I remember this post from a while back, I'm more curious about the newer developments such as the CNC head getting me there.

I am right there with you.

I'll be following your results of the CNC heads on OE bottom ends and what gains you'll be seeing as well. Do you think that would be a viable option for that power range without forking out for a built motor?

 

That's exactly what I was thinking.

Drop a whammy head on a low RPM build, or even OE, see what it looks like.

Seems like the head wouldn't hurt durability, at least.

But if you're not going OEM bottom end, long rods should decrease side loads by a bit, and balancing might be of assistance... curious how much or if 85.5 bore hurts anything.

For the street, even with my quiet exhaust, 4.3 and six speed, I don't like remaining steady speed above 4k, and the powerband is really 3500 and up. This build is a completely different direction, but the durability and intake manifold, possibly the head are very interesting for a more lasting engine instead of an all out build.

 

Why 12.0:1, is that the limit for E85?

 

I don't want to thread drift anymore but I am glad I am not alone in my thinking.

My understanding if the CNC head is combined with OE cams or BP5A cams you won't have any excess wear on the engine. I just want a very long lasting engine for my purposes.

I am excited to see the platform to continue to develop, 200WHP with ITBs or even a STB is a salivating thought.

 

Nope. I just have a set already gathering dust in the shop.

 

+1. The biggest issue with a long-rod motor for an engine that's going to live much of its life under 8000rpm IMO is that the long hang times on the piston that lower the acceleration times also decrease midrange torque. Dropping the piston at OEM speeds will draw air into the chamber better at low-midrange RPM, where air velocity is less of a factor. Rev the motor to the stratosphere and the air velocity overcomes that issue. At the end of the day, as much as people like the idea of revving the nuts off the engine, the BP was not built to rev, and doing a longrod, lifting the wrist pin into the oil rings and incurring all that extra cost just isn't worth it in the vast majority of naturally aspirated application.

The motor in Rover is what Emilio described. 85.5mm 11:1 Supertechs, 130mm Carrillo Pro-As, our own cylinder head, ARP heads/mains, ACL bearings, BE oil pump, ST +1 valves, double springs, SUB lifters, thermal coatings, etc. Basically every race trick we know, but stock cams for PTE. That motor will produce ~145wtq and close to 170whp on pump gas with stock cams. Add a set of small cams and the power will go up without hurting torque much at all - the nice part about having springs and SUBs is that you can add a lot of curtain area without much additional overlap. That means power gains with no loss in low-end torque. Add big cams and you can see big power gains, at the behest of a bunch of low-end torque, if that's what you want/need to make the motor work for you.

Emilio or I can build a cylinder head for a stock motor, but you'll end up with a ~9.5:1 1839cc motor, not a 1951cc 10.5:1 motor. The compression drop comes from the chamber work and deshrouding - there are flow gains to be had there, but you have to increase chamber size to get them. We compensate for that with a higher-compression piston, even though we don't necessarily want 11:1 compression at the end. There are still gains to be had with a head swap, but that displacement/compression difference makes a substantial difference in the torque and power numbers, and takes away your ability to rev the motor much past the factory redline without hurting the bearings or the rods. The cost of the cylinder head is still going to be close to $3k with SUBs. For a street car where you won't ever overrev it and have no delusions about spinning the thing to 8k on the way to work each morning, just the head will work for you, but especially for a track motor, it's worth it to get the whole longblock.

It's worth mentioning that after 100hrs, if you've been nice to the motor (no sustained 8000+rpm blasts, no overheating, good oil, good OCIs, vigilant oil analysis), you can have us rebuild it for under $1500 with new bearings and rings and go right back to racing.

 

That is an incredibly informative post, thanks. I think I will keep that in mind when I get to that point of head swapping or throwing a built engine in.

 

That's awesome, thank you for the post.

One thing that I'd like to ask, I think the durability people here are dual using their cars... instead of 100 hours, would that hypothetical engine do 50 hours on track and 100,000 miles on the road? Last 150k on the road like a stock engine?

>=145 wtq from 3500-7000 would be pretty much ideal for this application. On the road, high revs is just like waiting for a turbo without the payoff, since you start so much lower. Not the biggest fan.

 

Hours at race rpm.
Hours at race rpm are at least 10x more wear than hours at street rpm/load/heat.

So 80mph lap average x 100 hrs = 8000miles
1000hrs at say 60mph might be 60,000miles

 

Wow, I did not know that, even with 'race' components, you do not have the ability to rev the motor past the factory redline. Unless i am misreading this. What is the cause, the heavier high compression piston?

"pump gas" = E85 still, right? my brain still reads 'pump gas' as 92, I've only seen one E85 station in my life.

What about a dry sump oiling system? Have you (sav/emilio) done any testing with that? If so, which brand pump?

Awesome info here, I'd love to see this 200 WHEEL hp BP done!

 

Pump gas = 91, 92 or 93 octane gasoline or E10 dependig on what state you are in. E85 is E85.

Dry sumps are expensive and only relevant to racing engines in the context of BP engines. I can do a dry sump, make 10whp more than no one in the community will ever be able to duplicate. Dozens of people have duplicated the "rental" formula. The next step is these 1952cc 10.5:1 gas or 12.0:1 E85 builds that are easily duplicable, affordable and meet the goals of many.

