Stumped on my dyno numbers

[squidz]

Hi guys,

I'm stumped by the dyno numbers of my 347.

I recently redynoed and the numbers were the relatively the same.

The first time I dynoed on a Dynojet with 301hp/309tq to the wheels
the second time was on a Dynapack with 310hp/320tq
I have a comp roller cam 290hr, rpm airgap intake, patriot sbf heads
1.6 roller rockers... scat 347 stroker.... full MSD

This is all running through a toploader 4sp through a detroit locker rear
i taked to a few mustang guys and they said i should be getting at least 350-400 to the wheels.

what gives???? where am i losing hp? HELP!?!

 

[SadbutTrue]

Hi guys,

I'm stumped by the dyno numbers of my 347.

I recently redynoed and the numbers were the relatively the same.

The first time I dynoed on a Dynojet with 301hp/309tq to the wheels
the second time was on a Dynapack with 310hp/320tq
I have a comp roller cam 290hr, rpm airgap intake, patriot sbf heads
1.6 roller rockers... scat 347 stroker.... full MSD

This is all running through a toploader 4sp through a detroit locker rear
i taked to a few mustang guys and they said i should be getting at least 350-400 to the wheels.

what gives???? where am i losing hp? HELP!?!

I think you're roughly where you're supposed to be. Maybe 330 to the wheels, though you wouldn't be the first person on this board to have trouble with the Patriot heads.

Anyone who said you were going to get 400 to the wheels with that was on some quality stuff. Not an insult, but that just isn't gonna happen.

What compression? Exhaust? Carb?

Off the top of my head, your intake might not breathe high enough for your cam. I'm only familiar with Compcams non-roller cams, but 290HR sounds pretty aggressive. Might see some gains with a Vic Jr.

 

[squidz]

cr is at 10.5, exhaust is magnaflow2.5inc with tri-y's and carb is a 670 street avenger.

So where can i get the greatest improvement? Swap out the heads?

 

[SadbutTrue]

cr is at 10.5, exhaust is magnaflow2.5inc with tri-y's and carb is a 670 street avenger.

So where can i get the greatest improvement? Swap out the heads?

First, I have a 670 street avenger and so far I'm not totally pleased with it. Though I'm going to do quite a bit of tuning on it over winter break and report back before I condemn the thing.

What are the cam specs? I have a hydraulic 274XE (non roller) and it pulls to 6000. I checked Compcams' site and didn't see a 290HR under the 5.0 cams, but comparably 'numbered' cams were all built to rev to 7000 rpm. If that is the case... your carb and intake might be limiting you (and maybe the tri-y's). Tri-y's, the RPM Air Gap, and the 670 SA are all better matched to a cam that is pulling to 6000 rather than 7000.

If you got a Vic Jr, a carb in the 750-850 cfm range, and some hooker super comps (big primary/longtube, tri-y's are more for mild engines from what I've heard).... you could see some pretty big gains.

Or, you could downsize the cam to something a little less ridiculous and your combo will be better matched. Peak HP might not change much but you'd have a much better torque curve, it'd run better ETs, get better mileage, drive better etc.

Tough to say without the actual cam specs though.

The Patriots... they're hard to say. Their specs are good and from what I've heard they're Chinese made AFR ripoffs with some strange (ie hit and miss) quality control. Good examples of the heads are definitely going to put up big numbers, but if you google 'SBF patriot heads' you'll find a lot of horror stories. You made decent power so i doubt they're that big an issue, you might make a little more power with some Trick Flows or AFRs but probably not worth the time effort.

 

[squidz]

Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 3,000-6,500
Intake Duration at 050 inch Lift: 230
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 230 int./230 exh.
Advertised Intake Duration: 290
Advertised Exhaust Duration: 290
Advertised Duration: 290 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.544 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.544 in.
Valve Lift with Factory Rocker Arm Ratio: 0.544 int./0.544 exh. lift
Lobe Separation (degrees): 110

 

[SadbutTrue]

Cam Style: Hydraulic roller tappet
Basic Operating RPM Range: 3,000-6,500
Intake Duration at 050 inch Lift: 230
Exhaust Duration at 050 inch Lift: 230
Duration at 050 inch Lift: 230 int./230 exh.
Advertised Intake Duration: 290
Advertised Exhaust Duration: 290
Advertised Duration: 290 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio: 0.544 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio: 0.544 in.
Valve Lift with Factory Rocker Arm Ratio: 0.544 int./0.544 exh. lift
Lobe Separation (degrees): 110

Yeah, I'd say the intake, carb and headers are holding you back a bit. Heads... again, probably wouldn't hurt to swap to Trick Flow or AFR but its really hard to say whether it'd be worth the money.

Your combo is where a single plane intake becomes recommended, I believe. A Vic Jr may be in order.

That'd be my recommendation, anyway.

 

[Bullitt]

Posting the chart or graph will help a lot too in diagnosing your problem. One thing to remember is that while peak numbers are great for bragging rights, the average power is what is going to kick butt for a street car.

What was your basis for picking the combination? It's all about matching parts. For instance, my 306, with a smaller roller cam, box-stock Trickflows, hooker longtubes, non-airgap RPM, and a 750cfm edelbrock carb made 325 HP to the wheels, 317 tq (thought a TKO and a 9").

Anyways, post that chart if you can. I think SadbutTrue's comments are pretty on the mark though. I don't know anything about the Patriot heads, but I don't think Tri-Ys are a good choice and the carb could be bigger, especially if it's a vacuum carb.

