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Old 12-24-2012, 06:54 PM
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Input on my 383 setup

I've been reading threads for weeks now, I think I'm close to the set up I'm going with. I'm looking for some input on the final choices to make sure I got it narrowed down to where I need to be.

My main concerns:
1st- Make sure I have the best parts combination that compliment each other.
2nd- Street performance, low-mid range torque

Going in a 69 C10, about 3800 lbs, 12 bolt 3.73 (gears can be changed), 700r4 (haven't decided on stall yet, possibly 3000), Fast EZ EFI (I don't have it yet, but 99% I'll go with it), won't spin over 6000 rpm.
I just assembled my 383 two days ago. Everything is brand new.
350 hyd roller 4 bolt .030" over
0 deck
Scat 9000 3.750" crank
Probe forged flat tops -4cc valve reliefs
5.7" H-beam rods

I'm looking for 9.9:1 to 10.3:1 CR I've checked this on 3 diff CR calculators, but just wanting to make sure I got it right. I'll run 91 octane.

Heads I'm looking at.......
Trick Flow 195's w/72cc w/.040" gasket 10.28 cr
Trick Flow« Super 23« 195 Cylinder Heads for Small Block Chevrolet TFS-30400013-M72 - SummitRacing.com
AFR 195's w/75cc w/.040" gasket 9.9 cr, milling to raise cr can be done
AFR 195cc SBC Eliminator Street Heads 1036 - SummitRacing.com
I'm a little geared towards the Trick Flows because of the smaller intake valves and I don't see the AFR cnc'd runners benefiting me that much.

Intake I'm looking at......
Performer rpm air gap
Edelbrock Performer RPM Air-Gap Intake Manifolds 7501 - SummitRacing.com
The cam Lunati recommended, 20080130. This is with the AFR 195's, I haven't requested with the TFS yet.
BareBones - Chevy Small Block LT1, LT4 Hydraulic Roller Cam and Lifter Kit 276/286 - Lunati Power

I'm open to hear any suggestions on which of these parts will work the best together, or other intakes, cams, heads that I haven't mentioned.

Thank you, Daniel

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Old 12-24-2012, 07:17 PM
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If you haven't purchased your intake or fueling system I would HIGHLY recommend looking into a multiport system, perhaps a ram style intake.

Also, I'd go with the MS3 system if you need all the bells and whistles on your controller, it'll control pretty much anything you can dream up and is VERY user friendly. To be honest and MS1 or MS2 system is also pretty damn good though has fewer options for a lower price.

Either the TFS or AFR heads will work very well, but the AFR's seem to be slightly favored.
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Old 12-24-2012, 09:03 PM
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Suspect, you're right where you want to be with the compression ratio. With the 72cc heads I'm getting a static compression ratio of 10.23, with the 75cc heads I'm getting 9.92.
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Old 12-24-2012, 09:39 PM
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ap - This is the first time I've heard of this MS3. Ez Efi seems like a sure thing, plug n play, no maintenance. Plus I haven't ran onto one bad thing about it. I just did a few quick searches on this Megasquirt and it seems pretty interesting. I'll spent the next week or 2 checking out this set up. Thanks.

BigEd - Thanks for checking out those CR's.
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Old 12-25-2012, 03:09 AM
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I'm wondering if that's a 'long' enough duration cam for 10:1 CR ON 91 octane?
Seems like it would be right on the edge to me, what do you gurus think?
I might be wrong, just thought I'd bring the point up...

Duke
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Old 12-25-2012, 07:52 AM
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Quote:
Originally Posted by thinwhiteduke View Post
I'm wondering if that's a 'long' enough duration cam for 10:1 CR ON 91 octane?
Seems like it would be right on the edge to me, what do you gurus think?
I might be wrong, just thought I'd bring the point up...

Duke
I'm getting a DCR of 8.14 with the 72cc heads, 7.9 with the 75cc heads, using the advertised durations for the Lunati cam. That's right in the middle of the 7.5 to 8.5 recommended by Pat Kelley for street engines using pump gas figured using the advertised durations. Using the KB calculators "intake closing angle plus 15 degrees" I'm getting 8.94 with the 72cc heads, 8.67 with the 75cc heads. Using these figures the DCR with the 72cc heads might be a little high, I believe using the ".050 duration plus 15*" rules the desired range is 8 - 9:1. Maybe techinspector1 will chime in on this, I'm sure I've seen him recommend 8 - 9:1 using these figures. From Suspect's posted info, he will have modern heads, flat top pistons with a very good .040" squish/quench height, using 91 octane I think he should be "good to go"...........fast!
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Old 12-25-2012, 08:33 AM
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I know a higher CR, the longer duration cam you can run. But I don't know where that sweet spot is. Plus a 10:1 - 10:3 CR is a comfortable place on pump gas.
DCR is new to me, so I have a lot to get educated on. I appreciate you guys looking into this. That's the input I'm looking for.
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Old 12-25-2012, 01:44 PM
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Quote:
Originally Posted by suspect View Post
I know a higher CR, the longer duration cam you can run. But I don't know where that sweet spot is. Plus a 10:1 - 10:3 CR is a comfortable place on pump gas.
DCR is new to me, so I have a lot to get educated on. I appreciate you guys looking into this. That's the input I'm looking for.
There's a sweet spot with any static compression ratio that you use. The trick is finding the intake closing point that works best with your combination. The one that closes the intake valve at exactly the right time to generate max cylinder pressure for the fuel being used.

This chart is far from scientific, but it will give you an idea of what works with what.
http://www.crankshaftcoalition.com/w..._compatibility
I originally put it together by using information from Crane Cams.

