How much lift for these flow numbers

[Orr89rocz]

Thanks Eric for the reply. Still teaching?

WOW! A 12 degree split in duration, ok.

What about the other end of the lsa? What if it was on a 112 lsa? Would that make it tamer?

I left teaching this year.

The longer duration on exhaust helps carry the peak longer when your exhaust port is just good but not great.

The 112lsa would make it very tame at idle bit you would give up torque and horsepower especially down low. On low compression motors I try to get the cam to build cylinder pressure. The valve events can be adjusted in some ways to give you similar numbers. Ie smaller duration wider lsa.

For the record no matter how good a cam guy is after you get data from one motor run with the cam if you’re smart you can figure a better camshaft.

I currently in between teaching jobs. It gets harder to stay in with all the crap that continue to put out. Unfortunately, the education is system is dominated by one side and that makes it harder as well.

I follow what you saying on carrying the peak longer.

I follow what your saying on cylinder pressure and makes good sense.

What cranking compression should I be looking at? 195 psi to 210 psi seem safe to me on 93 octane here in Florida.

What is your impression of the cam I already have? A 280/288 and 226/234 @ .050 with .530/.530 on a 112 lsa. It is just sitting there.

Probably a cam from Straub or Cam King would be better.

That be a smooth driver but would have higher crankin compression, may need premium fuel. I would do a tighter lsa tho. And more lift unless thats a 1.5 rocker at .530.

[tcb3274]

I always shoot for 195 psi on cranking compression or something in that area.

That .530 lift is with 1.5 rockers.

[David Vizard]

tcb3274

Here is my ten cents worth on the spec for a flat hyd cam for this build.

• With 383’s there seems to be a sweet spot as far as the CR goes at 10.5/1 rather than the 10/1 you were opting for. If you put the CR to 10.5 and run it cool (170F) pump gas should be OK.
• With the 10.5/1 CR and the following:-
• 2.05 intake (your heads probably have 2.02 but ported by an expert such as Eric the low lift flow (not given) could well look more like a 2.05 valve hence the use of such for the purposes of specing the cam)
• Peak power used for spec – 6100 rpm – this was chosen after checking for a decent idle vacuum of 13.5 inches HG.
• In. RR 1.7 ( again chosen after checking what a 1.65 would do. Many rockers are a higher ratio than they say on the box. Ie the Crane 1.65 is actually 1.69. Some of PRW and Scorpion rockers are up in the high 1.7’s
• Running these numbers through TorqueMaster gives the following results:-
• Cam - In duration 287 @.006 EX 292@ .006, Lobe Center line Angle 107, cam advance 3.7 degrees for an intake center line of 104.3.
• Overlap 75.5 degrees
• Minimum lift – in 0.585 (recommend 0.600) Ex 0.562 (recommend 0.580)
• This spec cam will give 13.4 inches of vacuum at approx. 800 rpm
• Dynamic CR will be 8.0/1
• Cranking compression will be 206 PSI assuming zero leakage
• Peak torque will be 506 lbs-ft @ 5000 rpm
• Peak power will be 537 @ 6100 rpm
• Intake airflow required at recommended min lift will be 277 cfm
• Assuming stock port intake center line length port volume required will be 196 cc

At this point we have locked in certain factors for a cam to be capable of producing the results listed.
If the power /torque figures are satisfactory and the vacuum is OK Then the LCA and overlap are locked in so the duration figures are a function of these two factors.
But these figures say nothing about the 0.050 and the 0.0200 and so on. This makes the next step one of profile selection. For this I will refer to TorqueMaster’s hydraulic flat tappet profile data base. This has approx. 550 profiles from the best cam designers in the business. Using the numbers that are locked in the data bank is addressed to see what falls in closely to the cam so far provisionally calculated.
Using the TorqueMaster data bank it took less than 10 seconds for 4 very close candidates to be selected. As it happens out of the 550 or so cam selections there was no 75.5 overlap cam only 75 or 76. The four cams shown by TorqueMaster have the profiles speced out with the following parameters given:-
• Duration @ 0.006
• Duration @ 0.050
• Duration @ 0.200
• Major and minor lobe intensity
• Lobe lift
• Lobe area in lift x angle
• Mean lobe lift in inch-degrees (this is a measure of absolute aggressiveness)
• Valve lift with the rockers chosen

Let’s assume we want to choose the most aggressive profile cam of the four selected. The part number for that cam is TSCW5418/5214-07 ( PM me if you want to source this cam)
It looks like the heads that Eric did for this build are going to be good enough for the job with a little to spare. I suspect the port volume and thus the CSA may be a shade more than is needed but we can address that when you find out what that volume may be. I am also assuming that the flow ratio, intake to exhaust, is about 70%. This selection also assumes a good nonrestrictive intake and exhaust.

If you had not already got the parts the next step from here would to go back into the data bank and select rockers by their REAL opening ratio’s starting at instantaneous ratio off the seat, ratio at TDC and ratio at full lift. It’s amazing how far the real NUMBERS ARE FROM THE ADVERTISED ONES!

