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Discussion Starter #1
Hello everyone,
I’ve NEVER built an engine before and I have a k24a4 and would like to build an engine capable of revving to 9k rpm that is reliable. Is a budget of 2-3k for the long block realistic? I’ve read the best flowing vtec head is the PRB k20a2, but I would need to swap pistons and I might as well swap rods.
Can I use oem k24a2 pistons and rods or should I use forged aftermarket piston and rods?
Do I use the k24 chain, guides and tensioners?
Can I use the k24 valve cover with the k20 head?
Which k24 head gasket should I use?
What machining should I get done on the block/head?
For the oil pump Hybrid Racing says stock k20a2 pumps can cavitate past 8500 rpm. Should I go with a ported k20a2 oil pump or an f20c oil pump or will the stock k20a2 pump be sufficient to rev to 9k.
What camshafts and valvesprings would work best on a budget?
Should I use a 25° or 50° Vtc gear?
Can I use the k24a4 sensors, accessories, coil packs and injectors?
Sorry if there are any dumb question I don’t know much at all about engine building, any help is appreciated.
 

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Arouse the DAMPFHAMMER!
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I am not the right one for low budget project experience, so there are maybe cheaper, less reliable solutions possible. Just my two cents in advance, a 9 krpm revving 99 mm stroke makes no sense when you call 3k USD your budget limit. Engine preparing, tuning hardware and hours, header and IM as well as exhaust will eat about 3-4 k USD, the engine is even not touched. Just my two cents.

would like to build an engine capable of revving to 9k rpm that is reliable. Is a budget of 2-3k for the long block realistic?
Reliable at 9000 rpm? What is your expectation of reliable? In any case, that level of engine speed is not working long for high silicon casted aluminium pistons. The piston-liner-clearance will cause piston seizure. You need a well chosen clearance for the material you are going to choose. Both are depended.

Also depended on your base small block type (A2, A3, Z1, ...) the rods need to swapped for more resilient ones. While e.g. the PPA coded K24A1 block has pretty light rods there are other OEM rods which are maybe stronger like the 06-08 RBB from the K24A2 block. But a more resilient rod would be recommended (not all aftermarket can be listed for that). At this point you already have exceeded your budget as you need a tune and tuning cabable ECU too.

I’ve read the best flowing vtec head is the PRB k20a2
For the head it would be a good basis. But to make a sense in revving to 9000 rpm you need maybe a better flowing modified intake port and valve timing = cams. Already out of your budget.

Do I use the k24 chain, guides and tensioners?
TC yes, OC yes, TCT maybe a K20A2 one, if not the same.

Can I use the k24 valve cover with the k20 head?
Yes

For the oil pump Hybrid Racing says stock k20a2 pumps can cavitate past 8500 rpm. Should I go with a ported k20a2 oil pump or an f20c oil pump or will the stock k20a2 pump be sufficient to rev to 9k.
As I said, if you invest around 4-5 kUSD (beside the 3 kUSD for IM, H, E, CAI, muffler, ...) in your longblock for pistons, rods, gasket, head, valves, seats, guides, cams and valve springs, it may worth to rev to 8500 or even 9000 rpm. Keep it simple and easy, use the K20A2 pump, mod it to fit your K24 block and go with it.

This are maybe not good news for you, but it is like it is. NA engines, revving to the moon need some rational parts and capabilities. The stock K24A2 is designed for 197 or 205 hp at 6800 or 7000 rpm. Increasing the engine speed means a lot for the engine design, as load and wear are almost doubled.
 

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Discussion Starter #3 (Edited)
I am not the right one for low budget project experience, so there are maybe cheaper, less reliable solutions possible. Just my two cents in advance, a 9 krpm revving 99 mm stroke makes no sense when you call 3k USD your budget limit. Engine preparing, tuning hardware and hours, header and IM as well as exhaust will eat about 3-4 k USD, the engine is even not touched. Just my two cents.

