IE Cast Pistons. Advice Please.

[PaulTWinterton]

I'm rebuilding an engine with the IE 90mm cast pistons.  I took the advice of an FAQ member to have the machine shop "bore each hole to match a piston.  4 different hole sizes for 4 pistons mated.  I passed that on the machine shop.  No problem.

 

I just got a call from the machine shop to say that there is 4 thousands (over) difference between the pistons.  They needed to inform me as it may be problematic in heat and balance.  Bottom line is they would write a disclaimer, as this is not an ideal situation.

 

Should I be concerned?  Have others used irregular cast pistons without issue?

 

Thanks for reading and replying.

 

 

[Preyupy]

I am shocked there is that much difference between the pistons.  As far as difference in balance,  you are having everything balanced, right?  On a cast piston I expect there to be some difference in the weight of each piston (the internal dimensions are not as carefully controlled as a forged piston so there is some difference in weight to be expected)  so this will be easily taken care of in the balancing process.  as far as heat dispersal and other considerations I would not be worried about it at all as long as the piston to cylinder clearances are correct (this is why we bore the block to fit the pistons once we have them in hand, If you had bored to just one piston you would have either excessive or tight  clearance on 1 or more pistons).  I would however call Jeff Ireland and tell him what you have found,  he needs to talk to his supplier.   

[PaulTWinterton]

2 hours ago, Preyupy said:

I am shocked there is that much difference between the pistons.  As far as difference in balance,  you are having everything balanced, right?  On a cast piston I expect there to be some difference in the weight of each piston (the internal dimensions are not as carefully controlled as a forged piston so there is some difference in weight to be expected)  so this will be easily taken care of in the balancing process.  as far as heat dispersal and other considerations I would not be worried about it at all as long as the piston to cylinder clearances are correct (this is why we bore the block to fit the pistons once we have them in hand, If you had bored to just one piston you would have either excessive or tight  clearance on 1 or more pistons).  I would however call Jeff Ireland and tell him what you have found,  he needs to talk to his supplier.   

 

Please excuse my lack of knowledge.  Until now, balancing was not discussed.  Thanks for your advice.  I will follow it.

[TobyB]

Not so much would I trust those.

 

The casting is machined- I would expect a few tenths, not thou.

 

Call Jeff.

 

t

[Naz]

Hello Paul, I'm actually having my 2000tilux engine being rebuilt by the same machine shop. Alec automotive. I am also having the same issue as they called me today as well. Here are the measurements they gave me.

#1= 3.5408"
#2= 3.5432"
#3= 3.5411"
#4= 3.5410"

You should give me a call. I'm wondering what the measurements of your pistons came in at and if they mixed one of yours with mine?

Naz
6043539819



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[Naz]

Maybe #2 is yours? Just a thought. My pistons are for the 121ti head. Here is a pic of them




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[PaulTWinterton]

Hi Naz,

 

I will call you.  But not a mix-up.  My pistons have a black coating on the them.

[Naz]

Ok Paul. I was grasping perhaps. Did you get the exact measurement from them?


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[TobyB]

What did Jeff say?

 

t

 

[goofycarp]

Hi,

 

I am very interested to know the outcome as I am looking to purchase a set.  Do the forged ones have better tolerances and what other choices are there for 9.5:1 compression ratio for an E12 head? I see there is a set of "euro" Kolbenschmidt tii pistons on ebay but they are asking $1k used.

 

Thanks, Cort

[Preyupy]

Forged pistons (depending on the manufacturer and alloy) tend to grow more with heat and need to be set up with larger clearances.  This is more of a problem with street cars because we want to just jump in and drive away in our street cars, this is hard on the piston skirts until they warm up and grow.  I don't usually advise anyone to use forged pistons on a mostly stock street car engine.  If you are building a high compression, high RPM engine or you are running a ton of boost they make sense.  I have them in my 2002 but I don't even THINK about moving the car or going over 2500 rpm until I have the water temp to at least 160degF, I also don't lean on it until the oil temp is up to at least 140degF

[kbmb02]

2 hours ago, Preyupy said:

Forged pistons (depending on the manufacturer and alloy) tend to grow more with heat and need to be set up with larger clearances.  This is more of a problem with street cars because we want to just jump in and drive away in our street cars, this is hard on the piston skirts until they warm up and grow.  I don't usually advise anyone to use forged pistons on a mostly stock street car engine.  If you are building a high compression, high RPM engine or you are running a ton of boost they make sense.  I have them in my 2002 but I don't even THINK about moving the car or going over 2500 rpm until I have the water temp to at least 160degF, I also don't lean on it until the oil temp is up to at least 140degF

 

What alloy are you using?

[Preyupy]

The best thing to do is look at the manufacturer's spec for piston to cylinder clearance.  Many years go Venolia spec was 0.004-0.005" on a 90mm bore (that is a LOT)  current CP spec is 0.003-0.0035" for Forged pistons.   Cast pistons usually run 0.0015-0.0018" for the same 90mm bore. 

[goofycarp]

Hi, 

 

Did IE ever give a response to the variances or the engine builders chime in? Would like to know, Thanks.

[rstclark]

Bump

 

So  

1. Is the recommended best practice to bore each cylinder to match each piston ?   It sounds like a smart thing to do given the amount of variation reported here in the piston size, and

 

2.  What is the recommended cylinder clearance for  IE cast pistons ?