Once the rockers are selected the springs for the cam and rockers can be chosen. Next P/Rods can be selected from those advised, also lifters,
Once the valve train is done there is a data bank of all the currently manufactured SBC heads with flow curves that are reviewed by the program and tell which heads have the flow required at the lift being used (not the peak lift/flow unless that is what will be used)
Next on the agenda for the cam selection process that TorqueMaster goes through so the user is fully informed is the choice of an intake manifold for this combo. Should it be a single plane or a two plane? TorqueMaster selects it by part number as it does the carb size and type.
There is more such as headers and mufflers but I am sure you get the picture here.

Now why have I gone into all this detail? It is hopefully for those guys who think I am a beginner and I need reminding about this or that factor that I may have over looked. Like the guy who told me that dyno’s can read different like I had not had enough experience to know that.
By the way I designed dyno’s for over two years as a consultant engineer. The one I spent most time on was an inertial dyno that could deliver steady state figures and figures at any acceleration rate to a very high accuracy.

Well tcb3274 I have wandered off the subject here but If the cam required was actually a hyd roller let me know and I will run the numbers again.
DV

[tcb3274]

tcb3274

Here is my ten cents worth on the spec for a flat hyd cam for this build.

• With 383’s there seems to be a sweet spot as far as the CR goes at 10.5/1 rather than the 10/1 you were opting for. If you put the CR to 10.5 and run it cool (170F) pump gas should be OK.
• With the 10.5/1 CR and the following:-
• 2.05 intake (your heads probably have 2.02 but ported by an expert such as Eric the low lift flow (not given) could well look more like a 2.05 valve hence the use of such for the purposes of specing the cam)
• Peak power used for spec – 6100 rpm – this was chosen after checking for a decent idle vacuum of 13.5 inches HG.
• In. RR 1.7 ( again chosen after checking what a 1.65 would do. Many rockers are a higher ratio than they say on the box. Ie the Crane 1.65 is actually 1.69. Some of PRW and Scorpion rockers are up in the high 1.7’s
• Running these numbers through TorqueMaster gives the following results:-
• Cam - In duration 287 @.006 EX 292@ .006, Lobe Center line Angle 107, cam advance 3.7 degrees for an intake center line of 104.3.
• Overlap 75.5 degrees
• Minimum lift – in 0.585 (recommend 0.600) Ex 0.562 (recommend 0.580)
• This spec cam will give 13.4 inches of vacuum at approx. 800 rpm
• Dynamic CR will be 8.0/1
• Cranking compression will be 206 PSI assuming zero leakage
• Peak torque will be 506 lbs-ft @ 5000 rpm
• Peak power will be 537 @ 6100 rpm
• Intake airflow required at recommended min lift will be 277 cfm
• Assuming stock port intake center line length port volume required will be 196 cc

At this point we have locked in certain factors for a cam to be capable of producing the results listed.
If the power /torque figures are satisfactory and the vacuum is OK Then the LCA and overlap are locked in so the duration figures are a function of these two factors.
But these figures say nothing about the 0.050 and the 0.0200 and so on. This makes the next step one of profile selection. For this I will refer to TorqueMaster’s hydraulic flat tappet profile data base. This has approx. 550 profiles from the best cam designers in the business. Using the numbers that are locked in the data bank is addressed to see what falls in closely to the cam so far provisionally calculated.
Using the TorqueMaster data bank it took less than 10 seconds for 4 very close candidates to be selected. As it happens out of the 550 or so cam selections there was no 75.5 overlap cam only 75 or 76. The four cams shown by TorqueMaster have the profiles speced out with the following parameters given:-
• Duration @ 0.006
• Duration @ 0.050
• Duration @ 0.200
• Major and minor lobe intensity
• Lobe lift
• Lobe area in lift x angle
• Mean lobe lift in inch-degrees (this is a measure of absolute aggressiveness)
• Valve lift with the rockers chosen

Let’s assume we want to choose the most aggressive profile cam of the four selected. The part number for that cam is TSCW5418/5214-07 ( PM me if you want to source this cam)
It looks like the heads that Eric did for this build are going to be good enough for the job with a little to spare. I suspect the port volume and thus the CSA may be a shade more than is needed but we can address that when you find out what that volume may be. I am also assuming that the flow ratio, intake to exhaust, is about 70%. This selection also assumes a good nonrestrictive intake and exhaust.

If you had not already got the parts the next step from here would to go back into the data bank and select rockers by their REAL opening ratio’s starting at instantaneous ratio off the seat, ratio at TDC and ratio at full lift. It’s amazing how far the real NUMBERS ARE FROM THE ADVERTISED ONES!

