Weird dyno "curve"

[Martin460]

Tryed dyno pull yesterday with my 1972 Sixpack RR . Started at 4000 rpm, torque converter is 3500 stall Streetfighter. Kickdown linkage is disconnected and 3-rd gear used. Rev. limiter is 6000. I think somewhere is major misunderstanding . Somebody seen curve like that. Power is in kw...that is approx. 270 rwhp.

 

[1967coronet440]

Can you provide more detail on the motor, intake, carb cam etc...

 

[RT K_line]

I would think that with the kick down linkage not connected it would be slipping some in high gear under that kind of load. Torkflite transmissions need that linkage connected and adjusted properly to function correctly. Not an expert here but I've never seen a pattern like that. JMO

 

[Budnicks]

Looks like it drops off power wise after 4000 rpm
it ain't liking that specific combo...
Shouldn't drop off that drastically after 4000 rpm
maybe after 5500 or so, but not that much...

just spit-balling here,
not knowing your specific combo;
They should fall of a bit in HP even a little TQ
after reaching the camshaft power range
& what the valve-springs will handle
or what the uintake carbs, heads, valves,
intake & ex. ports can flow
but that's like it's starving of fuel or way too fat
or ignition timing way off, ignition curve way off,
the coil or resistance wrong etc.

Probably something not getting power to the rear axle
trans &/or converter or even gear ratios, is killing it
bogging it down etc. or something is obviously way off...
What kind of shift kit or valve-body ? If any ?
The kick-down/Throttle bypass linkage,
should be hooked up other wise, unless it has a kit
or valve-body that reroutes the fluids...
That is a strange graph...

More details on what's been done,
may help diagnose it better...

I'm not a big dyno guy either...

 

[Martin460]

Thanks for advice so far. My mistake i didnt write more information about the engine.
Engine is Mopar 440HP sixpack from 1969y. As seller
said about the engine:"...has done some modifications"thats all. So...nobody knows
nothing.

During the last year checked engine and found high dome pistons 12:1 comp
ratio. Original Mopar 906 iron heads. Balanced all inside parts etc.
Engine revs up really quick. Have 3500 stall converter in 727 transmission
and 3.55 ratio with limited slip in rear. 26x12,5x15 Mickey Thompson
sportsman pro wheels. MSD ignition at idle 18deg. and 18deg. on
distributor. Two blue light springs and maximum advertaising stops at 2700-2800 rpm. No vacuum advance. I drive only on some weekends during the
summer so its only for show. Cam is Cam Dynamics with unknown specs.Some numbers stamped in the end of camshaft. Yesterday i write to cranetech and asked some specifications and here is answer:
We don’t have a spec card showing the 306H for the B Mopar, but I was able
to find a card for the LA engine. The specs will be similar to the big
block.

What i was thinking here is first and third carburetor of sixpack setup. How i know they really open at wot??? They are vacuum operated from center carb bet as you know vacuum at wot is ZERO inside the carb!!! Maybe 1-st and 3-d was closed and engine is air/gas shortage? Thanks again and sorry my english.

 

[Martin460]

Some more info. Air filter is all around open K&N Six Barrel filter. And spark plugs AL 85 (autolite) 0,035 gap. I checked roughly with some vacuum tester and seems center carb dont have any vacuum even 4500-5000 rpm. After some days i can borrow big vacuum tester from proffesionals and made test drive to read correct data.

 

[Ski 61701]

What do your sparkplugs look like? Are they burning ok? After you check those let us know what they look like. So we can help diagnose things.
You mention that you have a 6 pack on your motor. From what I understand they are not very forgiving with big cam shafts. If you haven't already, do a search on 6 pack tuning, i recall a year or so ago someone here posted a lot of good tuning information on them. You mentioned vacuum leaks, if you have access to a propane torch, turn it on and with the motor running direct the unlit torch gasses at the carbs and intake /head area to make sure you don't have any external leaks. If you do the propane will smooth the idle out.
By the way your English is quite good. Better than some people who live in America