Piston to bore problem...please help

[blackGSX2g]

Alright, I have a 6-bolt block bored .020'' over and honed by Buschur Racing. I just put in my Weisco pistons (which I bought from Buschur at the same time). Question is, when the pistons are at TDC, I can physically move them front to back (from intake relief to exhaust relief). Is this normal? Piston to wall clearences on Weiscos are supposed to be .003 at the piston skirt, I measured this when it was BDC and it seemed ok...its kinda hard to fit a feeler gauge down there, but I tried. I was just worried sick when I saw the movement at TDC. Any help is greatly appreciated. Thanks

Matt

 

[alexg1323]

every motor ive built has been able to do this to some extent. If your real worried your gonna have to get a caliper guage, and dial bore guage and subtract your 2 measurements.

 

[1fast97gsx]

yea a little movement is normal ... hence why you need clearance. ( well and for expansion ) Just take some measurements and calm yourself down .

 

[blackGSX2g]

yea a little movement is normal ... hence why you need clearance. ( well and for expansion ) Just take some measurements and calm yourself down .

Yea, when I searched I found some of your posts asking pretty much the same question, there just wasnt a definitive answer.

I figured a little play was expected, how much would you say a little is? I can see the piston move a fair bit. I might go back with the feeler gauge and measure exactly how much it moves. I would trust Buschur to do good machining, but this is my first real motor build, so I was worried.

 

[alexg1323]

did you check your ring gap before you installed those pistons?

 

[blackGSX2g]

I checked ring gap and it was gapped per the instructions that came with the Wiseco piston/ring set.

 

[anconover]

did you measure the piston per wiseco instructions and use a dial bore gauge to make sure your clearance was correct?

 

[blue1]

The top of the piston is smaller than the bottom when they measure to get the bore clearence it is usually done across the pin area. the taper on the pistons is to allow for expansion when they are at operating temp so you will notice the piston rocking at tdc. From what i have heard about busher racing they know what they are doing, if you have any doubt contact them they surely will explain this better than what i just tried too!

 

[TSIfreek]

Does BR do the machine work on the motors they build I dought it guys.

 

[blackGSX2g]

Well its the same place that does the machining on BR's pre-built motors. They did it just the same as if I were to go in and purchase a pre-assembled motor with .020'' Weiscos.

 

[alexg1323]

i second blue1, he said it best. you should post some pics up here so we can see how its all comin along.

 

[1fast97gsx]

we can't really tell you "how much" play you should have ... but you can meassure your wall clearance, pistons diameter, and bore diameter as well as double check ring gaps and if all checks out then all is fine.

 

[Maglin]

Ahhhh... Ok ... Forged Pistons Expand at a higher rate than cast pistons... The skirts are bigger than the tops of the pistons cause the tops will expand more than the skirts cause the tops are basicly solid billit and the skirts are just hanging around so to speak... On Weisco pistons you DO NOT measure the piston to bore clearance at the pin... You measure it at the skirt 90 degrees from the pin bore... If you measure it at the pin you will have it to tight and score and ruin your pistons... The pistons will rock in the block when they are cold... If BR did the machine work i'm almost 100% positive they measured each piston for each bore for the piston to wall clearance.. Also Weisco says to have .004 not .003 and they suggest you increase that by .001 for every 10 pounds of boost you will be running them over 15 PSI... Well that is what I recall for the extra clearance but that may be a tad off but not by much... I personally love tight motors and would set it up at .004" and not run over 20 lbs. of boost until I hit 2K miles.... I wouldn't go over 10 lbs. of boost until 1K miles... You want to break in the motor with boost so the rings will seat by the pressure and not seat in N/A mode and possibly not seat up once cylender pressures start to rise due to added boost...

YOu don't have to listen to me... I'm no wiseman... but I don't need to be to know the facts... If BR did you block you are ok.... If not and you get a scored piston I'm positive they will fix your problem as it would be their mistake... Did your pistons have cylender numbers on them when you recieved them??? They should have... Good luck...

 

[blackGSX2g]

Ahhhh... Ok ... Forged Pistons Expand at a higher rate than cast pistons... The skirts are bigger than the tops of the pistons cause the tops will expand more than the skirts cause the tops are basicly solid billit and the skirts are just hanging around so to speak... On Weisco pistons you DO NOT measure the piston to bore clearance at the pin... You measure it at the skirt 90 degrees from the pin bore... If you measure it at the pin you will have it to tight and score and ruin your pistons... The pistons will rock in the block when they are cold... If BR did the machine work i'm almost 100% positive they measured each piston for each bore for the piston to wall clearance.. Also Weisco says to have .004 not .003 and they suggest you increase that by .001 for every 10 pounds of boost you will be running them over 15 PSI... Well that is what I recall for the extra clearance but that may be a tad off but not by much... I personally love tight motors and would set it up at .004" and not run over 20 lbs. of boost until I hit 2K miles.... I wouldn't go over 10 lbs. of boost until 1K miles... You want to break in the motor with boost so the rings will seat by the pressure and not seat in N/A mode and possibly not seat up once cylender pressures start to rise due to added boost...

