Piston slap issues.

[half-cocked]

OK it just came to my attention on how much piston wall clearance I have and its a little much. (my own ignorance I know) Quick run down, 6 bolt rebuild bored without a torqueplate with Ross 8.5:1 on big rods. The pistons build sheet calls for .006" of piston-wall clearance and add some if a torque plate is not used. My machinist (first time using him and he was reccomended to me) set it at .0065" - .007". Excessive I know but I just came accross this info today and this engine is 90% together.

So, I call the Ross Tech line and relay my setup to him and he says .006" sounds good, I could even go as tight as .005". Well I tell him my clearance and he says to expect audible slap when cold (which I expected anyhow) and possible slap when warmed up, which I dont mind but my concern is if the knock sensor picks up the slap as knock and retards my timing. He says it could. I dont know if he has any experience with 4G63's but I would like to hear some feedback on what I can expect. My machinist says there is no real concern. Bottom line is this engine is not coming apart right now, and I will ditch the MAFT/SAFC combo I had planned on for tunning for some thing I can control timing with be it an EMS whatever. Is there any other issues that could come up, any comments?

 

[Defiant]

My machinist says there is no real concern.

Shit. Explain to him there's no real payment until that thing's run a thousand miles without problems.

 

[Cesar]

I had to make this same decision recently with the same pistons. The original machinist that bored my block went to about .0035. I wanted to run .005 (I called ross and that is what the tech dept. specified also). My original machinist didn't want to do it. I told him to go you-know-where and took it elsewhere. I run .005 clearances.
My motor has 300 kms so far. It sounds better than any engine I've ever had. No slap.
I havent had much of a chance to put mileage on it since I take transit to commute to and from work. I live downtown Toronto.
I may have slap during canadian winters, but I don't think I will be driving it in the winter, I may not even own the car for much longer since it is for sale.

As far as your clearances go, do you have the option of finding another block? I know that line boring, decking, honing again would put a dent in your pocket, but you should consider all possibilities.
If the tech. dept. at ross didn't say it was going to be a huge issue then go through with it. Run a hotter thermostat. Monitor knock. Who knows...you may get lucky.

 

[half-cocked]

Yeah at this point its too late to start pulling stuff apart, un fortutnatly it was my own ignorance that missed this detail, I guess I had too much faith in the machinist. My main concern is is slap being registered as knock, I can live with a little slap.

 

[TSIfreek]

Why use a machinist without a torque plate?? That was a mistake to begin with. I would never have an engine with forged internals that I plan on making some big power with bored and honed without one. No matter if he used a plate or not you still have that excessive clearance and may cause you problems with engine longativity. If you deside on keeping it the way it is I would run syn 15 50 mobil to keep the noise down slightly but its just a band aid.

 

[half-cocked]

I coud not get a torqueplate when I had the work done, that why I didnt use one and the actual need for one has been hashed out too many times on this board. As far as engine longevity, if it goes 50,000 miles I would be stoked, as this is my first non-stock rebuild. I will use the oil weight you suggested and go from there. Like I said its not the slap I am concerned about, my main concern is the knock sensor picking up the slap and retarding timing all the time. In which case I will have to get something I can control timing with. My final plans will include a 50 trim, and while I am good on maintenance, I am really hard on vehicles. I am considering a hotter thremostat, but where I live has an ambient temp of roughly 127 - 131* in the summer. I have HEARD a member of another DSM board saying his ross pistons clearanced at .006" make a slight drone upon cold start up, so I am not really sure what to expect.

As far as controling timing, I know all stand alones control ignition maps, but I think they are a little advanced for me, but I will learn the EMS if there is no other choice. I know VERY little about DSMlink's abilities, and with the 1G version supposidly coming out soon as got my attention. Does the 2G version have control over timing and does anyone know if the 1G might also? If so I will just have to tune to a Wideband and EGT's and error on the side of saftey and run a little rich.

EDIT: Just got off the phone with my machinist and he said it was set about .0065". The reason for it was that he has seen engines running forged pistons sieze up in the summer here sitting in traffic due to the extremly hot temps.

 

[1LE]

I wouldn't worry about it too much. One of my friends had an engine built by a well-known DSM shop last year. It slaps like crazy and the shop isn't at all concerned. He's been daily driving the car like that for about a full year. It'd be better if it DIDN'T slap like that, but it doesn't seem to be as big a deal as I used to think. Doesn't cause phantom knock for him.