View Full Version : Cam selection 383 SBC
Currently running a 383 SBC with Vortec heads (2.02 &1.60) with substantial port work.
Comp hydraulic roller:
3.0 overlap @.050
54. overlap @seat
10.0 static CR.
Stainless marine exhaust. This motor pulls hard to 5400rpm, idles well at 800rpm in neutral and idles decent at 650rpm in gear. No Reversion issues.
I've built a new 383:
AFR 195 heads
10.2 static CR.
My question is cam selection. I want a "little" more cam, but still want decent driveability and not worry about reversion.
"Ultradyne-Bullet" cams have several grind profiles that are a step up from the Comp profile. I can have these ground on any LSA. How much is too much duration @.200 or too little?
How much overlap can my exhaust handle?
You don't need more cam.
The AFR's are such a good head that you don't need more cam duration. In fact, they should easily extend your rpm range just like another 10-15 degrees of cam duration would on your Vortec heads.
In fact, you could lose some duration if you wanted to build more low/mid range torque and still keep your 5400rpm hp peak.
Get ready for take off! Your 383 is going to turn into a whole 'nother animal.
Thanks for the "Good News" CFM.
But my real questions are: How much camshaft overlap can Stainless Marine Exhaust handle in a SBC idleing at say 800r's?
On the camshaft duration @.200 question, I see grinds with 230 duration @.050 that have duration at .200 anywhere from 133 to 153. Is the higher number going to build more torque or is the lower number? Somewhere in between?
Both :shocked: Kinda anyway, follow along.
If you know this I'll throw it out so others reading can learn a little something.
The below is very generic and quickly typed so don't take it as 'Gospel.'
Overlap, as you know, is the prime factor with reversion.
It takes a lot of time to get a valve off it's seat and especially a valve back down on it's seat. This is where a lot of overlap comes from. Look at the 60's camshafts ! 330 + degree duration on factory Hot Rod motors. :eek:
Times have changed. Companies can make cams with much less seat duration while still giving more duration at higher lifts.
So, given the same seat duration, the cam with more duration at .050" and duration at .200" will typically make more power everywhere. Why? It will have the valves open at meaningful valve lifts (where air can flow enough to fill the cylinder) longer than the slow opening/closing cams that waste more time at no/little air flow lifts.
Whatc out though, many cam companies use different lifts for their 'advertised durations.' many use .004" lift while some companies like Comp Cams use .006" lift which makes the cam look faster opening/closing than others.
So, that's why we are finally seeing values at .200" lift. Years back, the industry finally started publishing .050" duration so that cams could be compared better, but now with the .200" lift (in addition to seat and at .050")we can start seeing a better picture of what their profile is like.
In all honesty - we would be best off to see the whole lift range/duration but that would make it too easy for other grinders to copy.
As far as your question for reversion/cam/ with your pipes - I cannot answer that.
Trying to get this information from people that may know is like pulling teeth.
I went thru this this past winter with my BBC build, so I went conservative with cam and tested for reversion on the dyno just in case.
Anyway - with using AFR heads you don't have to run as big as a cam as you would with many other heads. That's the good news !
FYI: same deal with the Canfield and AFR BBC heads. That's how I made hp/torque with a small cam that had less than 225 degrees at .050" .
It's all in the heads. :bigsmile:
06-28-2005, 10:35 AM
Better heads, less cam, will make more power because the cam doesn't have to do alot of work to make power. Duration at .200" is very critical but duration and lift numbers are based on the flow numbers, rpm, and CID of the engine.
Hey C - he's got more cam (Comp hydraulic roller:
presently in his 383 than I do in my 502. :bigsmile: :bigsmile: :bigsmile:
06-28-2005, 10:50 AM
Yeah, he defineately doesn't need to go bigger.
06-28-2005, 11:01 AM
With those heads and some one that shaped them properly, cams down in the 208 to 218 @ .05 lift range will produce unbelievable results. Are the new heads as cast or ported?
5.7's with the 180's and non roller cams around 220 at .050" will make 400hp and pull to almost 6k.
We stuck a set of unported 180's on a 11.5:1 5.7 and thru it in a 3200lb 10" tire car and ran 11 teens.
Had them ported with no other changes and ran high 10.80's.
Thru a 125 shot of juice and ran 10 teens.
This was way long ago - like 10yrs maybe?
Anyway - just one of my examples on how good these heads are.
06-28-2005, 11:34 AM
Would want to know actual air flow figures for old and new heads. Air speed changes are what could stub your toe on this one. Differances in port volume. I have seen bigger heads loose so much at low RPM (and at top) that it wasnt worth it. Pulling hard up to 5400 RPM with your current set up would mean your pulling around 245 or better CFM through those Vortec heads and intake you have. More air more cam bigger ports may not produce power were you want it.
