engine builders advice wanted

[Dimitri]

i want to fit some ae92 pistons to some ae82/6 type rods. mostly to achieve a little more CR.

its pretty common knowlege that ae92 wrist pin is floating and 20mm o.d where as ae82 type is press fit 18mm o.d.

ive spoken to terry obrien who has told me he's done it before. and it has been mentioned on the old forums also.

apparently there are 2 ways to do it. either bore the little end of the rod and fit a bronze bush or simply bore the little end to 20mm and float the pin in the rod.

i am thinking i would prefer to try method 2 as it seems less involved and costly. it is only a cheap motor that is never likely to see more than the factory ecu's rpm cut.

id like to hear from people with experiance with this set up. and also some oppinions on what diametre EXACTLY i should bore the little end to. i am just thinking there might be slight differances in expansion of a bronze bush as apposed to the rod itself so i might want to run it a little tighter/looser than the factory spec.

also will oiling be an issue? should i add a chamfer to aid this?

cheers for any help

[Dimitri]

BUMP. changed title.

[myne]

Anything stopping you sourcing AE92 rods and crank aswell?
The main bearings are the same, so there's no issue but the flywheel.
Maybe a whole 7-rib bottom end?
It's quite a length to go to I guess, but atleast it'll be that little bit stronger in most regards and bushing things just feels dodgy to me.

[Big T]

I played around with this idea for a bit when building my engine.

http://forums.toymods.org.au/index.p...38ac1acabfa7ab

I abandonned the idea due to the advice of a couple knowledgeable people, Oldrollas (he's a metalurgist so KNOWS the kinds of pressures these materials go through) and Bill Sherwood. Bill just recommended i find an entire smallport bottom end to fit GZE pistons.

The other reason was that my setup was always going to be turbo so the forces are far greater than in an NA setup. If i'd stayed NA, i probably would have pursued it further just for the hell of it. It has been done at least a couple times in the States. Club4ag should have some info on it. I'll try and dig up the thread...

Eddie.

[DigitalPho3nix]

The other reason was that my setup was always going to be turbo so the forces are far greater than in an NA setup.

Not true for high-comp high-rev NA applications (I'm talking 10grand rpm plus)

[Big T]

Not true for high-comp high-rev NA applications (I'm talking 10grand rpm plus)

Yeah but then you wouldn't even be thinking about using modified stock rods would you? Builds like that would use aftermarket H-beam rods.

Eddie.

[YelloRolla]

IF the metal is there, then I would bush it. Either way, if you're not a machinist then you wont be doing it youself. I would take the rods to your favourite engine machinist and ask for his/her advice.

bushing things just feels dodgy to me.

this is how floating pins are done... From factory Toyota to Carillo.....

I bushed 3 sets of 3T GTE conrods just on a year ago and I didn't worry about drilling oil holes in the top of the rod. More recently we pulled down one of these engines (head gasket issues due to concaved deck and copper HG, but that's another story) and i was able to inspect how well they were doing. The "tightness" of the wrist pins/bronze bushes was unchanged from the day that I took them off my milling machine (that particular engine sees about 20lbs boost every day and is driven harder than most every time it is taken out). 3TGTE conrods don't have much meat around the small end, BUT, there is enough. I wouldn't make a call on yours without seeing them.
Boosted engines tend not to make too much difference in tensile loads on corods - remember tensile loads are the ones that break engines (esp conrods), boost increases compressive loads.

Bushing conrods costs only about $35/rod, so is not that expensive in the wash up.

I hope that this is of some help.

[Dimitri]

i started writing a reply and my connection f'd up..

most stress on the little end of the rod is at the point when the piston is changing direction. the inertia of the piston going up and the road trying to pull it back down...

ANYWAY, what i can take from your post is it would (obviously) be better to have a bush, but it would be ok without? and oiling wont be an issue?

another reason for wanting to try this is 4age's are getting really old. especially big ports. i would like to see if an inexpensively rebuilt early 4age can be reliable, and also perform. this means keeping costs to an absolute minimum. i.e re using fasteners, ect. $35 per rod is certaintly resonable, but it will all add up. the pistons i can get for free, so i am considering trying it.

[YelloRolla]

i started writing a reply and my connection f'd up..

most stress on the little end of the rod is at the point when the piston is changing direction. the inertia of the piston going up and the road trying to pull it back down...

correct = tensile load

ANYWAY, what i can take from your post is it would (obviously) be better to have a bush, but it would be ok without? and oiling wont be an issue?

I cannot state that it will be better without a bush. Bronze is self lubricating, I don't think that teh conrods are made of a material that will have the same effect. My tests so far show that drilling for lube is not that necessary.

[oldeskewltoy]

Have you given any thought to running the OEM Singapore and EUG piston? They are identical to the 4AGEC pistons, except they are 10 to 1 instead of 9.4 to 1. The OEM small port slugs are 10.3 to 1, so the Singapore slugs will NOT give the same compression boost, but they will give a .6 point boost. They'll fit perfectly without any machining/fitting/fabricating

Original bore 13101-16030
1/2mm O/S 13103-16030

Rings for those....
original 13011-16180
O/S 13013-16050 or 16180