Different fellows will use different calculators to figure the DCR and that can lead to confusion. I have used the KB calculator for years and am comfortable with recommending 8.5 as a soft limit for pump gas. I have seen feedback from builders who have built 8.9 motors off the KB calc that worked well on pump gas, so maybe I'm leaving some on the table. Every combination is different though, so I try to be careful in what I recommend, because I could be putting $5000 of someone else's money in jeopardy.

Some fellows will say that adding 15 to the 0.050" tappet lift closing point isn't real. Well, we are only dealing with one side of the lobe, the closing side, so if you were to add 15 to the closing side and 15 to the opening side, you'd have roughly 30 degrees difference between 0.050" and advertised. I'm sure that John Erb, chief engineer for KB, had something to do with setting up the KB calculator, so I trust his judgment.

The thing to do is to build a few motors and document the results. Then with whatever calc you're using, you'll know the sweet spot to shoot for next time. To me, the key is using only one calc.

Crane Cams will tell you that about 165 psi cranking pressure is roughly the limit for pump gas, but I have seen fellows build 200 psi motors and operate them on pump gas, so never say never.

Last edited by techinspector1; 12-25-2012 at 01:54 PM.
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Old 12-25-2012, 01:58 PM
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Thanks BigEd36 for that info.

I was under the impression that street engines using pump gas should shoot for a DCR of 7.5 to 8.5:1 and that race engines using high octane race gas could tolerate higher DCR's in the 8.8 /9.1:1 range.
I agree, quench is good, flat tops and modern heads - good.

I think that the .050" timing durations are the ones to use, not the advertised.
I got 248 @ .050" with SCR a hair over 11:1 , flat topsand.035"quench and 200psi cylinder pressures running on 98 octane (that's the highest octane pump gas without ethanol). Then there's 95 (no ethanol) then there's 91 (10% ethanol). At some selected stations you can also get 100 octane which contains ethanol. I'm assuming that we rate our fuels here in Australia the same as USA.

I got an older '68 model car with steel tank, lines etc so the ethanol is 'out' for me. I'd be scared to run it on 95 though. I'm curious now?
I hope techinspector1 can chime in, wanna make sure Daniel gets it right.

I read this somewhere on this forum:-

The DCR is always lower than the SCR
The DCR does not change at any time during the operation of the engine


Why it matters: A 355 engine with a 9:1 static CR using a 252 cam (110 LSA, 106 ICL) has an intake closing point of 52║ ABDC and produces a running CR (DCR) of 7.93. The same 9:1 355 engine with a 292 cam (having an intake closing point of 72║ ABDC) has a DCR of 6.87, over a full ratio lower. It appears that most gas engines make the best power with a DCR between 7.5 and 8.5 on 91 or better octane. The larger cam's DCR falls outside this range. It would have markedly less torque at lower RPM primarily due to low cylinder pressures, and a substantial amount of reversion back into the intake track. Higher RPM power would be down also since the engine would not be able to fully utilize the extra A/F mixture provided by the ramming effect of the late intake closing. To bring the 292 cam's DCR up to the 7.5 to 8.5:1 desirable for a street engine, the static CR needs to be raised to around 10:1 to 11.25:1. Race engines, using high octane race gas, can tolerate higher DCR's with 8.8:1 to 9:1 a good DCR to shoot for. The static CR needed to reach 9:1 DCR, for the 292 cam mentioned above, is around 12:1.
This lowering of the compression ratio, due to the late closing of the intake valve, is the primary reason cam manufactures specify a higher static compression ratio for their larger cams: to get the running or dynamic CR into the proper range.

Duke

......thanks for that info tech, I'm a slow at typing.

Last edited by thinwhiteduke; 12-25-2012 at 02:05 PM.
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Old 12-25-2012, 03:41 PM
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....just learned reading from another thread, that USA and AUS DON'T use the same measurement for rating octane! F-BIRD'88 says that New Zealand,s 98 octane is equivalent to USA's 92 octane.....now everything starts to make sense.
Thanks firebird!!!

Sorry for any confusion,

Duke
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Old 12-25-2012, 07:12 PM
How fast is fast enough?
 
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your cam is a little on the small side for your planned compression BUT with a perfect tune it should be okay. a good EFI system and a perfect tune make a hell of a difference when you're walking that thin line with a street engine.
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Old 12-26-2012, 04:47 PM
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techinspector - Thanks for the link. I'll for sure be looking more into this DCR stuff.

ap - Yeah I hear ya, I just want to have my CR in the safe high side so I can play with cam swaps in the years to come. I'm pretty sure I'll be going with the AFR 195's w/75cc, they're only about $150 more, so might as well.
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Old 12-26-2012, 06:03 PM
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Suspect, this website has a good explanation of dynamic compression ratios. There's also a DCR calculator that includes a cam degree calculator, you can download this DCR calculator and use it off line. The figures you get using it are within about .002 from the figures you get using the Wallace Racing cam degree calculator and the KB-Silvolite dcr calculator (I don't know about you but 2 different calculators coming up with figures only two one-thousandths of a ratio different are close enough to be the same to me.)
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Old 12-27-2012, 05:01 AM
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Thanks again. I'm starting to get a good idea on what's happening. Even though I'm not able to point fingers and make calls on some custom grinds I need, it's still nice to visualize what's actually going on inside my engine.
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Old 12-27-2012, 07:09 AM
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I have a 383 in my 78 Camaro. What you're wanting to assemble sounds very similar to what I have. However I used world products sportsman 2 heads. Just thought I would mention those heads since you haven't yet.
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