 

Misread/confusion, sorry. What I meant was that a race head with a factory bottom end can't exceed ~7400rpm or so on a regular basis. Past that, the stock rods begin to fatigue. With a built bottom end, you can spin the entire motor safely to ~8000rpm, with short-burst overrev to 8400rpm. (to avoid a pair of shifts, i.e. stretch 3rd instead of shifting to 4th, then right back to 3rd for the next corner). No way a stock rod will deal with that, which is why we swap them for Carrillo Pro-As which weigh a lot less than a stock rod and don't even bat an eye at 8500rpm.

When I say "safely to 8000rpm", I don't intend to insinuate that continually revving it to 8000rpm isn't going to shorten the life expectancy of the motor. I mean that the components won't catastrophically fail if you rev them to 8000rpm (whereas stock rods, stock VVT valvetrain, and stock dampers/throttle bodies will). 50 hours at 8000rpm is hard on a BP no matter what's inside it - expect to shorten the life of the valves and bearings specifically if you insist on constantly revving the engine that high. Another one of the benefits of having a built bottom end is the extra displacement, which fattens up the torque curve so you don't have to rev the snot out of the thing to go fast on track.

It's godawful expensive. No doubt there's power to be had there, but that's not a reasonable thing to expect a street guy to do, and a lot of race classes don't allow it or penalize it heavily. The factory Miata system copes well with high G-forces and the tiny bit of braking starvation that a well-driven car on Hoosier A6/R6s isn't going to harm the motor.

 

1 hour of race use is the equivalent of ~400 full-throttle highway onramp pulls (assuming ~9 seconds WOT to highway speeds). If you autocross, 1 hour of abuse is the equivalent of 40-60 runs.

Assuming you drive like a 17 year old whose parents pay their speeding tickets, let's assume you do 5 WOT pulls every day, 5 days a week, and 10 a day on the weekends. That's about 7 minutes a week of WOT. In a year, they would put just under 6 "race" hours on the engine, or about what one of our cars sees in a normal HPDE weekend.

Use that to calibrate our "race hour" wear numbers to your application

 

/Awesome./ Now those are numbers I can understand. So yeah, about six hours a year... but with a clean driving record. I never speed. I just always get to cruising quickly.

Subbed for awesomeness applicable to weak 7400rpm build.

 

You might be surprised at how much go fast can be had with a 6800rpm shift point.

Andrew and myself have both built lap record destroying motors that almost never see 7500rpm. Each of those could safely be buzzed to 8500 now and then without issue. Displacement, a little compression, BP6D head, bitchin ports, chambers and tuner who understands cam timing. 150 lbs/ft @ 3800rpm?

High peak power means spinning it high and big cams. After several experiments we settled on the fact that the best low rpm torque with the BP6D comes with stock cams.

IOW, the performance envelope and longevity you seek are a piece of cake. BTDT.

 

Hate threadjacking you further, sorry, but is there an optimal IM setup for that application yet, or will you be producing something better? Is there a general cam timing for the stock exhaust cam with an adjustable gear other than it depends (starting point)?

It seems like at least one other person than me is interested in going with that low rev 949/TSE recipe if they knew it.

 

That's essentially the recipe I'm going to go with for my TTC build (VVT engine to follow next winter while 2014 season will be used to get used to 949 BGK i'm about to install on the car).

Get the NA as light as possible, which lowers my whp limit, which means I don't have to build as crazy a motor.

My plan is essentially, VVT engine + I/H/E + Standalone + take the stock head and deck it 0.060" and tune for E85.

I'll apologize for further threadjack, but can't wait to see where this build ends up.

 

USDM NB1 manifold with the VICS crossover point at about 3000 rpm. cams have to be tuned on the dyno. That's like sending you an ECU map and saying here this is perfect for your particular use. It will never happen. Gotta tune on a dyno.

What I am getting at is the motor your dream about is just a phone call away. We have already done it. You just need to find someone who can tune.

 

I can understand that build, but I'll definitely be going for a built engine in case of overrev. SUB/rods = happy overreved 7400 rpm engine.

Phone call away, definitely support those who share data.

Edit: As a wanna be engineer, I just really don't like the idea of putting a high failure cost component through literally millions of cycles right at the edge of where it begins to fail. It's cheap to replace a stock engine, waste the money for the track day, get towed somehow back, downtime, finding a hopefully good engine with no issues then having to find the time to do yet more work. It might not be cheap to put a rod through the block and spin, start an oil fire or put down an oil slick that takes out someone behind you. Just something I worry about.

 

The bearings and rings are the wear items on these lower hour high hp NA motors? I would have thought for sure the issues would have been in the head with the valves separating or the valve seats being smashed into submission. But I may have been eyeballing significantly more aggressive cams than being considered here.

What can we do to decrease this bearing wear? Higher oil pressure is the only thing I can think of since once the engine is running and up to temp there should be zero wear on the bearings unless the oil film is insufficient. Though there are coatings for bearings that make them more tolerant to low oil conditions. But swain explained them to me as basically insurance for loosing oil pressure in a race. If you loose oil pressure on an uncoated bearing its toast, even if you shut the car down right when the oil light comes on. With the coating if you shut the car off when the oil light comes on the bearing should be ok. Anything else gets much more involved, like machining the crank and getting custom rods with wider big ends for wider bearings.