Engine Dyno/Vs Chassis - Powerloss?

[mattF]

Just joined but i'll put one out for you problem solvers.

Engine set up
Stroked 440/522 - Extreme energy comp cam, PW aluminum heads, rpm performer intake mani, Holley sniper, hooker headers and 3" exhaust.
TCS 2800 stall converter on a built 727 auto (cant give detail on the tranny since that was done by previous owner)

With stock heads and a 850 demon carb it did 500hp and 630tq
since the build we did the PW heads and Sniper EFI

Chassis Dyno last week - see below for chart
But hits max HP around 4000rpm and just dies off... torque numbers are extremely low as well

Something isnt right...
- My current predictions - Valve float since we swapped heads post engine dyno - Maybe incorrect pressure/height (getting the height/pressure checked this week by an engine builder)
- torque converter is inefficient/not working correctly and causing massive driveline loss
- 727 Tranny is causing the loss...

I have plenty of fuel - leaning it out a bit added a couple HP so i'm ruling out the sniper.
Played with the timing on a few pulls and again minor hp changes.

Spoke with a couple mopar/engine builders they predicted 550-600hp to the crank with 20% loss avg on these older set ups/2800 stall to be more around 450 whp.

What am i missing?

Thanks in advance

[ek3]

combination of  heads don't like cam, intake is better with the factory heads ?? air flow is key to hp... a direct flywheel / dyno to dyno would rule out drive line issues.

[RUNCHARGER]

First guess over the internet would be valve springs or fuel delivery. We had a similar event with an Indy 572 that ended up having a bunch of wrong parts/assembly from Indy. I would check it over carefully, the 572 died around 5000rpm and was 100HP short. We changed the incorrect camshaft and then later discovered the springs/height were wrong from Indy as well. Greg got lucky but I don't trust any engine builder now.
Your curve stops suddenly just like Greg's did. So I am betting valve float. Who assembled the heads? I know a real trustworthy head guy in Kelowna if you don't have one down there.

[mattF]

Very surprising about Indy - i've always heard positive things.

Sounds very similar - i've talked to quite a few people the camshaft i have should work quite well for this set up - and i can rule out fuel delivery - all of my tuning charts were on point A/F and had plenty more to add in if i wanted.

I'm taking it tomorrow morning to Terry @ Kershaw Performance in Langley - he originally did the engine Dyno after the build and i trust him - especially since we have narrowed down the problem. I did the head swap myself - The Comp springs should have been a direct swap for the PW head according to Mopac but i'll be honest i didnt shim or check anything - i've built bottom ends but this was my first time doing head work. So crossing fingers it was my error and a simple fix with out valve interference in the motor already.

Once you guys had that sorted with the valves springs- it came back to life?

[mattF]

do you still have the dyno chart from when you ran it?

[RUNCHARGER]

No, I think I deleted the dyno  sheet, it was like yours though a steady climb and then dropped like a rock. Kershaw is a good builder from what I've heard, he'll probably sort it for you. The Indy experience was not good unfortunately. When I installed the engine for Greg I was tempted to pull it apart and check everything but I didn't listen to my inner voice and I should have. It runs hard now though, extremely violent package. Your car really has a nice look to it BTW.

[mattF]

Ya he is solid - i'll have a report by tomorrow and hopefully solved! haha hey hindsight is 20/20 but at least you guys got it solved!
Thank you - Its a work in progress, just finished work now to do a bit more wrenching on it  

[Chryco Psycho]

Welcome from Panama . for sure a mechanical problem the way it drops off .
Racing dynos is always a problem also , for example Mustang dynos are heartbreakers , it is tough to get a good # , take the same car to a Dynojet & you will gain 15% so the actual # is not as important as repeatability for tuning etc . running a # at the track will relveal a lot but can lie also with tire slip etc .
I am no fan of Comp cam grinds they always seem to be down on power , I would look at Lunati or Engle or get a custom grind as I generally did for my builds . I can help with that if you need .

[mattF]

I appreciate that- i've been considering swapping to a roller - Big difference in drivability and power?

What cam do you guys recommend for this build?

[Chryco Psycho]

4 types of cams
Hyd flat tappet
Hyd roller
Solid flat tappet
Solid roller .
each have advantages & disadvantages
Hydraulics limit lift as the hyd can fail under higher spring loads .
Flat tappets need special oils to protect the cam .
Rollers can starve the roller for oil in street situations where there is a lot of idling & limited oil splash up to the lifters although there are EDM rollers to feed a small amout of oil to the roller  , they also require bronze dist drive & fuel pump pushrod .
Virtually all will benefit with Roller rockers , I used Bushed Stainless steel for street applications not alum & no needle brg roller against the rocker shafts .

