Dissapointing day at the dyno

[sixty9cobra]

Well the good news is it didn't blow up. The bad news the numbers were very disappointing 415hp and 465tq. I was embarrassed needless to say. The owner of the shop has a 390 Fairlane. and it did 50 more hp with 60 cu.in less and basically the same set up. Af was 13:1 he said it was lean, I thought anything under 14:1 was OK. I thought I knew what I was doing but its clear that I don't. I was expecting at least 500 hp. The car sounds mean just but it makes a little more hp than my Suburban. Any suggestions would be appreciated. I was planning on going to Maryland at the end of the month but now I have my doubts.



So here's the specs
428 block .040 over Eagle 4.25 stroke crank, Scat rods, Cp 10.5:1 pistons, Barrys cnc ported Ed heads intake 310cfm exhaust 178cfm I think. custom Comp cam solid flat tappet very simialar to a 294, ported Streetmaster, Msd ignition, Hooker 1 3/4, flowmaster 50s 2 1/2 out the back, Holley Hp 850, fidenza aluminum flywheel,TKO-600, 389 rear. I think that covers it.



Suggestions welcome somewhere there is 100 plus hp hiding

[jayb]

These are chassis dyno numbers, correct?  Especially through the mufflers, I'm not sure you are that far off.  Your combination ought to make around 500 HP at the flywheel with open headers, and you are going to lose 15% or so in the driveline.  That would put you at 425 HP at the rear wheels.

Regarding air/fuel, you usually will want to shoot for somewhere between 12.5:1 and 13:1, so if you were over 13:1 there is power to be had by jetting up.  Also, to me your combination looks cam limited; a 294S cam will hold you back some, even if you have 460+ cubes like you do.  What is your total timing set at?  The carb is a mechanical secondary carb, right?

Do I have something wrong here?  Please explain further if I do.

[sixty9cobra]

Yes Jay chassis dyno, thru mufflers, 850 dbl pumper. timing locked at 38 deg. I also have a mechanical fuel pump and Stainless steel flex fan if that matters. It pulled till good till 5400 then rolled off. The exhaust is 2 1/2 I corrected the original post. I appreciate your help.

[jayb]

Can you post the dyno data?  I'd like to see what the horsepower curve looks like when it rolls off...

[sixty9cobra]

Heres the dyno data as an attachment.

[jayb]

Thanks for the chart.  It doesn't look like there is a dramatic fall off after the HP peak, which means that probably the valvetrain is staying under control.  However, I noticed that the HP peak is only about 1000 RPM over the torque peak, and that may indicate that the engine needs more cam and/or compression to reach its full power potential.  Normally you'd like to see about a spread of 1500 - 1700 in those numbers for an engine that is optimized.  Unfortunately if you go up with the cam, you will probably need to go up in compression a little as well.

I saw your post and the responses on the FE Forum, and if you have the Streetmaster installed without removing the "ears" in the plenum, that could be hurting you despite the presence of the 1" spacer.  I found during my dyno testing that even at the 425 HP level, porting the intake and removing the ears in the plenum added a substantial amount of power.  It could only be bigger at a higher horsepower level.

Before doing anything, I think I'd take the car to the track.  If you have a good weight on the car with you in it, the MPH number at the track will be a good, reliable indicator of the power you are making.  If you have 410 HP at the rear wheels, and your car weighs 3600 pounds with you in it, you ought to be running 113-114 MPH, and the ET could be down around 11.9 to 12.0 when the chassis is sorted. 

[sixty9cobra]

I agree on that et that's the disappointing part. What would you consider substantial horsepower? I'm starting to believe its the intake that's 3 different cams 2 hydraulic one solid,3  sets of heads stock gt ported gt and now Edelbrock. 2 differant strokes 3 differant carbs  and it never pulls really hard over 5500. The only common thing is the intake. I posted the dyno vid on Youtube    http://www.youtube.com/watch?v=DV3FmQgkLmQ

[jayb]

The Streetmaster intake starts losing out at the top end when you approach 500 HP.  For example, on my 390 Stroker dyno mule the peak HP of the unported Streetmaster was 472; with port matching and plenum work it went to 484.  The Performer RPM unported was 493, and port matched it was 504.  But both manifolds peaked in power around 5500-5800 RPM.  The Ford tunnel wedge intake, which made 524 HP on this engine, also peaked in HP at 5800 RPM.  The point is that the intake manifold will not play a significant role in the RPM where the engine makes peak power, except in extremely mismatched combinations.  So if you thing the issue you are having is related to the engine not making power past 5400, I wouldn't be looking at the intake.  The cam is the primary reason why the engine is peaking in power where it is.

You said you've tried three different cams?  What were the specs, and how many cubes was the engine in each case?  If you went up in cam duration, but increased cubic inches at the same time, you may not have moved the peak power point.  With the same cam, more cubic inches will lower the peak horsepower RPM.

