more displacement from a 60 degree?

[killercamaro]

Has anyone tried to offset grind the rod journals for more stroke? im about to start a 3.4 swap in a feiro and would like to know if any one has done this kind of machine work on a 3.4 before. this swap would be way cool if it was a 3.7 or something like that. i know this is a very popular method of gaining displacement in import 4 bangers. any comments are welcome. thanks.

[SappySE107]

RE: more displacement from a 60 degree?

I know its been done to the new 3500 crank to retrofit into the older motors. Im not aware of anyone doing this to the stock cranks in the older motors though unless ARI does it for their "stroker" motor.

[Doubt_Incarnate]

when you offset grind the crank, you have to keep in mind the pstons will come further up. you have to either go buy the limitaions of the pistons, or get custom ones made. and even if you do, i think the block is the biggest factor.

i have iron head pistons in my 3.1, if i stroke it enough to get 0 deck on it i'll gain 1 mm in stroke, and end up with something like 12.5:1CR. and maybe 50cc's

[eliteweapons]

You have to go billet for that. and get new pistons made. you may also have to get new rods depending on how much you stroke it out or de-stroke it.

[killercamaro]

custome pistons are not a problem. what i was wondering was if any one has had any problems with having enough clearance inside the motor to do this. also how far to grind the crank safely and how much extra stroke is possible. why do i need to get a billet crank?

[eliteweapons]

unless you can find a raw forging for the 3400 you will have to get a billet because thats the only way to go if no forged cores are around. I think the 3400 uses the same crank as the 3100 but I am not positive. If that is the case you will have to go billet. You will have to spin clearance the factory crack and see where the problem areas will be and if there is enough room to take the material out without losing structure. Also you can only go so far due to the oil pan width. I don't think you will be able to go much past 3.5 on the throw thou if the crank area is the same as the 3100.

[SappySE107]

3100 and 3400 use the same crank. You would be best off getting a 3500 crank from GM and modifying it. Cheaper than getting a billet crank and its still forged steel.

[Guest]

Any time an offset grind is performed new rods are needed to match the new (smaller) diameter of teh rod journal. Welding up the outside of the rod journals to try an use stock diameter rods is not going to happen either, the 3.31" stroke is probably about as much as you are going to get in these blocks. I believe the webbing and sizing of the 3500/3900 block was changed to accomate the longer stroke.

[eliteweapons]

I was able to get mine out to 3.456 with 5.7 inch rods that keeps the rod ratio down to 1.649

[SappySE107]

You want the rod/stroke ratio to be around 1.72:1 (stock is damn good) or higher. Are you sure the extra displacement is worth the worse ratio?

[eliteweapons]

I'll let you know when its finished.