4A-GE bigport rebuild questions

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Grant
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4A-GE bigport rebuild questions

Postby Grant » Wed Oct 13, 2021 11:54 am

I am currently doing my first real rebuild of a 4A-GE, and have some questions due to the many options available for engine internals.

What I'm starting with:
  • 3-rib 4A block
  • Stock bigport head
  • Upgraded 20v oil pump, OEM water pump, all gaskets, etc
  • Stock ECU

Upgrade/performance parts planned so far:
  • Tomei 16v poncams (264 duration, 8.15mm lift)
  • HKS valve springs
  • Replacing all engine fasteners with ARP studs/bolts (head, main studs, rod ends)

I found that one of the OEM pistons already has bad ringlands, so I'll probably replace all four. The problem is I cannot find OEM bigport pistons anymore...
If I swap in smallport pistons, that means the rod pins and crank diameter changes as well right? Should I just buy aftermarket pistons that fit the 18mm wrist pin like Wiseco or Toda pistons?

I'm not looking for crazy power with this build, just a mild increase and reliability because it's a street car, not a race car. I would be fine swapping in different pistons, but I'm afraid I'll no longer be able to use the stock ECU at that point, and I want to avoid getting too deep into customization if possible.

Thanks in advance! 8-)

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Thu Oct 14, 2021 8:41 am

If you don't mind adding a bit to your build budget Molnar makes a set of rods that fit the 40mm rod journal with the full float 20mm pins. Since you're going with those cams the compression bump you get with the high comp pistons would be better, or even some forged pieces. If you're not looking for a lot "Safety" makes a decent pistons for not much. Or Maybe just look into aftermarket pistons. Wiseco has an off the shelf sets available for 18mm pins.
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sirdeuce
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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Thu Oct 14, 2021 8:42 am

If you don't mind adding a bit to your build budget Molnar makes a set of rods that fit the 40mm rod journal with the full float 20mm pins. Since you're going with those cams the compression bump you get with the high comp pistons would be better, or even some forged pieces. If you're not looking for a lot "Safety" makes a decent pistons for not much. Or Maybe just look into aftermarket pistons. Wiseco has an off the shelf sets available for 18mm pins.
One shot, one kill.

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Grant
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Re: 4A-GE bigport rebuild questions

Postby Grant » Thu Oct 14, 2021 10:27 am

Thanks for the reply. Yea I'm thinking if the stock rods and crankshaft check out OK at the machine shop, then I'll continue to use those with new pistons and 18mm pins. I'm not going over the stock redline, so it should be okay?

Most aftermarket brands like Toda have options for 18mm or 20mm pins.
https://www.toda-racing.co.jp/en/produc ... 4ag-1.html

I've heard some people on here really don't like Wiseco pistons, so I'm hesitant to go with them. :?

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Thu Oct 14, 2021 12:39 pm

I've run the stock 40mm rods at 8500 RPM without issue. At that level the block tends to be the weak link. So stock parameters are good. Honestly, my favorite build is the light weight 40mm crank and rods with a light flywheel. The engine is so much more responsive. Do a little clean-up in the ports just above the valve seat and have a good valve grind done, and balance the rotating assembly. The cams you have will pull right through the fuel cut, so you'll bounce the limit often enough.
Block good? Need to go oversize?
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Grant
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Re: 4A-GE bigport rebuild questions

Postby Grant » Thu Oct 14, 2021 12:51 pm

The block is being checked out right now at the machine shop, but the cylinders looked to be in good shape when I disassembled it.
That said most research I've read says if you try to reuse 81mm stock bore pistons/rings, the risk of blow-by is pretty high, so going a tiny bit oversized and using 81.5mm rings is suggested.

