quick info needed.., from expirienced 7a engin builders.....plz Options

[mandrek]

hello all, i just have a quick question.. I'm in the process of gathering parts for a boosted 7a.. i have located a set of OEM, from the factory, Toyota 4agze pistons, and for a great price since the guy is just looking to get rid of them (change of plans..#.. thing is that they are .050" oversized..

now my question is.. is this a option that was made available to give Toyota service techs a slug that would provide tighter clearance on an old motor? #as i am suspecting# or is this an OEM replacement for use in a motor that has had to have the cylinder walls worked on #say to remove scoring) and thus the reason for the increased bore diameter..

the motor I'm looking to put these in is a 96 7a, and had 218K on it.. the walls of the cylinders are smooth as glass, and there are next to no markings showing wear. ill post a pic if need be.. but i don't think that it would be needed to answer my question..

i guess that what i am really getting at, is this... if i get these pistons will i need to have the block bored to accept these, or is this kind of o/s a tolerance check measure?

thank you..

This post has been edited by mandrek: Oct 22, 2011 - 11:24 AM

[mandrek]

i hear ya.. but i already have 3 7a's all torn down, and are in the process of doing a full rebuild w/ the intention of boost on the one I'm am working on. i am set on using the 4agze pistons, (semi-forged and with a ceramic coated crown) since the are relatively cheap, and are good for up to 400whp. and are looking at (as a posibility-only if i have the funds for it-) belfab 7a rods with ARP bolts and ACL bearings. my target of 350 is not necessarily a goal, but a design target for the motor being able to handle it.. if i build it to be able to handle 350 w/o problems, then i know that i will not encounter any issues with it between the 84.6 it had and the 350 i would be ok with.

i regularly auto cross the car, but it will serve as my primary DD.

i am well aware of the other options.. and even the possible directions i can go, even with this platform. but right now i am at the - rebuild the motor- phase.. i have new oil and water pumps. new timing belt and tensioner, as well as a whole set of new gaskets. looks like i have the head studs situation sorted (thanx to you all, -specifically stephan_lee-). i have the cooling system sorted and on order. and if i can pull it off, i will have the internals to handle what i need it to do.

Future plans for the motor is a turbo build based around the ct26 (twin-scroll, best for my auto-x), a fuel system able to support the increased volume for the boost with E85, and a Trust E-manage ultimate to control it all.

my overall build will go like this:
-rebuild motor phase-: get the car on the road and running as it should.
-adding the e-manage-: start data logging and tweaking the tune, see what i can do with what i got.
-turbo-: once i have all the parts and the motor well broken in, here comes the boost.
-E85-: use all that i have learned, dial up the boost and see what the limitations of the set-up are.


oh and (-puts on flame suit-) this is on an auto.. i know, i know, but it IS still my primary DD (and D.C. traffic sux) and i really like the way the auto works for me in an auto-x. (i do have a manual sitting on the shop floor atm) The auto suits my needs so I'm keeping it. (if i can find an LSD that will work i would be set.. )