383 rebuild - old dyno results & new cam ideas

Indycars said:
I've sent an email to Larry Atherton, the lead software developer about the sharp changes in
the graph. I'm waiting to see what he says before I proceed.
Click to expand...
Larry got back to me last night with an answer to my email. He said, "The Filling & Empty (FE) method
uses step rpm of 500, if I switched to Wave Action I could set the step rpm to 200.

So the graph is a straight line to/from every 500 rpm data point to the next when using the FE method. When
the graph line is changing fast like it did at 3000 and 4500 rpm points, it creates a distinct change in direction.
 
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I guess if no one else is going to post curves, then I will.

Since the CompCams had 4° advance ground into the cam I went back and retarded it 4°, so now
it's installed straight up (split overlap). I did the same for the other two Crower camshafts, they
had the same 4° advance ground into them also.

Sim03_Crower00429_Sim02_Sim01.JPG

Sim02_CamManager_Crower00422.JPG

Crower_SR_00422_546_564.JPG

Sim03_CamManager_Crower00429.JPG

Crower_SR_00429_614_620.jpg
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AFR 195 heads they choke out at certain lift go see my thread why I sold mine. Told by numerous cam guys and the guy who designed them. Those heads will run great similar numbers with a good hydraulic roller. The simulation does show the roll off from higher lift. I would not want to be spinning too much past 6k on a 2 bolt stroker either. Mains are known to rock. Will be allot of money for extra hp I know. 500hp area can be done decent on the wallet the next 50+ get expensive quick on a 383. Just my .02 on this.
 
The SCR of 10.3 seemed low for a camshaft of that level of performance. So I raised the SCR to
12.0 and increased the primary header tubes to 2 inches.

The average HP/TQ from 2500-7000 rpm for Sim03a is 428/470.
The average HP/TQ from 2500-7000 rpm for Sim03 is 411/452.

Sim03a_SCR12_2InchHeaders.jpg

DCR Calcs.JPG

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Indycars,

Thank you for taking the time to run and post the simulations, I appreciate it. I was surprised the curves of the 00429 were so similar to the others though, I expected the tight 104 LSA to shew the graphs a little more. What do you think?
 
I'm working on an idea to compare several of the head flow numbers. It may not prove anything, but
it should be at least interesting. I have to leave for work at 2pm, so if I don't have something posted by
then, it will be tomorrow.
 
Drew Pedersen said:
Indycars,

Thank you for taking the time to run and post the simulations, I appreciate it. I was surprised the curves of the 00429 were so similar to the others though, I expected the tight 104 LSA to shew the graphs a little more. What do you think?
Click to expand...

Your welcome, I enjoy doing this so it's not work for me.

When I read your "What do you think?", below is where my thoughts went. Wouldn't know if
there was anything there until I did the work to compare.

The two flow files for AFR 195 Street and AFR 195 Ported both have nearly identical flow and
the same sharp corner at .400 inches of lift. I have to wonder if this doesn't explain somewhat
the sharp corners in the HP/TQ graphs. After .400 lift, then the ported head shows better flow.

Keep in mind that every 10 cfm increase is approximately worth 20 HP.

HP = 0.25714 × CFM × No. of Cylinders ......... https://www.hotrod.com/articles/airflow-research-cylinder-power/

Your heads don't flow much more at .600 lift, than they do at .500 lift. The cam may have more
lift, but your heads can't take advantage of it. The Crower 00429 does have 8/9 degrees more
duration than the Crower 00422 that helps, but that's just one side of the equation.

Below you will fine the results of the Excel spreadsheet that I did to see how all the heads compared.
I only had time to do the intakes, but I hope to do the exhaust side tomorrow. You know what they
say ..... "if you can't get it out, you can't get it in".

SBCPortFlowComparison(1120).jpg
SBCPortFlowTable.jpg

I add this exhaust graph a couple of days later, but also wanted to post it here so both graphs were
available to view together. I also updated the Excel file for download.

SBC_ExhaustPortFlowComparison.jpg
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Attachments

  • SBC Port Flow Comparison.xlsx
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keep in mind when viewing the head flow graph posted above , that there are other , important factors in any engine combo,
head flow is critical but it must match the other parts selected,
those brodix 200 heads are known to make good power, now looking at the graph, you might think, they can,t compete,
but if your intake manifold only flows lets say 260 cfm they may be the hot ticket!
its not the individual part but the total combo that maters,
few dual plane carburetor intakes exceed 270 cfm in individual runner flow
http://garage.grumpysperformance.com/index.php?threads/carburetor-intake-manifold-test.58/

http://garage.grumpysperformance.co...ing-parts-and-a-logical-plan.7722/#post-85144

http://garage.grumpysperformance.co...e-springs-and-setting-up-the-valve-train.181/

http://garage.grumpysperformance.com/index.php?threads/is-backpressure-hurting-your-combo.495/

http://garage.grumpysperformance.com/index.php?threads/calculating-required-exhaust-pipe-size.11552/

if your intake won,t flow 270 you heads can,t be expected to exceed that flow rate,
if your auto transmission shifts at 5700 rpm it does not hardly mater if you are basing choices
on engine port flow you might see at 6700 rpm
Id also point out the exhaust scavenging,
EXFLOWZ4.jpg

and cam timing has a pronounced effect on intake port flow,
at lower and mid range engine rpms max head port flow is seldom reached.
yes you should get the best heads you can afford, but posted flow rates are seldom achievable,
without extensive intake porting modifications , proper cam timing and an open long tube tuned header.
theres an old sawing... "a chains only as strong as its weakest link"
with engine durability and air flow a similar process is involved.
one tip youll learn over time is that your generally better off buying fewer high quality parts,
than more lower quality parts, and all the parts used,
must match the intended rpm , stress levels and power range.
 
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