Motor for an Ultima

[j-rho]

Have asked on different forums, thought I'd try here too.

In addition to long life, low maintenance, simple, high hp on pump gas (gee, I'm starting to sound demanding here! ) I also need to limit torque to keep the gearbox from exploding.

Has anyone built a wildly oversquare BBC? Been playing with Desktop Dyno (which I know is questionable) - a 4.5" bore, 3" stroke 10.5:1 BBC, a cam with very very mild lift and ramps, super high-flowing heads and optimized tunnel-ram intake, purports to do over 800hp at 7500rpm, where I'd set the rev limit, with only a little time a little over 600ft-lbs.

I know an approach like this leaves a *ton* of midrange on the table, but this is a super-light car with 6 closely-spaced gears, whose main performance calling is the road course. That torque would just be limited by traction control in low gears, or risk breaking stuff in higher gears.

Would a setup like the above be reliable, able to spend a lot of time in the 6500-7500 range without quickly wearing itself out?

A smaller-bore engine could probably produce similar output but to do so wouldn't it need more aggressive cam lift and ramps, or more revs, reducing longevity?

[Dave Koehler]

I have run 3.5" x 4.250 and 4.375.
They are a beast when spun up and also make good sense for a street car.
You will still have more bottom end and mid range than most street machines can handle.

[englertracing]

Psssttt do a ford.
BBC ports are sort of um retarded....
Kasse boss 9 heads....
I've got an unfinished can am IR manifold 494 style thats looking for a home...

[j-c-c]

The OP's project is really cool. I can't imagine how though 800hp? in that car can be put to the ground on the street.
On a motor, can't see a flat torque curve requirement really needed, yes traction control a must, but then that kills a lot of the fun.
Being a mopar guy, The V10 is enticing, but with all the moving parts to get the car dialed in, don't try and re-invent the wheel and just add to your headaches sorting another big unknown out, drop in a suitable LS in and focus on driving and having a blast.

[j-rho]

The power won’t be usable on the street of course, track only. Even there, probably not fully usable until at least third gear. But once a bit past 100mph the aero bits really start to work, drag goes way up, and once above 130 or so the really fast cars start to distinguish themselves. Below 100, will be counting on motorsports grade traction control to help me out.

My last Viper was making about 700 crank but with the ACR aero package was only so-so from 120-150, and fell on its face at 150 (shift to fifth). At the end of the long straights I was giving up 25mph to the McLaren 720s and Porsche GT2RS, despite matching or exceeding their straight entry speed. The Viper was 1000lbs. heavier than the Ultima will be, but at higher speeds it’s more about drag.

When I mention flat torque curve, I should have said at track RPM, say from 4K to redline. Any v8 will have sufficient torque to get the lightweight car rolling.

[j-rho]

Psssttt do a ford.
BBC ports are sort of um retarded....
Kasse boss 9 heads....
I've got an unfinished can am IR manifold 494 style thats looking for a home...

Ok ok, just for you, I’ll email them tomorrow. Have about 6 different conversations started, still looking for a builder excited to be part of the project. Have nothing against Ford, just need to make sure I can get it dry dumped and mated to my transmission.

[j-c-c]

The power won’t be usable on the street of course, track only. Even there, probably not fully usable until at least third gear. But once a bit past 100mph the aero bits really start to work, drag goes way up, and once above 130 or so the really fast cars start to distinguish themselves. Below 100, will be counting on motorsports grade traction control to help me out.

My last Viper was making about 700 crank but with the ACR aero package was only so-so from 120-150, and fell on its face at 150 (shift to fifth). At the end of the long straights I was giving up 25mph to the McLaren 720s and Porsche GT2RS, despite matching or exceeding their straight entry speed. The Viper was 1000lbs. heavier than the Ultima will be, but at higher speeds it’s more about drag.

When I mention flat torque curve, I should have said at track RPM, say from 4K to redline. Any v8 will have sufficient torque to get the lightweight car rolling.

I think you made the case in your above response, a flat torque from 4K to max will hardly serve your purpose on track, in that you have a light car, drag in your case is now aero DF dependent on cars speed, and you need the Hp ( not torque) for end of straight passing advantages, if I understand your needs correctly.

[j-rho]

I don’t run wheel-to-wheel and won’t in this car. The flat torque curve is ideal for road course use because it means the car will behave predictably when you go to the power at corner exit.

Was thinking by using DBW, can artificially limit midrange torque with the ECU. This would allow for a motor with traditional stroke and more theoretical midrange, de-tuned to aid in transmission life. Can maybe let it go full rip in fifth and sixth if I ever do a top speed run.

