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

[Smaay]

.050 is way too much, the most you want to bore out on a 7A is .040 any more than that you take a chance on compromising cylinder strength. are you not confusing .5mm because thats the same as .020 over? 350 can be done but i would NOT use OEM pistons! get something like Weiscos. the 7A stock rods i think will handle that just fine. they are much stronger than 1ZZ rods. just make sure you have a good tune

[mandrek]

.050 is way too much, the most you want to bore out on a 7A is .040 any more than that you take a chance on compromising cylinder strength. are you not confusing .5mm because thats the same as .020 over? 350 can be done but i would NOT use OEM pistons! get something like Weiscos. the 7A stock rods i think will handle that just fine. they are much stronger than 1ZZ rods. just make sure you have a good tune

smaay, i am not sure about the o/s size.. the reference that i noted is from the seller's fs/ thread. all he said is that they were .050" o/s..

after pouring over the net for tha last 2 days, i was starting to think the same thing myself about there actualy being .5mm over.. i have seen a few builds w/ the block bored to 1mm over. but idk.. as to the pistons.. there are rollas out there w/ 400whp on the stock gze pistons.. BUT w/ the complications of using the gze slugs, in reguardes compresion ratio, i am starting to re think the use of the gze slugs and just going to some aftermarket pistons for the 7a, that would get the compresion ratio i am looking for.

as far as the 7a rods, i have seen that same point come to, a few times about how strong they are. but correct me if i am wrong, it is not the actual rod that boosted 7a's are having issues with, but the stock rod bolts stretching.... then BOOM!!!

to take ARP rod studs the stockers would have to be re-drilled and tapped, and by the time the machine shop has that done i might as well just get better/ stronger rods w/ the ARP hardware already.. would you not agree?