Engine Build. Should I?

[RYU]

I was perusing the local classifieds one day and noticed a listing that was too good to be true. A few days later I ended up with all this under the promise that I would use them wisely. These were sitting in an older gentleman's garage for several years having sold his NSX years before. It was interesting chatting with him for he was recalling names I've only seen in very very old threads here on prime (early 2000s?).

Here are the parts to get me started in this adventure.
* Virgin stock short block (missing the two center pistons and rods) but otherwise complete with the stock crank still in place.
* Stock unopened 5spd (in snap ring so i'll need to tear into it anyway)
* Stock gear set (not sure yet on if it's JDM or USDM. Honcho?)
* Extra Crank (i'm guessing this is stock but I need to confirm. can anyone from the stroker club chime in here?)
* Some other odds and ends like an extra axle, new OEM clutch set + fly, etc.

Now the big question... What should I do with all this? Unfortunately, i've got a big effort ahead in sourcing heads, oil pan, and all the other odds and ends. If anyone has a blown block i'd be interested in buying your parts.

I'm thinking 3.5L NA w/ ITBs?. Happy to hear your thoughts!

 

[SFDreamer]

I'm thinking 3.5L NA w/ ITBs?. Happy to hear your thoughts!

I am thinking you're a smart man . I think something like that would make you real happy!

 

[Ponyboy]

I wholeheartedly encourage you to go the ITB route. It takes the NSX into a whole other level especially on a bigger engine.

It's how the NSX should have come from the factory.

 

[RYU]

I agree with both of you guys. An NA ITB build has been something on my NSX bucket list. I never gave it any serious thought until I acquired all these extra parts that puts me one step closer to the build.

Shawn, i'm glad you chimed in. Can you help me understand some of the basics involved? When you did your stroker build did you source an entirely new donor motor or did you build up your original block? I have a lot of homework ahead of me!

 

[MrHugo]

3.4 or 3.5L NA ITB. That's what I would do and will do one day for my car.

Sell your SuperCharger and get on to this project.

 

[clr1024]

Why not a 3.8L stroked N/A motor?

 

[Ponyboy]

Shawn, i'm glad you chimed in. Can you help me understand some of the basics involved? When you did your stroker build did you source an entirely new donor motor or did you build up your original block? I have a lot of homework ahead of me!

I starved my engine of oil in a corner at my local track so it was busted at the outset. You're in a good area - either Jon Martin can help you should you choose to source everything yourself or an easy drive to Chris at Science of Speed or Shad up north.

What kind of basics do you want to know? The build parts are all out there online. The big choices you'll have to consider are if the car will be a track or street car. That determines compression, octane, where you want your power curve, etc. That said, those previously mentioned guys have forgotten more about the engine building than I know. I know Chris and Shad personally and both are supremely qualified to assist.

The only thing I would have changed in my build is to install the billet main caps. If you have any specific questions, just let me know - I'm happy to help.

 

[NSX167]

Why not a 3.8L stroked N/A motor?

eggshell thin cylinder wall I guessed.

 

[RYU]

Thanks again Shawn. I'll have to pay Jon Martin a visit soon.

I suppose my goal is to use as much of the existing parts. It's my understanding that the max displacement on a 3.0L block with the stock crank was 3.5L. I'll review SOS's 3.6L parts list when I get home but i've also read their "Stroker FAQ". Very helpful.

I'm curious of your head work.. I'm not sure what stroker folks are doing here at the moment.

As far for my build/driving intentions, I would really like to build a motor in the spirit of what could have been at home in an NSX-R if that makes any sense. This means not something which can overpower the chassis but will be free-revving and around <350whp.

 

[RYU]

eggshell thin cylinder wall I guessed.

Pretty much among other things. I would like a bit more safety margin though a friend locally is quite happy with his JM 3.8L.

 

[scorp965]

Definitely a good purchase, what's interesting is he's been trying to sell these parts for over a year, with no takers.

I came close to buying them a few months ago, but it turns out it's a snap-ring tranny, and I had no use for the rest of it. The seller also had these parts on prime, perhaps 5-6 years ago.

 

[Ponyboy]

As far for my build/driving intentions, I would really like to build a motor in the spirit of what could have been at home in an NSX-R if that makes any sense. This means not something which can overpower the chassis but will be free-revving and around <350whp.

This was exactly my intention. But what I got was a near race car (I'm not complaining except for the lack of A/C). Though I'm still waiting on SOS for the finished airbox, I wanted to keep my engine bay as OE looking as possible. We're keeping the stock airbox and adding lenghth of according tubing that connects to the CF airbox.

