L head flow numbers

[DISLEXICDIME]

Well be careful with those ring lands

[Arkrider410]

Explain

[Arkrider410]

I'm not being a jerk about anything I just gathering information to make the best decision I can using the block and head I have

[wayno]

He is not ideally located for the acquisition of Datsun parts, they didn't start putting them together here in the US till the mid 1980s(Nissan Badge).

[Arkrider410]

That's what I'm saying, in my area I've seen 3 620's mine,a rv, and one more. There are none in junkyards that I know of.

[DISLEXICDIME]

The l series ringlands do not like a lot of boost .

[datzenmike]

I don't want to overbore it that was your idea not mine.I know that a l18 or l20 would be better but I got to use what I got.

 

 

Actually it's your idea....

 

It is for goblin and I have an a87 head on a l16. I want to build a turbo engine out of it with l18 rods a 240 pistons.

 

The L16 is 83mm bore. L24 is 85mm. No way to run what you want without increasing the bore size.

 

Now if I was doing a junk yard build I would use a l16 with a u67 head

Compression would be 7.72 a real barn burner.

[DISLEXICDIME]

Yah but it would be more likely to live

[Laecaon]

Mike, you keep stating the L24 is 85mm bore. But its not. Its 83mm bore. And so is the L26.

 

Please double check your sources.

[datzenmike]

Yes, I really got off on the wrong foot there. L24 are 83mm not 85mm. Thanks Laecaon

 

For best results you should still over bore to the next over size as the L16's bore will surely be worn.

[Arkrider410]

I'll have to check the bores but if needs it then I don't have a problem boring it but to bore it for the sake of boring it no

[Stoffregen Motorsports]

The stock cast pistons won't hold up to anything more than a few pounds of boost. Then there's the rings. You need to use a good chromoly ring too. There are good rings for the cast OEM L pistons, but still, the piston probably won't last.

[datzenmike]

Most stock turbo engines use ordinary hyper eutectic pistons, and they are good for 6-8 PSI of boost and will last forever. The Shelby Daytona 2.2, Ford 2.3 the 280zx and more. These are all EFI engines with good a/f control and some with ignition  retard and knock sensors. These are not home made 'built to last for the summer' turbo carb the shit out of them because if 8 PSI feels good 16PSI will be twice and 24 PSI four times as good, engines. Yes they will melt down.

 

 

I'll have to check the bores but if needs it then I don't have a problem boring it but to bore it for the sake of boring it no

 

Have a shop check them. You need close fitting tolerances and used L24 pistons are unlikely to fit perfectly into worn bores.

 

Nissan grades their pistons and bores into four groups. It's too expensive to bore or lathe to exactly 82.975mm which is exactly the perfect size for the proper clearance on a perfectly sized 83mm bore.... it just doesn't happen. Stock L16 pistons are anywhere between 82.985 and 83.035. Likewise, the bores are not exact either but range from 83mm to 83.050mm Obviously an 83.035mm piston won't even fit in an 83.010mm bore. But an 82.985mm piston will and give the required clearance. An oversize piston can fit an oversize bore and nothing goes to waste. This is why you may find a number stamped on a piston or the top of the block. It tells in a glance to the assembler that a number 3 piston is a perfect fit to a number three bore.

 

BTW the perfect clearance between a piston and the cylinder bore is 0.001 to 0.0018" Roughly 1 to 2 thousandths of an inch. Less than a sheet of paper.

 

Another advantage of a fresh bore and hone is perfectly round cylinders. This allows you to use extremely hard chrome rings. If you are expecting to just hone the cylinders to 'break the glaze' then new rings, then use softer cast rings that will wear in to the out of round cylinders, but don't expect to get many miles out of them and never with a turbo.

 

OK so now that you might have been convinced to over bore your block it's going to cost the same amount to go 0.1mm as it will to go 1mm over. Same with pistons and rings. Might as well get the largest over size.  A one mm increase is 38 free cc's of displacement.

[Arkrider410]

Ok I'll have it checked asap

[Arkrider410]

When it's boosted its only going to have 6-7psi anyway

[scooter]

If your only gonna boost 7 psi leave the compression alone. Otherwise its going to be a turd

[datzenmike]

Stock L16 is 8.5.

 

L16 with L24 flattops and A87 open chamber (the most common) is 8.63 and perfect for this. In theory 6 PSI would add almost 30 hp to the very top end. You would feel something from 3K  gradually building.

 

Again, find a scrapped L20B and you have this without a turbo. Then add it later. Same thing but 130 hp.   

[Arkrider410]

So basically do stock rebuild if necessary to get it on the road then find a l20 and add a turbo later

[datzenmike]

Well if you can find an L20B build it while driving the L16. It will cost the same to rebuild either.

Now this may not be feasible for you. If so, and all you have is the L16 then build it.

[Arkrider410]

I found a l18 crank and that's all so far

[Arkrider410]

What would compression be if I used a l18 crank with l16 rods and l24 pistons.

[Doctor510]

Probably NOT a good option, pistons will stick up out of the block, use L18, L26 or L28 rods are you'd be good to go.

[Arkrider410]

What's the highest compression that these engines will take

[datzenmike]

What would compression be if I used a l18 crank with l16 rods and l24 pistons.

 

The L16 rods are about 3mm longer than the L18 rods so the pistons will try to rise about 3mm above the surface of the block. The will hit the head at about 1mm. If you can source a set of L18 rods you would be building an L17 (1688cc) engine.

 

If L16 block, L18 crank and rods with L16 pistons the compression with the stock 210 head would be.... 9.03

Above but with closed chamber head like the A87 compression would be................................................. 8.6

Above but with open chamber head like an A87 or U67 the compression would be .................................. 8.1

 

If L16 block, L18 crank and rods with L24 pistons the compression with the stock 210 head would be....10.27

Above but with closed chamber head like the A87 compression would be................................................. 9.7

Above but with open chamber head like an A87 or U67 the compression would be .................................. 9.08

[scooter]

What's the highest compression that these engines will take

On pump gas, probibly not much more than 10:1 or so.

 

Avgas, not sure how high but mine is great at 12.3:1

 

On race gas or alcohol you can crank it up to 14:1

 

Anything more than 10:1 or if stock compression with more than like 10 pounds of boost your going to want some kind of forged piston cause the top ring lands will say bye bye.

 

The stock rods are pretty sturdy, with arp bolts in them you can push them pretty far. Lots of rods available for l16/l18.. Not so much for l20b's except custom.