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Piston clearance need help asap

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russell3123

russell3123

15+ Year Contributor
187
0
May 6, 2006
peabody, Massachusetts
i have manley .020 pistons, machine shop just checked ptw and on 3 cylinders it was .0040 and 1 cylinder was .0050., should i buy a new block and bore it or isthis clearance ok?. goal is 450awhp and car will only be driven 4-5k miles a year and longest trip will be about 300 miles at a time. Need help asap, trying to get car back together by end of this mounth.
 
russell3123 said:
i have manley .020 pistons, machine shop just checked ptw and on 3 cylinders it was .0040 and 1 cylinder was .0050., should i buy a new block and bore it or isthis clearance ok?. goal is 450awhp and car will only be driven 4-5k miles a year and longest trip will be about 300 miles at a time. Need help asap, trying to get car back together by end of this mounth.
Click to expand...

I would recommend a new block. That is a pretty large difference. What did the sheet that came with your pistons recommend for the PTW clearance?
 
What mashine shop are you using around here?

Are those the numbers after they bored it or was it already bored? either way I am with RoyBarron on this. You could always go 40 over too if its cheaper to get the pistons than another block.

Recommended piston clearance .0035" measured 1.100" from the bottom of the oil ring

Right off the Manley performance cite...

good luck
 
some 1 else bored it.. i got the block like this.. i see a lot of people running .004-.005 clearance. but it seems a little lose for my likens. but funds are dried up so im kinda screwed.
 
dsmcrzy said:
What mashine shop are you using around here?

Are those the numbers after they bored it or was it already bored? either way I am with RoyBarron on this. You could always go 40 over too if its cheaper to get the pistons than another block.

Recommended piston clearance .0035" measured 1.100" from the bottom of the oil ring

Right off the Manley performance cite...

good luck
Click to expand...

Aww come on man at least spell it right, its roRy! :p
 
russell3123 said:
nope. shiny all around. http://www.manleyperformance.com/dl/tech/piston.pdf
i have searched all over the forums and every one runs different ptw.. i have seen everything from .0025 to.0065. i know ross recommends .0060. i just dont want to waste my time putting everything together to have it blow.
Click to expand...

The link you show says .004. Our cars are considering sport compacts. Ross will have their own tolerances since they have their own pistons. That is like saying Nike says you wear a size 9 shoe, well in Reebok it may be a similar shoe but in Reebok you wear an 8.5 or 9.5. So you basically answered your own question! :thumb:
 
Yeah, follow whatever manley says, manley has their clearances for a reason. Ross im sure has a different style piston as well as material, this means it expands diferent from other brands, not to mention wrist pin offset, skirt coatings e.t.c
 
I'm running .004" on my Wiseco's. Large clearances will experience piston slap until the engine gets warmer. I'm not having any ill-effects on mine though. What is your ring gap at? I would consider running them..
 
russell3123 said:
Ring gap will be. 018 on top and. 020 bottom. I'm not worried about the. 004 on the 1st three pistons,itsthe. 0050 in the 4th piston I'm worried about
Click to expand...

Well at the end of the day do you trust your machine shop's judgement? Ask them what they think about it. If anything PM a few guys on here that can give advice, I believe bogusSVO and bastarddsm both know something about machine work.
 
The guys at Manley, suggest .0035 clearance, Another .0005 I doubt will give you issues.
the one at .005 gives me a moment of pause tho. Once more wear occurs in that cyl. you may have some piston slap.

Being you sayy you are going to drive the car 4-5k a year, you may be just fine.
Is this a fresh bored block? and they just over honed the one cyl?
Are they sure that how they measured ia accurate?

The thickness of a sheet of paper is appox .003, so you are aover bt appox 1/3rd of a sheet of paper.

I will say that I doubt that if .0035 is spec, that you will get piston slap at .005

But your .018/.020 ring gaps seem just a touch tight, at that spec, if you run lean you will run the risk of the end gap touching and flexing, and if the ring flexes then you can crack or break the ring land.
 
I would run it then as long as ring end gap is in spec then.

Your ring gap seems very tight, especially if you run a lot of boost like you say you will. I run a .024 top and .026 bottom.
 
what brand of pistons and rings do you plan on running?
 
When you recive the rings from Manley, there should be an info sheet with them.

On the info sheet there is a chart with a formula and factors depending on the build you plan.
This will be a guidline, and you can adjust the ring gap according to your skill level and tuning ability.

I have a Wiseco info sheet, and I am fairly sure the manly chart will be about the same.
The 4g63 has a STD bore of 3.346 or 85mm and your block /piston combo is bored .020 or .5mm over
That makes your base factor 3.366 or 85.5mm

Now you have a choice of 2 factors
(1) Street-Moderate turbo
top ring .005 x Bore 3.366 = .01683 or .017
2nd ring .0055 X 3.366 = .018513 or .019

Those seem a bit tight unless you are a super tuner and will NEVER run lean

Now the second choice on the chart is
Blown Race only
Top ring .0065 x 3.366 = .021879 or .022
2nd ring .0070 x 3.366 = .02356 or .024

This is the more common ring gap used in most builds I have seen here on the Fourm
 
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