Are These Pistons Good For This Block?

[Turbo SOB]

OK, so I have a block that someone had over-bored by 0.020. It's been sitting around collecting dust, but now I am in a situation with my current engine that requires me to build a whole new engine. Doh. I have bought a set of Wiseco pistons for the new engine.

So here's the piston skirt measurements: Pistons, Wiseco, 2.5L, 8V, +0.020 over:
#1 = 3.4610, #2 = 3.4610, #3 = 3.4615, #4 = 3.4610

These measurements were taken with the Mitutoyo digital calipers in my office, so I am very confident they are accurate.

The spec sheet for the Wisecos says recommended bore clearance is 0.0035", so the bore size I am looking for is:
#1 = 3.4645, #2 = 3.4645, #3 = 3.4650, #4 = 3.4645

Now, I measured the cylinders with a very accurate bore gauge. I measured about every half inch down the cylinder wall.

Here are the series of fore-aft (i.e. piston skirt) measurements of the block:
Meas--- Cyl #1 - Cyl #2 - Cyl #3 - Cyl #4
1------- 3.4652 - 3.4649 - 3.4650 - 3.4650
2------- 3.4650 - 3.4646 - 3.4648 - 3.4646
3------- 3.4650 - 3.4645 - 3.4648 - 3.4647
4------- 3.4650 - 3.4645 - 3.4648 - 3.4648
5------- 3.4654 - 3.4649 - 3.4651 - 3.4650
6------- 3.4655 - 3.4652 - 3.4657 - 3.4653
7------- 3.4655 - 3.4652 - 3.4656 - 3.4652
Average- 3.4653 - 3.4648 - 3.4651 - 3.4649

Here's the measurements of the block in the side/side (i.e. wrist pin) direction:
Meas--- Cyl #1 - Cyl #2 - Cyl #3 - Cyl #4
1------- 3.4659 - 3.4654 - 3.4655 - 3.4654
2------- 3.4657 - 3.4653 - 3.4655 - 3.4653
3------- 3.4656 - 3.4654 - 3.4655 - 3.4652
4------- 3.4657 - 3.4655 - 3.4656 - 3.4653
5------- 3.4658 - 3.4656 - 3.4657 - 3.4655
6------- 3.4656 - 3.4655 - 3.4657 - 3.4653
7------- 3.4649 - 3.4650 - 3.4651 - 3.4647
Average- 3.4656 - 3.4654 - 3.4655 - 3.4652

So, to use piston #3 in cylinder #1, here are the OVERSIZE spec. That is, each cell = measurement - (piston measurement + recommended clearance):
Meas--- Cyl #1 - Cyl #2 - Cyl #3 - Cyl #4
1------- 0.0002 - 0.0004 - 0.0005 - 0.0005
2------- 0.0000 - 0.0001 - 0.0003 - 0.0001
3------- 0.0000 - 0.0000 - 0.0003 - 0.0002
4------- 0.0000 - 0.0000 - 0.0003 - 0.0003
5------- 0.0004 - 0.0004 - 0.0006 - 0.0005
6------- 0.0005 - 0.0007 - 0.0012 - 0.0008
7------- 0.0005 - 0.0007 - 0.0011 - 0.0007
Average- 0.0003 - 0.0003 - 0.0006 - 0.0004

So, you can see that some measurements are as high as 0.0012 over the recommended diameter.

The question is, should I scrap this block and get a whole new block and get the cylinders bored out to the exact spec, or is this good enough?

Thanks,
Jeff

[22shelby]

i would call wiesco and figure the min and max for that piston, im not sure, even tho i just did this last yeah with wiseco... some like em tight some like it loose, some like em fat some like em skinny, me i shoot for right in the middle.... thos differances to me in MY opinion would fly...

[Juggy]

your at .004" clearance right now....honestly id run it!

you could pay to have it done at a shop. but good chance it might just come back out with same sizes. so why pay for something thats already done?
your only worried about .0015" at most.

[turbovanman²]

.004" run it, hell, I've run .012-.015", :eyebrows:

[4 l-bodies]

Your Wiseco pistons were obviously made for a .020 overbore. If cylinders are in good shape. Put those pistons in! Just make sure the dish and valve reliefs are for the correct crank/head.
Todd

[Directconnection]

I think you'll be ok, but.....

