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 Post subject: l20b bottom end
PostPosted: Wed May 11, 2005 8:31 pm 
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Location: New Zealand
Having finally pulled the head on my rally motor i have discovered it has the a87 head with opened up ports and a cam. I am happy with the head but what should i do to the bottom end? The block has been deburred, but i think thats about all. Are the standard pistons dished? Because that is whats in it now. I'm not sure that i want to get too involved with the bottom end as it is not smokey and it has 143 hp at the wheels at the moment.
Any ideas?

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 Post subject:
PostPosted: Thu May 12, 2005 10:55 am 
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Location: Brisbane
if its got 143bhp at the wheels, don't **** with it!!!


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PostPosted: Thu May 12, 2005 12:28 pm 
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Location: Melbourne, Vic
^^^^^^^^^^^^^^

What he said, thats 106rwkw.

Dave

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 Post subject:
PostPosted: Thu May 12, 2005 7:04 pm 
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But I want more!! You know what its like!! I ran a z18 turbo in it for a while but it was too wild for the gravel. Heaps of fun to drive though. Took it out as it was no quicker than the trusty l20b and it was shredding tyres.
So there is nothing recommended for a bottom end upgrade? Low cost of course.... I wondered about some flat top pistons but not sure what iI would use?

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PostPosted: Thu May 12, 2005 9:15 pm 
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Location: north brissy
gotta love the old L series :twisted: btw what work has been done to the engine and is it injected?

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 Post subject:
PostPosted: Thu May 12, 2005 9:30 pm 
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It has the closed chamber a87 head, big ports, cam (of unknown spec but the grind looks quite aggressive) Twin 45's (dellorto) deburred block, modified sump and 2 1/4 inch exhaust. I am not sure what has been done to the bottom end. It was originally certified with forged pistons but that isn't what it has now! I am suprised just how much it puts out considering the spec! You don't want to know how much torque it has...

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 Post subject:
PostPosted: Thu May 12, 2005 9:34 pm 
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Location: Brisbane
rally510 havng just been down that road myself one thing you need to look at is the head size, has it had a lot shaved off it and raised the comp anyway.

My l20 has a stock bottom end with lightened flywheel and it spins nice and quick. If its already making good hp i wouldnt play with it but would look at some rings, bearings etc just to freshen it up.


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 Post subject:
PostPosted: Thu May 12, 2005 9:41 pm 
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Good point. It has had about 1.5mm of the head, going on standard head thickness. Not a problem with the 107+ octane it drinks...

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 Post subject:
PostPosted: Fri May 13, 2005 11:53 am 
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Location: Melbourne
Got a dyno? Thats one of the highest outputs of any N/A L4's I've heard.

I wouldnt be touching it

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 Post subject:
PostPosted: Fri May 13, 2005 12:43 pm 
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Massive comp and revs should see 106rwkw happily.

I would think if you want more power you first need to see where its making it at the moment and then work out what is the restricting factor. Never an easy task.

Dave

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USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD


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 Post subject:
PostPosted: Fri May 13, 2005 5:32 pm 
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I have the dyno sheet. We got 144 then played around some more but no improvement then backed it off just a little. It has peak torque from 4-6000rpm and peak horsepower @6500rpm. It pulls well past 8 (or so my co-driver tells me). I want more power for two reasons, the first being obvious and the second being a mate has spent near 10k on a 4A-GE and it only has 145bhp. :roll: I sent the cam away today to get specced up. I'll see what they say but if its all maxxed out then it might be new rings and bearings and chuck it back in. That will be boring! Might have to get some weight out of it instead. A close ratio box would help too. Oh well, its only money. 8)

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 Post subject:
PostPosted: Sun May 15, 2005 2:19 pm 
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Can you post the dyno sheet up for us to drool over.
Could you be more accurate with you peak torgue figures, hard to understand peak torgue being 4-6000rpm. Wouldnt it be a set rpm like your peak hp ? and how much torgue ?

As above members have posted, if it aint broke dont mess with it.

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 Post subject:
PostPosted: Sun May 15, 2005 3:30 pm 
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Ok, Peak torque is at 5000rpm but it has a big flat curve from 4-6500rpm
I have no way of posting the sheet but if i find someone with a scanner i will do. It might be going on again soon as it had a blown headgasket for these figures... Just depends what happens while its apart.

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 Post subject:
PostPosted: Sun May 15, 2005 4:13 pm 
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Location: Melbourne, Vic
<skeptic hat>
I'm finding that hard to believe, (partially because I want more specs/info). What compression ratio is it running? What fuel again? A L20B with 1.5mm shaved off the head and A87 head (assuming its 39-40cc?) gives a compression ratio of 10.2:1. Nowhere near enough to make the power you're talking without being way above 8000. Or is there something else I'm missing? Like a turbocharger on the side? ;)

Dave

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USA Daily: 2014 Nissan GT-R, very minor modifications for the track
USA Project: 1978 280Z, minor suspension upgrades, VK56DE conversion in progress. SOLD
AUS Race Car: 1973 240Z, L28ET, Autronic, GT35R. SOLD
AUS Project: 1972 1600, 3200km old S15 SR20DET, ground up rebuild. SOLD


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 Post subject:
PostPosted: Sun May 15, 2005 4:38 pm 
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Location: New Zealand
Believe it!! and it still doesnt have enough power. I am going to measure the dish in the pistons and get the cam specced this week. Then will work out c/r. 107plus octane gas straight from the airport.

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