Reliable at 9000 rpm? What is your expectation of reliable? In any case, that level of engine speed is not working long for high silicon casted aluminium pistons. The piston-liner-clearance will cause piston seizure. You need a well chosen clearance for the material you are going to choose. Both are depended.

Also depended on your base small block type (A2, A3, Z1, ...) the rods need to swapped for more resilient ones. While e.g. the PPA coded K24A1 block has pretty light rods there are other OEM rods which are maybe stronger like the 06-08 RBB from the K24A2 block. But a more resilient rod would be recommended (not all aftermarket can be listed for that). At this point you already have exceeded your budget as you need a tune and tuning cabable ECU too.

For the head it would be a good basis. But to make a sense in revving to 9000 rpm you need maybe a better flowing modified intake port and valve timing = cams. Already out of your budget.

TC yes, OC yes, TCT maybe a K20A2 one, if not the same.

Yes

As I said, if you invest around 4-5 kUSD (beside the 3 kUSD for IM, H, E, CAI, muffler, ...) in your longblock for pistons, rods, gasket, head, valves, seats, guides, cams and valve springs, it may worth to rev to 8500 or even 9000 rpm. Keep it simple and easy, use the K20A2 pump, mod it to fit your K24 block and go with it.

This are maybe not good news for you, but it is like it is. NA engines, revving to the moon need some rational parts and capabilities. The stock K24A2 is designed for 197 or 205 hp at 6800 or 7000 rpm. Increasing the engine speed means a lot for the engine design, as load and wear are almost doubled.
Thanks for the answers! I now realize how naive I am for thinking a k24 at 9k rpm could be possible/reliable for $3k. I read on another forum that a k24 at 8k rpm has the same piston speed as a k20 at 9k rpm.
 

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Arouse the DAMPFHAMMER!
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Thanks for the answers! I now realize how naive I am for thinking a k24 at 9k rpm could be possible/reliable for $3k. I read on another forum that a k24 at 8k rpm has the same piston speed as a k20 at 9k rpm.
We have plenty of budget builds here with different levels of output. Just do a bit a search here, e.g. @KBuilt thread or in the here Official: Dyno Chart Comparison & Calibration Registry | Honda / Acura K20a K24a Engine Forum. There are tons of information what which parts can help to your aim and which not.
 

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Thanks for the answers! I now realize how naive I am for thinking a k24 at 9k rpm could be possible/reliable for $3k. I read on another forum that a k24 at 8k rpm has the same piston speed as a k20 at 9k rpm.
I’m actually doing a “Stock Build” it’s not budget friendly but it is compare to most.
The best flowing head is FD2 K20Z4 comes in the Civic Type R. Reason I went with this head, it comes factory NSX port job. Has a 312 CFM compare to K20A2 299 CFM. Reason why CFM is crucial is these K series love air and the more air you can find more power. I’m doing a setup without pistons and rods. All oem parts you can get
I hope for 270+ my tuner says it’s possible but will see.
I went with
K20Z4 Head/With SKUNK2 Drop in Cams so I don’t have to do a whole valve train setup.
Grams 1000cc injectors
Ported RBC
72MM TB
Hybrid Racing Cold Air
Type S Oil Pump, With windage Tray, Tensioner and new chain
355 Fuel Pump
ACT 11.5 Flywheel
Battery Relocation Kit
Torco 10W-40 Oil
AMS Transmission Fluid
Oem Honda Coolant
Cosmics K24 Head Gasket
KTuned Idle Air Assist Valve
Lower Timing Chain Guide
RBC Gasket
Hybrid Racing Fuel Rail
SKUNK2 MEGAPOWER Exhaust 3inch

I’ll Be installing everything this weekend tuner saying we can make over 265+ I’ll be running straight E.
In total I say 4,700. I try to kept this build oem as possible for everyone who still wants reliability and not have to do Pistons and rods👌🏻
 

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Arouse the DAMPFHAMMER!
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The best flowing head is FD2 K20Z4 comes in the Civic Type R.
That's correct, and it is an amazing engineering design as well. No compare to the other K-series ports.

