Big block road race build 572

[Protech Racing]

The all alloy BBC is a little under 550. I was comparing to iron BBC to alloy bits of SB2.

It looks like a limited tire rule class and tons of fun.
Of course- The best lap times are the result of applied power/torque . The more pedal that you can keep down= the faster the lap. Having peeky torque or abrupt bumps in the torque curve will spin the tires and force a lift . Tire management comes into play also. Roasted tires can get greasy and not return grip for a complete session.

[Outlaw383]

If you are traction limited you might want to look at a wider lobe sep cam. Talk to Mike Jones on here or Russ Yoder at Erson Cams either will be able to grind you what you need.

Chris

[dannobee]

Are you racing for money? Or just a trophy and bragging rights? If it's just a trophy, well then...

https://moretraction.com/

[hoffman900]

Out of curiosity, how much do your lap times vary over the course of a race? Do your lap times fall off at the end? How about your competitors?

It seems in a class like this, saving some power, if they can fix how the tires fall off, could be worth more over a race distance. That said, I know you're going to do what you want, so I agree with softening the torque curve a bit.

A family friend ran a 289 Cobra in SCCA BP competition in 1969-1970. He set several lap records, 2x Div Champ, finished 2nd at the Nat'l Championship to a new 1969 Corvette. His lap records were often faster than the big-block Cobras and Corvettes at the time. Part of that is driver, but a big part was the small block cars just handled better. Photos here: http://siouxautomobiles.com/csx2009

In vintage racing here, the big block cars are only marginally faster despite having several hundred HP more.

Good example here. Vintage Trans Am 1969 Camaro. The two Corvettes in front are 427ci cars (to the 302 in the Camaro):


Boss 302 just behind the camera car:


Bill-C on here is involved with those engines from that shop.

[richiev88]

Yes tyres do go away towards the end of a race, best laps are usually lap 3/4 for most people.
In my class I can run any tyre I like, however there are not many options that you can get good cycles out of and are not too expensive.
Most of us choose to run the control tyre of our sister class, which is a hankook c51 ventus, max size available 275/40r17.
Couple of our guys run big dunlop sports sedan size tyres which are full slick, but don't last many heat cycles ( 4 or 5)and are 3 times the price.
Most of our races are only 6 to 10 laps, with practice and qually, and 4 races per race weekend, its nice to get a weekend out of a set of tyres.
The hankooks last a weekend no problem, but they are a little small most agree, but everyone seems to work around this.
Nope no money to be won, racing for a thirst!
I will get another cam designed, I totally agree with everyone on that. Shorter stroke would be nice, however we need to see how the Covid thing plays out, It will impact on racing budgets.( we too are in lockdown, not sure for how long, has big impact on income)
I hope with some short shifting and a long travel throttle pedal, it will be drivable .......
Drivetrain should all be ok, I've got full floating rear end, 31 spline axles, nascar prepared third member, G force 4 speed, Tilton clutch.

[hoffman900]

With a carburetor, you don't have much ability to control the pedal, but an old motorcycle trick is to change the throttle ratio. So with throttle cam designs, you can make it progressive, digressive, on / off, etc. Look at your data and see if this is something that can help you.

Much easier to do with drive by wire, but obviously that is out of the question.

6 lap sessions are short, so I see what you mean there. The full slicks will be worth a lot in lap time (if they're anything like our cantilever or radial slicks here over the DOT-R tires (like the Hankooks)). Can you guys get Hoosier R7's there? They are "DOT-R" tires, but will run circles around stuff like the Hankooks. They won't last too long though.

[richiev88]

Out of curiosity, how much do your lap times vary over the course of a race? Do your lap times fall off at the end? How about your competitors?

It seems in a class like this, saving some power, if they can fix how the tires fall off, could be worth more over a race distance. That said, I know you're going to do what you want, so I agree with softening the torque curve a bit.

A family friend ran a 289 Cobra in SCCA BP competition in 1969-1970. He set several lap records, 2x Div Champ, finished 2nd at the Nat'l Championship to a new 1969 Corvette. His lap records were often faster than the big-block Cobras and Corvettes at the time. Part of that is driver, but a big part was the small block cars just handled better. Photos here: http://siouxautomobiles.com/csx2009

In vintage racing here, the big block cars are only marginally faster despite having several hundred HP more.

Good example here. Vintage Trans Am 1969 Camaro. The two Corvettes in front are 427ci cars (to the 302 in the Camaro):


Boss 302 just behind the camera car:


Bill-C on here is involved with those engines from that shop.

