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Discussion Starter · #1 ·
Photos speak thousands of words?
Ok, my son and I gathered these 2 pieces, my son will work the chassis, I'm building the motor.
Target is 10,000 rpm 400hp N/A in a mid engine car weighing less than 2000lbs.
I look forward to the adventure ahead.
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10000 rpm K24 will last minutes at these revs, if at all. That would be a pure drag racing engine.
I don‘t see a way to get to make a 99mm stroke engine to last on the street reving that high.
That 4piston k24 reving to 10k had aluminium conrods. They are purely for competition purposes. Ragging it up and down the highway on the limiter will end in a desaster.
I guess 99,9% of people go turbo or supercharger on a K24 to get to 400HP.
Good luck. Let us know how it went. :)
Fiero is nice. I always liked them.
 

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Discussion Starter · #3 · (Edited)
10000 rpm K24 will last minutes at these revs, if at all. That would be a pure drag racing engine.
I don‘t see a way to get to make a 99mm stroke engine to last on the street reving that high.
Likely 99,9% of people go turbo or supercharger on a K24 to get to 400HP.
Good luck. Let us know how it went. :)
Fiero is nice. I always liked them.
You assume I intend to daily drive at 10k rpm.
I want the potential to see 10k.
 

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I don't belive it's terribly difficult to oversquare this engine.
You better believe it. To get the 2.4 over square you'll need to destroke it. The max bore limit is around 90mm so that leaves you with a stroke over under 90mm to make it over square
 

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Discussion Starter · #9 · (Edited)
You better believe it. To get the 2.4 over square you'll need to destroke it. The max bore limit is around 90mm so that leaves you with a stroke over under 90mm to make it over square
I'll introduce myself a little further.
First engine I modded back in 1986 when I was 16 years old was a lawn mower. Grew up in a marine/autoshop owned by my father. Played with 4 stroke, then at 18 years old did my first 2 stroke build, a cr125 dirt bike, then many more, learned alot about tuning an expansion pipe and getting 15k rpm from a bike. Then jet ski motors. Then big HP boosted diesel.
I'm no rookie at this.
I'm just new here.

And please make no mistake. I know nothing, if I knew everything I would not be here. This is my first good look at this mill. But I belive the right rod/piston combo can get me over with a 90+mm bore.
Unknown to me is how light I can get those bits and how well my machine shop can balance the rotating assembly. How light to make that rotating assembly but still strong enough to go stupid rpm.
 

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I'll introduce myself a little further.
First engine I modded back in 1986 when I was 16 years old was a lawn mower. Grew up in a marine/autoshop owned by my father. Played with 4 stroke, then at 18 years old did my first 2 stroke build, a cr125 dirt bike, then many more, learned alot about tuning an expansion pipe and getting 15k rpm from a bike. Then jet ski motors. Then big HP boosted diesel.
I'm no rookie at this.
I'm just new here.

And please make no mistake. I know nothing, if I knew everything I would not be here. This is my first good look at this mill. But I belive the right rod/piston combo can get me over with a 90+mm bore.
Unknown to me is how light I can get those bits and how well my machine shop can balance the rotating assembly. How light to make that rotating assembly but still strong enough to go stupid rpm.
90mm bore is no small task. Most people settle for an 87 or 88mm bore to keep some reliability in the block. A sleeved block at 90mm is one hone job from being scrap.

Besides all that. Over or under square has little bearing on the ability of an engine to rev high. Stroke length is the ultimate factor.

By all means I'm excited to see the n/a 400hp build. It can be done. You might be methanol to get you there but it can be done.
 

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Discussion Starter · #12 ·
90mm bore is no small task. Most people settle for an 87 or 88mm bore to keep some reliability in the block. A sleeved block at 90mm is one hone job from being scrap.

Besides all that. Over or under square has little bearing on the ability of an engine to rev high. Stroke length is the ultimate factor.

By all means I'm excited to see the n/a 400hp build. It can be done. You might be methanol to get you there but it can be done.
I like meth 😉
 

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Discussion Starter · #13 ·
90mm bore is no small task. Most people settle for an 87 or 88mm bore to keep some reliability in the block. A sleeved block at 90mm is one hone job from being scrap.

Besides all that. Over or under square has little bearing on the ability of an engine to rev high. Stroke length is the ultimate factor.

By all means I'm excited to see the n/a 400hp build. It can be done. You might be methanol to get you there but it can be done.
Also.
Water pump. I've not seen that addressed here.
I've seen folks deal with oil pumps that cavitate at high rpm but what about a water pump cavitating with a thinwall overbore?
 

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Under drive the water pump if necessary. You probably won't be spending enough time over spinning the water pump for it to cause problem. Short bursts of cavitation in the cooling system aren't going to be detrimental like in the oiling system.
 

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Discussion Starter · #15 ·
Under drive the water pump if necessary. You probably won't be spending enough time over spinning the water pump for it to cause problem. Short bursts of cavitation in the cooling system aren't going to be detrimental like in the oiling system.
Electric water pump.
Makes life easy in a swap just needs a little plumbing.
 

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found this on facebook from 4piston
4Piston/photos/90







90mm stroke 90mm bore 2.3l, 11500 rpm NA engine based on a k20 block.
"90mm bore K20 going together today with some goodies. 90mm Bryant Crank, 4P Super99 Cnc head, Xceldyne titanium valves, and Web Camshafts"

With that rod to stroke ratio, it is likely only good for drag racing as piston acceleration and side loads will be enormous.
There is very little space between the cylinders. If you get the sleeve protrusion (stepped deck) right, head gasket should work.

What's you expected budget for the engine alone?
 

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Discussion Starter · #17 ·
found this on facebook from 4piston
4Piston/photos/90







90mm stroke 90mm bore 2.3l, 11500 rpm NA engine based on a k20 block.
"90mm bore K20 going together today with some goodies. 90mm Bryant Crank, 4P Super99 Cnc head, Xceldyne titanium valves, and Web Camshafts"

With that rod to stroke ratio, it is likely only good for drag racing as piston acceleration and side loads will be enormous.
There is very little space between the cylinders. If you get the sleeve protrusion (stepped deck) right, head gasket should work.

What's you expected budget for the engine alone?
Outta the gate I'm looking at $2200 canadian for oil pump, water pump, pistons, rods.

Still looking at cost to sleeve/bore, valves, springs and cams.
I need to sit down with a laptop pilot before I get nuts.
 

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10000 rpm K24 will last minutes at these revs, if at all. That would be a pure drag racing engine.
I don‘t see a way to get to make a 99mm stroke engine to last on the street reving that high.
That 4piston k24 reving to 10k had aluminium conrods. They are purely for competition purposes. Ragging it up and down the highway on the limiter will end in a desaster.
I guess 99,9% of people go turbo or supercharger on a K24 to get to 400HP.
Good luck. Let us know how it went. :)
Fiero is nice. I always liked them.
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