PTW clearance (Make sure you specify!)

[mitsuturbo]

Apparently i screwed up and didn't tell the shop what (specifically) to set PTW clearance at, and told them to follow the spec card which shows Mahle Recommendation. Well, the spec card says run them from .0025 - .0030 and add an additional .001-.003 for severe duty "such as forced induction/filled block/nitrous".

The machine shop set it up at .006"

Soooo.. Yep. I'm going to get another block punched out to accomodate these brand new Mahle .040" over pistons. I'm not even going to think about trying to go and run brand new EVERYTHING and have .006" ptw clearance (slop). NO WAY!

I'll use the one block they went too big on in my other gvr4. I figure i can throw some 4g64 (86.5mm) pistons in there after they bore it another .020 (.060" over, total). I suppose it should work out okay as long as i don't go crazy with boost. I dont know what the ring lands look like on a stock 4g64 slug, but i imagine they'll live about as well as non turbo pistons do. I've run the 4g63 9:1 NT's in the past, and they worked fine until i put 20+ psi to them and the ring lands broke. My only concern with this setup would be valve reliefs... I wonder if it's possible to use a 4g64 piston with a 16 valve head.

Time to do some more research. Any input is appreciated.

 

[fuel]

4G64s come out 16V right? both SOHC and DOHC in the 7G and 8G Galants

also I would make it the machine shops responsibility to rectify the over-bored situation - they really should either supply you another block machined to the correct tolerances, or bore the block out further and supply you the next step oversized pistons (0.060"?)

 

[Barnes]

I'm confused. They machined it within tolerances, but it is too loose? I don't see how the shop is to blame on this one. Unless I'm reading something wrong.

 

[TylerAdamson]

I agree with Barnes. You told them to follow the spec card and they did exactly that.

 

[IncorpoRatedX]

/ubbthreads/images/graemlins/uhh.gif it's in spec...

 

[bazeng]

I've run 5 thou ptw with wiseos and they did rattle a lot cold and hot. 6 is rather excessive for a street car. Is this a full drag nos big boost monster?

I've also run 2.4 pistons in a 2 liter block. So far so good but I've only run 10psi on it.

 

[mitsuturbo]

Quoting TylerAdamson:
I agree with Barnes. You told them to follow the spec card and they did exactly that.



You're correct. Like i said, i made a mistake and didnt SPECIFICALLY say what to set PTW at. I'd think a decent machine shop (this one's been in business for 50 years) that's been around a while would KNOW what a good PTW tolerance is. I was wrong, and when i called to check on things, it was too late.

Now i'm just going to have to pay them for their services and do what i can with what i'll have.

 

[iceman69510]

So what would you have preferred it to be, 0.0035" (low end of spec)?

 

[fuel]

ah, right I misread the spec, I thought you said that it was recommended to run an extra 0.0001 to 0.0003 rather than 0.01 and 0.03, so yeah 0.06 is at the extreme end of the specs.

 

[fuel]

The other thing, are you able to get those same mahle pistons in 0.060" and then sell off your 0.040" pistons? might work out less hassle.

 

Quoting mitsuturbo:
Quoting TylerAdamson:
I'd think a decent machine shop (this one's been in business for 50 years) that's been around a while would KNOW what a good PTW tolerance is.


You have more faith in humanity than I. These days I'm impressed if someone is good at what they do. I don't give a sh*t if its making pizzas or building aerospace parts. Really. When parts come back from the machine shop I clean them throughly myself, I have seen an engine die due to a chunk of metal in a oil galley. Today my buddy was just complaining about getting screwed by our best machine shop in town. Gave them a 22RE head, told them clean inspect and pressure test it and let him know if its good. They got back to him and said it was good, so he said go ahead and shave it. He gets it back pays for it, and asks "Ok what do you recommend for headgasket thickness?" The guy measures it and goes "Ooooh this is .040" under spec, this head is garbage." My buddys is like "WTF? YOU just machined it, shouldn't you have checked this before machining it?!"
Like absolute rookie BS mistake and they aren't even owning up to it. Great NOW where am I going to take my machine work? The next best shop in town is WAY more expensive.
So is this a shop that deals with a fair amount of performance motors or is it just slamming out small block chevys? If they are not used to dealing with high performance engines you can't blame them too much. You would be surprised how loose tolerances are in GM factory engines these days. Its dissapointing. Just slamming out mass production crap.

 

[mitsuturbo]

Quoting iceman69510:
So what would you have preferred it to be, 0.0035" (low end of spec)?



Well, after calling Mahle's tech dept. to confirm, they recommend .003"... or .0035" and i'm quoting here "if you feel a little nervous about it"
Their definition of "extreme duty" is NOT simply forced induction, although i can see how reading their spec card MAY lead someone to believe this is what is meant.

I got the other block pulled out and stripped down last night. The JEs in it are done, so they won't be usable for anything other than paperweights. Story on those is that i put a brand new (topline) oil pump on the engine and it made it all of about 3 blocks before seizing. Not quite sure what happened, but i'm not the first it's happened to with the topline oil pumps. I had to drive the car from SLC to Seattle, so i threw on a used OP, cleaned some crap out of the engine, replaced a couple valves... and drove it home. I thought it had rod knock. It turned out that the rod bearings were the ONLY part of the bottom end that was still good! Main bearings are bright and shiny! yay? /ubbthreads/images/graemlins/bawling.gif And the pistons were slapping around like the 3 stooges.

Oil starvation is BAD!

 

[jepherz]

That sucks. Oh well, you live and learn.

Isn't .06 REALLY oversized? Maybe not, but I thought even .04 was on the large end of things. This coming from someone who has never rebuilt an engine...

 

[mitsuturbo]

.06" is VERY oversized, but should be okay. As far as i know and understand, the 4g63 and 4g64 blocks are of the same casting. The difference being that the 4g64 was decked 6mm higher(due to 12mm longer stroke) and bored 1.5mm larger. Taking a 4g63 bore to 3.405" or 86.5mm is basically putting it at stock bore for a 4g64.

The car the block will be going into is only going to be running a b16g at stock boost levels.

 

[misterfixit]

Quoting fuel:
ah, right I misread the spec, I thought you said that it was recommended to run an extra 0.0001 to 0.0003 rather than 0.01 and 0.03, so yeah 0.06 is at the extreme end of the specs.



YOU ARE A FACTOR OF TEN OUT. 0.039" =1mm /ubbthreads/images/graemlins/smile.gif

Rich