2g block with evo8 pistons/conrod

[pmp285]

currently stomped on this one.... some people say i will get a compression ratio of about 8.0:1 - 8.2:1... any ideas? pros and cons?

and btw i will be getting the pistons for free...

 

[broxma]

I am not going to answer this question directly because I don't have the numbers in front of me, but I believe that CR you have been told is low. 1G's are 7.8, 2G's are 8.3 and Evo VIII/IX's are 8.8 to 1. I don't believe there is a huge difference, if any at all, in the CC size of the head but I may be wrong. To have less compression in the 2G block with a higher compression piston, on the same length rod makes no sense.

As for doing it? If you need the rebuild sure. The OEM rings for the Evo pistons are on the high side. If you have to press the piston on your rods, may as well just wait and get fully forged in my opinion. I have Evo slugs on my 1G rods and it cost me almost as much as going full forged would have. The evo rods slap onto the 2G crank though which is nice.

/brox

 

[pmp285]

im actualy getting the pistons and rods for free... so might as well use it... my old pistons and valves met... so its time for a rebuild... evo 9 valve springs are going in as well...

 

[GSX_TC]

Quoting broxma:
I am not going to answer this question directly because I don't have the numbers in front of me, but I believe that CR you have been told is low. 1G's are 7.8, 2G's are 8.3 and Evo VIII/IX's are 8.8 to 1. I don't believe there is a huge difference, if any at all, in the CC size of the head but I may be wrong. To have less compression in the 2G block with a higher compression piston, on the same length rod makes no sense.

As for doing it? If you need the rebuild sure. The OEM rings for the Evo pistons are on the high side. If you have to press the piston on your rods, may as well just wait and get fully forged in my opinion. I have Evo slugs on my 1G rods and it cost me almost as much as going full forged would have. The evo rods slap onto the 2G crank though which is nice.

/brox



2g's are actually 8-5-1

 

[strokin4dr]

I have an evo 9 piston/rod setup in a 99 eclipse (revised) block. There is no way that this setup makes less compression than the stock 2g pistons.

 

[pmp285]

revised block? what setup are running? pros and cons?

 

[belize1334]

IIRC the evo heads have a smaller dome volume. So, using an Evo piston does not give you as high of a compression value as stated for use in the evo engine.

 

[pmp285]

meaning? i would be getting around 8.5:1 CR? any way to compute this?

 

[AnotherNewb]

information

 

[curtis]

Not sure of the CC of the head but its just simple math... you need the cc of the head, thickness and dia of the gasket, know if the piston is down in the hole or flat or sticking out. Dia of the piston and bore and total height of the ring to top of the piston. This gives you all the info. For bench racing numbers can all probably be found but if the head has been milled, different valves which means valve job and the valves are sitting further from the piston, if the pistons are flycut etc etc all this comes into play if you want exact numbers.

Here do math son

 

[pmp285]

dang! but head and block is all stock...also got an o.e head gasket for it