ok im trying to do the formula at that link, but i dont know all the info

bore in inches: im going 30 over, i dont know what that is in inches

stroke in inches: im doing a 383 so correct me if im wrong but i think its 3.75

static compression: 11.5

inlet valve closes abdc: ??? i have know idea how to figure this out

boost pressure in psi: 0

target altitude: im at like 4500 feet but i go to sea level sometimes so ill say 0 feet


so once i figure this out then how do i know if i can do 11.5 or not??

 

The bore is 4.030 and you HAVE to know the advertised duration of your cam,if you have a good program it will tell you the IVCP. If you know your spects give them to me and I will do it on my program. I need your ILC(intake lobe centerline and advance) & Lsa(lobe seperation angle) and advertised duration not at 50 ( send @50 if it's all ya got,I'll figure it out)and your rod length,head gasket thickness piston in hole depth, head CC's,type of piston,CC's in valve relief.
See, it gets a little complicated and most people won't take the time.
Send me your spects and I will do it for ya. It has to be ALL what is listed or my program won't work. Garbage in-Garbage out

 

you guys need to listen to this dude...^^^^^

he is EXACTLY right!!

 

1Racerdude how does cam advance/retard affect the dynamic cr? I went to the link and put in my info and it's telling me my dcr is 10.44. My combo is a 383 with ported LT1 heads 59 cc chambers, SRP ft with 5 cc reliefs .013 down the bore, 6" rods, 3.75 stroke, felpro 1074 hg .039 thick, GM 847 cam 296* advertised intake duration with intake closing 79* abdc @.004 tappet lift 112 lsa. I have my cam installed 4* retarded, can you run my combo and tell me if I'll be ok on pump gas, thanks.

 

Why in hell did you retard the cam?????
Presuming you have flat top pistons and the gasket bore is .100 and the cam is 229I-229E here is what it is:
@ -4*retard a 116 centerline Static is 11.429
DCR is 7.586
@ 0 a 112 centerline Static is 11.429
DCR is 7.93
@ +4*advanced a 108 centerline Static is 11.429
DCR is 8.26
You can live with a 9.0 Dcr on 92 octain,in your case your are low,safe, but low. Bumping it up to 9.0,you can tell a difference. Get the cam advanced and you will notice it too.


EDIT: Look Below>

 

This is also presuming the ICL is 112* and a LSA is 112* with a 4*retard it is 116* ICL (GUESSING) and that don't make for good accuracy.
Using the guess figures-- with a 108* ICL and the .022 Impy gasket ---- Static is 11.96
DCR is 8.63
That would be a LOT better and it's safe.

 

Thanks 1Racerdude, I retarded the cam to reduce some of the low end tq and give me more mid - upper rpm power to help the car launch without blowing the tires off. The rest of the combo is as follows ported LT1 carb intake, BG 750 dp carb, DUI/HEI with custom advance curve, TCI 3000 lockup converter, Art Carr 700R4, 3.98 geared 9" all in an 87 Monte Carlo SS. My thought process was with a 3.06 first gear & 3.89's the car will launch better with less tq am I wrong here? You're saying the engine will make more power with the cam straight up or 4* advanced?

 

You are right in your thinking.But you aren't going to make enough HP to BLOW a good set of DR's or ET streets off with the auto. You would need a 5000 stall and trans brake or a stick to BLOW them off.
It's going to drive like a t*** around town too.
IMO advance that cam 4* and use the Impy gasket,, you will be a lot happier with it.
The only reason to retard a cam is if you got the wrong cam and it's WAY off'.

 

Ok thanks I can do that since the engine is still on the stand and not in the car.

 

With a 383 and a -14 cc dish in the piston that has a zero deck ht, the 55 cc chambers of my heads, a head gasket that is .040 thick (Fel Pro 1074), you will have a DCR of 8.86. That is still fine with 92 octane. Most agree you can run up to 9.2 with 92 octane and a good tune.

Yopu can usually remove the decimal from the DCR and that will tell you whta kinda octane you need.

I would not wanna use cheap fuel with the 8.86 DCR though. Just use Supe unledede and get a good tune and you will be perfectly safe.

The cam was designed to be used with a 11.6-11.8 to 1 383 and still work on pump gas. If it was a 12.0 (or higher) to 1 motor, we would need a lil octane booster, racing fuel or run more fuel/less timing to make it OK for pump gas with that cam. For pump gas and a 383 with that compression, we would wanna use a slightly diff. cam to reduce the DCR for best results.




this is what lloyd told me i trust him but i just want a second opinion.


thanks

 

I tried the calculator that was posted with the stock lt1 with the hot cam using the cam card that came with the 847 and came up with a dcr over 9.0 what gives? I was going to use the impala hg when i swap cams but now what??

Your engine summary is as follows: Bore 4.00 inches, stroke 3.48 inches, rod c-c length 5.7 inches, with a static compression ratio of 10.25 :1. Your camshaft specifications call for an inlet valve closing of 44 degrees ABDC (after bottom dead center).

Your chamber volume is 77.47 cc's. With this camshaft your dynamic, or effective stroke is 3.12 inches. Your dynamic compression ratio is 9.29 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 192.71 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 0 PSI is 9.29 :1.

 

Give me your head CC's,piston in hole distance,valve relief CC's,ADVERTISED duration of cam,gasket thickness,piston type,and I will figure your DC on my program.

 

That compression should be fine for the street. Only reason it would be too much is if u wanna put a blower or turbo on it. Stick to 93 gas and youll be fine.

 

1racerdude every thing is stock the cam is the gmpp 847 I don't why I said hot cam. I dont have the advertised duration but the cam card reads as follows: Grind#12370847,

Lift: I@cam 359 @valve 539 w/1.50 rocker
E@cam 372 @valve 558

cam timing @ .050 tappet lift
opens closes max lift duration
intake 10 deg btdc 44 abdc 107 234
exhaust 58 bbdc 4 atdc 117 242


thats all I have Thanks for you time and help I am wanting to get the .029 thick impy gaskets if I can but it is nice to be able to make a educated desicion rather than a stab in the dark.

Also this is in my daily driver so what would you suggest as the intake center line? If I am reading the cam card right it is 107 right? Or should i advance it 4deg for better bottom end? Prolly will end up with a 2600 stall and 4.10 A4.

 

The cam is advanced 5* already.
Give me the rest of the figures I listed above or I don't have enough input for my program to figure it.
Is it stock engine you are just putting a cam in?