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computer projections for torque and power?

2K views 28 replies 7 participants last post by  BuzzLOL 
#1 ·
I have to modify my engine build to get what I want in a street only engine. I have a car that weighs 2000 pounds, manual four speed transmission and 3.25:1 final drive ratio. This car will NEVER see a track, it is for driving on country roads and for freeway cruises. I want a SMOOTH idle and the engine has been put together to red line at 5500 rpm. Here is what I have and the cam I will be using:

Engine: 1975 351W
351W +.030; 357.2cu” Bore: 4.030; Stroke: 3.5
Compression: 9.3:1; Quench: .035”
Intake: Edelbrock Performer
Carburetor: Holley #1850-3 600 CFM vacuum secondary
Balanced; block decked square
fitted scraper; baffled oil pan


Cam:
Crower part number: 15520 (cam kit # 84561S)
Grind Number: Hydraulic Roller RETRO FIT


Advertised Camshaft Specifications:
Intake: Duration: 274 Lift: .480 Clearance Hot: .000
Exhaust: Duration: 278 Lift: .480 Clearance Hot: .000


The specifications above are based on a rocker arm ratio of 1.6 intake and exhaust


Recommended Valve Spring Information: Cam Kit #84561S


Intake/Exhaust- Dur @ .050” Lift: 210°/214°
Rocker Ratio: 1.6/1.6
Gross Lift: .480”/.480”
LSA: 112°
RPM: 1200 to 5300 Redline: 5800 (smooth idle; peak HP: 5200 rpm)
Event timing:
Intake opens: 3 degrees BTDC closes: 33 degrees ABDC
Exhaust opens: 43 degrees BBDC closes: 9 degrees ATDC


Headers: Tuned to 4000 RPM
Equal length 4 into 1 headers.
Primary tubes: 1 5/8” x 38.8”
Collector: 2 5/8” x 20.9”


Cylinder head: 1975; Mildly Ported
Flow at 25” water; lift (inches)- flow intake/exhaust
.1 - 69/45, .2 – 111/80, .3 – 154/108, .4 – 185/115, .5 – 190/115

My question is: What does your software predict for torque and power?

Thanks for taking the time to help me,
Paul
 
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#3 · (Edited)
The computer in my head says ~250 grossHP at 4,000 RPMs and 345 lb.-ft torque at 3,200 RPMs for your 357 Magnum...

Your cam has the capability Joker guesses, but your heads are horrible... intake flow is respectable for those heads, but you have no exhaust flow... as is typical of those smog heads... did you remove the A.I.R. injector bosses from the exhaust ports?

Need to get your exhaust flow up to at least 140 - 150 CFM by .400" lift and 25"...

Your cam will prolly have a slight lope to it, but nothing to get concerned about... it's also not too badly matched to your compression ratio...

I went through this with the '77 351W in my boat... ported the heads out till I struck water... welded the holes back up... added a Crane 216/228 cam... added KB 151 2 eyebrow flat top pistons... finally got a big jump in power with World/Dart Windsor Sr. 2.02/1.60 valve ported 195cc heads with radiused valves and seats and backcut valves... 10.4:1 compression ratio... 425 HP @ 5750 RPMs... 430 lb.-ft. torque @ 4,000 RPMs...

Other possibilities are the rare 1969 - 1970 351W heads (290 HP stock)... GT heads... GTX heads from Exploders... all kinds of aftermarket and iron heads... even lower priced imported ones now...
 
#5 ·
Never mind.....used 1.840"/1.540"

Motor made the best power and torque with the cam advanced 4 degrees to 7-29-47-5.

With standard Performer manifold....
RPM....HP....TQ
1500...103...361
2000...151...396
2500...190...400
3000...224...392
3500...266...400
4000...292...384
4500...307...358
5000...299...315
Dogleg 2500-3500, might improve with open spacer
Max volumetric efficiency 84.4% @4000
Max BMEP psi 168.7 @3500

With Performer RPM....
RPM....HP....TQ
1500...99....348
2000...147...385
2500...186...391
3000...232...405
3500...278...417
4000...312...410
4500...341...398
5000...351...369
5500...308...294
Max volumetric efficiency 88.0% @4500
Max BMEP psi 176.2 @3500
 
#11 · (Edited)
The cam is ground with 4 degrees advance.
The valve sizes are 1.88 intake and 1.55 exhaust. The flow numbers are at 25 inches of water instead of the standard 28 inches so they are lower than the "standard" flow rates. I have converted them to 28 inch values if that would help.
.1 - 73/47.6; .2 - 117.4/84.6; .3 - 162.9/114.2; .4 - 195.7/121.7; .5 - 201/121.7

If I switched to the Performer RPM I would have to cut a hole in my hood and it shifts the torque up 500 rpm, away from the bottom end. The increase is only 17 pound feet.
The Performer RPM does the same to the HP. It is shifted up in the RPM band where it is rarely used.

Remember, this is a street machine. How often am I going to be above 3000 rpm with a 3.25 rear gear?
 
#12 ·
I put the flow into the software at 25", there's a place for it there. Hey, if you're happy with a low-rise intake, I'm happy with a low-rise intake.