Having said that, there is probably power to be had with a different intake setup.  Around the 500 HP level the multiple carb intakes start doing better than the single four intakes, so if you are thinking about changing the intake setup I'd give some consideration to a 2X4 intake, either a tunnel wedge or a medium riser.  You could also try a Victor with a Dominator carb, which has much the same effect as multiple carburetion because of the size of the carb.

[sixty9cobra]

Jay I"ll have to look up the cam specs. I am at work and been doing a ton of OT so it may take a while. One was Comp 284H extreme on a .040 428 with ported heads that flowed 278 in. The other cam was basically a stock Gt type cam by speed pro on a.040 428. I lost the card on that long ago. The cam I have in this stroker is at home, its a custom cam for a local builder that does alot of Cobra stuff. He also used to race FE's back in the day has since moved onto clevelands.

[sixty9cobra]

Here is the current camshaft specs.

                          Intake                      Exhaust
valve adj               .014                         .014
gross lift               .620                          .620
duration  @
.015  tappet lift     .289                          .297


valve timing         open                           close
@.050            int  18  BTDC                   54  ABDC
                     exh  62 BBDC                   18  ATDC


thes specs for cam Installed at 108.0 intake centerline


                            intake                             exhaust
duration at .050       252                                  260
lobe lift                   .3520                              .3520  
lobe sep                  .110.0

[Joe-jdc]

That is a healthy camshaft.  I think your problem is the intake and headers.  Did you get a flow sheet with the heads?  I know you said you thought they flowed 310, but anything close to 300 cfm should give you 550+HP with that combination.  Joe-JDC.

[sixty9cobra]

I bought them from Barry R that was the advertised flow for his CNC ported Edelbrocks Pro port I belive they are called. ON the FE forum Werby says im leaving 50hp on the table with that exhaust. To me thats alot of hp.I be happy spendsing 700 for the magnaflow 3 and getting 50hp. That sounds to good to be true.

[Joe-jdc]

Harry, if you decide to do anything with the intake manifold, I would be glad to help.  I quit porting for the public, but when someone has a problem like yours that they are stumped with, I would be glad to try to help get that manifold, or another one, to work like it should, and give your numbers to back up what I did.  I would be willing to do it for shipping both ways, and only charge would be for flowbench time, no labor to re-port it for you.  If you wanted a new manifold ported, I would have to charge for that.  But to fix your existing manifold, NC, just give me credit if it worked better. Joe-JDC.

[jayb]

Joe, do you still have that ported Streetmaster that you lent me for the dyno testing on the higher horsepower engines?  If you still have that and could lend it to Harry, he could just bolt that on in place of the existing Streetmaster to see if there was a major difference.  Not trying to rope you into anything here, but I saw that you offered your porting services to Harry, so I thought I would bring this up as an alternative.

Harry, I'm not sure I'm in 100% agreement with Joe on the cam.  That is a reasonable cam, but at 252 @ .050 its quite a bit smaller than the 260 @ .050" cam I used in my 390 stroker engine.  That cam peaked in power around 5700-5800 RPM, with more duration than your cam has, and fewer cubic inches.  So again I would say that your peak power RPM is probably about right given the cam, and I would be surprised to see any significant shift in the power band with just the change in intake or exhaust.

Also, that exhaust is probably hurting you some, and going to 3" pipes and better mufflers will be a help.  But I doubt you'll get 50 HP doing that.  If you want to try an experiment, you might consider this:  Get yourself a pressure gauge calibrated in inches of water, from zero to 100 inches.  28 inches of water is equal to 1 psi.  You can get the gauge at a place like McMaster Carr's online site (www.mcmastercarr.com).  Plumb it into one of your header collectors with a steel tube and a fuel line hose, and watch the gauge as you accelerate at full throttle.  If you have 0.5 psi (13 inches of water) or less, that's pretty good.  If you have more than 1.5 psi (38 inches of water), that's pretty bad.  You can get an idea of exactly how bad your exhaust system is hurting you if you get these numbers.  See the graph on page 207 of my book for more information on power loss vs. exhaust system back pressure.  At 5500 RPM on my 427 dyno mule, the difference in horsepower between 0.5 psi and 2.5 psi was only about 30 horse.

[Joe-jdc]

Hi, Jay, yes I still have the Streetmaster.  I wanted to try it on my 468 Shelby engine.  It is an icon now, so I will keep it!  LOL.  Also still have the Victor, and BT 8V, and PI you tested, an RPM, TW, 3 CJ's and have acquired a Holley Street Dominator to try to tweak a bit.  The reason I feel the camshaft is healthy is the lift is substantial, and anything over 250* is starting to get into race territory on most engines.  I must say I have not run a stroker FE greater than 452CI yet, so I am going on past experiences.  A local class racer uses a 252/259* 525" lift camshaft in his class legal fairlane that runs 10.82 @ 3480#.  I ran the F276 Crane in my 452 in my Mach I that went 10.94/123.6, and it was a race only piece.  I am sorry you had such terrible time with the new car, hope you get all those issues sorted out to your liking.  I agree, the paint is too bright on the Shelby clone---but then I am prejudiced! Ha, I like white/white/with blue stripes.  Joe-JDC.