I’m doing a setup without pistons and rods. All oem parts you can get...K20Z4 Head/With SKUNK2 Drop in Cams so I don’t have to do a whole valve train setup.
My recommendation would have been the TSX 06-08 cams instead of the S2 DIC.

Technical Information 06 TSX Changes (hondata.com)
06 TSX cams vs 06 Si cams at 9800 RPM k20 89mm ported head | Honda / Acura K20a K24a Engine Forum

Torco 10W-40 Oil
I don't recommend that, it has a low wear protection capability while still having a medium to high ZDDP if we speak about their TR-1 racing oil. I had recently an example where a PennGrade 1 10W40 full synthetic was used. The liner wear was just after less then 1000 racing miles tremendously. I would recommend Amsoil Signature Series 5W30, Ravenol VSW 0W30, 5W30 Quaker State Ultimate Durability or Mobil 1 0W40 FS if oil temps are really high. On a stock engine, I wouldn't use a 10W40, it is too thick for DD driving, as the oil temps rarely go over 100 °C. On my customers racing engines I recommend, depending on bearing clearances and oil cooler setup, the oil weight. There is rarely a reason going to SAE40 weight. The tribology of an bearing or a cam surface needs in 1st priority oil mass flow. If there is no flow, no oil can build up a film layer. In a second order the dynamic of the tribology has to setup right. Stock bearing clearances are below 50 µm, average is around 40-45 µm on the mains and a bit bigger on the big journals. Race engines are operated and designed to keep the oil temperature around 105-118 °C, depending on pump capacity and engine speed bandwidth an SAE 30 or 40 can be the optimum. All my customers run SAE30 weight on racing, no matter if 1/4 mile, circuit racing, hill climb and so on. For an DD engine, which is in any case limited to 7800 rpm at maximum, the oil temps most likely won't see temperatures above 98 °C at higher engine loads, only on track days, depending on the oil cooler setup.

Cosmics K24 Head Gasket
You know that you need a Z-type, e.g. from the K20Z4, gasket to have the oil coolant passages matched correctly?

SKUNK2 MEGAPOWER Exhaust 3inch
Also header from that model (S2 Megapower)?

over 265+ I’ll be running straight E
You have access to Ethanol all the time? You know you can't drive gasoline or any mixtures of gasoline and Ethanol without having it tuned or at least to have an Ethanol sensor and tuned for setup?
 

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That's correct, and it is an amazing engineering design as well. No compare to the other K-series ports.

My recommendation would have been the TSX 06-08 cams instead of the S2 DIC.

Technical Information 06 TSX Changes (hondata.com)
06 TSX cams vs 06 Si cams at 9800 RPM k20 89mm ported head | Honda / Acura K20a K24a Engine Forum

I don't recommend that, it has a low wear protection capability while still having a medium to high ZDDP if we speak about their TR-1 racing oil. I had recently an example where a PennGrade 1 10W40 full synthetic was used. The liner wear was just after less then 1000 racing miles tremendously. I would recommend Amsoil Signature Series 5W30, Ravenol VSW 0W30, 5W30 Quaker State Ultimate Durability or Mobil 1 0W40 FS if oil temps are really high. On a stock engine, I wouldn't use a 10W40, it is too thick for DD driving, as the oil temps rarely go over 100 °C. On my customers racing engines I recommend, depending on bearing clearances and oil cooler setup, the oil weight. There is rarely a reason going to SAE40 weight. The tribology of an bearing or a cam surface needs in 1st priority oil mass flow. If there is no flow, no oil can build up a film layer. In a second order the dynamic of the tribology has to setup right. Stock bearing clearances are below 50 µm, average is around 40-45 µm on the mains and a bit bigger on the big journals. Race engines are operated and designed to keep the oil temperature around 105-118 °C, depending on pump capacity and engine speed bandwidth an SAE 30 or 40 can be the optimum. All my customers run SAE30 weight on racing, no matter if 1/4 mile, circuit racing, hill climb and so on. For an DD engine, which is in any case limited to 7800 rpm at maximum, the oil temps most likely won't see temperatures above 98 °C at higher engine loads, only on track days, depending on the oil cooler setup.

