You probly couldn't build an engine with that if you had to, me either!