My Desktop Dyno Figures
 

Hello Good People. I have had some good feedback from you guys about my cam choice which has made me wonder about the whole engine.

I am trying to design the best engine I can for my next cobra and was looking at the 351w block.

I want to be able to drive the car in traffic here in the UK, because there's always loads of it.

However I want it to take off like a rocket and scare the pants off me and my passengers.

So when I started putting the engine together on desktop dyno I was looking for the tallest graph that I could without going the forced injection route. I really didn't want the noise of a blower and don't want to be bothered with all of the messing around with turbos.

Please could you have a look at the attached desktop dyno file and let me know what to alter so that I can fulfill my criteria.

I wouldn't really mind a little lumpy tickover but need it to pull from low down. This is what I thought that I had done but it seems that my cam choice isn't good???

Any help would really be appreciated.

Regards
Vince Gledhill
Limey from Leeds UK

Vince,

My regret is not installing the 393 stroker kit before installing the engine in the car. Have no regrets installing retrofit hydraulic roller cam.

If I had to choose between a flat tappet hydraulic cam and 393 stroker kit, or retrofit hydraulic roller cam and stock displacement; I'd take the 393 stroker kit and flat tappet hydraulic cam hands down!

Of course, if I could have the hydraulic roller, AND the 393
stroker, that would be my ultimate choice.

If I were building an engine with the idea of upgrading as funds became available, I'd do the 393, and have the machine work to install the roller cam later done to the lifter valley. Then, it's a simple cam upgrade.

Be sure to use the right heads on the motor that will accomodate your upgrades. A 393 will need the 2.08/1.60 valves so you don't want to do this twice. Lots to choose from; TFS, AR, etc.

If you were going to stroke the engine, then why not stroke it to 427? These kits are available.

Regards
Vince Gledhill
Leeds UK
website www.left-handed.com

Vince,

I have my engine stroked to 416 and a friend has his at 410. Going to the 427 in a Windsor block is really asking for trouble and the most reliable with tons of power seems to be the 392 or 393. If you want a 427 then go to a real one or get a 390 block. Just my .02 cents worth based on what I have seen happen.

%/ %/

Agreed.

A good, trouble free 351W stroker is 393. Gobs of power, just under 400ci in a 2400# car. SCAT makes a very good crankshaft for this making it reliable.

From here, reliablility and buildability goes down exponentially. One can get 427ci with a 351 block (4.030 x 4.17) but there are better choices.

Hi Vince, here are some thoughts and opinions, take them with a bag of salt :D

CAMS
You've picked a pretty nice Comp cam. I like that it has asymmetrical lobes and is of the more modern designs. Here are three cranes that are rated for 10:5:1 10.5:1 and 11:1 that seem to do better than the 35-324-8

Comp 35-324-8
http://www.cobralads.com/dyno2000/vince5.gif

Crane 448601
http://www.cobralads.com/dyno2000/vince1.gif

Crane 448031
http://www.cobralads.com/dyno2000/vince2.gif

Crane 448511
http://www.cobralads.com/dyno2000/vince3.gif

Comp 35-324-8 519@6000
Crane 448601 554@6000
Crane 448031 554@6000
Crane 448511 556@6000

that's 35HP, just by picking a different cam


STROKERS
I know everyone loves a stroker. If I was building an engine from scratch, I would go 351 or 351 030 over which is a 357 or 358. You can then use all stock, easy to find components. What does stroke really do? Stroke changes engine size. You get more torque from a stroker, not because of the stroke length, but only because you are making the engine cubic inch deplacement bigger. HP is directly correlated to RPM, where TQ is correlated to cubic inches.

What this means is that you can make as much HP with a 351 as you can with a 427 stroker, AND save a pile of money, AND avoid the dangers of higher cylinder wall sideloads and high piston speeds.

Anyone believe me? Here is a 351, this is the exact same engine from Vince1 above. Notice HP is the same, only moved right 500rpm
http://www.cobralads.com/dyno2000/vince4.gif

Crane 448601 551@6500

If you can melt the tires off any cobra at 300TQ, what is the purpose of 500TQ? Melt tires faster? One of the fastest street cobras that I have read about is Quik1 on the FFR boards. He runs a 289 with tons of HP. Hooks up everytime. Runs low to mid 10s.

If you own 40,000 acres of corn and a drive a big green tractor, then the pursuit of torque is a good one :D If you own a 2500lb convertible that melts tires in all 4 gears, you might consider the pursuit of HP.

I think we often over value stroker kits.


DYNO2000
You might check you AFR205 numbers. I believe the data on the AFR site is @ 28H20 rather than 25 and I think the the exhaust valve is 1.6" rather than 1.4
http://www.airflowresearch.com/pages/205sbf_rh.htm

One other setting you might try are the sidepipes. I have found the setting that will bring you in closest to magazine engine dyno nymbers is small tube header to open exhaust. You choice is also a good one since the mufflers keep the data to the conservative side.


hope this info is interesting :D I think you have picked some excellent components on your engine.


