POPO1984

iTrader: (1)

Ok guy im getting a hyd. roller 383 built
HEI
750 holley
rpm air gap
patriot freedom 185cc heads 72cc (mild portwork)
comp 12-423-8 224/230 .502/.510 (will this pull up to around 6000 rpm)
18cc dished pistons forged SRP
zero deck (should I)
200r4
about a 2000 rpm stall

Any guess on hp/tq

What head gasket do you guys recommend (thickness)

wanna keep it below 9.5:1

This is going in my almost DD 72 c10

POPO1984

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Come on guys no suggestions at all

NWIAdam

Why 9.5 compression? Compression wakes up a sbc.

POPO1984

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I figure I wont have to worry about detonation and I can run 87 octane

toby

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i'm going to guess 400hp. it definetly leaves a lot on the table, but for what your using it for should be a good motor.

POPO1984

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Would I really gain that much by going to a higher cr say like 9.8:1
I could just mill the heads down to a smaller combustion chamber

POPO1984

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Would I really gain that much by going to a higher cr say like 9.8:1
I could just mill the heads down to a smaller combustion chamber but could I run regular gas

pancherj

Check out these builds...
http://www.compcams.com/Community/Ar...?ID=1945664039

I've talked with Scott about his and he really likes it. His 383 is a little pricey, but it shows what can be done. I would shoot for 10:1 compression. If you have to run 87 octane on ocassion, just dial back the timing a few degrees. I ran a 10.5:1 406 with trick flow heads that was fine with 92 and probably would have been okay with 89 octane. I currently have a 10.2:1 350 with pretty agressive timing that runs fine on 89 (I usually use 92 octane). I NEVER use any octane booster.

BassProCamaro97

iTrader: (10)

First question is why the dish with the 72cc head?? I run 22 dish but that's becuase my heads are 55cc.

I'd say dial it up to 10 1/2 and run 93 in it all day. I don't think that combination of heads and pistons will get you there though. This is all good if you plan to add a super/turbo charger.

What is the LSA on the cam?

~Jim~

POPO1984

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well I dont have the heads yet but the guy building the engine wants me to get the 72cc heads. he wants it to be around 9.2:1. because he said that is what he likes. I personally want it around 9.5 or a little higher since the aluminum heads will make it less subceptable to detonation. The cam is on a 110 lsa

BassProCamaro97

iTrader: (10)

"This is going in my almost DD 72 c10"

I missed this line the first time through. Whats the use/goal of the setup? DD with some pep or do you want whatever you can get out of the 383?

I wouldn't be worried about detonation with 10:1 and that cam. If you were at 11 or 11.5:1 to one then I'd say yes, but not at sub 10:1 but maybe I'm missing something.

What lift rockers will you be using?

~Jim~

POPO1984

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Ill be running comp hyd. roller lifters and pro magnum 1.5 rockers. the engine builder says the 72cc heads are better for lower cr and less valve shrouding.

POPO1984

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I could get a 64cc heads and that should put me around 9.8. I dont want an all out race engine but I wanna be able to hold my own at the track and on the street when a cammed 6.0 truck pulls up next to me.

BassProCamaro97

iTrader: (10)

With that big a head there really is NO reason to be running a dish in my opinion for a NA engine. For some reason you/builder are looking at low compression. I'm not real sure why but 9:1 is low for an NA motor on pump gas in my opinion.

You could always go with a flat top or dome piston and bump the compression up to 10.5:1 and spec out a larger cam to take some pressure off the engine. However, then you may be defeating the purpose of the build with a wilder cam.

At the very least I'd get in touch with another builder and tell him what you are doing.

Here is my disclaimer I'm not a engine builder so take this for what it is worth

Good luck

~Jim~

draggin97s10

iTrader: (2)

i for sure agree with jim. id probably shoot for 10 to 10.5 to one. i read this lastnight and didnt quiet understand why you want to run such low cr. ive seen guys running 12to1 motors with a properly specd cam in a normal coolant flow sbc get away with 93 octane. when set up correctly with no detenation and these wernt trick setups either (i.e. meth/water injection). i am also no engine builder. but ive built several engines. and ive beat the hell out of all of them. even the ones that i put in my buddys cars.

pancherj

With an .043" head gasket and zero deck, you are going to be right around 9:1. As everyone else said, that is too low. If it had iron heads, I would try to be in the 9.5:1 range. Go with the 64cc heads. Personally, I'd spend a little more cash and get a better set of heads. $500 extra spent now will make you a lot happier down the road! I have owned Trick Flow and AFR (both around 190cc runner volume). Both performed well.

POPO1984

iTrader: (1)

I have looked at the 195cc fast as cast heads and am thinking about getting them. I guess I will get a pair of 64cc heads and zero deck it. Thants about the best I can do since I have already bought the pistons and have had the block honed for the pistons.

1 FMF

iTrader: (1)

http://www.csgnetwork.com/compcalc.html

assuming you're bore/stroke is 4.030/3.75 and a 0.040" head gasket thickness and zero deck clearance, with 72cc combustion chamber and -18cc dish pistons that's coming out to be 8.96:1 compression ratio.

a piston with 5cc relief will result in 10.17 CR with a zero deck,
9.95 with 0.010" deck clearance, 9.74 with pistons 0.020" in the hole.
I would double check the measurements with your builder before you do anything, primary what your deck clearance is going to be and then choose the correct piston.
And you will need to know what rod length you're using, 5.7" or 6", to then figure out piston selection. I think you could be fine with the 72cc heads provided you size the pistons properly, and you might want to do some reading on forged pistons vs hypereutectic; I think you would be better off with hyp. pistons for being a mild daily driver NA setup. forged pistons are not always better than hyp. pistons.
I also agree with everyone else, shoot for as close to 10.0 CR, what will be most important is you're piston to head clearance a.k.a. quench, you want that as tight as possible, that is what prevents detonation or what let's you run higher CR without detonation. do some search on ls1tech and google for 'quench piston head clearance'
you also might consider 1.6 rockers, they are pretty much the norm as long as you have the piston to valve clearance with them.

POPO1984

iTrader: (1)

It looks like im just gonna go with a 64cc head. That will put me at 9.85:1. getting new pistons is out of the question. Ive already bought those the heads are what I havent bought yet and am what Im gonna have to do to adjust my compression ratio

BassProCamaro97

iTrader: (10)

I'm guessing your budget is on the smaller side since you don't want to buy new pistons but you really should be matching all your parts to work together.

What I mean is, a good piston that compliments a good head that compliments a good cam grind. The problem you are running into is you are stuck with incorrect pistons and now your compromising your top end to match an incorrect piston. If there is any wiggle room in the budget I'd look at the option of new pistons. Even if it sets you back some time. Do it once do it right. However, with the smaller CC heads you'll be able to play with your CR based on gasket thickenss more effectivley. (easier to raise and lower the CR)

Give another reputable builder in your area a call and see what he says about what you have. Doesn't hurt to ask!


Would you be against a super charger? That would compliment the 9.5:1 compression nicley!!!!

~Jim~