You may want to take a look at my 3.6L Build gallery here on Prime when you get a chance.

 

[Honcho]

I'm drooling over this, dude. Amazing. If using existing parts is your goal (and one I would share), you can go 3.3L keeping your crank and rods stock. This is using the biggest piston available (95mm) and sleeves. Another option is offset grinding the crank to get you some extra stroke (maybe 2 to 5 mm). This way you get to use your existing crank but you do pick up a little torque/displacement. This practice is common in muscle car applications, so I see no reason why you can't do it on a C30A. The trick is finding a good machine shop, but in southern cal, I doubt that will be hard. You could probably get to 3.5L this way without buying a new stroker crank.

I think you should build a 3.5L ITB ripper! Make it all stealth to look OEM like Shawn is doing. Tune the ECU to make it streetable. I love the idea of what the NSX-R should have had from the factory.

So:

Sleeve Block
95mm high-comp pistons
Offest Grind Crankshaft
MLS head gaskets
ARP studs
CT Adj. Cam Gears
SOS ITB
AEM Series 2

Go for it!

 

[RYU]

Definitely a good purchase, what's interesting is he's been trying to sell these parts for over a year, with no takers.

I came close to buying them a few months ago, but it turns out it's a snap-ring tranny, and I had no use for the rest of it. The seller also had these parts on prime, perhaps 5-6 years ago.

Ok, in a strange way this makes me feel better. For the price he gave all this to me for, I felt like I stole it from the poor guy!

You may want to take a look at my 3.6L Build gallery here on Prime when you get a chance.

I just skimmed over your build thread. It's all coming back to me now. Just need to come to some conclusions on the head work. I've yet to source those bad boys (will take a while i'm sure).

I'm drooling over this, dude. Amazing. If using existing parts is your goal (and one I would share), you can go 3.3L keeping your crank and rods stock. This is using the biggest piston available (95mm) and sleeves. Another option is offset grinding the crank to get you some extra stroke (maybe 2 to 5 mm). This way you get to use your existing crank but you do pick up a little torque/displacement. This practice is common in muscle car applications, so I see no reason why you can't do it on a C30A. The trick is finding a good machine shop, but in southern cal, I doubt that will be hard. You could probably get to 3.5L this way without buying a new stroker crank.

I think you should build a 3.5L ITB ripper! Make it all stealth to look OEM like Shawn is doing. Tune the ECU to make it streetable. I love the idea of what the NSX-R should have had from the factory.

So:

Sleeve Block
95mm high-comp pistons
Offest Grind Crankshaft
MLS head gaskets
ARP studs
CT Adj. Cam Gears
SOS ITB
AEM Series 2

Go for it!

Got that gear tooth count for me yet? lol Dude... i'm nipping at the bud at even the slightest possibility I have JDM gears here but chances are I do not so it's probably better if you take your sweet time haha

Really interesting note about the offset grind. That didn't even come to mind. I have 2 extra cranks now so I suppose I can take the risk (never thought I'd ever say that!). This might also force me to scrap my CTSC F/IC project and just get the EMS S2 from the get go. It will give me a chance to be more flexible if in case this build does come to fruition.

The biggest question mark for me is how to complete what I have so far into a proper working engine. Seems like I need to find myself a blown donor motor to keep the costs reasonable.

 

[ken sampson]

I have 5 rods and a spare stock crank if you need them send me a PM.
Ken

 

[Valhalla]

To answer your original question, YES. Yes you should do this build. With all the work I've put into my engine, I SHOULD have done a Stroker build. But then hindsight always is 20/20.

 

[RYU]

Definitely a good purchase, what's interesting is he's been trying to sell these parts for over a year, with no takers.

I came close to buying them a few months ago, but it turns out it's a snap-ring tranny, and I had no use for the rest of it. The seller also had these parts on prime, perhaps 5-6 years ago.

btw.. did you end up selling your stock rods? I remember you had a few for sale once upon a time.

I have 5 rods and a spare stock crank if you need them send me a PM.
Ken

Good to know. Thanks!

 

[Honcho]

Got that gear tooth count for me yet? lol Dude... i'm nipping at the bud at even the slightest possibility I have JDM gears here but chances are I do not so it's probably better if you take your sweet time haha

Not to give you false hope, but did you ever consider that maybe your extra gear stacks were the USDM ones removed to replace with JDM? In other words, that trans may have JDM gears in it...

