Not origional.... Damn!

[datzenmike]

'78-'80.

[jmunky90]

Nah, I think I'll just build the 18 up.  I've already got the flex plate and accessories for the 18 and square port and it'll come out way cheaper in the end,(I do a lot of business with the machine shop)  Thanks anyway.

 

Anybody have suggestions on cams, exhaust, carbs?  I have a couple DHLA's sitting around and i see they have manifolds to put those on, or i was thinking about making a manifold to mount a Mikuni 34300 rack on her.  The factory squirtbox isn't in too bad of shape, but doesn't look like much fun to work with, I hate Hitachi carbs on bikes, (not to mention ugly as fuck)...  

 

I was reading the discussions you guys were having about manifolds vs. headers and my header is in decent shape, but the ports look quite restrictive to me.  There are large round protrusions in the mouths of all 4 and quite a large depression in the middle of the Siamese runner.  Maybe I'm over thinking this engine because I work on high performance motorcycles all day, but I really want to smooth that kind of shit out, if not replace it.

 

Im gonna lay her down a bit too, nothing too dramatic, just your standard torsion adj and blocks.  I like the way they look with the modern Nissan truck wheels on em too, so I might start looking for a set in the local yards.

[flatcat19]

L18 with some Z car 86mm flats with a U67 head with the right carbs could be a mean little combo. 

[Boxcar]

Find an A-87 . You won't be sorry.

[flatcat19]

Find an A-87 . You won't be sorry.

 

U67 has bigger valves and more volume to allow flattop pistons some breathing room. 

 

If keeping stock pistons try to find an A87 closed chambered head, for sure. 

 

 

 

With the cost of rebuilding and upgrading an L18 you can easily do a KA swap or beef up an L20B. 

LZ22 is always an awesome option when there is money to be thrown around. 

[Boxcar]

 

U67 has bigger valves and more volume to allow flattop pistons some breathing room.

 

If keeping stock pistons try to find an A87 closed chambered head, for sure.

 

 Well if you're going to run flat tops to add compression, Why give sed compression away by running a larger volume head???

The rest is self explanitory.... Yes a closed chambered A-87.

 And yes I agree an L-20B would be the way I'd go, But he owns an L-18 . Same rebuild cost, But he'd need to buy the L-20...............Or for that matter the KA....

[flatcat19]

High compression equals detonation. 

Savor the sweet spot. 

[Boxcar]

You're joking right???????

[flatcat19]

You're joking right???????

 

Absolutely not.

You should read some more threads. 

[datzenmike]

A87 came in 45.2cc open and 41cc closed chamber.

U-76 only was made open chamber.

Stock L18 with open chamber chamber (stock) head...... 8.43
Stock L18 with closed chamber chamber head............... 9.00
Stock L18 with open chamber chamber L16 head........... 9.38

Flattop pistons are a double whammy. Not only is there no piston dish but the cylinder bore increases the displacement.
L18 with 86mm flattop pistons open chamber head.......... 9.18
L18 with 86mm flattop pistons closed chamber head........ 9.85
L18 with 86mm flattop pistons open chamber L16 head...10.30

[Boxcar]

 

Absolutely not.

You should read some more threads

 

I think I'll stick to building.. :bye:

 

 Thanks for the Tech Mike.

[datzenmike]

I love working that stuff out. Had one this morning for KA pistons in an L18 http://community.ratsun.net/topic/54656-basic-lz22-build-w-flat-top-sss-su/page-11

 

Looks like maybe a KA24DE head for it in the future.

[flatcat19]

I think I'll stick to building.. :bye:

 

 Thanks for the Tech Mike.

 

Too high of a compression level and you can no longer run pump gas. And that number is kinda low.

The heat built up from a higher compression motor will create pinging. 

The L heads really don't flow as well as, well-almost any other design. 

All that built up heat and no where for it to go. 

[Boxcar]

Well there is always this theory...

There are two main combustion chamber designs, commonly known as “open” and “closed,” or “peanut,” referencing the similarity of the closed-chamber shape to that of the typical peanut shell. 

Put simply, the open heads resulted in lower compression ratios. The open chamber design reduced hydrocarbon (HC) emissions for US offerings and did not do much else beneficial to the 510 enthusiast. With their lower compression the engines were tuned less aggressively and produced somewhat less emissions but as a result were less efficient and more susceptible to detonation.

 

The closed heads were designed with a good amount of quench area, the flat bottom of the cylinder head exposed to the combustion chamber. This quench area helps to add turbulence to the intake charge as the piston rises to TDC on the combustion stroke. This turbulence is beneficial because it helps to mix the air and fuel, providing a more homogeneous mixture and a stronger power stroke upon ignition. As typically the closed heads were fitted to engines with flat-top pistons to maximize the benefits of the closed-head design, there was minimal space between the top of the piston and the quench area (often just the thickness of the head gasket). The one downside of closed chambered heads is that the quench area can shield a small amount of the fuel from igniting, resulting in higher HC emissions. Thus the closed chambered heads were not selected for meeting USA emissions requirements.

 

[flatcat19]

That, and anything near 10:1 compressing pings from all this heat-needing to run a higher octane fuel to compensate. 

 

That's why I said to find that sweet spot. Too low; poor performance. Too high; detonation. 

 

There is nothing wrong about what you said, but there is more to it. 

[Boxcar]

 I run pretty much 10 -1 in all my L-20's.

92 octane pump gas. No ping , no pre. det. I am anal about my set up though.

 I'm not sure I fallow you're heat theory.

Oh well , to much to think about today. I'll try to wrap my head around it later. 

[bananahamuck]

The old ( yes if your reading this ,, you are old ) L motor freaks say run as much compression as your wallet can afford at the pump..

[Boxcar]

oh, yea!!!!! :thumbup:

[jmunky90]

Oh Jesus Save Me!  I was just looking for pistons and maybe a cam and I end up learning sophmore auto-tech basics all over again......  thanks for the theory guys, but im just trying to find the parts I need....  Anybody know where I can get the parts????