Your correct - I missed the part about 'Substantial Port Work' and the larger valves.
The Vortec stock are decent, but the small runners really do start to step on airflow in the higher rpms on the small motors, and of course mid-upper rpms of the bigger motors.
I would stake my life that the 190's-195's , even out of the box, will be the best head for a strong 383 that is looking for best sub-6000rpm power.
06-28-2005, 12:09 PM
CFM or shop has pulled 250 CFM @ .5 lift with vortec heads just corn rolling runner and bowl and good seat work. Look at AFR s flow charts between 180 and 195 cc heads only only 2 to 5 CFM differance in air flow?
If I add 5 cc to a port and got less than 20 to 30 CFM at most lift points see what I am getting at.
That's good #'s with the Vortec.
I understand the negligable difference in flow with the jump in port size thing.
I've seen both 180's and 190's and 210's at the track (street motors and race) on various motors, and heads swapped within the same motor.
Perfectt way to find out what happens when flow bench data is close but the head intake runner CC is different.
Real world performance !
The 180 is very flexible head and will work well on the 383. The 190 will be a bit better and will have the flexibility to go on a higher powered application for future use.
I'll take me for an example.
If I go AFR for my 5.7 build up there is a good chance I'll go with the 190's.
Why? In case I go to a 383 or 406 or supercharger later. They won't be as ideal on a 5.7 as the 180's, but they will still work extremely well and I won't have to buy another set of heads or sink a bunch of money into the 180's to make them work better for the bigger motors.
I'll lose a little 'ideal hp/torque' if it is less on the current motor than lose more if on a possible engine upgrade.
Anyway - the AFR's are so flexible with what they go one, choosing one blind will still lead to happiness. :bigsmile:
06-28-2005, 01:42 PM
Looks like I have a couple SBCs to work with now. Was never much impressed with their design. might take a beating for that remark. The siamiesed ports & weak main webbing turned me towards small block Fords and big block Chryslers. The latest gen SBC Chevy stuff is their best work so far as have seen. Would like to turbo a pair of them for the Apache. Stuck with Gen I for now.
Ah, you changed it. Damn. :bigsmile:
No, I won't give you a beating. Others should not either.
Many times you think outside of the box, nothing wrong with that.
It's what makes things better.
Now, have you seen a lot of AFR build ups? Oooops. Let me be more specific. I'm talking AFR on Chevy motors. :bigsmile:
06-28-2005, 02:04 PM
Sorry got a carrot in there that wiped out most of my text back up and reread.
06-28-2005, 02:23 PM
We have flow tested a few and consider them a good head. What I have seen is in a case such as started this thread is the ported heads out perform the bigger heads because the engine needs to be bigger or turn more RPM to make use of the larger port volume. Air flow is the same just need a bigger or faster pump than before. Power output ends up real close possibly the same. The RPM range at witch it occurs is just higher.
In some cases the peak power is up on the bigger ports say 20 HP 1500 or so RPM higher. Looking at a dyno sheet a loss of 100 HP over the total power curve on the big ports vs the small port might occur. I look for torq not relay interested in HP.
06-28-2005, 02:32 PM
Quite a few years back now our shop started to specialize in small block Chevy, Ford and Chrysler stuff when most were working on Big block stuff. We had done the big block stuff but saw everybody was doing it. So we specialized a bit. We have 305/307 heads with stock valve flowing 220 CFM at .5 lift.
I've done a little work to these 195 heads. Mainly smooth out the grooves in the ports where the CNC cutter comes in at different angles, also Squared up the "D" exhaust ports and made a back cut on all of the valves. I found an article "Profiling an AFR 195 head" and tried to imulate that work. Honestly without a flow bench, I don't know how much I've helped(or hurt).
On my camshaft Q. I have decided that I am going to run a Comp. 224/230 on a 111 LSA.
I actually had this motor together for about 3 hours, discovered an oil leak, pulled heads, found unusual wear (scratches) in cyl. walls, pulled it the rest of the way down, was shocked at the roller lifter wear on the cam lobes.
Found out that the oil leak was from the head surface, a .003+ machine line the length on the heads right in the middle of the oil return holes. Apparently the 10105117 .028 GM head gaskets couldn't compensate for this. Also had some oil in the cylinders and saw slight detonation areas on the head surface, a couple of valves tips had the tell tell signs of "X" valve float and I suppose that the detonation issue could have been responsible for the cam lobe wear (trying to force the valves closed).
