Just bought a 521

[mainer311]

2 hours ago, d.p said:

If you do I would think you’d want a 5 speed as well?  Does anyone prefer a four over five nowadays? 

I’m sure it’s nice, but I don’t plan on driving on the highway with it anyhow.

[Greaser2]

14 hours ago, d.p said:

If you do I would think you’d want a 5 speed as well?  Does anyone prefer a four over five nowadays? 

I do enough highway driving that the 5 speed is nice over the four. 

[d.p]

Me too albeit not much it does suck in 4th at highway speeds.  What if anything does a 4 speed have over a 5?  

[thisismatt]

It has that it's what's there and doesn't require more work? 

[datzenmike]

17 hours ago, mainer311 said:

I’m also looking into the “long rod 2.1” frankenmotor with Z22E pistons and Z20E rods, bored to 87mm. Looks like I can run an open chamber head with that combo.

  

I would always go with a displacement increase. Long rods, in theory anyway, are more comfortable at high revs but in fact hardly ever rev there is practice. A larger displacement engine will kick you back in the seat at all other times.

 

 

15 hours ago, d.p said:

If you do I would think you’d want a 5 speed as well?  Does anyone prefer a four over five nowadays? 

  

 

37 minutes ago, d.p said:

Me too albeit not much it does suck in 4th at highway speeds.  What if anything does a 4 speed have over a 5?  

 

If you don't use it you don't need it. With smaller displacement engines they have to rev to make enough power to pull the vehicle along at highway speeds. If you commute on a highway you might gain a very small amount of gas mileage by running an overdrive, but be conservative, say 12%. Too high, like a zx with 25% OD and you'll be down shifting for hills or into the wind. If running a larger displacement engine with more torque there are more gains to be had with a 5 speed, if you drive a lot on the highway. Likewise a lighter vehicle like a 510 or 1200 can tolerate more OD.

 

If driving mostly in town a 5 speed isn't much use. If your vehicle came with a 4 speed this is what it was designed to run with and a 5 speed may not help. Keep in mind an over drive is for highway cruising. It isn't so you can go faster. In many cases you can go faster in 4th because the engine is revving higher and making more power to push through the air. Wind resistance is such that it takes 4 times the power to go twice as fast.  

 

[mainer311]

Yes, velocity factor is exponential. That’s one of the first things you learn in fluids.

[mainer311]

18 hours ago, datzenmike said:

Actually 10.87 with 86mm bore.

Do you think this would be fine on pump gas? I always run a minimum of 91. I’m assuming with a motor like this, that mechanical timing has to be somewhat conservative.

[mainer311]

Just got this block apart. It wasn’t all that seized, but I did have to sand a bunch of crud out of #4 to get it apart. Looks like it was bored .040” over already, so it’s sitting at 86mm right now. If I do run 280 flat tops in it, I’ll probably step up to 86.5mm.

 

What’s the max bore diameter on an L20b?

[d.p]

When I was reading all about L20bs with mine I read somewhere max bore was 2mm but who the fuck knows if that is true or not.  

[datzenmike]

2mm is 0.80". If you bore 2mm off the walls you have an 89mm bore. It's been done but a bit scary for me. I have an 87mm Z22 block bored 1mm that's a 2mm total increase out to 89mm.  Boring an 85mm bore out to 87 is safe enough. This would allow Z22 pistons to be used on a Z22 crank for a LZ2.2.

 

If going with 280z flattops go 1mm over or 87mm. Totally do-able with an 85mm L20B block. Maximize your displacement.

[mainer311]

13 minutes ago, datzenmike said:

If going with 280z flattops go 1mm over or 87mm. Totally do-able with an 85mm L20B block. Maximize your displacement.

I think I’ve decided this is going to be my path, but stick with 86.5mm in case it ever needs to be bored again. That way I still have room to go. Plus it looks like 280z flat tops are readily available in 0.020” over. 

[banzai510(hainz)]

L18 pistons are fine also(if you can find them in 1 mm over size as they are  less dished than the  L20b 11.35cc  but might be ezer to get the 280zx non turbo pistons.

heard of lot of Headgasket issues with the flattop and closed chamber head. Don't know if cause of Felpro gaskets. But just to let you know.

 

This is just me and only me IF ONE CAN FINDE A L18 PISTONS and 1mm oversize would be a perfect ratio of higher compression on the safer side with closed chamber head/ quality of gas issue. but in Washington stae we only have 91 if one really believes it at ARCO

Edited November 2, 2020 by banzai510(hainz)

[mainer311]

I've been reading, and I thought the peanut heads were supposed to be less prone to detonation because of the larger quench area? I understand my compression ratio will be higher, but I thought they were better running heads?