Yes great historic racing, is this your car ?
Those cars in the video run bias ply tires ? Ive run on bias plys, the car do move around on those tires a lot. We do have a lot more grip than that type of tyre. The nascar engines do work well for our class because traction is limited, but are high maintenance racing engines, a lot of this decision for me changing from a SBC to a BBC is engine life. Most seem to get 10-15 hours out of a SB2 or SBC, we are hoping for 50 hrs between strip down and re fresh.
The HP gain is not the major goal, though it will be nice not to loose positions made up in the corners.

[richiev88]

With a carburetor, you don't have much ability to control the pedal, but an old motorcycle trick is to change the throttle ratio. So with throttle cam designs, you can make it progressive, digressive, on / off, etc. Look at your data and see if this is something that can help you.

Much easier to do with drive by wire, but obviously that is out of the question.

6 lap sessions are short, so I see what you mean there. The full slicks will be worth a lot in lap time (if they're anything like our cantilever or radial slicks here over the DOT-R tires (like the Hankooks)). Can you guys get Hoosier R7's there? They are "DOT-R" tires, but will run circles around stuff like the Hankooks. They won't last too long though.

Yes, onto that, will be changing the cam on the throttle shaft, can also change the pedal ratio on the pedal box.
I ran the R7 in my first season although on a 15inch rim, times seem to be very similar to the C51, the c71 soft is about a half to a second faster.
Unfortunately cost is always a issue, tyres here are expensive compared to you guys, the Hoosier r7 are around $600ea, hankook are $350 ea, dunlop slicks I believe are around $7-800ea......

[hoffman900]

Out of curiosity, how much do your lap times vary over the course of a race? Do your lap times fall off at the end? How about your competitors?

It seems in a class like this, saving some power, if they can fix how the tires fall off, could be worth more over a race distance. That said, I know you're going to do what you want, so I agree with softening the torque curve a bit.

A family friend ran a 289 Cobra in SCCA BP competition in 1969-1970. He set several lap records, 2x Div Champ, finished 2nd at the Nat'l Championship to a new 1969 Corvette. His lap records were often faster than the big-block Cobras and Corvettes at the time. Part of that is driver, but a big part was the small block cars just handled better. Photos here: http://siouxautomobiles.com/csx2009

In vintage racing here, the big block cars are only marginally faster despite having several hundred HP more.

Good example here. Vintage Trans Am 1969 Camaro. The two Corvettes in front are 427ci cars (to the 302 in the Camaro):


Boss 302 just behind the camera car:


Bill-C on here is involved with those engines from that shop.

Yes great historic racing, is this your car ?
Those cars in the video run bias ply tires ? Ive run on bias plys, the car do move around on those tires a lot. We do have a lot more grip than that type of tyre. The nascar engines do work well for our class because traction is limited, but are high maintenance racing engines, a lot of this decision for me changing from a SBC to a BBC is engine life. Most seem to get 10-15 hours out of a SB2 or SBC, we are hoping for 50 hrs between strip down and re fresh.
The HP gain is not the major goal, though it will be nice not to loose positions made up in the corners.

Not my car, we raced a Triumph TR4 in a slower class. This is us:
(fast lap starts at 5:20)
At this track / weekend, the TR4 and the 2nd place Super 7 were the fastest production cars there (faster than the medium bore and big bore cars). Drivers were a big part of that and their ability to carry momentum (listen to how much the driver is on the throttle). Video from the trailing Super 7: https://onedrive.live.com/?cid=8099505b ... HGyBkOegXA

Yes, bias ply per rules. Suspensions are basically stock type, with no relocating points, but things like shocks, spring rates, sway bars are free. So you see things like modern Penske shocks, etc. on the front running cars. We actually found bias ply tires to be faster on vintage stick axle cars. They don't need as much camber, which you cannot get with a solid rear axle (at least without aftermarket (not allowed by rules)) and the front suspensions don't have the camber gain you need with radials (cannot change the geometry).

Can you just run the SB2 at lower RPM? Bill-C on here has mentioned the Spintron work they have done on the big block Chevy's in that series, and how they would lose valvetrain control after some time. The geometry in a SB2 should be better and theoretically should last longer, as long as you don't spin it. How big can those blocks go?

Ah, yeah, prices are tough in NZ and Australia compared to here. Tires make the biggest difference, but you know that.

[mohrperformance]

If you can hook that torque, you need an emco DV46 with 1st gear deleted. Gforce will not last long mag parts often.

[richiev88]

If you can hook that torque, you need an emco DV46 with 1st gear deleted. Gforce will not last long mag parts often.

Its a 4 speed dog box, nascar. Why would you make it 3 speed ???