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Re: 4A-GE bigport rebuild questions

Postby jinx » Thu Oct 14, 2021 4:22 pm

when u see a $47 oem gze piston and a replacemnet DSM piston @ $90 per set!!! dyno 550+hp
...... noisy expensive forged pistons are a complete waste of money to me.... especially for a weak 100hp build
these blocks wear well. Was there a ridge ?

browse the net for similar bigport builds. You shouldn't have to guess at an outcome

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Re: 4A-GE bigport rebuild questions

Postby Grant » Fri Oct 15, 2021 10:16 am

jinx wrote:when u see a $47 oem gze piston and a replacemnet DSM piston @ $90 per set!!! dyno 550+hp
...... noisy expensive forged pistons are a complete waste of money to me.... especially for a weak 100hp build
these blocks wear well. Was there a ridge ?

browse the net for similar bigport builds. You shouldn't have to guess at an outcome

Yea I've been doing more research on these builds, and it sounds like there isn't really much benefit to the Tomei Poncans besides at redline unless they are paired with higher compression (at least CR 11). See the chart below.
Image

Also who is selling $47 GZE pistons? Sell me some. 8-)

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Re: 4A-GE bigport rebuild questions

Postby jinx » Fri Oct 15, 2021 5:19 pm

raised compression coupled with cams, for optimal performance.... is the case for all of them
More than enough 4 & 7AGE builds around, for you to hit a bullseye, first try imo

a member used to update his turbo progress, on stock gze bottom end. Denmark ? Norway ?
His 1.6 finally hit 613hp! At the time gze pistons were $47 each at the dealer

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Fri Oct 15, 2021 6:18 pm

GZE pistons are low comp. You'd be better with some high comp pistons, but those are 20mm pins. There are a set of OEM 10-1 ratio 18mm pistons. Someone here has the part#, maybe OST. Might try messaging him. Of course the Wisco isn't too much more and a bit lighter.
With the chart above keep in mind that's not a USDM engine, values will not be as high. The ECU tuning is different and is MAP instead of AFM. For just an around town car I'd keep the comp around 10.5-1 so using low octane fuel is an option. Getting that high with stock pistons won't be that easy. If you already have the PonCams, go with those, if not look for a set of cams with 10* less duration and as much lift as possible to work on that lower RPM range. Well it sounded like you wanted a better bottom end anyway.

Combo I ran in my AE82
Stock valve size big port head, mild port work in the bowl area, back cut valves with 5 angle seats (the shop did a lot of Hondas so they had the right cutter for that), HKS 256X8.35mm intake and 256X8.1mm exhaust, AEM adj cam sprockets. Small port injectors (2 hole)
7 rib USDM block with 40mm crank and rods, bored .020" over with Wiseco 10-1 pistons( got those used from a friend ) and a 9lb 212mm flywheel(another freebee). Pistons set at 0" deck and 1mm MLS head gasket.
Cheap ebay header and 2" exhaust to the cat, 2 1/4" after the cat. Pod type filter on the intake.
That thing had enough umph to pull the hills while being a little rocket. Never dynoed it but I'd say it was a good 140hp, maybe 115ftlb torque. Got really good mileage. LOTS of fun.
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Re: 4A-GE bigport rebuild questions

Postby Grant » Sat Oct 16, 2021 12:11 pm

Thanks for all the guidance everyone. I am planning on having OST clean up the bigport head, so maybe I'll see if he can hook me up with any additional parts. :)

sirdeuce wrote:If you already have the PonCams, go with those, if not look for a set of cams with 10* less duration and as much lift as possible to work on that lower RPM range. Well it sounded like you wanted a better bottom end anyway.

You're right that I probably should have gone with lower duration, but I read so many good things about the poncams being the best "drop in" that I didn't pay close enough attention to the effects of duration. I think they will still be okay though and I shouldn't lose power if the timing is set right (I also have Toda adjustable cam gears for that).