You know that you need a Z-type, e.g. from the K20Z4, gasket to have the oil coolant passages matched correctly?

Also header from that model (S2 Megapower)?

You have access to Ethanol all the time? You know you can't drive gasoline or any mixtures of gasoline and Ethanol without having it tuned or at least to have an Ethanol sensor and tuned for setup?
Yeah no doubt about the Type R head by far bang for the buck. Got mine for $850 USD with cams and everything great deal.
Good to know about Torco oil, I didn’t do to much digging in that as my performance shop recommended that pacific viscosity.
if I knew that about the SKUNK2 DIC I would’ve went with 06-08 TSX cams. I’ll probably use the Type R cams when I boost it.
Yeah I know about the EGR port of the head, I didn’t cut the RBC and got the Z3 Gasket directly bolts up👌🏻
as for header I’m running 1320 K24 header, I will be switching to skunk2 later down line.
As for Ethanol, I have the injectors and Fuel pump. I’ll be switching to E only, as of now I’m currently tuned on 91 for my stock K24.
I wouldn’t need a sensor since it’s straight Ethanol
 

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Yeah no doubt about the Type R head by far bang for the buck. Got mine for $850 USD with cams and everything great deal.
Good to know about Torco oil, I didn’t do to much digging in that as my performance shop recommended that pacific viscosity.
if I knew that about the SKUNK2 DIC I would’ve went with 06-08 TSX cams. I’ll probably use the Type R cams when I boost it.
Yeah I know about the EGR port of the head, I didn’t cut the RBC and got the Z3 Gasket directly bolts up👌🏻
as for header I’m running 1320 K24 header, I will be switching to skunk2 later down line.
As for Ethanol, I have the injectors and Fuel pump. I’ll be switching to E only, as of now I’m currently tuned on 91 for my stock K24.
I wouldn’t need a sensor since it’s straight Ethanol
Also Ethanol is convenient since a E station near me at all times, and it’s my race car so definitely want all the power I can get. I’ll be getting a daily soon for sure though
 

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Arouse the DAMPFHAMMER!
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Yeah I know about the EGR port of the head, I didn’t cut the RBC and got the Z3 Gasket directly bolts up👌🏻
I meant the head gasket between block and head.

Regarding oil weight. You can start with 40 weight oil and check the oil temperatures. For this you would have to install a oil temperature sensor, which I recommend to all who race from time to time. Below 105 °C (measured after oil cooler) I would swap to 30 weight oil. Oil sump temperatures are not qualifying for that decision when your engine runs an oil cooler. BTW, I would recommend using at least the stock K20A2/Z3...

 

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I meant the head gasket between block and head.

Regarding oil weight. You can start with 40 weight oil and check the oil temperatures. For this you would have to install a oil temperature sensor, which I recommend to all who race from time to time.
Oh yeah got the K24A head gasket since I know K20 bore are 86mm I’ll need 87mm for the K24A block correct?
 

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I meant the head gasket between block and head.

Regarding oil weight. You can start with 40 weight oil and check the oil temperatures. For this you would have to install a oil temperature sensor, which I recommend to all who race from time to time. Below 105 °C (measured after oil cooler) I would swap to 30 weight oil. Oil sump temperatures are not qualifying for that decision when your engine runs an oil cooler. BTW, I would recommend using at least the stock K20A2/Z3...

This is interesting perspective. My stock euro r k20a has sump oil temps as high as 140 °C when working hard. i never considered that the oil temps after the cooler might be sufficiently cool to maintain engine operation.

Would you consider sump oil temp to be not important compared with post cooler temps?
 

