Engine build ideas, need some help (looooong story)

[scooter]

Don't sweat the rod ratio soo much, it may make like 5 more hp with longer rods. If your still using stock oe or oe replacement parts it doesn't make sense. If your gonna go through the trouble to customize the rotating assembly it may be worth it to just phone up Carrillo and get them to build you a rod and piston.

 

I am very pleased how this engine runs on the bottle. I'd love to do a dyno analysis of it off the bottle vs on. I have a feeling I am getting a lot more hp out of the kit than what it's rated at.

 

The next lz will have a bottom end strong enough that I can spray it to the point that nitrous and fuel pushes out the carb stacks. ALL the NAWS

[flatcat19]

Danger to manifold, homie.

[scooter]

Danger to manifold, homie.

Pretty much, the cannon intake is soo hogged out if i ever have a nitrous backfire through the carbs the intakes gonna break in half.

 

If you dont wanna spend alot of money do the lz23 with l20b rods and ka pistons. Take the rest of your budget and put it in the head.

Going to 89mm bores means you can put fuck off big valves in it and not have horrendous valve shrouding. Even if you wanted to use an l20b crank it will still make way more power with the big bore 10 times out of 10.

 

Im probibly pushing the stock rods harder than anyone else on here right now. If u keep it in the 7000-7500 range they wont break.

 

It's admirable that you're willing to try something new, but...

 

The L motor has a max streetable horsepower of about 250. That's a fully punched out, stroked, L headed, dual 50 PHH monster. Building the bottom end to get the desired displacement is only half the battle. Getting the head to flow and building a valvetrain that will handle the cam required for that kind of HP will cost you, big time.

 

If you work backwards from a couple of questions, you can then decide what to do with the options available.

 

• What's your budget?
• What kind of HP do you want?
• Can you do the work; some, part or all of it yourself?

Ask yourself those three questions and go from there.

This. And to make that power you still wont be on pump gas.

[datzenmike]

L20B. half the stroke is 43mm so unless you change the crank this is what you have to work with. As the L20B and the Z20 and Z22 blocks are 227.45mm tall, this leaves 184.24 space to fit your rod and piston in and have the piston top level with the top of the block surface. Actually you can have the piston rise about 1/3 of a mm above but for this argument 184.45mm is it. The L20B rod is 145.9mm long and the piston pin height is 38.1mm or 184mm... just perfect. You could substitute Z20E 6" rods 152.5mm and Z20E flattop pistons, 31.75mm or 184.25... another good fit.

 

So what will a narrowed chevy rod on a ground down crank and a honda piston do that isn't already being done with the stock equipment???? 

 

Piston speed will be exactly the same just at very slightly different positions on the cylinder wall. The theoretical rev limit (red line) is also the same regardless of the longer or shorter rod lengths (rod/stroke ratio)

 

RPM X stroke in inches / 6 must equal 4,000 or less. More than 4,000 for a sustained time will result it a failure of the rod or piston. The acceleration / deceleration G forces will stretch and snap them.

 

7,083 X 3.3884 / 6 =4000.0062 Here, to be safe, I would just say 7K is the L20B red line. Rod length and pin heights do not alter the structural strengths of the materials used. To go higher longer and reliably would require exotic lightweight and or stronger metals. Face it this is a passenger car engine never intended to rev that high. 

[scooter]

Mike, if i take your math further 4000 fps would be equivalant to an 8350 rpm capable L16.

using a z22 crank lowers that to 6650 rpm. i run my lz23 up to 7500 all the time, which means theyre hitting over 4500 feet per second. i do have arp rod bolts in it, but still.

Those ol' l20b rods are pretty strong.

 

I agree with your rod ratio statement mike,

 

I believe these limits can be raised if the piston and wrist pin weight is reduced, which probibly Is a factor on why ive been getting away with it, as the pistons i am using are quite a bit lighter and the pin is considerablly shorter and alot lighter than the stock ones, along with being stiffer which puts less stress on the small end.

 

I also looked into the chevy rod thing and thats too much side play on the crank, you would have to go with a piston guided type rod thats had very mixed results and questionable reliability.

 

If you used a 4g63 rod and ground the crank it would work well but that still means custom pistons and i havint really found evidence of people trying honda rod journal sizes on datto cranks.

[datzenmike]

The Nissan rods are strong that 4000 is likely very safe.  I think the rod bolts would be the weakest thing as they are stretched by the extreme acceleration on the downward pull of the intake cycle to BDC and the sudden deceleration towards TDC of the exhaust stroke. The full weight of the rod and piston/pin has to stop from 4000 feet /min, to zero, in a distance of less than 1.5" and do this 100 times a second at 6000RPMs.

[Stoffregen Motorsports]

One huge aspect to this you guys are glossing over - the cylinder head.

 

None of these engine combos will make any power at these RPMs without a good porting job and a proper cam. Then, once they do make power up there, the wear on the valvetrain is substantial. Frequent inspections are important to make sure the cam, rockers, lash pads and retainers are in good shape.

 

A cylinder head capable of big HP and high RPMs will probably need rebuilding every couple of years.

[datzenmike]

Covered already, though lightly.

 

Depends on the engine this is all going into. L16? The block does not have much bearing on engine power so you could spend the moon on it and still make 80 hp. A good strong bottom end helps with longevity. Power is made by the head.

[Stoffregen Motorsports]

You guys are beating a dead horse over rod/stroke ratios. It's not really an argument anymore, since combos have been proven.

 

The only pertinent argument here is what can you afford? If you want to use over-the-counter parts and save a buck, that is a decision that needs to be made at the beginning of the process.

 

Back to my three questions. If you can't afford to build the motor of your dreams, then what can you afford? The decision is made for you by the answers to those questions.

[Stoffregen Motorsports]

Reading through my last comments, to make sure I'm not being offensive, I'm trying to find a way to put into perspective. it boils down to cost. It always does. If this isn't understood, then it's just bench racing.

[scooter]

I completely agree with you stoff, to make good power with these you need to spend a lot of time with a grinder, and hopefully a flowbench, and some knowledge.

 

A lot can be had even if you use a completely stock bottom end and everything you got thrown at the head.

[datzenmike]

HP = torque X RPM /5252. A dynomometer measures torque only. HP has to be calculated.

 

80 ft lbs @3,000 RPMs = 45.6 HP

 

Notice what happens when you double the RPM.

 

80 ft lbs @ 6,000 RPMs = 91 HP

 

An engine should double it's output power every time the RPM doubles. Working twice as fast makes twice as much.

 

 

 

 

 

Here is an L16, nothing special, but it makes about 45 hp and 75 ft lbs.@3K. So why does it not make 90 HP at 6K??? Because the torque value has dropped off starting about 3,750RPM. Engines are just huge air pumps.More air in more power out.

 

This is not the fault of the block and pistons. Just under 4K the engine starts to starve for air. Remember twice the RPM needs twice the air. Maybe carb too small. Valves (both intake and exhaust) are now too small or shrouded for the maximum air needed to go through them. Intake and exhaust ports too small for the air needed. Intake and exhaust manifolds restrictive. Cam not holding valves open long enough for the air needed. It's all the fault of the head.