cam choice for heavy chevelle 383 sbc

[grumpyvette]

"Hey guys I need some help choosing a new cam for my 383 stroker.
I have a 72 Chevelle. And my goal is to have her run low 11's. First here is my whole setup:
-383 stroker, all rebuilt, 1500 miles on motor, trans, drivetrain.
-Hedmann long tube headers
-11:1 compression hypereutectic pistons
-Current Cam specs:
INTAKE: Duration: 278º Lift: .461
EXHAUST: Duration: 284º Lift: .468
-DART Iron Eagle sbc heads
-roller rockers
-Edelbrock Tranctula TM-1 Intake
-Holley 750 vacuum secondary carb
-Msd ignition
-Turbo 350 trans, shift kit, b&m star shifter
-4.33 gears, 35 spline axles, swarr auto rear
-Mickey Thompson ET Street Drag Radials 295/65/15
-Full interior
It has not been to the track yet but will be this summer. What do you think she would run as of now? I think high 11's low 12's?
Can I get my car to run low 11's with just a cam? I know the one i have now is a small cam. What size should i be looking at? Just looking for some opinions. Thanks. "



personally Id sell that intake or throw that intake in the nearest dumpster
ID USE THIS INTAKE if you have the hood clearance

http://www.summitracing.com/parts/HLY-300-110/

every choice you makes a compromise in some way,but assuming you want to retain as much as you can of the current parts list,
ID BE SELECTING A SOLID ROLLER CAM, an 1.6:1 roller rockers and swapping to the correct valve springs and checking clearances , and get any required head machine work done, ID have the heads bowl area and ports cleaned up, and get a 3 angle valve job, and ID buy a good rocker stud girdle, and a 4400 rpm stall converter , (contact a good converter manufacturer and discuss whats correct) ,and good slicks, ID also think about adding a 150 hp nitrous plate system, yes HYPEREUTECTIC pistons and high rpms are not a great idea with nitrous, but careful tuning , limiting the shot to 75-100hp,and keeping the mix rich and staying under about 6300rpm should let you get by, if you don,t go with the mild nitrous shot get a RPM air gap intake, but the nitrous boost will help.
that way you concentrate on maximizing the potential power in the 4200rpm-6300rpm power band

http://www.summitracing.com/parts/EDL-70050/

http://www.summitracing.com/parts/LUN-91656/?rtype=10

viewtopic.php?f=52&t=5078


youll need race octane fuel
http://www.leesracing.com/fuelspec/g7.html

in an ideal RACE combo your power curve would look similar to this and youll have a converter stall speed and rear gear ratio and tire diam. that allows the engine to stay in (in this case the 4000-6500rpm power band) but thats hardly ideal in a street car engine combo

but CALL THE CAM COMPANY OF YOUR CHOICE FOR MORE INFO

 

[Indycars]

Looks like it's going to need some race gas or octane booster for that DCR of 8.83:1.

Even retarding the cam timing 4 degrees will be doubtful with cast iron heads.

 

[grumpyvette]

your 100% correct, its a almost given that your going to need to use a race octane fuel to push what is undoubtedly 3600 lb or heavier full interior, chevelle with a 383 SBC with 11:1 compression to run 11 second times, the idea here is to maximize what he has and make as few changes (ADDING EXPENSE) as possible , and yet both reach the goal and retain as much of the current components as possible.

youll need race octane fuel
http://www.leesracing.com/fuelspec/g7.html

 

[mathd]

Looks like it's going to need some race gas or octane booster for that DCR of 8.83:1.

Even retarding the cam timing 4 degrees will be doubtful with cast iron heads.

You sure, i though we could run up to 12.8:1 on super"92 octane"
My holley/weind supercharger tech say its safe to use a "Effective compression ratio" of 12:1 on highoctane pump gas.

Nitrous by itself help cooling the cylinder temp too, thats like a boost cooler, it reduce detonation.

 

[grumpyvette]

Looks like it's going to need some race gas or octane booster for that DCR of 8.83:1.

Even retarding the cam timing 4 degrees will be doubtful with cast iron heads.

You sure, i though we could run up to 12.8:1 on super"81 octane"
My holley/weind supercharger tech say its safe to use a DCR of 12:1 on highoctane pump gas.

you can! run 81 octane in a 12.8:1 compression engine, its simply a question of how long,............. because its usually just going to result in pistons crumbling and melting from detonation

youll need race octane fuel
http://www.leesracing.com/fuelspec/g7.html


re-reading this thread, its rather obvious that theres a great deal, about the listed combo thats being assumed to be correct in the combo that more than likely needs to be checked and verified ....so ID strongly suggest anyone reading thru this delve a good deal deeper and read thru the links below before proceeding

viewtopic.php?f=52&t=181

viewtopic.php?f=52&t=5078

viewtopic.php?f=44&t=38

viewtopic.php?f=52&t=3802

viewtopic.php?f=52&t=727

viewtopic.php?f=52&t=322

viewtopic.php?f=53&t=3897

viewtopic.php?f=53&t=341

 

[mathd]

Looks like it's going to need some race gas or octane booster for that DCR of 8.83:1.

