Small base circle cam or not?
Hi! Every body...
As i said before, i'm on a 406 sbc project. I don't know if i need or not a small base circle cam. My interest is on the Hydraulic Roller Voodoo Retro-Fit Lunati 20120711K (60111). It seems to have what i want. Great acceleration, torque and throttle response to have fun stop light to stop light.
-RPM Range: 1800 - 6000
-Duration @ .050": 219/227
-Advertised Duration: 270/278
My car specs:
-406 sbc (approx. 10:1 cr with 75 cc, AFR 195 and 7 flat top)
-auto. transmission 2500 tci stall.
-5.7 con. rod
-373 rear end
My question: Do i need or not a small base circle cam? If you have any suggestions, let me know.
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I would first
1) use a bigger cam
2)not use a split duration cam with AFR heads
the reduced base circle cam is the same price,so use one if you are worried
I would have to think with a stock stroke it would be no, plus if its a retro-fit cam it would already be set for what you need
Stock 5.7 rods in a 400 should hit the cam and block. Also the 400 crank will required lots of work to fit the 5.7 rods (cutting and balancing).
You can buy "stroker 5.7 rods" which are already clearanced.
Since you are building a street engine, consider using stock 400 rods. Avoids lots of pit falls and cost.
No need for a split duration cam with afr heads. Intake and exhaust duration should be the same with those heads. If you don't use headers or have a restrictive exhaust system then the extra exhaust duration will be good.
I would use a cam with 230 degrees duration at 0.050" on both the intake and exhaust, 110 LSA, headers, dual 2-1/2 or 3", and setup the engine with 10:1 cr. Should make close to 500 hp with any rod.
Howard's 110885-10 specs:
Basic Operating RPM Range: 2,000-5,800 Intake Duration at 050 inch Lift: 225 Exhaust Duration at 050 inch Lift: 225 Duration at 050 inch Lift: 225 int./225 exh. Advertised Intake Duration: 278 Advertised Exhaust Duration: 278 Advertised Duration: 278 int./278 exh. Intake Valve Lift with Factory Rocker Arm Ratio: 0.525 in. Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.525 in. Valve Lift with Factory Rocker Arm Ratio: 0.525 int./0.525 exh. Lobe Separation (degrees): 110
Camshaft Manufacturers Description: Fair idle, street high performance. 2,200+ stall, aftermarket intake and headers recommended.
I wrote to Howards Cams Online Support and they suggested me the small base circle version of that cam part #119995-S but, i can't find it anywhere.
Basic Operating RPM Range: 1,800-6,000 Intake Duration at 050 inch Lift: 231 Exhaust Duration at 050 inch Lift: 241 Duration at 050 inch Lift: 231 int./241 exh. Advertised Intake Duration: 285 Advertised Exhaust Duration: 295 Advertised Duration: 285 int./295 exh. Intake Valve Lift with Factory Rocker Arm Ratio: 0.470 in. Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.470 in. Valve Lift with Factory Rocker Arm Ratio: 0.470 int./0.470 exh. Lobe Separation (degrees): 112.
I know! That's not as durable/long life as a roller one but, i do less than 2k miles per year so... It doesn't matter to me and is less expensive. Also, is a small base circle with over 230 duration, the torque/hps broad range at 6000 max rpm performance range desired with 112 lsa. A plus for my power brake.
I saw that setup on 383 at car craft with Canfield 195cc Heads so, with AFR, it shouldn't be worst performant? I know! It's a split patern duration. I don't already have the AFR heads so, if it's gonna be a problem, i'll buy an other kind like the Brodix IK 200 with less flow numbers.Oh! It's hard to be setted. :confused: I really need the american knowledge like all of you. I believe in you! :D
Big Torque 383 Build - Car Craft Magazine
Euhm! It seems approaching what i want like performance.
P.S. As you can see, my english is not as good as yours. You know, as i said before, we speak french in my province of Quebec so...
To answer the original question, the base circle is irrelevant. Get the cam with the specs that you need for your engine combination.
Lobe lift is the difference between the lobe peak and the base circle. Lobe peak is limited by the diameter of the cam bearing journals (the lobe needs to pass through the cam bearings when installed in the block). If you need more lobe lift than you can get by increasing the lobe peak, the only alternative is to go to a smaller base circle to increase the difference between the two.
