In the process of building up a 383. Here's what I got in parts...

383 4 bolt 2 piece seal
Forged Crank and Rods (Eagle)
Hypereutectic Speed Pro ZH859CP Pistons
Felpro 1044 Head Gaskets
RHS Pro Action Heads
- 180cc Intake
- 74cc Exhaust
- 72cc Chambers
- 2.02/1.6 Valves
Performer Air Gap 7501 Intake
1.6 Ratio Crane gold Full roller Rockers
No Carb yet (Probably a 700 cfm)
No Headers (probably 1 3/4)
Hydraulic Roller Cam
- 230/238 @.050
- 110 LSA/ 106 ICL
- .565/.565 Valve lift (with the 1.6 rockers)

So whatcha think? I need some input... Good. Bad. Possible changes???.... Also, I need someone that REALLY knows engines to chime in here... I don't wanna hear go with AFR's or something ridiculouss like 220cc heads. THIS IS FOR A DAILY DRIVER. That being said... How's this engine gonna perform with the selected parts? I got a few questions to ask, but I'll leave those for a later time.

 

Only problem I see is you are going to be way low on compression with a 12cc dish
and massive 72 cc heads unless you are going forced induction?.
The duration of the cam is going to bleed down ( lower DCR ) your compression as well
Read this
http://members.uia.net/pkelley2/DynamicCR.html

There is neat calculator at bottom of page you can download and install.
It lets you put in your engine specs to calc CR and DCR

 

Done a quick calc.
Have your current combo at 9.0:1 static CR
6.86 DCR using Crane #119661 230/238 cam
http://www.cranecams.com/product/car...detail&p=24188

Going to a 5cc flat top piston (ZH860CP ) or 64cc heads only brings DCR up to 7.3 ,still below recommended range
"It appears that most gas engines make the best power with a DCR between 7.5 and 8.5
on 91 or better octane."
Zero decking the block with either the piston or head change gets you in the sweet spot
at 7.78

 

Interesting. The cams a custom grind and it actually nets a DCR of 7.09 as per your calculator. Or going to a .039 thick/ 4.08 bore gasket, gets me a SCR of 9.3:1 and a DCR of 7.3... How would this motor theoretically run if I just changed the head gasket to get the DCR up a little?

 

Also bad choice of head gasket.Gives bad quench
Read
https://www.thirdgen.org/forums/powe...ce-vs-dcr.html
http://www.camaros.net/forums/showthread.php?t=124935

#1044 is too thick ( 0.051 ) and bore size (4.200 ) too big
Lowers your CR from what I originally calculated above using gasket below from 9.0 to 8.77
and the DCR to 6.68

Should use # 1043 ; 0.039 thick and 4.080 bore

 

Funny thing is this was not my choice of parts, but rather parts chosen my the "ENGINE BUILDER"... Only parts I chose were the heads. Wanted to keep it on a slight budget.. Also chose the 72cc just solely based on the fact that they had more material and if I wanted to mill the heads, there's more to work with.... Here's what I was thinking... Either 1 of 3 things... 1) Mill the heads to bump compression/ change to 1043 gasket and keep that cam. 2) Change pistons to something like this (http://www.summitracing.com/parts/UEM-KB134-030/) that would change the compressed height to 1.433 instead of the 1.425 that I have now... Would bring the piston to .002 piston to deck height/ 1043 gasket (giving me a quench of .041) or 3) change cams... Don't know what to do... It just pisses me off that the builder tried to convince me that the engine would be a 9.8:1 SCR with everything all said and done. The biggest thing is I still don't understand how the engine would run with a 9:1 as it is now vs a 9.8:1 like the builder said it should be... "Theoretically"

 

double post... SORRY

 

i'd be inclined to try a 108 lsa on a the cam, duration is great for a 383 but it would work good on a 110. RHS 200's would be perfect. 180' will work but are a little small. Consider 195-200cc RHS heads from Chad Speier? he mildly ports them and gives them a good valve job with good springs to match hydraulic rollers. Or can try is Profiler 195's. All about same price

I also agree, get compression higher, mid 10's to 1 will work great with aluminum. 64cc will help that but as said, keep quench in the .038-.045 range

Just mill the heads down but that doesnt make sense when you could have gotten them in 64cc. 10 to 1 with a cam like that is great on pump gas. I ran 11 to 1 with a 230/245 cam on a 109 lsa just fine on 93 oct. Could easily daily drive it as it was extremely driveable on the street, except it was loud.

 

The Advertised duration, as per cam card is 284-292. Builder told me it was gonna be 9.8:1 SCR... I said go with the 72cc's... Seems it woulda been about 9.8:1... BUT with the 64's, not the 72's... Plus he didn't say anything when I said 72cc's... So I rolled with it... Mind you I didn't know all the specs on the motor before hand cause they already had a short block assembled when I decided to work with them on this build. I would have thought that with their reputation, they would have noticed that the cam... THEY ORDERED!!!... needed more compression... Honestly, I'm not about to go drop a GRAND on some other heads... I guess I could try to sell these possibly seeing as they haven't been run yet or go back to the builder and tell them to sort this out.

 

I just did the math and got 9.2:1 SCR....

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

is he talking DCR?

If you go with a .020-ish head gasket instead of a .039 gasket you'll get 9.5:1

Edit:I was assuming a .030 overbore. Why arent you going to bore the block? Is it a new block with perfectly round bores?

 

9.02:1... its a .030 over bore. 72 heads.3.75 stroke. 4.200/.051 gasket, 72cc heads, 12 cc pistons and .010 PTD clearance... ??? Is new, as stated it was already assembled before... The guy that it was built for never picked it up, so they said it'd be a nice foundation to go off of. So I agreed.

