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Desktop dyno help?

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67funcar

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Discussion starter · #1 ·
Would anyone care to help me estimate power & torque on a 355 ci SBC that I want to build for my 72 ElCamino?

I'm wanting a fairly mild but torquey engine. The combination I'm thinking about is:

355 c.i.
9.5-1
Edelbrock Performer RPM heads (#60739)
Edelbrock Performer intake (#2101)
Comp Cams XE256H-10 cam (part # 12-234-2)
flat tappet - 212/218 @ .050", .447/.454 lift
HEI ignition

I realize this is very limited information but even a rough estimate would help me to know if I would be satisfied with this engine.

Thanks
67funcar
 
#4 ·
77wolf10.85 said:
272 hp at 4500 and 362'# at 3000 on dynosim.

I don't know how to do the print screen thing or I'd give you the graph and data.

had to put you a .025 head gasket to land it at 9.5cr w/ .025 DITH and 5cc vr's
Click to expand...
Hey Tim, hit CTRL and prt scr/sysrq (print screen) next to scroll lock and pause break
Then paste it into a document that you can use a link to insert as a pic with.

I bet with 9.5:1 you could go with a tad bigger cam to get over 300hp.
Because if you have 272hp roughly at the crank you will probably only make 180hp at the wheels...
 
#5 ·
I can printscreen it into Paint, but not Notepad or directly into the "reply" dialogue box. I normally just print them as a pdf then attach them to the reply, but there's got to be a way to just drop it in the reply. It irked me and I blew it off.:D

here, usually page 6
yes Mike, over 200 hp at 0 rpm. :)
 

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#8 ·
with that camquest freeby software, you can set up your engine and arrow down through the cams while watching the graph change with each cam. Only drawback to the instant gratification is they divide the cams up by category, so you have to change that too sometimes.
 
#9 ·
With headers or stock exhaust manifolds? Any idea what those heads flow? Desktop Dyno 2003 is showing about 300 HP @ 4500-5000 RPM and 380 Tq @ 3500 RPM with the specs I plugged in (my experience this is a little optimistic). The XE268H cam like was suggested would give you about 20 HP more with a little less peak torque.
 
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#10 ·
Some what off topic but...

when you guys have cam specs that say (using a comp cams 286 for example) 286* duration advertised and 238* @ .050 and .490" gross valve lift do you use "seat to seat" or "@.050"

I have desk top dyno and never can figure out which to use... .050" or seat to seat...
 
#11 ·
As inaccurate as a sim is, I normally just use seat to seat.

I'm thinking it's an either/or deal.

I've gone in and put all the 50 numbers and valve events. Haven't messed with it too much lately so I may be remembering wrong but it seems it doesn't make much difference.

That's one of the nice things about dynosim, with a comp cam with a part# you just select the part#. It's the custom cams and other vendors cams where all the inputting can lead to errors. Which is probly how comp likes it.
 
#12 ·
Desktop Dyno allows you to enter cam specs using either at .050" or seat-to-seat.
 
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Discussion starter · #13 ·
Thanks for your answers, guys.

Anyone else have an opinion on my engine combo? I want to try to get at least 300 HP and hopefully 380+ ft/lbs out of a mild engine that will idle nicely and get decent mileage (I want to drive this car almost daily).

Any other cam recommendations?

Thanks,
67funcar
 
#14 ·
What is your gear ratio? What tranny are you running?
My combo is identical to yours except for I'm at about 9.1:1 and am using the XE268 cam. My power brakes work well. The XE268 is kinda lopey but not bad. I don't think you could go wrong with the XE262 or XE268. If you will never go past 5k rpm, I'd suggest the XE262. You will have good low end torque and still have decent mid range.
 
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Discussion starter · #15 ·
My gears, etc. do not lend themselves to a great street performance car but I want to use this car as a frequent driver so I am going to retain the 2.73 gears and TH350 tranny. I'm also going to use the stock exhaust manifolds.

I just want a good torquey engine. When I want more, I'll get into my 68 Camaro 427!

Thanks for your help. I will look at the XE262 specs.

67funcar
 
#16 ·
I'll rerun Desktop Dyno with the XE262 cam. What size carb, 600 CFM?
 
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Discussion starter · #17 ·
Carb is Q-jet (I think 725 cfm?)

I see Edelbrock advertises crate motors with same heads & intake as mine, one with 8.5-1 comp - 310 HP & 375 # torque and the other with 9.0-1 comp. - 320HP & 382#

Both these engines use a mild flat tappet cam: 204/214 @ .050 and .420/.442 lift.

It seems odd that desk dynos see me making less power than this with more cam (212/218 & .447/.454)

Am I missing something here?
 
#18 · (Edited)
Desktop Dyno is a simulation that approximates average power. A company like Edelbrock put a package together and probably spent several days professionally tuning and dialing it in for max power, so their marketing folks could have big numbers to throw out to help with sales. I'm pretty sure they used open headers (no mufflers), that's typical when using an engine dyno. You also can't just compare the duration and lift on cams, lots of other cam specs can influence power.
 
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#19 ·
I don't know if you are using stock ram's horn manifolds are later model log manifolds. I also don't know exactly what to plug in for the flow rate on those heads, so I guessed. With the XE262H cam, DD is saying 310-320 HP and 370-380 TQ. You may seriously consider a good pair of headers. That jumps power up to a tad over 340 HP and about 400 TQ.
 
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67funcar
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