I had that cam hardness tested on a "Wilson-Rockwell 2000" machine, watched them achieve 46.1 on the ramps, 51.1 on the nose. Sent that cam to Comp with my findings, recieved a phone call from "RED" saying my cam checked fine. HUH? They agreed to build me one on a Billet blank -9 core(the hydraulic roller cores they use are austempered -8 core). Recieved my 08-000-9 cam, opened up the box, and it's an austempered cam. Long story short he says they don't have a billet core for a 1.050 base circle. So I tested this new cam, 48.3 and 51.3 respectively. I suppose I will put this motor back together the same way except I'll use 1010 Felpro HG.
I had .010 shaved from the heads, but now using a .039 head gasket with a .016 deck I am concerned about the .055 quench. I guess I'll find out.
So if it were not for the oil leak that forced me to tear this motor apart, I suppose over time it really could have done some damage.
06-28-2005, 03:12 PM
What lift are you running and RPMs ?
With 1.6 rockers, 535/544 lift.
With a 23" powertech and 1.6 gears I'm turning 5400 @66.+ MPH
This disease "SPEED" now has me on a vendetta for 70MPH
So with my 23, I'll need at least 5700 out of this motor, or turn my 25" labbed mirage + to 5300
06-29-2005, 07:24 AM
What intake ?
These are the specs of current motor:
3.75 stroke Scat 9000 series
4.040 bore = 385ci
SRP 16cc dish
Eagle 6" H-beam
.028 Gaskets = .049 quench
61cc Vortec heads
Comp 224/230, 535/544-112.3LSA 110 IC
RPM Air gap
Holley-9015 750 Vac. sec.
Mallory magnetic marine dist.
Hi-fire VI-A box
4.030 Wiseco flat top -5.4cc
Scat 6" I-beam 7/16 bolts
.039 Gaskets = .055 quench
68.5 cc AFR 195 heads
Upgraded to REV valves, 1.530 springs
Comp 224/230, 535/544-111LSA (haven't degreed cam yet) Warranty cam degreed in @111.3 LSA, set IC @110.5 with Cloyes Hex Adjust
Same induction and ignition
06-29-2005, 11:40 AM
If you have iron vortec's and you are going to aluminum heads, even though your calculated numbers on compression come out on paper in reality you are a full point short on compression when the engine is running do to the thermal ineffiecency of aluminum and the growith of the chamber as it gets to temp. That why people try for a point more in compression when switching to aluminum heads.
What kind of boat is this? Weight? Etc, etc?
06-29-2005, 11:57 AM
You have well ported Vortex heads. I will assume you do. Now you have ported AR heads. My experience is Performer RPM or Air gap version wont flow but about 10 or so CFM better than factory as cast heads which is what they were primarily designed for. I would go with a Torker or Victor Jr. Since acquiring my two SBC I have been looking more seriously at intakes for them. The Motown intake looks interesting also. Unfortunately haven't had a chance to flow any intakes lately for SBCs and when we did didn't record the data for the intakes. Plus we don't do intakes often or have people send them to flow with the heads very often. A cheep test would be to purchase a Torqer there only about 100 bucks. Also some real headers such as Lightning makes for a SBC might be a big help. I might try the torqers myself since my engines are susposed to be 320 to 370 HP.
FYI: I have not done an Air Gap on any AFR's yet. They have all used Victor Jr's, Super Victors, Bowtie Single Plane, or Brodix.
V Jr's on lower rpm or smaller cid stuff, and the others on the screamers.
I'd be interested to see what the Air Gap RPM does on these. I've been contemplating it also.
This is a Crownline 202, 3400LBS empty.
I have been running on 91 octane, approx. 50hours on current engine. I still want to run on pump gas hence the reasoning for keeping the comp. ratio in the low 10's. If I took another .010 off the deck, that would ideally tighten up the quench and raise CR. to almost 10.5-1, What do you think?
This boat does everything I want it to do (except hit 70mph). Bone stock, this was a 45mph boat so I've done some good.
06-29-2005, 12:27 PM
I have stated this before I had a 7.4 in my 236 Seebold. Stock except for a 830 Holley and Performer RPM intake. It ran 75 just about any time. I put Edelbrock Oval ports on it with 2.18 intakes pocket ported it to 290 CFM at .500 lift. left the short bolck stock cam factory stock. 830 with RPM manifold bow rise quicker acceleration than before. Tried a 750 carb same thing. Put a torker II on it no bow rise just popped up on plane better acceleration than RPM hit limiter 5200 RPM and 75 felt more like a jet boat. Tried both the 750 and 830 on it couldn't feel a difference. Bought the Air Gap which ran just like the RPM. Went back to the torqer it had better low mid and high end performance. With headers a better intake would have been a real ride. Definitely needed a better prop. It performed so well I don't even think a cam change was necessary.
LMAC - I personally wouldn't raise the compression any further.
I think you are doing the right thing.
If you think it needs more power, change the intake.
If the intake doesn't help, the performance issues are in the boat.
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