6G Celicas Forums

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

4agze pistons should be same size as 7a so, yes if the are .050 over you will need to bore the 7a block *edit, btw .050 seems like a lot?

This post has been edited by al94st: Oct 22, 2011 - 11:46 AM

thank you.. hmm yeah idk, this is my first venture into building an engine, dont know if .050" is alot or not.

.020 is normally one size larger than stock, .050 is quite a bit larger.
you will definetly need to have the block bored.

thank you presure2.. in your opinion, with a motor that has 218k on it, would i be better off to just get the block bored and get these slugs? or should just look at getting a set of oem diamiter, and compensate for any kind of age wear, with the rings? im not looking to go insane powa!!!. just a target of 350.. if that.. t

thank you.

If your looking for 350hp, I'd forget about the 7afe and start saving for a 3rd gen swap.

350 is pretty insane power for a 7afe lol. like presure said, dont bother trying on a 7a. Options really are buy another car or do a swap.

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.. )

.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?

everything in your post is correct. the bolt is the weakest link in the rod. the only problem is i dont know any companies that make a high performance rod for the 7A. it was never a performance engine.

1mm over is the same as .040 over and yes you can do it but you are pushing the limits of the cylinder, thats why i recommend only .020

as for pistons, i have used Diamond pistons in the past. i sent them a stock piston and for about 550 bucks they sent me a new set of machined pistons with wrist pins, rings, and clips. sometime next year i need to rebuild a friends 7A-FE and ill have to do the same thing.

If ur still unsure and need a set of pistons i have stock bore size forged wiseco pistons with the pins and high performance rings, id sell them to you 400.00 cost me way more but sold car so got a whole hp engine rebuild kit with toga racing bearings and two diffrent head gaskets one metal one copper... whole kit will cost you over 1000.00 but id sell it all for 750.00 ?let me know..

to answer ur rod and bolt question, paughter racing sells 7a rods but going to cost you 792.00 but they come with rod.bolts rated to well over 600 hp and rods are pretty much indestructable... www.importperformanceparts.net

hmm i may have to take you up on those pistons.. would you happen to know what the compresion ratio is on em?

And yes pauter sells a set for a bit too much than what i would want to spend on a single component of this engine. no doubt that the pauter rods are solid, but they are WAY over-kill for the power goals attainable by most who are working with the 7afe.. there is another option though. Belfab racing makes a set for the 7afe for $425. they are of an H-beam design and come with some fasteners that i do not recognize, but i know that if you call them prior to the order(or to make the order) that they can use specified ARP hardware, or at least give you the specs so you can some your self (what i plan to do).

Smaay, personally i agree with you on the boring of any block. personally i like the concept of maintenance machining, and nothing more (as far as the rotating assembly goes). but materials wise. this block can take a 1mm over, and run high boost, its all in the tune. and in regards to the general idea of this not being a "performance motor" i agree. but not to the extent of not using it as a platform.. the short block is regularly used as an upgrade for the hatchi, and has a good bit of potential under boost. but the head (as i am sure you know) was designed as a fuel conservation head (at the time), so what we get is this torque happy (relative) motor and a head that does not like to breath up top.. lol but this does not mean we cant just SHOVE more air down its throat though.. lol