[dannobee]

Has anyone built a wildly oversquare BBC? Been playing with Desktop Dyno (which I know is questionable) - a 4.5" bore, 3" stroke 10.5:1 BBC, a cam with very very mild lift and ramps, super high-flowing heads and optimized tunnel-ram intake, purports to do over 800hp at 7500rpm, where I'd set the rev limit, with only a little time a little over 600ft-lbs.

Pretty sure a 381 cu in engine won't make that kind of torque with a mild cam. The best you're gonna see in a streetable engine of that size will be is about 530 and even that will take a bigger cam. And even that is gonna need the stars aligning and the wind at its back on a freezing cold day. Big heads and tiny cams don't match very well.

Which tranny will you be using with this? A Mendeola or Albin? I hope not a G50. One of the Porsche trannies with a 9" ring gear might live for awhile, but it's still marginal at 500lb ft torque. I have a GT2 with a G96/88, and Porsche put the cooler, pump and spray bar in those trannies just to make them live on the track. If it's mid engine, you can't even use those because IIRC, the tranny is mounted upside down.

[j-rho]

Has anyone built a wildly oversquare BBC? Been playing with Desktop Dyno (which I know is questionable) - a 4.5" bore, 3" stroke 10.5:1 BBC, a cam with very very mild lift and ramps, super high-flowing heads and optimized tunnel-ram intake, purports to do over 800hp at 7500rpm, where I'd set the rev limit, with only a little time a little over 600ft-lbs.

Pretty sure a 381 cu in engine won't make that kind of torque with a mild cam. The best you're gonna see in a streetable engine of that size will be is about 530 and even that will take a bigger cam. And even that is gonna need the stars aligning and the wind at its back on a freezing cold day. Big heads and tiny cams don't match very well.

Which tranny will you be using with this? A Mendeola or Albin? I hope not a G50. One of the Porsche trannies with a 9" ring gear might live for awhile, but it's still marginal at 500lb ft torque. I have a GT2 with a G96/88, and Porsche put the cooler, pump and spray bar in those trannies just to make them live on the track. If it's mid engine, you can't even use those because IIRC, the tranny is mounted upside down.

Planning on a g96/50, very similar to your GT2 box. With a few minor mods I’ve been assured to 600ft-lbs., though less would be better. I only ever plan to use street tires so it probably won’t hook up until third gear anyway. Also plan to have it set up for an external cooler. Several modern Ultima guys with 650-720 horse LSes using them without issue. Well, they’ve been wiping out the thrust bearings and then their whole motors using Porsche clutches, but no issues with the transmissions

I probably need to stop trusting what Desktop Dyno is telling me Now that I’ve considered the ECU torque limiting, a normal-stroke BBC (or other big cube motor) might be just fine, still want it to live a long time revving to 7k though.

[englertracing]

https://youtu.be/iEgojxvUcLM
Here's a 4.5 x 3.75 big block Chevy
Should make more power with a proper intake and... if you did one that starts with an F where all the ports point in a sensible direction (unlike a BBC with 4 looking okay and 4 bad ports) could make more yet...

[dfarr67]

https://youtu.be/iEgojxvUcLM
Here's a 4.5 x 3.75 big block Chevy
Should make more power with a proper intake and... if you did one that starts with an F where all the ports point in a sensible direction (unlike a BBC with 4 looking okay and 4 bad ports) could make more yet...

OK we get it- thousands of competitive BBC's out there racing every year- too bad the owners haven't heard how much of a pos they really are and the better choices available.

[englertracing]

https://youtu.be/iEgojxvUcLM
Here's a 4.5 x 3.75 big block Chevy
Should make more power with a proper intake and... if you did one that starts with an F where all the ports point in a sensible direction (unlike a BBC with 4 looking okay and 4 bad ports) could make more yet...

OK we get it- thousands of competitive BBC's out there racing every year- too bad the owners haven't heard how much of a pos they really are and the better choices available.

the faster ones have heads that make sense

here is a symmetrical BBC head.

I would imagine it may limit intake manifold selection.

all im saying is, Power is made by ports and cams....
If your going to spend 15-20-30-50K why on earth would you want to start with a crippled design unless forced at gunpoint or by rules.

[dfarr67]

For $50k I don't think his budget includes poor design. We're 60 years out from any base platforms anyway anything worth keeping is rotating assembly and that probably is an improved aftermarket purchase. For the record I suggested a Hellcat crate- almost there with current platform and oem tune. I would however agree that the shortest most reliable and less expensive option from A to B whatever that may be.

[ptuomov]

So how about LS7 with a cam and custom exhaust for that about 750 hp?