These heads are not that much different from any run-of-the-mill small block Chevy head. You could make one hp per cubic inch with most of them and you can make one hp per cubic inch with these Ford heads, although you have to use a taller intake manifold to do it.
 
#14 ·
Wow, that means that the intake valve is opening after TDC. Techinspector1, I want to thank you for your time and work. The numbers prove out to about what I expected, perhaps a bit lower in the HP but when you are running at low RPM you can't expect a lot of power. The engine should have good street manners and pull well from off idle through any RPM that I will use.

One quick question: Does your software accept the parameters for the exhaust headers?
 
#21 ·
TechInspector1,
You seem to be the only one that can accept the build parameters that I intended for this engine. Most others want to make it into their engine. I think this engine will be fine in my application and, I hope, it will last long enough for my son to inherit it at an age when he needs the same.
Thanks for your help and courtesy.:cool:

To the rest who want to "help" build more power; I would be happy to help you spend your money to build and maintain the engine you want.:evil:
 
#25 · (Edited)
This motor will be a dream to drive on the street. I don't know the transmission you're using, but I'm bettin' it would be big fun using a wide ratio toploader with a 2.78 first gear and a 3.55 rear cog for a first gear final drive ratio of 9.869:1......


Oh yeah, and to answer your question about exhaust on the DynoSim, yes I have choices of....
Stock manifolds and mufflers
High Performance manifolds and mufflers
Small tube headers with mufflers...................(this is what I used for your combination)
Small tube headers with open exhaust
Large tube headers with mufflers
Large tube headers with open exhaust
Large tube stepped race headers

With large tube stepped race headers, no mufflers, the torque bowed up to 435 ft/lbs at 2500. BMEP went to 183.9 psi.....pretty cool....I just love tinkering with this stuff....

.
 
#22 · (Edited)
Didn't mean to badmouth your engine, just didn't want you to be expecting 350+ HP if you hadn't put the parts together yet... give you a chance to hog the exhaust ports out, correct the bowls and valve seat to bowl transition, re-shape the short turn radius, etc. for some more flow... for 50+ more HP and freer revving engine with current parts... Don't know if you do your own porting... Paying for porting is another story... My neighbors know I do my own porting as they call the cops on me at 3:00AM from the loud scream of the air die grinder... LOL !!!
I'm sure the engine starts and runs fine as is and as you say, doesn't start feeling constipated until above 4,000 RPMs... I went through all that with my 351W... it now idles with a slight lope at 550 RPMs in gear, partly because of the special Crane lifters that bleed down duration/lift a bit at idle... then it's super strong everywhere above that to 6,500 RPMs with good worked over heads... and gets good MPG (for a boat)...
The manufacturer's RPM range for a cam is at best a guess since they don't know what kind of engine build it will get put into... a stock 7.6:1 slug engine or a 11:1 good quench build... or something in between... some companies are real conservative with their guesses to avoid being sued, others give higher numbers...
Chevy has a L46 cam that makes 290 HP and 311 lb.-ft. in their 7.6:1 350" crate engine, 350 HP and 390 lb.-ft. in their 11:1 350" engine, and prolly 435 HP and 425 lb.-ft. in a 350" with aftermarket heads... so hard to blanket predict what a cam will do without knowing what it's going into...
.
 
#23 ·
Buzz,
My remark was all in fun. I have a very thick skin (head?) and don't get my feeling (at my age I only have one left) hurt. If you have the time or interest I would like to hear about your boat engine - maybe in a PM so it doesn't disrupt the conversations here. I have done some work on boats - flat bottom drag boats and cruisers both with carburetion and ignitions but it was all back in the mid 70's.
 
#24 ·
Actually, I wrote my comment above before I saw your comment #22 above. I hadn't wanted to sound only negative. I just got off into other things before finishing it and posting it... I respect your sensible combo of parts, I just didn't want you to be disappointed if you hadn't assembled it yet... Since you asked about power projections, I was concerned you were expecting big HP... just wanted to help you get it... I don't really push buying expensive parts, mainly try to help people maximize what they already have... show them how to do it if necessary... If you read some of the other current threads here, you'll see I usually talk getting power with the stock heads... usually the much-maligned Chevy -882's... other's push buying heads... I already got into the boat engine in posting #3 above... I've helped my friends tune flat bottom boats, but mine are all deep V hull family/fishing/cuddy/sport/runabout/bowrider types... used to get Hot Boat magazine before it folded...

 
#27 ·
64nailhead,
i have software that computes the size and length of the tubes for proper tuning at any rpm you select. It's a lot easier than doing all that math with a calculator or longhand.

TechInspector1,
Is the software you use available for Linux?
 
#28 ·
TechInspector1,
Is the software you use available for Linux?
No, Sorry. Windows XP, Vista, 7 and 8.
I'm currently using Dyno-Sim 4.2 with Pro Tools. There has been an upgrade since I bought mine, Dyno-Sim 5.0 with Pro Tools. I will purchase it in the next few months, along with CamDisk 8, which adds the profiles of 6000 cam grinds. Both will cost me $150, $100 for the 5.0 and $50 for the cams.
 
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