cohocarl

I'm building a 383, and would like some opinions on what to set my cam timing at before I put the tins on.

I don't know if I want to run my new build at "straight up", or advance it 4 degrees. From what I've read, advancing the camshaft timing will move the tq peak to a lower rpm.

Since the 383 is typically a lower rpm engine as compared to say a 302 or 377 which has a larger bore to stroke ratio than a 383, I would think installing the cam advanced would be better. I'm not planning on spinning it super high anyways. I'll probably set the rev limiter at 6K. It's a Saturday night cruiser with maybe a couple trips to "test & tune" nights now and then.

First off, I am running a 750cfm carb, not the T.P.I. I have a Torker II single plane, and Weiand Street Warrior dual plane manifolds to choose from. I think I'm going to go with the dual plane. Below are specs of the build:

4.030" 4 bolt block,
3.75" Scat crank
5.7" Scat I beam Pro Comp rods
Probe -10cc pistons, 1.44" compression dist. (zero deck) (+/- 10.3:1 cr)
64cc Edelbrock E-210 heads (2.08" intakes)
1.52:1 CC Pro Magnum steel rocker arms
Lunati Voodoo 10120704 (60104) Cam:
•Advertised Duration (Int/Exh): 276/284
•Duration @ .050 (Int/Exh): 233/241
•Gross Valve Lift (Int/Exh): .504/.525
•LSA/ICL: 110/106
•Valve Lash (Int/Exh): Hyd/Hyd
•RPM Range: 2200-6400


I have printed out a degree wheel from a pdf file onto 4 sheets of paper to glue to a round piece of mdf to make myself a 15" wheel.

I will verify with the degree wheel that Lunati "built in" 4 degrees advance, which if the timing gears are installed "straight up" is already there, but I'm thinking of installing the lower sprocket advanced 4 degrees.

Any comments would be appreciated.

383vett

I would call Lunati. They ground the cam, they know what works. It sounds like you are trying to out think them.

cv67

Id put it in straight up. Those 2" advance retard keyways can be off sometimes. Using the degree wheel will tell you all anyway

Sleazy Rider

at 106 icl built in, that was what i advanced my l98 cam to. i don't think i would advance it any further. it did pick up the torque there and made more usable power and torque with the tpi setup.

rklessdriver

By putting the ICL on 102* all your going to do is move the powerband down by 300 RPM.

As stated those 3 key lower gears are almost never correct.

Neither of those intakes are sutiable for what your trying to do.
Will

cohocarl

Thanks for the replies everyone. That's probably what I should do.
No, I'm not trying to "out think" them, just trying to understand how much of a difference advancing the cam a few degrees would change the behavior.

Lets say for example the cam's installed "straight up" (4 degree advance built in from the cam maker) and peak power is at 6,500rpm. Would advancing a cam say 4 degrees lower the peak power closer to 6K, or retarding it 4 degrees raise the peak power to 7K?

Until I get enough ***** to cut up the hood, that's about the only ones that will fit.....

Thanks again for the replies. I'll contact Lunati and see what they say and post their response.

Curveit

For a 6000 redline, your Heads and Cam are too big, in my opinion. I would suggest AFR 180 or 195 Heads and a Cam around 224 degrees with as much lift as you can get. I think the combo you have listed would be happier at 7000+. A dual-plane intake is the better choise; the Torker 2 is not a good intake.

Black89Z51

I've used both of those intakes on my mild 350. I ended up going to a Holley 300-25 at the advice of Will. Dyno numbers in 2 weeks. I'm expecting 30-40 more rwhp, and that's not even on a stroker motor.

captcolt

Man do i have advice for YOU. Lol. Cam selection at THIS point isnt so much about rpm band power placement but COMPRESSION ratios. What is your static comp? Basically since you increased the stroke you obviously changed the static compression ratio. This is all most look at. But depending on the CAM and where the intake valve CLOSES after tdc it is in EFFECT totally different. This is DYNAMIC comp. What the cylinders and fuel mixture ACTUALLY experience. Youre going to need a cam with late closing time. Like 250-260 degrees at .050 lift. If you have 58 cc closed chamber heads. Wallace racing has a dynamic calculator (and static) on their website. You wanna aim for a dynamic comp of about 8.5-9.5. Play with the calculator and see what lands you Bout 9:1 dynamic. You gotta account for how many degrees it OPENS before tdc too. And subtract that from it, the you have 180 degrees to bdc. Subtract that. The remainder is your closing time at .050 after bottom dead center. Here to answer your questions... cheers

cohocarl

Captain,

Wow...That site is now bookmarked, and e-mailed to myself at Gmail so if my computer totally crashes I wouldn't lose it.
AMAZING all the calculators on there.

Going to be a rough few days with some family matters coming up, so I won't have time to play with the engine. Once I get the cam and degree wheel installed, I'll see what cards I'm dealt with.

Thanks again for the info......you may be getting a P.M. in a few days...

captcolt

Lol. No problem. Yeah wallace has been a god send ill tell you that much. If you have any other questions duely pm me and ask or better yet i like to discuss these thing where others may benefit from them. Forums have been a HUGE help to me over the years. I learned this lesson on cam selection the hard way. Bought a 383 trans am only to have it make it 3000 miles before she shattered the rings. 12.3 static with a TWO SIXTEEN cam. God. The dynamic was 11.7... it ran out of breath at 4 k and would just spin tires till then. You CAN run a static that high with the right cam. This is why you see 11:1 11.5:1 statics in the old muscle car engines. They ran bleeder cams. Also another reason people put cranes "big ****** thumpr" cams in a lower comp engine and its gutless. Cause theyre bleeding off a third of the compression. These are good cams for us though doingnthe 383 thing with closed chamber heads. Another thing youre going to have to sort out is ignition timing and advance curves. Important to avoid those knocks. cheers!

cohocarl

I didn't really understand this part, but by inputting the numbers from my cam card which shows the intake closing at 42.5 ABDC, I had a little time to play with the dynamic calculator and it's showing dynamic to be in the 9:3X range whether I run the cam @ dot to dot or 4 degrees advanced (at the crank, 2 @ cam). Those were using figures off of my cam card. I haven't had time to play w/ the wheel yet to verify.






After I read a few threads about "dynamic" compression, I think I understand the theory... Basically, dynamic compression is calculated from where the intake valve closes ABDC, not bdc as static compression is calc'd. For example, a camshaft with less duration as mine (keeping lsa's =), would have a higher dynamic compression.

But, this is at 0 rpm, and does not take into account the inertia of the air/fuel at rpm. (ie the theory behind our beloved T.P.I.)

Anyhow, I'm getting a headache just thinking about this again.

So after I verify my cam is closing the intake around 40 abdc, my dynamic would be around 9:39:1. That should be in the ballpark.

captcolt

Very good!