Overboring cylenders??

[Ortie666]

I am building a 2.8L RWD and using the 3.1L crank and what not.. and I am getting new pistons, i was wondering how far the RWD 2.8L motors can be borred over??

[SappySE107]

RE: Overboring cylenders??

You should have it sonic tested before you attempt to go to extremes. You shouldn't go over .060", but i have heard of someone going .120". You should bore it over just enough to get the cylinders round, as the extra displacement you would get from going further making the walls thinner than they need to be.

[SappySE107]

RE: Overboring cylenders??

btw, if you have an 84 block with the small journal crank...toss it. They had issues with them breaking and switched to the larger journal crank which has been used for years.

[Ortie666]

the journal's from the 3.1 fit in, there the same size exact

[Guest]

the journal's from the 3.1 fit in, there the same size exact

Then it was replaced at somepoint. in 1985.5 the journal size was increased to the size that is still used today in the 660 (except for 3500/3900 IIRC).

I will agree with Sappy, no need to go anymore than what is neccissary to clean up the cylinders. The small increase in displacment going anymore than that will not be enough of an increase to warrant such a task.

[Ortie666]

but a 3.4 has been made out of a 2.8L? would u have to sleve it?

[SappySE107]

I really don't know what ARI does, but you would be best off finding a 3.4 block from a 93-95 camaro if you want a 3.4. Their resell value is dirt for the most part so picking one up to use shouldn't be too expensive. Otherwise, stick with the 3.1.

[sharkey]

i just recently did a 2.8 ironhead build up. i was looking hard at the 3.1l crank, but there is no aftermarket off the shelf replacment pistons, just oem replacments.

if you can get one, the 3.4l block would be the way to go. an idea would be go with 3400 pistons and top end, and swap the car over to mpfi.

[Ortie666]

ohh, ya.. well im using 3.1 crank, rods, pistond heads.. and a bit of a modified intake manafold.. ill get pics on heer after its done.. I bought a aluminum carb plate, and iwelded it onto a box, witch om going to weld onto the chopped apart intake manafold.. so it juss may be the first 4bbl 3.1 w aluminum heads.. anyone know how much boost one of these motors can handle.. Ill be juss using stock new pistons??