B20 rod/piston options.

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Miksa89
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B20 rod/piston options.

Post by Miksa89 »

Looking good choices for B20 rod and piston combos.

One way is grind crank to 85mm stroke and B2xx rods with vw 92mm 35mm compheight pistons,but is the 5mm stroke worth the 600e money?

Second change is to find long rods that can be paired with 92mm 35mm comp vw pistons with original stroke.

I have 8 bolt B20 and if you have some good choises for ligh rod/piston combo with not so high money, let me know your thoughts. 8)

And one reason for VW pistons is that they are cheap and light. :D
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Re: B20 rod/piston options.

Post by Miksa89 »

Should this be okay:
Original stroke.
154 long rod.
VW 92mm 35 kompheight pistons.
Block decked about 2mm to bring pistons over deck slightly.

Rods are narrower than original but is it okay to center rod at piston side?
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Moparboy440
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Re: B20 rod/piston options.

Post by Moparboy440 »

If you are going with a 92mm bore i would use B21E pistons. Cheap and simple.
How can you make good ideas sound so bad? I'm an engineer!
Miksa89
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Re: B20 rod/piston options.

Post by Miksa89 »

Moparboy440 wrote: Thu Apr 21, 2022 10:11 am If you are going with a 92mm bore i would use B21E pistons. Cheap and simple.

Yes 92mm bore.

Ordered 92mm VW pistons with 35mm compression height.
Cheaper than B21E pistons and much lighter.

Rods are 154mm long.

Hope my cam is coming next week. Agap 272 with 105 LSA
Allready have new 48 Fajs carbs.

Need to order KG type 3 extraktor and bore block and many other things to do but hoping getting it ready this year. 8)
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Re: B20 rod/piston options.

Post by Miksa89 »

Are B2xx rods with 29.5mm big end width suitable to use with ofset grinded 8-bolt crank(85stroke and 49mm rod journal) without centering rod at piston end?
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Re: B20 rod/piston options.

Post by Miksa89 »

8-bolt crank is ready to be posted this week to grinding to 85mm stroke.
Ordered 152mm H-profil rods suitable to 49mm journals and 29.5mm width.
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Re: B20 rod/piston options.

Post by Erland Cox »

If you grind a crank to 85mm you must relieve the 4 sharp cut outs in the number 1 and 4 rod throw.
Make sure that the bottom corner is rounded instead of sharp.
Take the same amount of metal from number 2 and 3 beföre balancing.

Erland
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Re: B20 rod/piston options.

Post by Miksa89 »

Erland Cox wrote: Sat Oct 15, 2022 10:42 am If you grind a crank to 85mm you must relieve the 4 sharp cut outs in the number 1 and 4 rod throw.
Make sure that the bottom corner is rounded instead of sharp.
Take the same amount of metal from number 2 and 3 beföre balancing.

Erland
Need to check that when able to try pieces in their places.

Any good succestions for what kinda bearing clearance is good for pretty hard street use? Mains and rods.
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Re: B20 rod/piston options.

Post by Erland Cox »

between 5 and 7 hundreds of a mm should be OK.

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Miksa89
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Re: B20 rod/piston options.

Post by Miksa89 »

Erland Cox wrote: Mon Oct 24, 2022 10:39 pm between 5 and 7 hundreds of a mm should be OK.

Erland
Measured H-rods with bearings and vertical ID is 49.05mm and 45deg from parting line crossmeasured 0.015-0.02mm bigger?

Should the journal be 49.00 so there is a 0.05mm clearance at tightest point?

Measured main bearins same way and result was 63.28-63.295mm so compared to Greenbook volvo tolerance for journals 0.25mm undersize is 63.197-63.21mm there is pretty huge clearance even when compared to volvo tolerance upper limit?
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Re: B20 rod/piston options.

Post by Erland Cox »

Rods should be fine but what undersize are your mains?

Erland
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Re: B20 rod/piston options.

Post by Miksa89 »

Erland Cox wrote: Sun Nov 20, 2022 10:25 pm Rods should be fine but what undersize are your mains?

Erland
First undersize 0.25mm made by NPR/Ne

E:Need to bring the block inside house to get roomtemperature and measure again. Those result were in cold garage with cold micro and boregauge. Figured today that thats not helping if measure device and block are same temp because checked mikrometer kalibration to 75mm verifying bar at room temp.

Bad english so some words may not be correct. :D
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Re: B20 rod/piston options.

Post by Erland Cox »

As long as you are not above 7 hundreds it will be OK.
More will work but requires a thicker oil.

Erland
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Re: B20 rod/piston options.

Post by Miksa89 »

Erland Cox wrote: Wed Nov 23, 2022 12:38 am As long as you are not above 7 hundreds it will be OK.
More will work but requires a thicker oil.

Erland
Should mainbearing oil clearance be measured 90degrees from parting line or should results be equal with 90deg and 45deg cross measured from parting line?
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Re: B20 rod/piston options.

Post by Erland Cox »

90 degrees.

Erland
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