I am in the process of building a LE2 383. I need some help with some key issues on this build.

What Should My Deck Height Be?

Piston In The Hole?

Quench? (And How To Measure It?, Should i just have my machine shop do it?)

Compression?.. I understand that static compression is not a huge deal, but dynamic is what will determin what octaine I must run. Can someone remind me what good dynamic compression is if I want to run 93 octaine. Is it 9.something?

Here is the specs:

Speed Pro Hyper -12CC Dished Pistons
5.7" Eagle I Beam Rods
Eagle 3.75 Stroke Crank
LE Ported Heads
53.? CC Combustion Chamber Heads (Will update when I find out for sure, its between 53CC and 54CC)
Fel Pro 1074 (.039")
LE2 383 Cam (236/236 @.050" - 107LSA)
.030" Over If That Maters?

As it sits now, I had the blocked cleaned and punched out to .030" over. I did not have anything else done. but now that I have so much into this engine I figure I might as well do it right. So here is what I will do:



Get The Main Line Bore Checked
Try To Get Optimum Quench & A Flat Deck
MaYbE Clean Up The Heads (Atleast Have Them Checked)

Anything else?..

 

Well, with my LE2 head/LE3 cam 383, I used FLATTOP pistons, 0 decked block, and 0.39 gasket for .039 quench. That gave me around 12.5 static and 9ish dynamic, and numbers in my sig on 93 octane. It does this on about 20* advance at peak power, so it must burn the mixture FAST. Cam installed straight up, 108LSA. Heads were 53.x CCs

With -12CC pistons I don't see how you can get the CR appropriately high without reducing the chamber volume. I'm pretty sure flattops are preferred.

 

http://www.wallaceracing.com/Calculators.htm

 

alot of great calculators there. thanks for that. seems to be some on there that are kinds funny tho, like hp from bore and storke.. lol. it says anywhere from 350-650hp.. Lol

so the ammout I cut is going to be based on my target compression and measurments of how deep the slug is in the hole?..

so what should I shoot for for compressin on 93octaine?.. should I even care about static compression? or just dynamic?


I need to get my exact head CC before I go on.

what about quench?.. is that somehting I measure? or do I just add how deep the piston is in the hole, plus head gasket thickness?.. what do I want to shoot for here?

thanks

 

Run a piston with 5cc eyebrows and zero deck the block. Then run a Fel Pro gasket and your quench is basically the thickness of the gasket. Good quench is generally under .040. You should care about both static and dynamic, but they should correlate to each other. Typically a DCR around 9 is pushing it, I ran about 8.9 and had some tuning issues, but I also made really good power.

 

Paying close attention to the details is where you'll find the power. If you tighten the quench up, you can run a bit higher DCR. Why wasn't the block decked when you bored it?

 

"Try To Get Optimum Quench & A Flat Deck"

I think trying to get a good quench is the main thing. How much to shave the deck will depend on what thickness head gasket you are using and how far the piston's are below the deck. This will tell you how much to shave the deck. Having a zero deck is not necessarily the best thing.

 

On both my 383's I went 0 deck and 0.039 quench with 1074 gaskets. My 9.4 DCR is pretty high but you can tune for it...I am proof of that.

 

With Cometic gaskets available in any thickness, a zero-deck doesn't hurt, especially if you need to do so to square everything up.

 

by "Try gettin a flat deck" I mean a true deck. not necsarlly a zero unless thats whats needed.

so it looks like I want to aim for 12.2ish SCR / 9.2ish DCR with .039 Quench? (is the tigheer the better as long as it does not hit?)

that should work nicely with a good tune on 93octiaine pump gas?


ok. It looks like if I zero deck it with the setup i have now I will get 11.6:1 static compression and .039" quench. I have not figured out how to do the math and to see when my intake valve opens and closes so I dont know dynamic yet, but since I already have the cam I should figure it out before I go to far, if im already at 9.X dynamic with that cam when my static is 11.6 then I guess thats what i need to stay at.

 

What is the cam?

Make sure and get a good tune and keep the car cool to keep the predenotation away. It can be done. I ran 9.2 DCR in Phoenix and 110F and NEVER any ping. Multiple tricks keep the issues from forming.

 

yep i am setting at 32

 

For a street car, I've read that closer to 8.5 would be more forgiving without giving up much power. Anything over that then you absolutely need a dyno tune. Mail order will not cut it, IMO. Here's a link to a calculator for DCR and SCR using different cams.

http://www.empirenet.com/pkelley2/DynamicCR.html

What cam are you looking at? Getting a custom cam once you have the rest of your setup done can give you the best power without pushing the DCR too high. You can always choose custom lobes from Comp Cams yourself as well.

Here's a good article on Compression and Quench:

http://www.popularhotrodding.com/eng...eze/index.html

 

I have access to a dyno and will be dyno tuning with tunercat. I am not afraid of tuning.

Thanks for that link. I have seen the calculator for DCR. but I dont know when my intake valve closes. is there some math I can do to figure it out. I know duration, Duration at .050", and lobe seperation. is that enough to do the math and figure it out?

as im sure you can tell by now, I have a cam already. i purchased it with a set of LE2 heads and le ported intake manifold. Its a custom grind done by loyd (on billet).

 

Is it the LE2 cam? I have a LE2.2 grind and I wonder if yours is the same.

With Pat Kelly's calculator, you enter the advertised duration, not the .050" duration, and the LSA and it will calculate the IVC for you.