question about forging MSP block???

[MZ ZOOM]

ok this might sound stupid or maybe not. im capable of rebuilding my block myself. i have 34K on the motor right now and its running in the vehicle with no problems. but i was wondering if any of you have gone forged with out machining and honing the cylinder walls? im wondering if i can just buy the pistons and rods and the rebuilt kit for my FS motor and built it myself? or do i have to get my block machine and cylinder walls honed before i can put in the forged rod and pistons? i need some answers before i start my rebuilt...thanks guys...

 

[mike2225]

It is possible to buy standard bore pistons and just drop em in but thats if the cylinder walls are in perfect condition.But at the very least you should hone out the cylinders.

 

[Fudgie]

You really have to hone the block (at the very minimum scotchbrite the cylinders) and have all the right tools and knowledge to measure the bore properly. Forged pistons grow quite a bit and all clearance issues need to be addressed before you drop them in.

 

[JDM Sam]

Don't cheap out and not hone the cylinders. You want a cross hatched surface for the rings to seat and seal. Take it out and get it machined and balance the whole assembly as well. I balance the rods and pistons by themselves to under 1 gram variance, and get the crank balanced. This engine will rev more smooth and effortlessly. Forged rods and pistons weigh more than stock parts! I would also align hone and use ARP main and head studs. You really need to use a reputable & capable machine shop if you are building a high performance motor. Balance and blueprint!

This is how a good crosshatched cylinder hone should look like.
http://mazdaspeedtuning.com/shortblock1.jpg

If you deck your block this is how it should come back as well.
http://mazdaspeedtuning.com/preppedblock.jpg

 

[igdrasil]

That will depend on the piston clearance. CP pistons need .003 clearance, which is close to stock clearance. Its possible that after some honing you will get the clearance needed.

Problem is. If you dont treat the cylinders, seals may not seal, its not always the case, i have opened this engine like 8 times, but this is the 1st time i go forged. But I have never had problems before. I just do the ring clearance thing and done.