#1) never use digital/dial calipers for real measurements. I do have a set of the same Mitutoyo digital calipers, and they are very accurate, but +/- .0005" that they are sometimes good for isn't close enough. I also hope you didn't set your dial bore gauge with them, too. Use a 3-4" micrometer and measure the piston 1/2 from the bottom of the skirt. Then w/out removing the mic from the piston, use the lock function to lock the mic for an accurate measurement transfer. (locking the mic while pressure is on it takes out all backlash which can be as much as .001 error or more)

Clearances are built into the piston.... so whether a JE or a Wiseco, a +.020" pistons means it is .020" more than the standard *bore size* In this case 3.4450 is stock, so 3.4650 is the bore the block should have been honed to in order to get the average clearance the piston manufacturer intended. Where I work... and I really hate this... we have to put the cart before the horse at times. Circle Jerk race car driver needs his motor ASAP to run this weekend. JE is taking a while for the custom piston order (ordered weeks ago) So, we get everything ready as far as we can so when they come in on Thursday, we can dyno it Friday morning and off to the races. So.... we order a set of +.040" JE's and bore/hone the block ahead of time. 99% of the time this works....

[22shelby]

right 99%!! i would alway measure and bore/hone block to piston... just how i learned it, and this is from guys that build 30,000 dollar motors...

[Directconnection]

right 99%!! i would alway measure and bore/hone block to piston... just how i learned it, and this is from guys that build 30,000 dollar motors...

We build more expensive motors than that, too. But we ALWAYS verify before assembling. Meaning, we know what the block was honed to exactly, and when the pistons come in, we measure and verify. That 1% means we just have to bring the block back to the CK-10 for a wee bit more clearance, then another final wash....

Nothing gets assembled w/out final measurements by the engine assembler.

[Turbo SOB]

I think you'll be ok, but.....
Thanks. As for the calipers, I'm not relying on them 100% to measure the pistons. I have the actual spec sheet for the pistons (see below) which says "Bore Size: 3.4640" and "Suggested Clearance: 0.0035". Measuring the pistons helped me figure out that "Bore Size" is actually referring to the bore of the cylinder itself, as the pistons actually measured closer to 3.4640 - 0.0035 = 3.4605. So, I'm really only relying on the digital caliper to tell me that piston #3 is a tiny bit bigger. Yes, it is a ±0.0005 caliper.

As for measuring the bores, I actually used a very large, expensive, almost new, metric dial face gauge with a "Master ring" that measured 88 mm. The master ring actually had a recent calibration certification on it, and so did the dial gauge. I can't say where I borrowed them from. I even made sure the block, the ring and the gauge were acclimated to the same temperature before using it.

By the way, I faxed Wiseco a request for their comment, and I have not yet gotten a response.


http://i10.photobucket.com/albums/a131/jeff_vs/parts/WisecoSpecSheet.jpg

The reason I'm being so damn picky about this is because I had paid over $800 many years ago to have a block sized for a set of Venolias. I was shocked and dismayed to find that the setup produced horrible piston noise even under full throttle. I don't want this setup to be noisy, even a little bit.

Here's the final chapter on those Venolias, by the way:

http://i10.photobucket.com/albums/a131/jeff_vs/parts/IMAG0305.jpg

[turbovanman²]

Don't blame the Venolia's, blame the machine shop. I ran some and with the proper clearance, I set them at .004", they were quiet, until I started melting them, :banghead:

[Turbo SOB]

Right, now that I'm older and wiser I have a better understanding of the build process, and can ask the proper questions to get the results I want.

I'm not hating on the Venolias, per se. Their wide piston clearance spec leaves much to be desired. Then again, Wiseco's spec sheet only mentions a "recommended clearance" and doesn't have a ± on it.

All I know is right now is I bought the Wisecos and intend to use them. I will price out having my last spare block bored out and honed to the proper spec, but if it's too much I'll just use the one I mention above.

[trannybuster]

Weisco, run them .0035, use that for min. Im not sure what can be held for tolerancing by a honing/boring machine, but I would want no more than +.0005. Weisco wont give you a clearance, NO aftermarket forged piston supplier would, they all recommend. Venolias can be run tighter as well...

[Warren Stramer]

I run Wiesco's @ .004 and they are quiet. You are not that picky, Bolt a torque plate on to the block with head gskt, then re-measure bores. Match fit largest piston to largest bore, smallest to smallest and so on.
If you can get .0038-.0042 run em, you will be fine. dont forget to file fit the rings, and while your at it give the cyls. a few strokes with a 400 grit ball hone with oil. But you probably know all this already:thumb:

[Directconnection]

You could probably run the wisecos at .006 and be ok (I wouldn't) a the 2.2 has a decent skirt. We have ZZ4 crate motors we build 100's of these things and the cast mahle pistons sometime show *almost* that much before swapping to +.020