Don Terrill’s Speed-Talk

Single-pattern cams VS dual-pattern cams., What is the difference between the two cams in performance, torque & Horsepower... For my small block i'm using AFR 210cc Competition heads I have 650lift hyd roller spring on the heads. I looking for help if u can explain, which one of the cams would be the best for a Street/Strip application for my SBC 383 engine to get me close to the 550 to 600 HP range to the flywheel but still can give excellent torque on the bottom end too? Just looking for some help if anyone can answer these questions for me, I'm just trying to build a Mean Street Machine...

FLOW CHART

intake/exhaust
.400 257/214
.500 296/225
.550 310/229
.600 318/235
.650 322/237

where did those flow #s come from

[quote="zums"]where did those flow #s come from[/q
The AFR book they sent me...

compression ratio, max RPM, weight of car, diff gears, stall RPM, max RPm intended use etc etc etc ??

In generic terms a single pattern cam will make a little more torque down low and a split pattern cam will hang on to the power a little longer after peak. However, running a split pattern allows you to open the exhaust a littler earlier and run a smaller exhaust valve (the earilier you open the exhaust the more compression you will need) making room for a larger intake valve. You can also run a lower rocker ratio on the exhaust allowing a more "gentle" profile which exhaust seems to like.

From what 900HP says, you can extend the reasoning to see that as the compression ratio rises (thus delivering more force to the piston early in the expansion stroke) the intake valve can be made larger and the exhaust smaller, and compensating for the latter with early EVO will cost little. Thus all else being equal, a properly-specced high compression engine will need more duration split than a low compression one.

That said, when you consider how different the requirements, pressures and valve sizes are, it has to be a huge coincidence if exactly the same duration and lift is ideal for both...

paulzig wrote:compression ratio, max RPM, weight of car, diff gears, stall RPM, max RPm intended use etc etc etc ??

compression ratio 11:1, Max Rpm between 6800 or 7000, wight of car 1985 monte carlo ss I believe like 3400lbs maybe, diff gear 3.89, Stall 3000- 3500

for any given engine application, there is an optimum intake valve lift curve for the desired RPM range, and an optimum exhaust valve lift curve.
Due to AFR's higher then average flowing exhaust ports, they normally don't require as much duration on the exhaust compared to other heads, so it's not uncommon for them to only need 0-4 degrees more exhaust then intake duration. There are other factors, so you should always run thru all your specs with the cam expert of your choise.

CamKing wrote:for any given engine application, there is an optimum intake valve lift curve for the desired RPM range, and an optimum exhaust valve lift curve.
Due to AFR's higher then average flowing exhaust ports, they normally don't require as much duration on the exhaust compared to other heads, so it's not uncommon for them to only need 0-4 degrees more exhaust then intake duration. There are other factors, so you should always run thru all your specs with the cam expert of your choise.

Alright thanks... My cam choices was either going to be Howard, Lunati or Comp cam.... But i'm really leaning towards Howards Cam But not sure if at @.50 @247/255 is to much for the street even tho its going to be a street/strip engine, but at the same time i'm trying to make 550 to 600hp with out losing bottom end, i'll take away a few Hp for More TQ.

Do I really need that much duration @.50 247/255 to get 550Hp or better with a sbc 383 stroker?

Desmosis10 wrote: Do I really need that much duration @.50 247/255 to get 550Hp or better with a sbc 383 stroker?[/b][/u]

Yes.

Desmosis10 wrote:

CamKing wrote:for any given engine application, there is an optimum intake valve lift curve for the desired RPM range, and an optimum exhaust valve lift curve.
Due to AFR's higher then average flowing exhaust ports, they normally don't require as much duration on the exhaust compared to other heads, so it's not uncommon for them to only need 0-4 degrees more exhaust then intake duration. There are other factors, so you should always run thru all your specs with the cam expert of your choise.

Alright thanks... My cam choices was either going to be Howard, Lunati or Comp cam.... But i'm really leaning towards Howards Cam But not sure if at @.50 @247/255 is to much for the street even tho its going to be a street/strip engine, but at the same time i'm trying to make 550 to 600hp with out losing bottom end, i'll take away a few Hp for More TQ.

Do I really need that much duration @.50 247/255 to get 550Hp or better with a sbc 383 stroker?

Thats a real good head for the cubic inch you have a single pattern cam would work the best, On the AFR's up to the 220 I have been single pattern cams and have been very happy with the results.

CNC BLOCKS wrote:

Desmosis10 wrote:

CamKing wrote:for any given engine application, there is an optimum intake valve lift curve for the desired RPM range, and an optimum exhaust valve lift curve.
Due to AFR's higher then average flowing exhaust ports, they normally don't require as much duration on the exhaust compared to other heads, so it's not uncommon for them to only need 0-4 degrees more exhaust then intake duration. There are other factors, so you should always run thru all your specs with the cam expert of your choise.

Alright thanks... My cam choices was either going to be Howard, Lunati or Comp cam.... But i'm really leaning towards Howards Cam But not sure if at @.50 @247/255 is to much for the street even tho its going to be a street/strip engine, but at the same time i'm trying to make 550 to 600hp with out losing bottom end, i'll take away a few Hp for More TQ.

Do I really need that much duration @.50 247/255 to get 550Hp or better with a sbc 383 stroker?

Thats a real good head for the cubic inch you have a single pattern cam would work the best, On the AFR's up to the 220 I have been single pattern cams and have been very happy with the results.

Is it true a single pattern cam make more bottom end TQ too...? What do u think about @.50 247/255 600/600 lift is it to much for the street even tho its a street/strip engine, Just not trying to lose out on Tq and keep HP still High in the 550- 600hp range???

CamKing wrote:

Desmosis10 wrote: Do I really need that much duration @.50 247/255 to get 550Hp or better with a sbc 383 stroker?[/b][/u]

Yes.

Thank... But will this cam @.50 247/255 600/600 lift Lobe Separation 110, Will it kill the bottom end Tq trying to kinda keep them both High HP and TQ with out losing to much of one another if possible What do think?

Have you given any thought to something like Bullet Cams profile:

HR312/410 250 @ .050 .410 lobe lift, asymetrical intake lobe
HR319/410 258 @ .050 .410 lobe lift, symetrical exhaust lobe

Bullet has been good about knocking off a few degrees on existing lobes which would prove useful on this exhaust profile. Say, 254 @.050 .395 ish

107 LSA

swatson454 wrote:Have you given any thought to something like Bullet Cams profile:

HR312/410 250 @ .050 .410 lobe lift, asymetrical intake lobe
HR319/410 258 @ .050 .410 lobe lift, symetrical exhaust lobe

Bullet has been good about knocking off a few degrees on existing lobes which would prove useful on this exhaust profile. Say, 254 @.050 .395 ish

107 LSA

ill probably just give them a call and see what what type of spec they come up with for a cam. Ill see if I would go with or not.