YOu don't have to listen to me... I'm no wiseman... but I don't need to be to know the facts... If BR did you block you are ok.... If not and you get a scored piston I'm positive they will fix your problem as it would be their mistake... Did your pistons have cylender numbers on them when you recieved them??? They should have... Good luck...

No, my pistons weren't numbered. The only numbers on them were the gram weights.

According to the spec sheet my pistons came with, it says .003 clearence, but I've heard .004 as well...depending on the break in method and amount of boost I plan on running just like you said. I plan on running 9psi (stock on the e16g) and do a few WOT runs in 3rd and engine brake it down to seat the rings, then keep it easy for 2k.

I'm going to go pick it up from my buddies garage tomorrow and have it checked by my machinist here and I'll post some pics. Like I said, I'm not doubting Buschur's work...I'm just paranoid by nature and want to make sure everything is perfect.

 

[1fast97gsx]

I don't blame you for double checking everything. Wish I woulda done that on my first motor

 

[Defiant]

I'm not doubting Buschur's work...I'm just paranoid by nature and want to make sure everything is perfect.

No, no, no. Paranoia is an irrational fear of imagined threats. What you have is psychosis

However, cars that aren't driven don't ever break, so even this has its payoffs.

 

[Maglin]

Sorry I should be more clear.... When I asked if the pistons where numbered it would have been in ink... Like they wrote numbers on the pistons cause those bores are tailored to those pistons... According to Weisco's site they said .004" clearance but it's a possibility for the small 4G63 it's .003 if your spec sheet said so.... But since it's a turbo .004" would be better yet... I wish you the best of luck... if they didn't number the pistons chances are they didn't cut the bores to each piston and just found the largest piston and cut each bore to that... Most machine shops even go a tad over that for the just in case factor... You get a more sloppy engine but you don't get as much angery customers returning cause they don't know how to break in a motor and they runined components and want to blame the Machinest...

 

[blackGSX2g]

However, cars that aren't driven don't ever break, so even this has its payoffs.

hahaha, good quote

Sorry I should be more clear.... When I asked if the pistons where numbered it would have been in ink... Like they wrote numbers on the pistons cause those bores are tailored to those pistons... According to Weisco's site they said .004" clearance but it's a possibility for the small 4G63 it's .003 if your spec sheet said so.... But since it's a turbo .004" would be better yet... I wish you the best of luck... if they didn't number the pistons chances are they didn't cut the bores to each piston and just found the largest piston and cut each bore to that... Most machine shops even go a tad over that for the just in case factor... You get a more sloppy engine but you don't get as much angery customers returning cause they don't know how to break in a motor and they runined components and want to blame the Machinest...

Yea, thats what I figured you meant. Does this hinder the longevity of my motor, or is it just a minor thing to deal with? Sloppier clearences would mean piston slap until its fully warmed up, correct?

 

[anconover]

Wiseco actually recommends .003 for most applications. .004 is a little loose for a street car, or a car not seeing high boost/spray, at least with wiseco's. Now ross pistons, that would be an appropriate clearance.

A looser clearance will cause a little more slap untill the car is fully warmed up and everything expands.

And because each piston probly isnt the EXACT same measurement, each bore is honed according to a specific piston to reach the correct clearance. Because of this, and the fact your pistons were not numbered, this is why you should of measured each bore and each piston before assembling. If something goes wrong, they may find this to be the cause and not machine work, hence not covering it.

 

[Maglin]

OK here it is straight from Wesico's Site... Lot's of good information here....
I was a little off of where to measure at but I was close... Just going on info that was in my head...

Here is the Link to this and more info: Wiseco Pistons's FAQ

What kind of piston-to-wall clearance can I run?

The factors that affect this are cylinder wall thickness, whether the block is filled, the overall compression height of the piston, piston material and thickness, and whether a marine engine is to see fresh-water cooling. Most small blocks get .004 piston to wall clearance and most big blocks get .005 due to the use of our 2618 high-strength alloy. For heavy blower and nitrous applications, Wiseco recommends adding .001 to the standard clearance. Special note: Clearance numbers are taken 1.300 down from the oil ring land-Not 90 degrees from pin centerline.



What is minimum piston to head clearance?

Rod material, the mass of the piston, and piston-speed are the factors that determine this. Steel rods in a big block usually require .045. Steel rods in small blocks require at least .036. Most imports can get by with as little as .030. Aluminum Rods generally require .010 more clearance than steel rods. *Remember, the compressed gasket thickness can vary from .025 in steel shim applications to .040 for composite and up to .100 for some copper gaskets.

 

[blackGSX2g]

Alright I haven't been to the shop in awhile. Here are some pics of the cylinder/bore.

 

[TSIfreek]

OK

 

[blackGSX2g]

OK

Just wonderin if the gap between the piston and the wall is normal. I've only done rebuilds with cast pistons, and there is usually no gap. For those who rebuilt theirs with forged, does this look normal?

 

[Maglin]

read the rest of the posts... It's normal.

 

[blackGSX2g]

read the rest of the posts... It's normal.

Thanks