Really interesting note about the offset grind. That didn't even come to mind. I have 2 extra cranks now so I suppose I can take the risk (never thought I'd ever say that!). This might also force me to scrap my CTSC F/IC project and just get the EMS S2 from the get go. It will give me a chance to be more flexible if in case this build does come to fruition.

It's really not that much of a risk. The key is finding a competent machinist who can measure/evaluate the crank and advise how much material may be safely removed for your application. Being in southern california, you have local access to some of the best race engine shops in the world. An offset grind job can be as little as $250 compared to almost $10,000 for a custom fabbed crankshaft. True, you won't be able to get the same amount of stroke as a dedicated aftermarket piece (like SOS), but you can still increase displacement for a low cost. I just think this is a way to work with what you've got as opposed to spending $$$ on new pieces.

The biggest question mark for me is how to complete what I have so far into a proper working engine. Seems like I need to find myself a blown donor motor to keep the costs reasonable.

That's your best bet. That would leave your "big ticket items" as only:

Pistons/Sleeves
ITB
CT Cam Gears
AEM Series 2

 

[RYU]

Not to give you false hope, but did you ever consider that maybe your extra gear stacks were the USDM ones removed to replace with JDM? In other words, that trans may have JDM gears in it...



It's really not that much of a risk. The key is finding a competent machinist who can measure/evaluate the crank and advise how much material may be safely removed for your application. Being in southern california, you have local access to some of the best race engine shops in the world. An offset grind job can be as little as $250 compared to almost $10,000 for a custom fabbed crankshaft. True, you won't be able to get the same amount of stroke as a dedicated aftermarket piece (like SOS), but you can still increase displacement for a low cost. I just think this is a way to work with what you've got as opposed to spending $$$ on new pieces.



That's your best bet. That would leave your "big ticket items" as only:

Pistons/Sleeves
ITB
CT Cam Gears
AEM Series 2

After yesterday's disappointment I might be done playing the JDM lottery. You bring up an interesting point though (damn you...lol)

Will definitely start the search for a speed shop locally. I may end up starting with Jon Martin and/or Nick @ Applied Motorsports and go from there. There are many Import and Domestic shops that have never worked on an NSX that may be worth looking into as you recommend.

Are the Cam Gears necessary? There are a few threads documenting stroker builds but they tend to get a bit vague when describing head work.

 

[Ponyboy]

I would definitely do the CT cam gears. And, blasphemy I know, but you may find the stock gearing more ideal considering the new hp/tq figures with the Stroked/ITB engine.

 

[RYU]

I would definitely do the CT cam gears. And, blasphemy I know, but you may find the stock gearing more ideal considering the new hp/tq figures with the Stroked/ITB engine.

CT cam gears. Check!

On the topic of cams... are most stroker guys satisfied with the OEM cams?

 

[greenberet]

Regarding offset grinding: the pairs of rod journals in NSX crankshafts are offset enough to allow for an even firing order despite the cylinders being arranged in a 90° V. As a result, the journals do not overlap 100% as they do in a typical V8 engine. If you offset grind the crankshaft, not only will you end up with smaller rod journals, you’ll have less material overlapping between the rod journal pairs, making the crankshaft weaker and more prone to twisting. If you discuss offset grinding with a local machine shop, I’d ask:

1. whether a further reduction in overlap is a concern
2. what’s the minimum rod journal diameter he’d recommend given the horsepower each rod is going to transmit

 

[sparky]

RYU ... the "stock gear set" shown in your first post is the countershaft assembly (page 13.29 of workshop manual).

I'd really like to now it's weight, if you could through it on some (good) scales please.

As to whether its USDM or not, I suggest count the teeth on the 2nd gear cog (the largest one), then someone will chime in with teeth count for USDM and JDM.

And if anyone knows the weight of the mainshaft assembly and differential moving parts please let me know...

 

[sparky]

Regarding offset grinding: the pairs of rod journals in NSX crankshafts are offset enough to allow for an even firing order despite the cylinders being arranged in a 90° V. As a result, the journals do not overlap 100%

I was trying to figure out what this all means greenberet. I found a diagram of crank in the service manual (page 7-11) which seems to depict what you describe. But how does this work? With 6 pistons and a four stroke I assumed firing every 120 degrees, but I can't see those little rod journal offsets bridging the gap from 90 to 120 degrees. Is that the idea?

 

[RYU]

I'd really like to now it's weight, if you could through it on some (good) scales please.

I won't be able to weigh it anytime soon since i'm a bit apprehensive about disassembling the setup. I can weigh it with all the gears in place if you'd like though my scale is only as accurate to the nearest 0.5lb.