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Arouse the DAMPFHAMMER!
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Would you consider sump oil temp to be not important compared with post cooler temps?
They are essential, but not for the viscosity decision. The sump temperature represents the collected oil from: oil squirt back flow, head back flow, bearing back flow and additional aggregates like Turbo, SC and so on. We can assume this to be the average temperature on the high end (not peak which differs locally). The conclusion out of that would be, this value is important for at least three properties: extraction of lighter fumes capability, thermal stress on the oil (degeneration rate) and a pre-cooling (mixed) heat extraction. The first two properties create a sort of bandwidth of necessary temperature, it should high enough to vaporize condensed or collected water (combustion!) and fuel but also cool enough not to oxidize/crack the oil too fast.

The later point is something which is especially something interesting when running an higher content of viscosity enhancer molecules, which are plenty in a 10W60 or 10W50. These polymeres crack with time and temperature. If the temperature is higher, they crack faster, if time is longer, they crack "faster" too. When they were cracked the viscosity drops as these molecules are responsible for the higher viscosity end, the 50 or 60 weight rating. This is the cause I would never ever use one of such oil formulations on an engine which see higher oil temps and longer usage time. This are racing oils, which are changed in very short intervals, like every race or so.

Base viscosity = function of bearing clearance, oil temp before bearings and some other stuff
Oil change interval = function of temperature household in the oil sump and oil path and other stuff

What you can't read in a datasheet of an oil is it's wear protection capacity. This is a mix out of the integrates and the base oil. A good oil design can be assumed of the ingredients and their concentration, but finally it has to be run and tested in the specific engine and application. My experience on that at an OEM engine company was even the oil companies don't know exactly how they should optimize their receipt or formulation of the oil. Every company has it's own procedure, different sources for ingredients and philosophy while the OEM's have the Norms and rules they demand for, like oil specification according ACEA and many others. Not every Norm or rule gives us the optimum for the application, even if it is done exactly for that purpose. Norms are just the minimum level which is demanded. E.g. Amsoil Signature Series 5W30 had for years no ACEA certification, but exceeded the specification for it. And it offers an amazing wear protection similar like the Ravenol VSW 0W30 does it, which full fills ACEA C3 and one of the hardest OEM oil specification of VW and have a GM recommendation.

Oil specification is one of the biggest discussion topics in engine development and testing. I don't know any single engine engineer who has all, the chemical, the physical and the necessary tribological knowhow to decide the best oil from a discussion of oil properties, I also don't know no single Oil company who made a direct hit for an specific engine without testing it. The only I know who are in both partly are guys who do scientific investigations on a single field of that much bigger topic oil-tribological system. So finally we all have to find it out the hard way, one take a longer road started with an oil which is far from optimum even if spec'd for the application and one take a shorter road, started from an almost optimum oil.

A lot of tuners still recommend, just to be on the safer side for themselves, irresponsible high oil viscosities. No one tells their customer that oil flow is the base number to start with, all tells them you need pressure. But oil pressure tells nothing about the oil flow. If there is an obstacle in the flow path, oil pressure will be high, but flow not. So is oil pressure the correct value to rate oil viscosity? No it isn't. Is oil viscosity an indicator for wear protection? No it isn't. What the heck does oil pressure help for? It is an indicator of the healthiness of the system. Once you choose an oil viscosity, oil pressure should always at the same level for same engine speed-load points. If it changes, worry about it! So it is a relative quantity we are interested in, so to say the quality of the difference to the start value (if it was already an healthy engine). Nothing more!

Of course oil viscosity and film thickness are correlating, means an higher viscosity gives an higher film thickness. But one should take in account that film thickness is a function of oil flow, relative speed of surfaces and oil properties like viscosity, temperature and so on. When at 9000 rpm the oil flow is lacking, the viscosity can't rescue it. How do one know when is the right oil flow achieved? Without a measurement of it we just can assume it. This is engine oil system depended, so no general rule then this. Oil flow is 1st priority, oil film thickness 2nd priority. So this means find the lowest viscosity oil giving you the right film thickness. Back again at what I mentioned above 😎.
 
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