which engine has more potential for more power?

sirdeuce
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Re: which engine has more potential for more power?

Postby sirdeuce » Tue Jan 06, 2015 2:07 pm

Increasing the size of the pin hole in the rod from 18-20mm and bushing it would remove a dangerous amount of material. Keep the 18mm pins. If you feel it is necessary bush the pin end go with the thinnest bushing possible and keep the 18mm, or go with aftermarket rods. For the most part the 18mm press fit pins are strong enough to handle whatever the crank and rods can. I drive the dog squeeze out of my engines! Only failure I've had with the 40mm components was due to oiling problems. I learned how to alleviate that as I posted earlier.
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burdickjp
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Re: which engine has more potential for more power?

Postby burdickjp » Tue Jan 06, 2015 2:33 pm

sirdeuce wrote:Only failure I've had with the 40mm components was due to oiling problems.


Oiling seems to be the weak link of the 4A.
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sirdeuce
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Re: which engine has more potential for more power?

Postby sirdeuce » Tue Jan 06, 2015 3:00 pm

Mostly the oil return, likes to stack in the head. The big port has the one return hole. With the combination of the PCV, blow by coming up through the hole and the cams getting an abundance of oil... The small port head has a secondary oil return hole that plumbs into the block to assist in the oil return. If you do a lot of spirited driving in the hills, or spend time on the track, baffling the pan and increasing the capacity helps to keep the pickup covered. Going up and down the grades seems to keep the oil in the head as well.
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oldeskewltoy
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Re: which engine has more potential for more power?

Postby oldeskewltoy » Tue Jan 06, 2015 3:32 pm

actually the largeport has 2 oil drains, both on the exhaust side of the head (why the engine leans that way in a longitudenal application, like the AE86) AND the large "mouth" for blowby, the smallport adds a drain on the intake side of the head, to drain down to the block.

Image

blue dots are oil related openings, while the red are coolant. Note the drain between cyl 1 and 2, and back by #4, the big mouth (center) is for blowby, the small yellow dot at the front of the block is the oil feed to the head

I've seen the early rods converted... to 20mm but kept the press fit pin to keep enough material. I have a set here, a friend of mine ran a similar set on a stock ECU for 25k miles. I would use them on a stock management equipped engine (redline 7500 or less)

The TRD stuff always ran the big crank.... the small crank was never viable for all out racing.... and besides... they never ran the big OEM crank, they ran a TRD crank

Image

By the way... the TRD crank is HEAVIER then the OEM "big" crank... by about a kilo :o

TRD rods used 19mm small ends, with the 42mm big end.


Now as to the racing series in Japan... (N2, Group A, or others) I do not know......
OST Cyl head porting, - viewtopic.php?f=22&t=300

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burdickjp
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Re: which engine has more potential for more power?

Postby burdickjp » Tue Jan 06, 2015 5:16 pm

oldeskewltoy wrote:Now as to the racing series in Japan... (N2, Group A, or others) I do not know......


According to the TRD Bible the AE86 N2s used a 40 mm TRD forged crank, part number 13401-AE801.
It ALSO, and this excites me, lists 3 part numbers for bearing for that crank. I'm entirely certain they're discontinued, but it's exciting to think they may not be, because that would mean awesome bearings for the 40 mm crank:
13281-AE801-01
13281-AE801-02
13281-AE801-03
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LewyG
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Re: which engine has more potential for more power?

Postby LewyG » Sun Feb 15, 2015 2:52 am

Some interesting reading in here.

Something you guys might be interested in is Ive built my engine up using a 3 rib 40mm crank set up and i managed to get some H - Beam forged rods wich Ledworth Racing where stocking.

Image

They came with the a 20mm pin aswell so ready to drop in no machine work required.