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Sat Oct 16, 2021 7:11 pm

All depends on what you are looking to get out of this engine. The PonCams are good for sure, but I've kicked down on my cams for a more "friendly" in town drive-a-bility. Seems everybody wants to scream their engine everywhere they go.
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Re: 4A-GE bigport rebuild questions

Postby Grant » Sun Oct 17, 2021 11:05 am

sirdeuce wrote:All depends on what you are looking to get out of this engine. The PonCams are good for sure, but I've kicked down on my cams for a more "friendly" in town drive-a-bility. Seems everybody wants to scream their engine everywhere they go.

Haha, yea I'm definitely not planning on redlining it everywhere I go. If the mid-range driveability really suffers I'll see about swapping the poncams, but I will give them a chance first.

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Sun Oct 17, 2021 11:43 am

That's the spirit!
One shot, one kill.

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Re: 4A-GE bigport rebuild questions

Postby jinx » Sun Oct 17, 2021 12:02 pm

264 cams still seem 'mild' to me
if going for torque/midrange/best street drivability..... I'd look to a stock rod 7AG, as long as there is a low budget piston option
vs wasting money on any $450 forged 1.6 piston - the added displacement will make a way bigger impact than forgies
Lotsa builders use cheap oem or replacement slug from another manufacturers' engine. Maybe 7AG guys found something

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Re: 4A-GE bigport rebuild questions

Postby sirdeuce » Sun Oct 17, 2021 2:16 pm

Don't get me started on the 7AGE! It's where I go for a more "user friendly" GE engine. If you(Grant) were curious about the 7AGE, think about the 4AGE with it's stock 115hp and 98ftlb torque and with a 7AGE using the 9.4 comp 4AGE pistons, stock head and cams getting closer to 120hp and 120ftlb torque without much more attention than the 4AGE. With your poncams and some mild head work another 20hp/tq are easily acheived. I do love that hybrid engine. But keep in mind, you will need a 7A block and 4AGE 20mm pin pistons, a reclocked crank sprocket and an exhaust mod with a few other little bits. It is well worth it!
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Re: 4A-GE bigport rebuild questions

Postby 24milespergallon » Tue Oct 19, 2021 1:07 am

Here's my "budget build" redtop bottom with bluetop rotating assembly, ported and polished big port head, ceramic coated the stock bluetop piston, gze cams and thats about it. Running t3/t4 turbo, boosted to 15 psi on E85. For fuel & ign, stock ecu, decapped scion tc injectors to 750cc, Walbro 255. Its been my everyday driver for 4 years now.

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Re: 4A-GE bigport rebuild questions

Postby Grant » Tue Oct 19, 2021 9:18 am

24milespergallon wrote:Here's my "budget build" redtop bottom with bluetop rotating assembly, ported and polished big port head, ceramic coated the stock bluetop piston, gze cams and thats about it. Running t3/t4 turbo, boosted to 15 psi on E85. For fuel & ign, stock ecu, decapped scion tc injectors to 750cc, Walbro 255. Its been my everyday driver for 4 years now.

A turbo with the stock ECU? I had no idea that was even possible. :shock:

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Re: 4A-GE bigport rebuild questions

Postby jinx » Wed Oct 20, 2021 11:16 am

A turbo with the stock ECU? I had no idea that was even possible

Lotsa entry level turbo 'kits' supplied fuel pressure regulators (FMU) to kick up pressure/richen mixture in boost
Its a 'hack' that works 'ok'. Some get even better results with more elaborate regulators, usually coupled with add-on timing retard device,
so can run higher boost for increased performance... all while retaining stock ecu. There is a learning curve tho
Some 4AGEs turbo like this. FMU 1.6 generally can reach high 14s 1/4 mile. Seen RRFPR go mid 12s. Street cars, stock motor, stock ecu
Here's my "budget build" redtop bottom with bluetop rotating assembly, ported and polished big port head, ceramic coated the stock bluetop piston, gze cams and thats about it. Running t3/t4 turbo, boosted to 15 psi on E85. For fuel & ign, stock ecu, decapped scion tc injectors to 750cc, Walbro 255. Its been my everyday driver for 4 years now

Then start a new thread. More details and pictures