 

[SadbutTrue]

I think SadbutTrue's comments are pretty on the mark though. I don't know anything about the Patriot heads, but I don't think Tri-Ys are a good choice and the carb could be bigger, especially if it's a vacuum carb.

I'm also the guy who built what should be a 400-425 horse motor that only dynoed 255 to the wheels

Though I'm far from surrendering... thats an issue for another thread (or 10)

A Vic Jr, a rebuilt from ebay 750 (or maybe bigger) double pumper and some super comps will do magical things for you, I think. Good thing is you can probably sell the parts you have and not lose a whole lot of cash on those three items (might actually make some on the carb), if you decide to swap stuff around.

And as bullitt says, posting the graph might yield some easy ponies. If its like mine, it'll have an A/F ratio measurement and other features of the graph which can hint towards how to tune it.

Did you make any changes between test 1 and 2?

Also, any pictures of the Patriot heads before you installed them? Would be interesting to see how good the ports and chambers look. Like I said, you'd see some seriously messed up amalgamations if you googled Patriot heads.

 

[SadbutTrue]

One thing to remember is that while peak numbers are great for bragging rights, the average power is what is going to kick butt for a street car.

On that note, even if you do make the changes I suggested (bigger carb, single plane, fatter headers) you may not run much better/faster, particularly on the street (where a fat powerband is what you want, and what your current combo probably has). Whether you can really take advantage of it would depend on rear end gearing, trans gearing, whether you can get traction with the current combo or not, etc

Your low/mid-range torque (and along with it mileage, drivability, etc) will likely take a hit, though it might not be too bad... I don't really have much hands on experience with single planes and double pumpers. For the purposes of a horsepower manhood measuring contest it might be what you're looking for though.

 

[dodgestang]

Welcome to reality. There are so many 450-500 HP at the back tire 13 second monsters running around I've lost count.

Dynos are a tuning tool. Most people when they go there always have their expectations realigned. The good news is that a good dyno tune session usually find HP that was being left on the table. When it is all said and done, running it at the track is the true test for power.

 

[10secgoal]

Those heads aren't the best at all. They barely flow more than stock. Pro Comps are the same way. 20cfm over stock

 

[57fairlane]

Thats weird how little torque you are making . . . something is definitely not right.

I ported a set of e7s that went on a 347 and it made 360rwtq (although it was fuel injected).

First things first, the RPM intakes are made for a 302 not a 331/347/352. Despite the larger runners, the RPMs seem to max out around 310-320rwhp with a larger motor. I would definitely suggest going to a victor jr. Also the tri-y headers are not helping things at all. "I" would run a 1 3/4" longtube given the cam that is already in there.

The street avenger is negligible. Can you make more power with a BG or larger double pumper, of course but that isn't the problem here.

The next thing is the heads. I would suggest getting them ported by someone who knows what they are doing.

The procomp/patriot heads ARE NOT for people simply looking to bolt them on and go. You have to check seats, springs and port them to make it worthwhile. The low cost upfront is negated if you can't do the work yourself.

lastly, I hope you broke in the cam with tons of lube and rotella . . .

 

[10secgoal]

Check the rocker also. Have a motor here (that a customer bought)that year one sells with those heads. The guide plates are too close center to center where the pushrods come through, causing the rockers to kick out. Half of the rocker is actually off the valve stem. Won't be long before there are broken parts.

 

[squidz]

I decided to go with the rpm airgap because of this article...


347c.i. Small Block Engine - Intake Tests - 5.0 Mustang Magazine

should i still try out a victor jr?

 

[GT350R]

Ok, am I missing something?

Your compaing THEIR engine on an engine dyno, versus your engine at the rear wheels.
THEY have 12.5 compression, and you have 10.5:1.

THEY ran 114 octane to keep detonation down, and I assume max the timing. You ran ? with ? timing? I am guessing sane streetable stuff?

The hit 415 peak from what I see. 115 over what you did. With 2 points higher compression, 114 octane and maxed timing , and before you calculate your drivetrane losses.

You used "Tri Y's" and they used Hooker Super comps.

Now this is all before "the details". How did you set you timing? Just throw number your comfortable with at it? Did THEY polish the combustion chambers. Did see where they ported the heads, but being an article that promotes their companies builds, you can bet they used "hand selected" cores.

Figure that drivetrain is going to cost you about 50 horse. Thats only 65 horse difference for Alllllllll of those differences?

I think you did alright. At the very least , your over the 1hp per cubic inch rule of thumb so its not like its a turd.

should i still try out a victor jr?

Do you have realistic expectations? considering all the differnces above?

 

[squidz]

Oh that article was by no means for engine comparison. It was strickly for intake reference between rpm airgap and victor jr because a few of the above posts we suggesting i try the victor jr... based on this article it didn't make too much difference. With that in mind, I'm just trying to pin point what the low numbers may be attributed to.

Thanks

 

[10secgoal]

I wouldn't bother. There is no way that thing requires a Jr intake with those heads. I'd look into some of the other things mentioned before the intake.

 

[squidz]

Ya the rockers have been adjusted... the studs were kinda offset
We remedied with the bigger pushrods and guideplate adjustment. The carb has been tuned....was running a little rich midrange so we down 2 sizes on the secondary jets. Getting afr 13 now.

 

[dodgestang]

Have you driven it yet (like at the track?)

 

[squidz]

Driven it hard a few times on the street. It goes... but i've just seen similar setups that make at least 50 more hp and waay more torque... if anything the torque really doesn't look right.