Andy

I have been playing with Dyno 2000 for a while as I am specifying an engine now for a GT40. Your original motor was square (4" bore by 4" stroke). I tried a very popular hyd. roller cam from comp cams which has rated durations of 282/290 and lifts of 0.565" and 0.574". This produces HP = 556 at 6000 RPM and 557 at 6500. Torque is 521 at 4500 and 527 at 5000.

Here is the updated dyno file (including the flow fixes mentioned). RENAME from ZIP to DYN.

I also made one similar to my final setup. I will be track running the car and wanted longevity at high power, etc. I elected to go with the Dart block, SCAT 4340 crank and rods, and JE forged pistons with internal ballance. Anyway the dart block lets you go up to 4.185" bore. I elected to use a 4.125 bore and 4" stroke producing 427 CI. Note this would be a better combination (at 427 CI) then the 4.030" x 4.17" combo. I also added a 825 CFM Demon Carb.

This produced HP = 575 at 6000, TQ = 548 at 4500. Basically you get the torque of your original combo down low and the significantly improved power in the higher RPM (above ~4000).

Here is the file (RENAME ZIP to DYN).

Hey G Gibbs

I tried your set up and I get HP 519@6000

if you check comp cams site, I think you might have a different cam than 35-324-8 since it is a 544 544 lift

http://www.compcams.com/information/...umber=35-324-8

also on the file you sent...the air flow still is at 25 H20 and has the 1.4 valve where I think it needs 1.6

I would try and upload these files but my server is temporarily overloaded.



Andy

Sorry for the confusion (my files should have the new numbers?? I did save a flow file on my computer that I did not upload). Anyway on my machine the two setups that I posted results for are for the 400 and 427 CI both using the XE282HR cam (rated duration 282/290 and .565/.574 lifts). The 400 CI I left at 750 CFM and the 427 I entered 825 CFM (per Demon recommendation for my motor). Let me know if you can reproduce my previously posted numbers.

Gary

Woo Hooo! Got HP557@6000 !

OK, here were the numbers we needed. The Comp cam part number for 282HR is 35-522-8 and is on the dyno2000 camdisk.


But that is with the 825 Holley. Keeping apples to apples

Comp 282HR HP 557@6000
Crane 448601 HP 565@6000
Crane 448031 HP 563@6000
Crane 448511 HP 564@6000

all four cams are very close :D


Andy

Thanks for that Guys.

Andy. I've removed the stroke, as recommended, and I've now changed the Head file and the port sizes as per your recommendations.

I've also added the cam that you have recommended.

However my figures are much different to yours. Please could you take a look at the enclosed file. I've got it making 594Hp but this is at 7500 revs. Red line screamer city.

Could you let me know what I have done wrong.

Regards
Vince Gledhill
Limey, Leeds UK

Guys,

Remember that peak horsepower is not what you see 95% of the time. When you punch it, you're almost always in the 2000-3500 rpm range. If you don't have the torque and response there, you're going to be disappointed with street performance.

Bob, those are great points and I often fall into the trap of chasing peak HP :D Now on the other hand, more often than not, the engine with peak HP also has the highest peak TQ as well, when holding all variables constant and only altering cam. As you stated though....peak HP is a long rpm way away from street driving and so initial TQ is just as important for street engine. Vince, here are additional points on some of the ideas being posted.


last dyno file - cam data
Here is why our files are different. I get 576@7000 on the dyno chart you gave me....so yes, it is still a screamer. Here is your dyno chart
http://www.cobralads.com/dyno2000/vince/vince351a.gif

and here is my chart of the same thing
http://www.cobralads.com/dyno2000/vince/vince351b.gif

one of the things that took me a while to learn using dyno2000, is entering cam data. Just one error and the chart becomes way off. I think this is one reason why many people distrust the software....really they have entered in some parameters incorrectly. Here are the two data cam files. This top one is yours and the next one is the one I got off the cam CD
http://www.cobralads.com/dyno2000/vince/vince_cam1.jpg
http://www.cobralads.com/dyno2000/vince/vince_cam2.jpg

the intake centerline needs to be 108 and then I think the lift numbers are just a little off. This is one of the reasons I use a lot of crane cams for examples...I find they give the data in an easier format on their site. Comp gives enough data, but it is trickier to enter. Here is the data website page on that comp cam. They give the lobe separation but not the intake centerline
http://www.cobralads.com/dyno2000/vince/comp.gif

Crane gives the two angles
http://www.cobralads.com/dyno2000/vince/crane.gif

and so you can use the intake as 108, and then you divide the two in half to get the lobe center. Here is a little tutorial page on how to use the crane spec card in dyno2000
http://www.cobralads.com/dyno2000/crane_spec_card.gif


tree puller vs screamer
It looks like Gary and I both lean toward the screamer style cam, where other folks lean toward the stump puller cams. Each cam is a trade-off. If you car is 90% street driven, you might prefer a cam that brings in TQ and HP sooner and at lower RPM. If you enjoy autocross and track events, you may prefer the higher revving HP cams. I think 3/4 people prefer low TQ and 1/4 prefer higher HP. Therefore the engine characteristics are often subjective, and you will have to decide what you think is optimal. You have seen the engine above that leans to the screamer side....now the other side of the spectrum is a cam that leans to the stump puller side.
http://www.cobralads.com/dyno2000/vince/vince351c.gif