The only downside to a reduced base circle cam is that you may need longer pushrods to compensate.
If you can squeeze the bank account,the roller cam is a much better choice,more power,better idle.
Before you buy the cam,you need the heads.
heads first,then match cam/intake/carb/headers.
The short block needs the CR matched and rods to fit.If you get a roller(highly recommended) then get a small base circle
what are the power figures that you want and what RPM range are you hoping to operate this engine?
I know that... There's several points to consider in a setup. What i want is exactly the result obtained with the Lunati (60111) 20120711 1800-6000 with great acceleration stop light to stop light and that's the one i wanted but... Is not a small base circle and i still don't know if it could work with my factory 400 GM block??? (Does it work? I don't know?) Some says not enough duration, is not a single patern so, not a good idea with AFR 195 etc. etc. To be certain, in my confusion, I am going to reproduce the 406 Impersonator and i'll use 1.6 rockers at the intake. If it worked one time, it should once again?
Chevrolet 406 CI Engine Build - Chevy High Performance
Howard's suggested me the small base roller #119995-S but, i can't find it anywhere. It has almost the same specs than the 110885-10
read the article
the roller cam engines usually have a wider spread in the sweet spot,closer to 2k,that type of engine is more than noticably better to drive. A lot of flat tappet hydraulic cams peak,then roll off in power very quickly.
Im not saying you have to rev to 6500 rpm,but once you feel that power you will at least understand why roller cams exist.
all the new cars rev 6500 from the factory
12340-SCA-432-C406 - Chevy 406 Reverse Dome -15.0cc Scat-Based Engine Kit
Air Flow Reasearch AFR-0912 SBC Cylinder Heads (Pair) 180cc Street Vortec Style Heads, straight plug, 65cc chambers, complete w/parts
Lunati 10120410K (Formerly Part Number 00010) Chevrolet Small Block V8 262-400 1955-Present Hydraulic Flat Tappet Bracket Master Complete Cam Kit RPM
What you need is a torque motor, one that will be producing minimum 400 ft/lbs of torque at 2000 rpm's. One way to achieve this is with a 406 using L31 heads, the other way is a 406 using AFR 180cc heads.
406 with L31 heads (64cc chambers), 22cc piston (9.75:1 SCR), Lunati 00010 flat tappet cam, RPM Vortec intake, 750 carb....dyno'd by Engine Masters 2004....
RPM HP TQ
2500 227 477
3000 282 493
3500 324 516
4000 292 515
4500 420 491
5000 428 449
Not so cheapo version (mo power)
Same motor with AFR 180 heads (68cc chambers), 22cc piston (9.43:1 SCR), Lunati 00010 flat tappet cam, RPM intake, 750 carb....dyno'd by Engine Masters 2004
2500 216 455
3000 282 493
3500 333 507
4000 401 527
4500 450 525
5000 478 502
5500 489 467
These results were found using 87 OCTANE fuel!!!!!!!!!:thumbup:
I suspect that slightly better results could be achieved using the 190 Vortec head from AFR, along with an RPM Vortec intake, but that is just my feeling, with no dyno proof available.
I ran much the same combo several years ago, 9.8:1 SCR with the L31 heads on my DynoSim software. Here are the results of that combo.....
RPM HP TQ
1500 122 426
2000 174 457
2500 217 457
3000 268 470
3500 315 475
4000 354 465
4500 380 441
5000 373 392
5500 326 311
Basically, tire-shredding torque from just above idle to 4500 rpm's. :thumbup:
Don't forget the steam holes in the heads. AFR will drill them for you if you purchase their heads. If you use L31 heads, you will have to drill them yourself....
Zero deck the block and use a Fel-Pro 1014 head gasket.
If I were looking for these same results with a hydraulic roller, this might be in the ballpark.....
If you have any leftover dough, I might purchase some full roller rockers at 1.6:1 rocker ratio. I would only do the 1.6 with a roller cam. Reduced friction could free-up 20 horsepower or so and full rollers will also lower the oil operating temperature.
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