Rebuilding a rebuilt 4AGE. . .

[GeeEss]

Hi . . .

I'm running a Bigport with Quads that was rebuilt ohhh; say 10-15K km ago.

I'd like to redo the bottom end with higher compression pistons & would like to know if I need to send the block out to be completely redone (i.e. disassembled / hot-tanked / re-honed / crank re-checked & new bearings installed etc or whether I can get away with a DIY hone (or just drop off block to a Machine shop & request a re-hone).

PS: Haven't rebuilt a block before but have a stand, tools & am prepared to Google . .

Would also like opinions regarding OEM V Forged pistons. AFAIK car will stay a road-car with occasional track work so I don't see the need for Forged pistons. I am leaning towards late 16V / Small-port units BUT would like to know if there are any other OEM pistons (no larger than 82.0mm) that are compatible with 4AGE with a higher CR.

[Jimmee1990]

With forged pistons your cylinder to bore clearance is a lot more crucial, using a dunny-brush hone and hoping for the best is a patch up job at best. Unless the bore is perfect currently I would personally be looking at boring over-size to get the clearances perfect.

Bearings is debatable, again I always replace them anyway. As far as I know there's no pistons that will slot straight in as a high comp equivalent, CA18DE or BP Mazda are what I've using in the past at 83mm bore.

[GeeEss]

OK; thanks for that. . .

In that case I may just rebuild a spare BT 20V block, crank & end-caps I have laying around with 10.3:1 small-port pistons.

[Matt]

If you have the blacktop pistons you can use them with a 16v head. The motor becomes interference, but keep the belt fresh and it wont be an issue.

Personally, I'd keep the motor you have complete and build a new one.

[GeeEss]

Yeah well I was sort of leaning that way; not by using BT pistons but by rebuilding a complete engine; a tired BT 20V (PSI: 160 160 180 180) I've had sitting in the corner of my garage for the last 4-5 months.

Reason(s) I haven't gone any further are;
1. It's way too easy to spend $7-8K on a tuned N/A 4AG & you can basically kiss that $$$ goodbye; no-one ever pays more than 1/3-1/2 your outlay if selling. I have been keeping an eye on various Forums hoping a cheap 4A / 7A build will come up but so far haven't even come across a 7AFE block. . .

2. A race engine builder I spoke to with some experience building 4As & 7As wasn't all that keen on 20Vs. He says they have a habit of dropping valves when abused & that my Bigpport is a better base for a rebuild.

FWIW the reason I bought the 20V was that after years of fart-arsing around getting a Cammed 16V 4AG with ITBs to behave itself* on the street w.r.t. a relatively clean idle & acceptable low speed running (and refining my ECU tuning skills in the process ) the option of going to a more advanced engine with Factory ECU (no more $$$ thrown at Tuners) looked quite attractive. . .

In the event I've come to realise that most of the fuel-smell issues at idle were due to the limitations of the hardware not the ECU; namely a misguided decision to retain the OEM pistons & bump compression by shaving the head & using a thinner HG. Having a Bigport those mods only raised CR to ~ 10: 1 which wasn't enough to make the engine breath in the low / mid range. Past tuners tried to fill the hole below 4000 rpm by increasing the overlap which had some effect but resulted in more unburnt fuel being pushed out the exhaust @ idle.

It was a flawed build from the start; but I think the character of the 16V suits the car < AE92 FX-GT > better plus it was a one-owner car before I brought it in from Japan so I'd like to keep it matching numbers.

Since it will remain a road car (with occasional track days) I'd like to stick with OEM type pistons for durability.

I'm thinking either 10.3:1 Small-port or these >> http://www.club4ag.com/forums/viewtopic.php?t=12235.

Having said that I may do an initial build on the spare BT block to minimise the time the car's off the road. That way I don't have to tap holes for oil-squrters or a knock sensor. (original block is a 7 rib Bigport & has same journal sizes as later 4AGs)

[Hen may possibly be a nut]

Soooo, if you're just going to be using the bottom end of that tired blacktop for a rebuild I'd happily take the head and throttles off your hands. Would hate for them to still be taking up space in the corner of your garage... :)

[GeeEss]

If someone would pay me what it's worth maybe; but I'm not giving it away and I'm not splitting it; I need a 2nd BT block laying around like I need a 3rd earlobe.

FWIW I paid $1700 for the engine + ECU. Want roughly the same or very close o/wise I'm happy to have it sit there. Who knows; I may still go 20V route if the 16V re-build doesn't light my fire.

I can't speak for AE86DC but too many guys on other Forums seem to think they "deserve" parts at greatly discounted rates just because they're on the Site.

I have a set of AE92 FA coil-overs I bought for $1800 that I can't even sell for $1200 ONO. Have only been on car ~ 1000 km.

PS: I just missed out on a 20V 7AG by a few days recently. A guy with a Hachi spent ~ $8K on it & decided 120 rwkw didn't cut it so decided to flick it & go 3SGE route. He had it on Toymods for 3 weeks before I saw it & was continually low-balled. He ended up selling it for only $3K. . .Because he "needed it gone. . ."

I'd offered him nearly $1K more than he sold it for. We were both spewing. . . . .

See what I mean?