[BILL-C]

I can share a tidbit of info on that Z-28 in the video hoffman900 posted than many will find very interesting. After ananlyzing the data logs on that exact race , we found that the driver used full throttle only 51 %of the time on his best lap. The rest of the time he was either off the gas totally or modulating throttle. With the 150 lb weight penalty for Jerico trans ( very much needed for 310 cid engine), the camaro and BB corvettes are very close to same weight and vette can run bigger tires! A \P big block vettes 68-72 are also allowed to run 468 cid and aluminum heads, so are definately the cars to beat in svra group 6. Our little iron headed 289's and 302's can't hang with them on the long straights, but put up a good fight everywhere else because the big block cars use 100% throttle opening even less than 50 %. The biggest, most powerful engine is just ballast if you can't apply the power properly.

[mohrperformance]

DV46 is six speed sequential designed for Dodge Viper V10. Very Big gears and shafts for big motor. At $24k also big $. Had one in an ex grand am tube corvette with 500hp ls6 no clutch up and down shifts 4 years racing only apart once.

[hoffman900]

I can share a tidbit of info on that Z-28 in the video hoffman900 posted than many will find very interesting. After ananlyzing the data logs on that exact race , we found that the driver used full throttle only 51 %of the time on his best lap. The rest of the time he was either off the gas totally or modulating throttle. With the 150 lb weight penalty for Jerico trans ( very much needed for 310 cid engine), the camaro and BB corvettes are very close to same weight and vette can run bigger tires! A \P big block vettes 68-72 are also allowed to run 468 cid and aluminum heads, so are definately the cars to beat in svra group 6. Our little iron headed 289's and 302's can't hang with them on the long straights, but put up a good fight everywhere else because the big block cars use 100% throttle opening even less than 50 %. The biggest, most powerful engine is just ballast if you can't apply the power properly.

Great post, Bill. Also shows the value of proper data acquisition.

As I mentioned in other posts, the top MotoAmerica / FIM Superbikes in the country, ridden by the best riders in the country, at most tracks they run at, they only are giving the rider 100% of the power 10-15% of the lap. Otherwise the bikes would be wheeling and high siding all over the place. It becomes a game of how to manage the power, not how to make more power.

[richiev88]

I can share a tidbit of info on that Z-28 in the video hoffman900 posted than many will find very interesting. After ananlyzing the data logs on that exact race , we found that the driver used full throttle only 51 %of the time on his best lap. The rest of the time he was either off the gas totally or modulating throttle. With the 150 lb weight penalty for Jerico trans ( very much needed for 310 cid engine), the camaro and BB corvettes are very close to same weight and vette can run bigger tires! A \P big block vettes 68-72 are also allowed to run 468 cid and aluminum heads, so are definately the cars to beat in svra group 6. Our little iron headed 289's and 302's can't hang with them on the long straights, but put up a good fight everywhere else because the big block cars use 100% throttle opening even less than 50 %. The biggest, most powerful engine is just ballast if you can't apply the power properly.

Totally agree, its mostly not about the power for me is engine life, and from a original look perspective I feel the big block is more period the a SB2, but again its more about the number of racing hours before rebuilds the all out best engine for speed.
Our fast guys mostly run Nascar engines, stroked to 410cu, top engines claiming 900hp. I totally agree it a combination not just brutal power.
Some also run bespoke SBC combos, still pricey and custom
Perhaps my point was lost in the mix, or I didn't explain myself correctly. I have been running a SBC chev, 23 deg brodix, 372cu, under 600hp. this was a short stroke combo 3.48 stroke 372cu. Engine life is about 3 seasons between refresh.
I have been developing the handling and made good gains. Unfortunately what was been made up in the handing was been lost in the straights buy guys with more "straight line handling" HP.
I looked at all my options to get to a 750hp, 650tq deal, and have good engine life. Most guys running SB2 seem to refresh most seasons, as this engines have been out of nascar for a long time now often components are custom order and expensive, and can take a long time to acquire.( so many have a spare engine)
So I decided to keep parts to a off the self deal, and see what would give the best engine life/ performance balance.
After some consultation and number crunching a 500cu bbc seemed the best option for hp goals v engine life, and it a engine that looks like it should be in a 70 camaro.
Unfortunately during the parts purchasing process, our $ weakened against the US$, my available spend decreased. A new build 509cu was ending up $45k.
My engine builder had a ex marathon boat motor BBC, low hours since a major rebuild ( crank, heads rods, valve train) I had paid for and shipped the alloy block already so decided to use the low hour BBC parts ( except the block) which was here and the same price as a pair of new heads ( budget constraints)
So that's how its got to 572cu, not by design. Now Im trying to work with what I have without blowing the budget.
I follow what you guys do with the Historic racing, is pretty neat, but I understand big $$ are still spent
I run my season on what some here spend per weekend..........
Cheers