Nissan/Datsun L4 project

General engine tech -- Drag Racing to Circle Track

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Re: Nissan/Datsun L4 project

Post by Xnke » Mon Apr 18, 2016 11:06 pm

That head needs some of these, I think...

Especially if you're going CNC masterless cam grinding...

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Re: Nissan/Datsun L4 project

Post by volodkovich » Mon Apr 18, 2016 11:45 pm

I'm not sold on that roller conversion. They have to be heavier than the stock slipper pad rockers. Smaller roller is a negative too, I don't think you would be able to run the same velocity as the stock slipper rocker. Reduced friction and ease of profile design (no oil entrainment to worry about) are about the only gains I can see, I'd be interested to hear others opinions.

TK is that crank trigger wheel aluminium? Has it got steel or magnet inserts?
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Re: Nissan/Datsun L4 project

Post by Leftcoaster » Mon Apr 18, 2016 11:52 pm

Very nice, thanks for posting

Are those flat top pistons? hard to tell due to reflections - - :(

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Re: Nissan/Datsun L4 project

Post by KnightEngines » Tue Apr 19, 2016 12:20 am

Yeah, I'm up in the air about roller finger followers, a customer has gotten hold of a roller cam & followers for a BMW M20 engine, working out the area under the curve it's no better than the old slider follower.
TK is that crank trigger wheel aluminium? Has it got steel or magnet inserts?
Yep, alloy, magnet inserts - it's an MSD universal kit, comes with all the bits & oversized brackets etc that you make fit.
Are those flat top pistons? hard to tell due to reflections - - :(
Yeah, crap photo - 7cc shallow dish with small valve reliefs.

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Re: Nissan/Datsun L4 project

Post by KnightEngines » Tue Apr 19, 2016 12:21 am

All done, manifold just sitting on, can't bolt it up till dyno time - have to fit the headers at the same time.
Dyno is about a month away unfortunately.

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Re: Nissan/Datsun L4 project

Post by modok » Tue Apr 19, 2016 1:21 am

I feel envy
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Re: Nissan/Datsun L4 project

Post by Runit » Tue Apr 19, 2016 9:54 am

I noticed you've bolted the carbs to directly to the manifold. Every Datsun I remember with sidedrafts required some kind of vibration isolation for the carbs. The Datsun comp isolators for 50mm carbs were seemingly the most popular. Some people went to the trouble of removing 1/2 of the rubber between the isolator flanges to make them even more compliant. Last I knew the isolators were NLA though. I guess the next best would be aluminum plates and O-rings and cushions under the bolt heads.

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Re: Nissan/Datsun L4 project

Post by Leftcoaster » Tue Apr 19, 2016 11:08 am

Tony, some quick calcs suggest the following; pls confirm

89mm bore x 92mm stroke gives 2290cc swept volume

6.5" rod equals 165.1mm, therefore 1.79 to 1 rod/stroke ratio

Don't know pin diam or block height so cannot calc piston compression height, crown thickness, or ring pack height - -

If the compression is 13.2 to 1 with 7cc dished pistons at zero deck and a 1mm head gasket, chamber volume must be around 36cc?

Would you have preferred a flat top piston and say 43cc chamber, but broadening the chamber and/or sinking the valves was impractical?

Beautiful handwork, progressive and effective mods, thanks again for posting

Hope someone produces the cam you deserve - - :D

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Re: Nissan/Datsun L4 project

Post by dfarr67 » Tue Apr 19, 2016 2:40 pm

Any links to Toyota 22RE that have been taken this far?

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Re: Nissan/Datsun L4 project

Post by KnightEngines » Tue Apr 19, 2016 6:52 pm

I noticed you've bolted the carbs to directly to the manifold.
Just dummied up for pics, we've got insulators for them, won't be bolted directly to manifold - harmonics with the Z22 crank would 'boil' the fuel in the float bowls.

Tony, some quick calcs suggest the following; pls confirm

89mm bore x 92mm stroke gives 2290cc swept volume - yep

6.5" rod equals 165.1mm, therefore 1.79 to 1 rod/stroke ratio - 6.05" rod, 1.67 rod/stroke ratio

Don't know pin diam or block height so cannot calc piston compression height, crown thickness, or ring pack height - - comp height 1.13", fairly compact ring pack, no support rail required.

If the compression is 13.2 to 1 with 7cc dished pistons at zero deck and a 1mm head gasket, chamber volume must be around 36cc? - 34cc, .050" head gasket, +.010" deck height.

Would you have preferred a flat top piston and say 43cc chamber, but broadening the chamber and/or sinking the valves was impractical? - nope, small dish & compact chamber will make more power than larger chamber & flat top, not a lot in it, but it's real.

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Re: Nissan/Datsun L4 project

Post by Leftcoaster » Tue Apr 19, 2016 7:10 pm

Many thanks

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Re: Nissan/Datsun L4 project

Post by F1Fever » Wed Apr 20, 2016 12:20 pm

I was no longer driving the car consciously. I was driving it by a kind of instinct, only I was in a different dimension.
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Re: Nissan/Datsun L4 project

Post by Xnke » Wed Apr 20, 2016 12:33 pm

L20B block is 227.45mm tall.

The rollers are 0.800" diameter in my finger followers, the valve tip roller is 0.375" diameter. They are only 4 grams heavier than the stock followers. The sliding friction is the enemy here, not so much the cam profile. The finger followers I posted above are from AU, WES engines.

It takes ~75HP to turn the L28 6-cylinder camshaft at 5000RPM, all stock springs and cam profile. With the roller followers, that gets cut down by a LOT. Free HP right there. ~25HP gain, right off the top, but it's hard to make accurate comparisons due to the differing cam profile and springs. Not so much that the roller cam was a big performance grind, but that it certainly wasn't optimized. Straight copied a Mitsubishi cam profile from a 4G63 SOHC.

And, no hunting around for oil that's harder and harder to find these days-Any quality synthetic will do.

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Re: Nissan/Datsun L4 project

Post by volodkovich » Wed Apr 20, 2016 7:33 pm

Do you have any evidence to backup your claim that it takes 75hp to spin the L6 valvetrain at 5000? Seems excessive to me. I have yet to put one on a Spintron but the biggest one they make is 75hp!

Valvetrain friction is more an issue at low rpm - hence why all the modern motors are roller now, it helps with emissions and economy. I believe most top end high rpm race motors are still slipper pad finger followers.

I'd agree going roller is a good idea for a street motor, it is a lot of money though - aren't those WES rockers something like $250 each?
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Re: Nissan/Datsun L4 project

Post by KnightEngines » Wed Apr 20, 2016 8:01 pm

Close?
Not far off at all!

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