[Crashtd420]

56 minutes ago, mainer311 said:

I've been reading, and I thought the peanut heads were supposed to be less prone to detonation because of the larger quench area? I understand my compression ratio will be higher, but I thought they were better running heads?

Technically the other heads dont even have a quench area to them, not to mention the pistons are dished... i believe the peanut head is better, plus the only way to actually achieve any sort of a quench is with flat tops..... 

You can always massage the camber a bit,  I gained 2cc just from descrouding the valves and cleaning up the sparkplug area..... just run 93 and have fun.....

[datzenmike]

Quench is the area where the piston top and the underside of the head are separated by the head gasket thickness, about 1.2mm, less than 0.050". For this you need a flat piston top and a flat head surface. The fuel and air is trapped and pinched out violently as the piston reaches TDC. This forces the air into the combustion chamber causing beneficial turbulence. The turbulence better and more completely mixes fuel and air and produces a more complete burn. There is less chance of a hot spot or carbon deposits occurring. If your pistons have any dish this won't work. All things equal, like compression, a peanut head is not just more efficient for the above reasons but has a smaller combustion chamber surface area to absorb heat freeing it to do more more work pushing the piston down.

[banzai510(hainz)]

My 510 L16 bored out to 85 mm  flattops with a peanut head I can run cheap regular gas with it no proplem

 

my 521 L16 flattops with U67open chamber L20 head had lots of run on pinging issues with cheap reg 87 gas.  Once I GO SUPER it got a little beeter then I went with a L20 dist it seems a lot better no pinging on going up a hill

 

[Stoffregen Motorsports]

On 11/2/2020 at 7:41 AM, d.p said:

When I was reading all about L20bs with mine I read somewhere max bore was 2mm but who the fuck knows if that is true or not.  

It depends. Some can go to 89mm or more. They should be measured first. The late M2 blocks are more consistent.

 

The best block for boring large is a Z20 block, but since they are so hard to find now days, L20B blocks are used. Z22 blocks have steam ports in between the 1-2 and 3-4 cylinders that can be accidentally bored into, so having the machine shop offset those bores is crucial.

[mainer311]

@datzenmike What would my compression ratio be with 280ZX flat tops (86.5mm) and a W58 open chamber head?

Edited November 5, 2020 by mainer311

[datzenmike]

I get 10.1

 

This is an un-shaved head with 45.2cc combustion chambers and a 1.2mm gasket.

[d.p]

No idea if this is a good deal or not

form NOS flat top pistons and rings.  $600

 

https://www.ebay.com/itm/274464834718

[mainer311]

Won’t work. I’m already at +.040”. Plus, no way I’m paying that for old stock pistons. I’ve read that the ITM pistons from Rock Auto are actually very good, but the rings they include aren’t. I can get 6 pistons for about $225. 

[d.p]

Heard mixed things about ITM but that was mainly around their rockers.  Might try Riley at Lynchburg Nissan see what if anything he has? 

[datzenmike]

1 hour ago, mainer311 said:

Won’t work. I’m already at +.040”. Plus, no way I’m paying that for old stock pistons. I’ve read that the ITM pistons from Rock Auto are actually very good, but the rings they include aren’t. I can get 6 pistons for about $225. 

 

Says Datsun L20B Flat Top OEM NOS 4 Pistons And Rings Set +.040” other than the price they would work. And they aren't old or stock, they're new unused +0.40" oversize. For $600 you could probably get forged. $225 is almost what these are worth from the dealer.... if you can find them.

[mainer311]

My cylinders need to be bored further than the .040" that they are already at. #4 isn't kosher. It has a little bit of rust pitting from sitting. I'm going to 86.5mm. (0.060" over stock)

Edited November 6, 2020 by mainer311

[banzai510(hainz)]

https://www.swmotorsport.com.au/

 

these guys had a good line up of stuff  at one time

 

I have ITM pistons and they made in Taiwan.  However I got 200k miles on the block so they are fine .  I forgot what kind a rimds I had on there but they where (the oil rings)rounded   like a coil along the edges if I remember right.  tops 2 were standard cast iron

 

 

maybe Datsport in Austriala is another source. I know they sell the 87mm headgaskets Graphite and regular type

Edited November 6, 2020 by banzai510(hainz)