[rikkitik]

I wanted to stay out of this (being new to the site and all) but.....
Just my 2 cents, but I wouldn't get to shook up about this, other than to maybe get your money back from the dyno operator, or have him rerun it until he can produce a relatively "smooth" curve without heavy application of the software smoothing function.
The waviness in your chart somewhat indicates tire slip. Also the way your hp went up, then stayed relatively flat (other than the "waves"), kind of suggests that was the limit of tractive force. By the same token, your torque descends at an almost linear rate. If torque stays flat through rpm, hp will increase on a diagonal line. And vice versa, if hp stays flat, indicated torque will decrease on a diagonal line.
"Most" engine dyno's measure brake torque, then calculate hp by torque x rpm.
"Most" chassis dynos, on the other hand, are inertia dynos, that measure hp required to accelerate a known mass during a timed cycle, then the software divides hp by rpm to calculate torque.
The more "jagged" areas of the graph, suggest tach pickup interference.
Like CP says, it's difficult to "race" dynos, and you shouldn't, they are just another "tool".
Definitely, check for mechanical issues, but also trust the "seat of your pants".
Does the "model" (dyno chart) agree with reality?
As in, does the car actually feel the way the dyno suggests?
Does it initially "jump", but then accelerate at a steady, somewhat lazy pace?
Anyway, it's just another "internet opinion" to ponder.
Best of luck sorting it out. 🍻

[mattF]

Good Summary/Info - Thank you

4 types of cams
Hyd flat tappet
Hyd roller
Solid flat tappet
Solid roller .
each have advantages & disadvantages
Hydraulics limit lift as the hyd can fail under higher spring loads .
Flat tappets need special oils to protect the cam .
Rollers can starve the roller for oil in street situations where there is a lot of idling & limited oil splash up to the lifters although there are EDM rollers to feed a small amout of oil to the roller  , they also require bronze dist drive & fuel pump pushrod .
Virtually all will benefit with Roller rockers , I used Bushed Stainless steel for street applications not alum & no needle brg roller against the rocker shafts .

[mattF]

Great info- and i dont have the experience to read these charts the way you do so thats good to know. I have an update i'll post right now as we made some changes and went back for another run

I wanted to stay out of this (being new to the site and all) but.....
Just my 2 cents, but I wouldn't get to shook up about this, other than to maybe get your money back from the dyno operator, or have him rerun it until he can produce a relatively "smooth" curve without heavy application of the software smoothing function.
The waviness in your chart somewhat indicates tire slip. Also the way your hp went up, then stayed relatively flat (other than the "waves"), kind of suggests that was the limit of tractive force. By the same token, your torque descends at an almost linear rate. If torque stays flat through rpm, hp will increase on a diagonal line. And vice versa, if hp stays flat, indicated torque will decrease on a diagonal line.
"Most" engine dyno's measure brake torque, then calculate hp by torque x rpm.
"Most" chassis dynos, on the other hand, are inertia dynos, that measure hp required to accelerate a known mass during a timed cycle, then the software divides hp by rpm to calculate torque.
The more "jagged" areas of the graph, suggest tach pickup interference.
Like CP says, it's difficult to "race" dynos, and you shouldn't, they are just another "tool".
Definitely, check for mechanical issues, but also trust the "seat of your pants".
Does the "model" (dyno chart) agree with reality?
As in, does the car actually feel the way the dyno suggests?
Does it initially "jump", but then accelerate at a steady, somewhat lazy pace?
Anyway, it's just another "internet opinion" to ponder.
Best of luck sorting it out. 🍻

[mattF]

UPDATE: Initially thought the reason it wasnt making power was due to when the aluminum heads were swapped over the springs were not adjusted.
Took it to Terry at Krenshaw performance and indeed the springs were not the correct height so we put in new shims to adjust the springs for the cam/heads (picture shows how much they needed to be shimmed - first two springs had been fixed the others where they were) - also checked lifter clearances etc. We found 2 plug wires that were arcing to the header due to the boot being burned through - all possible power reducers...


Dyno pull time... Got around to taking it back to the Dyno yesterday hoping those changes were the reason.. They were not, If they added any power they just made the problem worse putting it to the back tires.

Here is the vid of the pull hopefully that works
https://photos.app.goo.gl/RouNsspc8MUd995UA

The Car revs right up to 5800 RPM almost immediately while the wheel RPM reads its 3800 and climbing slowly, it takes about 3-4 seconds for it to catch up to the motor RPM. Max power was 275whp then runs down after that.

So this strongly leads me to believe the torque (630ftlbs on engine dyno) is blowing right through the torque converter when its put on the chassis - Does this work like a slipping clutch with too much power? because that's what it sounds like - either that or can the 727 Trans be causing slippage like this? The fluid was full, didnt smell burned and had good color.

If so i'll be pulling the torque converter out there to get it retuned or a whole replacement to handle the power. - Is there checks i should be doing on the 727 first before pulling it out and assuming thats the problem?


Thanks in advance

[RUNCHARGER]

Hmm: I had good luck with a TCS convertor and a 2800RPM stall should lock up pretty quick. Tires not spinning?