piston question ( pics)

OinkAodeOink

Founding Member

Jun 5, 2002

3,026

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Daytona bch, Florida

Mar 19, 2004

#1

• Mar 19, 2004

• #1

In the process of test fitting the rods, pistons, and i believe i ran into a problem.
Piston comes out of the bore by .050's at TDC.
All parts are Brand New, and have not been worked on, except for the block, which was not cut. Scat 347 stroker kit, with the 5.4" rod lenght, stroker crank, clevitte77 bearings, Speedpro Moly rings, and Ross forged dished(20cc) pistons. After matching up an old Felpro, which was .039 or so, the piston still comes out farther the the gasket. The heads dont have any sort of recessed cutout for the pistons.

Does this look like a problem, or do i just need a thick gasket.
By the way, i plan on having the heads o-ringed, if that makes a diference here. Do i need to have the piston shaved down, or the heads cut out for clearence?

 

5.0fox

Member

Feb 10, 2003

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17

buckley/enumclaw wa

Mar 19, 2004

#2

• Mar 19, 2004

• #2

its allright if it sticks out a little bit if you have enough valve to piston clearance

 

3

331 cobra

New Member

Oct 14, 2003

398

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Silicon Valley CA

Mar 19, 2004

#3

• Mar 19, 2004

• #3

That's very bad.

I think you want about .035" piston to head clearance minimum. .045" would be much more safe.

When the engine heats up, the rods and pistons expand, and the force created by decelerating the piston streches the rod also. These factors will reduce that .035" clearance to about zero at high rpm.

You will be starting out with negative clearance at room tempature, zero rpm.

You need to disasemble it and measure all of the relevant dimensions: piston compression height, rod length, stroke and deck height.

Unless you got a bad part, I think the most likely cause would be the block. Was it ever decked or line honed? Both of those things can change the deck height.

 

2

2stangs69-91

Founding Member

Aug 1, 2000

78

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0

Redding CA. USA

Mar 19, 2004

#4

• Mar 19, 2004

• #4

If it sticks up .050 you won't be able to turn the engine over much less worry about the valve clearence is the .050 acurate or a guess? anyhow call the place you got your kit and talk to them about it something is wrong. I have had domes milled off of pistons before but never the entire top.

 

9

90stangLX302

New Member

Dec 2, 2003

76

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Good ol' Bellaire Ohio

Mar 19, 2004

#5

• Mar 19, 2004

• #5

make sure you tightened the bottom of the connecting rods up when you are checking it all out, mine were almost the same then i noticed i didnt even tighten the nuts so it was sticking up to far,... just a stupid mistake i got all worried about that i thought i would warn you about

 

thumper460

Founding Member

Jul 24, 2000

3,022

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56

Orange Park , Fl

Mar 19, 2004

#6

• Mar 19, 2004

• #6

.050 is no good!!! your done!! something must be wrong... the block decked?? .045-.050?? doubtful !! the combo is wrong...?? More than likely!! You can have .005 out... but .050 wont work!! Have the BLOCK O-Ringed ..not the heads!! It will save you a lot of money in the long run... a lot!!

331Cobra is right on you need at least .035 top of piston to the head!! .045 is better, if the engine is going to see 6k or better!! IF you go to Copper gaskets, you can get up to .080 thick !! and that would give you the .030 you need!! but the block should be O-ringed for copper gaskets!! If not going with the .080 gasket...... I'd call the shop and see why!!!!! fixing the problem isnt the problem..... and if the piston IS out .050.. what else is wrong???

Just me..........................

Thumper

 

OinkAodeOink

Founding Member

Jun 5, 2002

3,026

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Daytona bch, Florida

Mar 19, 2004

#7

• Mar 19, 2004

• #7

well heres the deal... When i ordered the Stroker kit from Scat, i told them what i wanted specifically.. a 331(327 ci), standard bore, Forged crank/rods, and low compression pistons that would bring me to 8.58.8:1 compression.. I few weeks latter, the parts arrived after being balanced to 28oz. I get the box and see its a 347 kit, not a 331.... Atleast i think it is... And i measured the piston with a feeler guage, and it might not be .050, but its damn close ( +- .001) Here are some specs, from the invoice..

Balanced Scat 302 Ford crankshaft
Standard style, 4340 forged
3.400 stroke X 2.123/1.680 PIN
5.400 Rod Lenght, Nitrided

Scat 302 Ford H beam Rod set
5.400 Rod lenght /.927 wrist pin, bushed
2.123 Pin Diameter/ .830 Big end Width

Ford Windsor 302 Ross Piston 4.001 Bore X3.250 Stroke
5.400 Rod Lenght 1.160 CH .927 Pin Diameter


Shoot- Just realized my own problem, i think... Rod/crank are 3.400 stroke ( 347) and the pistons are 3.250 Stroke ( 331)... idiots!!!

 

3

331 cobra

New Member

Oct 14, 2003

398

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0

Silicon Valley CA

Mar 19, 2004

#8

• Mar 19, 2004

• #8

Yeah, they are idiots.

You need to either get a new set of 5.315" rods, and rebalence the crank with the new bob weight, get a new crank and ballence that, or get a new set of pistons and reballence the crank.

All of those options suck and I hope you don't get bit by it.

It always pays to check everything before you start assembeling and ballencing.

 

N

nitroponynj

New Member

Mar 1, 2004

27

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0

Mar 19, 2004

#9

• Mar 19, 2004

• #9

yu have the worng crank............

 

nitrousED

New Member

Oct 14, 2003

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Mar 20, 2004

#10

• Mar 20, 2004

• #10

if im not mistaken the srank should be 3.25 and rods 3.40