Even retarding the cam timing 4 degrees will be doubtful with cast iron heads.

You sure, i though we could run up to 12.8:1 on super"81 octane"
My holley/weind supercharger tech say its safe to use a DCR of 12:1 on highoctane pump gas.

you can! run 81 octane in a 12.8:1 compression engine, its simply a question of how long,............. because its usually just going to result in pistons crumbling and melting from detonation

Sorry it was a typo i meant 92 octane
What is the max safe dcr for use on 92 octane?

 

[Indycars]

Looks like it's going to need some race gas or octane booster for that DCR of 8.83:1.

Even retarding the cam timing 4 degrees will be doubtful with cast iron heads.

You sure, i though we could run up to 12.8:1 on super"92 octane"
My holley/weind supercharger tech say its safe to use a "Effective compression ratio" of 12:1 on highoctane pump gas.

Nitrous by itself help cooling the cylinder temp too, thats like a boost cooler, it reduce detonation.

We might be talking about two different terms. Dynamic Compression Ratio (DCR) and Static Compression Ratio (SCR or CR). When you say "Effective Compression Ratio, which one are you referring to???

I have never used Nitrous, but I thought you could NOT use it for the entire 1/4 mile.

 

[mathd]

I don't know ive never used nitrous.
The effective compression ratio from the supercharger tech info, its the Static compression ration + effective boost(formula prolly has something to do with VE?).
download/file.php?id=1679 Page 2

2. COMPRESSION RATIO, RING CONDITION, AND COMPRESSION PRESSURE. An engine being considered for a
supercharger should not exceed 9.5:1 compression ratio. Exceeding this limit requires a reduction in the amount of boost, water
injection, race fuel, or excessive spark retarding to prevent detonation (engine knock) and its destructive results on the engine.
Performing a compression or leak down test before installation is also a good idea. This will help determine ring condition and
valve seating. An engine with one or more cylinders reading 10-15% lower than the rest should have this condition checked and
repaired before supercharger installation. Check the factory service manual for proper procedures and readings.
EFFECTIVE COMPRESSION RATIO CHART
Comp.
Ratio
Blower Boost Pressure (lbs. per square inch)
. . . 2...4 ...6 ..8 ....10. 12. ..14 ....16 ....18 ...20 ...22...24
7.0 8.0 8.9 9.9 10.8 11.8 12.7 13.6 14.5 15.3 16.2 17.0 17.9
7.5 8.5 9.5 10.6 11.6 12.6 13.6 14.6 15.7 16.7 17.8 18.6 19.5
8.0 9.1 10.2 11.3 12.4 13.4 14.5 15.6 16.7 17.8 18.9 19.8 20.9
8.5 9.7 10.8 12.0 13.1 14.3 15.4 16.6 17.8 18.9 19.8 20.9 21.9
9.0 10.2 11.4 12.7 13.9 15.1 16.3 17.6 18.8 20.0 21.2 22.4 23.6
9.5 10.8 12.1 13.4 14.7 16.0 17.3 18.5 19.8 21.1 22.4 23.6 24.8
10.0 11.4 12.7 14.1 15.4 16.8 18.2 19.5 20.9 22.2 23.6 24.8 26.0
10.5 11.9 13.4 14.8 16.2 17.6 19.1 20.5 21.9 23.4 24.8 26.2 27.6
11.0 12.5 14.0 15.5 17.0 18.5 20.0 21.5 22.9 24.5 26.0 27.5 28.9
The above chart shows the effective compression ratio of your engine, which combines the static compression ratio with the
amount of supercharger boost. Note that for most street applications with 92 octane pump gas, you should keep your effective
compression ratio below about 12:1. On marine engines, you should keep the effective compression ratio below about 11.5:1.
For added protection against possible engine detonation (knock), we strongly recommend using a boost retard system, such as
Holley P/N 91070.

 

[Indycars]

The above chart shows the effective compression ratio of your engine, which combines the static compression ratio with the
amount of supercharger boost. Note that for most street applications with 92 octane pump gas, you should keep your effective
compression ratio below about 12:1. On marine engines, you should keep the effective compression ratio below about 11.5:1.
For added protection against possible engine detonation (knock), we strongly recommend using a boost retard system, such as
Holley P/N 91070.

I had forgotten that you are running a forced induction system. I don't know why you couldn't do the same type of thing with a DCR/Effective Compression Ratio table, the numbers would just be different.

I did some searching but didn't find anything using a DCR with boost pressure.

 

[grumpyvette]

http://www.gnttype.org/techarea/turbo/turboflow.html

http://www.turbofast.com.au/tfcalc.html

http://www.turbofast.com.au/javacalc.html



maybe these links help

 

[Indycars]

Whether you are using Forced Induction or Naturally Aspirated engine, the piston still cannot compress the gas contained in the cylinder until the intake valve closes.To me it seems no different when trying to decide if the engine/CR will run without detonation, DCR would be important consideration. No doubt you have to consider the amount of boost in a forced induction system, but again nothing gets compressed until the intake valve closes.

Comments anyone ???