 

Well looks like you got a lot of good parts, but I'd swap to some flat top pistons if you can.

 

I'm think the shop should do it, seeing as I paid them and all.... It just still doesn't sit well with me that the builder doesn't/didn't see a problem with this combo. Maybe he knows something we all don't know. Plus this shop is "REPUTABLE"

 

Well honestly, that cam is on the relatively small side too as far as duration goes. That cam is good for a medium-ish 35. On a 383 it'd be a little more conservative. The compression ratio and the cam match relatively well I think. I dont think it's a bad build, but the heads are capable of more than the cam and SCR will let you get. That IS a roller cam though, with some hardcore lifts on it, so it'd still make some decent power, but it's just that there's more capability in it.

I wouldn't say it's a bad build. For someone just wanting a street car it'd be great. But there's just power left on the table.

 

Well see, now that's were my limit of knowledge and experience halts... This, being my first build leaves me not understanding many aspects.... I figure that there's more potential... How much, well that I don't know... I guess what worries me is how this thing will run/act if the only thing i did was just change the head gasket to the #1043 and leave all other things the same. I know many guys wanna make sure all parts match well as do I... I just wanna make sure it's done right... Cause once it's assembled, I'm leaving it as is... No upgrades in the future... At least not in the near future.

 

RHS® Pro Action™ 180cc cylinder heads are the perfect bolt on head for smaller displacement
Small Block Chevrolet engines.
Ideal for 262 to 350 CID street engines, Pro Action™ 180cc cylinder heads are the hot ticket to making up to 325 flywheel horsepower.

 

Meh. they have more runner volume than vortecs. They're better than anything factory. People put garbage factory heads on 383's all the time. They're not AFR's or Trickflows or anything, but they're decent. At least I imagine they are. I'd assume they'd outperform Vortecs... is that not a safe assumption?

 

With that compression, small head and performer intake, i'd actually go smaller on the cam. The small heads and intake will limit power. It may not even make 1 hp per cube although I hope it does.

That cam would love a 195-200cc version of those heads and another full point and a half of compression.

 

What's the correlation between iron heads and compression? They say you don't wanna go over 9.5:1 for iron heads, what are they basing that on? So what happens at 10:1 with iron heads?

 

Static compression ratio isn't as important as dynamic, but regardless of that aluminum heads pull heat from the chambers faster than iron heads do. This results in a slight loss of power. So to compensate you up the compression ratio to get combustion temps into the corret range again. This is a layman explanation and hopefully someone who understands it better can explain it properly.

10:1 is just around the magic cut off (with iron heads) where running premium unleaded may not be enough to stave off detonation issues in the correct timing range. You can easily get into a situation where you have to retard the timing too far to stay out of detonation, and you leave a lot more power on the table by cutting timing than you do by cutting compression ratio. Above around 9.5:1 the increase in power you get by increasing the compression starts dropping off quickly too. The most common reason to increase compression ratio far beyond there is to compensate for large camshafts with overlap bleeding off pressure (Dynamic compression ratio) or for running fuels other than gasoline.

You can run more than 10:1 SCR on iron heads and run full timing and get away with it, but it just depends on a lot of different factors - it just gets tricky.

 

In a sense you answered my question I was thinking about next... Was gonna ask how guys run over 9.5:1 well in the range of 12 or so with no problem... Finally got the builder to send me the remaining clearances I asked for... This guy is really convincing and seems to think that the cam he ordered will work fine and as far as he's concerned it not too big at all... I don't get it but whatever... Seems recently they got the shop Camaro into the 4's in the 1/8 mile on 275 street radials (apparently that was a record of some sort)... I guess in order to do that ya kinda gotta know what your doing with engines (among other parts of the car).... This is one thing I was surprised to hear, apparently sometimes ya gotta slightly overcam (in a sense)... Now isn't that just contradicting of everything I've learned up to date...

 

You can run more compression with aluminum heads than iron ones 10 to 1 even 11 to 1 with aluminum heads on premium pump gas but 9.5 to 1 is about the max with iron heads. You need more cam smaller chamber heads and flat top pistons. Assuming you don't wanna buy heads the cheap fix would be small dome pistons.

 

Depending on the car's setup and goals, it may be necessary to run a bigger than optimal cam. Guys with mismatched converters/gearing may be forced to run more cam in order to take advantage of the too high stall speed. Extend the rpm range more. This happens when a racer has a budget and wants to go alittle faster than he currently is, but cant change the converter at the same time, so he is forced to use more cam.
Restricted intake or restricted head rules can change cam requirements. Guys setting records with cam only type builds on stock heads usually run big cams...much bigger than the heads typically would support, and much bigger in duration than whats normally needed to make peak hp in the rpm range they do. But it works.
Even the different types of racing out there require different cams. Like circle track/nascar stuff only typically operate in a set window rpm range of say 1500 rpms or less, maybe 2000 rpms. Some road race cars on twisty courses need a much broader rpm range, may do pulls from 3000 to 7000 rpm. So it all depends.

Lastly, when you have alot of compression and need to bleed cylinder pressure to run pump gas, you cam up.

But your cam isnt big for a 383...My friend runs similar cam in a 360" motor just fine.

 

I still got waaaay too much to learn... I'm just gonna slap some better suited head gaskets on there and call it a day, get everything installed and see what she does on the dyno. If I'm not satisfied then I'll look at alternatives... Thanks for the help/info guys.