Im fixing to start building my 383 and going to order the kit but before I do I thought Id ask to get some opinions to see what yall think. I want to stay on pump gas 93 octane, Im going to be spray Nitrous also so whats the highest compression ratio yall recommmend having for a 383 with nitrous on pump gas so detonation doesn't happen. Btw nitrous wont be used all the time just when needed and when running it at the track which is every once and a while, but which pistons are better for both all motor and when nitrous comes in dish or flat top?

 

you can go about 11.7 safely before you enter possible problems. i would stay within 11.0-1.5:1 to be extra safe. even 12:1 over 11.5:1 isn't much of a power gain. it is important to talk to a guy like bret bauer on a cam design to fit your 383 setup. a cam grinder can make a cam specifically for the compression you desire. shelf cams are nice, but they leave soo much on the table. they do this so the cams can be used in more of a variety of motors. depending on the piston you choose, pick a cam that allows you to run good compression without piston to valve clearance issues. i have a zero decked 355 with -5cc JE flat tops. my cam is a tad over .600 lift. with 11.47:1 compression, i have enough compression and piston to valve clearance. work with someone like bret to insure you make the right choices.

 

Yea I already have my camshaft though, Its the crane cam 109651. Its recommeneded for compression ratio of 10:5:1 - 12:0:1. I know my heads have to be milled .025 to be fixed since the car overheaded before I decided to go with this setup, block is going to be bored .30, My block deck is stock so I dont need to do anything with that. So what type of piston should I go with? Also which is better dish or flat? Im not quite sure which head gasket to go with either, .029,.039 or the lt4 which is .051

Block Deck Stock
Heads .025 milled
Bored .30
Head Gasket Choices .029, .039, .051

 

You really need to talk to an engine builder instead of asking on here. A stock block deck heighth usually isn't ideal. You could use the thin set of headgaskets that Mr. Gasket sells, and that would be ok. However, since the car overheated and you're getting the heads milled anyway, I'd just go ahead and get the block 0 decked to ensure a nice flat surface. I'm getting my block 0 decked and running the Fel Pro performance headgasket.

 

Ok but it is ok though to run like low 11's compression while spraying nitrous on 93 octane right? Cuz someone told me I should stay like 9:5:1 while spraying nitrous on pump gas so detonation wouldn't occur.

 

I would think that would be ok. I'll be running compression in the 11's and I plan to spray. You'll need to find some way to back the timing off though. You can do that by using an MSD or other aftermarket ignition box.

You really need to figure out the dynamic compression ratio using your particular cam, that tells more of a story than the compression ratio. Do a search on "dynamic compression ratio" and see if any of that helps you.

 

When you zero deck the block how much does that usually bump compression up?

 

It depends on what pistons you are running, thickness of the headgasket, CC of the chambers..... This is why I said you need to talk to a machine shop, there are too many variables to answer your question.

 

Don't believe the 9.5-1 that's BS. Figure your DCR and keep it about 8.9-9.0 or below( cam dependent) and get it dyno tuned and spray the hell out of it.
Ya need a timing retard box anyway,just plug in the right chip (2* for every 50HP) and go like hell.The retard activates when ya push the button. This way it'll run right on motor.

 

Using the DCR calculator from this site http://cochise.uia.net/pkelley2/DynamicCR.html
and using my cams Intake closing angle of 80 degrees
a -5cc flat top
5.7" rods
0 deck height
.029 head gasket
54cc? chamber volume
and 3.75" stroke,

the dynamic stroke length comes to 2.5" and the DCR calculates to 9.06:1. BTW, the static compression calculates to 13.06:1. My question now is.. if this information is correct does SCR actually mean anything? If you ran a more conservative cam would the DCR and SCR be much closer? Does this all look right? Should I be good to go with nitrous?

 

Ya got one hell of a cam with an 80* intake closing.Its bigger than 260*@50.If it is that big be prepared to shift above 7800RPM's
Ya got to use the advertised closing and not the @50 numbers
If ya go with a smaller IVC the DCR goes up. To run on pump gas ya need to stay at or below 9 to 1 DCR or be willing to do the things that have to be done to make it run right. Ya can't just pull timing and get it right.

 

its 240/244 @50, here's a link to the cam I'm looking at. So do you think all the information I got is right?


http://www.cranecams.com/index.php?s...51&lvl=2&prt=5

 

That's an awful late closing my sheet says 77* but who knows.
What do your heads flow?What is the ICL?How much advance?

 

So all I need to do is keep the DCR between 8.0 and 9.0 and Ill be alright spraying the hell out of it?

 

Umm, am I the only one seeing that he is trying to run a milled head, 0 decked block, and a .029" head gasket? Try that calculation over with the thicker .039" head gasket.