deck height / compression question
 

im looking to strecth my rods to increase comp. i purchased my engine in bits (3.3 turbo), the crank was no good and has been replaced with a 3.2 carrera crank with matching rods. Because i had no previous deck height figures i am assuming that im going to have to dummy build my bottom end, measure my deck height WITHOUT stretched rods, then strip and stretch the rods to achieve the desired compression (7.5-1). Am i missing anything or is this right?

Andy, UK

Andy,

Yes, you are correct. You should test assemble the engine and measure the clearances first. Only then can you make an informed decision. With close clearances you should test assemble a second time to confirm what the final clearances are.
All this effort can prevent a disaster. It is not a good situation to find out that at high revs the pistons touch the heads.

Are you going to install twin plugs also? How much boost?

Best,
Grady

no twin spark, 7.5-1 comp, sc cams, k27 high flow and 1 bar boost spring. what do you think?

the effective comp of the 7.5 to 1 piston/rod setup will be some what offset by the later valve closing of the SC cams. This combination should work well together, but high octane gas is a must. I am rebuilding a 3.3 turbo motor with 3.4 RUF pistons and cylinders which have a 7.5 to 1 comp ratio, and will probably limit the boost to .8 or .9.

were the ruf pistons and barrels new? how much is something like that?

No they have about 10,000 miles on them, but look excellent. Someone had installed them and then decided to go even bigger. My cost was $1300.

you wanna sell them? (!!)

Victor, where did you find those pistons? Do you know of anywhere online to get them?

you can buy 3.4 7.5-1 pistons from EBS. they just gave me a price of £995 for 6 97mm 7.5-1 (3.3). In conversation he mentioned that RUF use a 3.4 7.5-1 piston and that he can supply a JE equivilent that would be slightly more than my standard 3.3 pistons.

Heres there number 775 6731300


Andy

The cylinders I have are Mahle, 98 mm. the pistons are RUF. I bought these from an individual that had installed them and then decided to go even bigger. I do not know the source, but you could try the Mahle or Ruf web sites. I emailed RUF when I first bought the set, and did get back some additional information on the P & C's .
http://www.mahle.com/
http://www.ruf-automobile.de/

Vic

thanks vichang, i ended up buying some 8.5-1 pistons in the end. now all i have to do is space the barrels off the case and fit some thicker timing chain housing gaskets!

He says..........