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Quick Thought / Question I Am Sure Someone Knows


burndog

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If I replaced stock rods 134mm rods with the S14 144mm rods, what would the net effect in increased compression be considering it is a stock 8.5:1 compression with flat piston tops and no changes in stock deck height?

Edited by burndog
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The change in compression will be drastically negative when the pistons break against the head. The stock flat top pistons rise even with the top of the block when mated with stock rods. Unless you raise the pin height in the piston up by 10 mm, the top of the piston will rise past the top of the block and bang into the head. And even if you do raise the pin height in the piston to allow use of the longer rods, you won't gain anything in compression, as your stroke will still be the same as it was with the stock rods. You have to change the crank to increase stroke. Using longer rods simply changes your rod/stroke ratio.

You can do a variety things to increase compression, including shaving the head, milling the block, changing the hemisphere volume, and replacing the pistons.

Edited by williamggruff

williamggruff

'76 2002 "Verona" / '12 Fiat 500 Sport "Latte" / '21 Toyota 4Runner TRD Off Road Prem “The Truck”

 

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To use the longer rods, you'll have to use the S14 crank--not sure if the 144mm rods go with the 2.3 liter S14 or the 2.5, but someone on the board will.

 

mike

'69 Nevada sunroof-Wolfgang-bought new
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'91 Brillantrot 318is sunroof-Georg Friederich 
Fiat Topolini (Benito & Luigi), Renault 4CVs (Anatole, Lucky Pierre, Brigette) & Kermit, the Bugeye Sprite

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To use the longer rods, you'll have to use the S14 crank--not sure if the 144mm rods go with the 2.3 liter S14 or the 2.5, but someone on the board will.

 

mike

Usually the longer rods are used with those cranks that have taller stroke. However there is no such connection that using taller rods would require s14 crank.

The earlier reply from williamgruff was just about perfect answer.

Tommy

Racing is Life - everything before and after is just waiting!

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