Once the rockers are selected the springs for the cam and rockers can be chosen. Next P/Rods can be selected from those advised, also lifters,
Once the valve train is done there is a data bank of all the currently manufactured SBC heads with flow curves that are reviewed by the program and tell which heads have the flow required at the lift being used (not the peak lift/flow unless that is what will be used)
Next on the agenda for the cam selection process that TorqueMaster goes through so the user is fully informed is the choice of an intake manifold for this combo. Should it be a single plane or a two plane? TorqueMaster selects it by part number as it does the carb size and type.
There is more such as headers and mufflers but I am sure you get the picture here.

Now why have I gone into all this detail? It is hopefully for those guys who think I am a beginner and I need reminding about this or that factor that I may have over looked. Like the guy who told me that dyno’s can read different like I had not had enough experience to know that.
By the way I designed dyno’s for over two years as a consultant engineer. The one I spent most time on was an inertial dyno that could deliver steady state figures and figures at any acceleration rate to a very high accuracy.

Well tcb3274 I have wandered off the subject here but If the cam required was actually a hyd roller let me know and I will run the numbers again.
DV

Thanks Mr Vizard for your report and very informative reply.

I was looking for a hyd. roller.

[David Vizard]

tcb3274 - You got it - just hang on a while.
DV

[tcb3274]

tcb3274 - You got it - just hang on a while.
DV

No problem!

[David Vizard]

tcb3274


Here’s the part #: -TW13451/13453-107

I will send you a PM with a short excel file with the full specs.
DV

[cjperformance]

Op / DV, What are ambient condition, is it practical to keep it at 170F all year /driving season?
What is pump fuel consistency like in the area?

DV, those. 006" & o/lap figures suggest an idle that will rumble the china when the OP cruises thru the old folks home driveway! Im interested to see the .050 & .100 numbers.

[Orr89rocz]

My 383 was 11:1 with afr 195’s. 288/230. 306/245. 109 lsa. .603/.613 with 1.6’s. Idle chopped well but was stable. It was loud tho. 6250 rpm peak flat to 6600, shift 6800. Efi car, drivability well tuned. Pump 93 all day long

cams similar would work well imo

[JoePorting]

I wouldn't get too hung up on the perfect cam. Just run what you have and if you want to try something different in 6 months, change it. SBC cams are fairly easy to change.

[cjperformance]

Just 2 quick examples,,

286˚291
˚234˚238˚
.495".502" (@1.5:1 , i use 1.6:1)
110˚ (but i use on 108*)
Set 105/106 icl.

^^ this is a fave HFT of mine for a stout street 383, very good all round 10/10.25:1, 1.6 rockers. Ultra reliable and valve train friendly. Not rough but a fair rumble at idle. Likes EPS or VIC jr depends on stall/gears.

 HR # 757, 214/218@.050" , 123/124@.200" , 280/280 adv, .311" lobe, 110 lsa. (Valve train friendly and quiet)
1.6/1.5 rockers- .497"/.466" valve lift.

^^^ this is a ripper sleeper 383 HR cam. Smooth idle , excellent tq, great with TF 195 23deg heads. 10.3:1 will run aussie 91fuel.  On BP98 ran 11.98 @ (i think )112ish mph in a 1967 Parisienne, 2800 stall, T700 3.9 rear.

All depends wether you are pushing fir max hp for the combo or max practicality and reliability with no fuel and temp issues.

[gmrocket]

Did Eric port these heads for you??
If so probably best to ask for his recommendation on a cam for your combination,
If not then you would be best to give all the details of engine, trans, converter, rear gear etc etc
Can't pick a cam by flow numbers alone

Steve, yes he did port them for me.

I will place a call into him.

Details of the engine. 383, rpm intake, Holley 3310, 1 3/4" headers, 4 speed, 4:10 gear

I had a 67 Camaro with a similar setup. My favorite upgrade was going to a TKO-500 5 speed with an overdrive fifth gear. Made 70 mph at around 2500 rpm's.

Dang! You nailed it with the 67 Camaro reference

Your previous wild azz guesses without even knowing the cubes, compression, engine architecture, application or anything else was reeeaallyy close though

[tcb3274]

Do you think a EPS is ok for my combo, or a RPM Dual Plane?

[tcb3274]

Steve, yes he did port them for me.

I will place a call into him.

Details of the engine. 383, rpm intake, Holley 3310, 1 3/4" headers, 4 speed, 4:10 gear

I had a 67 Camaro with a similar setup. My favorite upgrade was going to a TKO-500 5 speed with an overdrive fifth gear. Made 70 mph at around 2500 rpm's.

Dang! You nailed it with the 67 Camaro reference

Your previous wild azz guesses without even knowing the cubes, compression, engine architecture, application or anything else was reeeaallyy close though

I don't follow you on what I guessed on?

[cjperformance]

Do you think a EPS is ok for my combo, or a RPM Dual Plane?

With those heads and being a street cruiser as you mentioned, i pick the eps. They respond well to a .5" open on the intake then .5" 4 hole on top depending on use. Great intake and cheap!