Most TQ cams make a very even M shaped pattern with TQ and HP evenly distributed. This is a great street driven cam. Massive amounts of TQ at 2000 rpm....how about 425TQ ...there aren't a set of performance tires made that can hook that up. This car will feel like a beast down low. Now lets take that exact cam and engine and compare it with a screamer style cam and see how they differ. Here are the specs

SEMI STUMP PULLER
449601 224 232 | .542 .563 angles 107 117
http://www.cranecams.com/motorsports...ler/449601.htm

SEMI SCREAMER
448601 246 254 | .579 .598 angles 108 112
http://www.cranecams.com/master/apps/ford34.htm

and here are the two cams on your engine with a 750 holley for lower ci 351. Solid line is stump and dotted scream
http://www.cobralads.com/dyno2000/vince/vince351d.gif

Notice PEAK TQ is almost identical.

the trade off
the trade off is initial TQ or peak HP. You can have 425TQ at 2000 or 365TQ at 2000, or you can have 575HP @ 7000 or you can have 490HP @ 6000. That is the tradeoff. Again, most people like kick in the pants, down low TQ. Then a few folks like me and Gary like to get that high peak HP. You must decide what is best for you (and you can always go somewhere in the middle).

best advice
the best advice in my opinion is to call the cam companies and talk to the tech support. They will ask you all about your engine and your driving needs. They will then recommend a couple cams to best meet your needs. They always have very good advice. I would even suggest calling twice because each tech person has their own favorite set of cams and two different people at the same company may recommend different products.

COMP
1-800-999-0853

CRANE
1-386-258-6174

ISKY
1-323-770-0930

LUNATI / HOLLEY
1-270-781-9741

CROWER
1-619-422-1191


hope this info is useful

Andy
http://www.cobralads.com

PS.
I just checked the comp 282HR cam again and I think that even dyno2000 cam disk has an small error. They have the intake centerline at 108 and I believe that is wrong since it throws the valve timing points off. Here is one way I like to enter comp cams. If you use their data, and seat to seat, you can enter the black area numbers, and then the last thing to do is guess numbers in the red circle. I start and the lobe center angle, in this case, 112, and work down one degree at a time. When the yellow areas match, you have the cam perfectly entered.
http://www.cobralads.com/gif/comp3.gif

Brilliant Andy. Thanks everyone for your input. Do you know if I can phone the 1-800 number from the UK?

Regards
Vince Gledhill
Limey From Leeds UK

I don't know if 800 numbers work worldwide or only in the US. I think it depends on the company. Here are the company websites. You can often fax them your needs....and some have tech email which would be less costly as well.

http://www.cranecams.com/CraneCams.htm
http://www.compcams.com
http://www.crower.com
http://www.iskycams.com/
http://www.holley.com/HiOctn/ProdLine/Lunati.html
http://www.camresearchcorp.com/

Make as much torque as possible in the 2500-5000 range, that is where the motor lives, even during a drag race. This becomes clear if you look at a time/ rpm graph of your motor during a drag race. Maximize area under the torque curve for the midrange. Also, if you shoot for peak HP, you need to spend gobs of money on a bottom end and valvetrain that will survive at such high RPM. Nothing beats displacement, even RPM. You can't have too much torque, and as long as the motor doesn't run out of steam by 5000 rpm, you will have the HP as well. I would rather have 460 lb/ft and 400 hp than 400 lb/ft and 460 hp.

horsepower sells cars and torque wins races - Myth?
We've all heard this saying, but is it really true? Here is a counter arguement for my old pal HP. I am paraphrasing this info from the excellent engine tutorials at GrapeApe Racing.

Torque gets the car in motion, but TQ and HP are always directly mathematically related and so you can't have one without the other. You can always gear HP to make TQ and therefore you can increase the rpm range of an engine to get greater HP, at the price of TQ, yet when all the smoke clears, you end up with greater rear wheel torque from the screamer. Here is the chart example given on grape ape

http://www.cobralads.com/gif/HPVSTQ.gif

The top engine is the torque monster and the bottom is the screamer. The screamer has 50 more HP at peak than the tourquer. The torquer has over 70 more TQ than the screamer at peak. This is a race example to make a point since such steep gearing is not practical on the street. Both engines have the same rear wheel speed, but the higher rpm engine makes more rear wheel torque when all is said and done. TQ and HP are always correlated.

Therefore, for racing, build HP, gear for TQ. There is no mathematical way of getting around that the engine with the greatest average HP for the rpm range will also have more average power.


Andy

If I could only get an infinately variable transmission with ratios from 1000:1 to 1:1 than I could do it all with a little briggs and stratton motor. This being the real world, you can only have so many forward gears, and their ratios can only be so far apart, so if you maximise torque just above your shift recovery point, you will go faster. It's tough gearing a car to maximise performance from 0-140 mph without tradeoffs.

This is a neat thread, lets keep arguing, it's fun