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Chassis dyno sheet....something isn't right

justavillain

justavillain

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I was at Roadkill Nights in Pontiac MI and they had a chassis dyno. I was strapped in and made a few pulls and feel like something isn't right with this.

A fresh build 440, 30 over, Hughes cam, forged pistons, alum heads with 84cc chambers, 1.6 ratio dbl roller rockers, msd ing, M1 single plane intake with 800cfm Holley 4150. My ignition didn't have enough on the top end it was kind of popping, and AFR was 13.5 on the top of the pull. 3.55 rear gear with sure grip. OE wheels

So I know it needs more fuel on the secondaries but the numbers don't add up, only 250 hp to the wheels?! It torques up super hard and plants the car, and rips.

I attached the dyno print off, and a link to some of the runs.







E4A74494-D79F-47EF-B9AE-FBAA830A9F79.jpeg
 
Last video sounds like there is a lot of hesitation like a fuel or ignition issue going on. Matching up with the graph about 4300 rpm it started and never recovered.
 
The timing is 5 degrees base with 35 total advance. Mechanical advance only.

Fuel AFR gauge in pass side about 3" behind the collector flange. Was pretty much just 13.x the whole pass
 
5 degree initial is way low, start playing with your timing. Typically BB Mopars like around 36-38 all in on pump fuel. Good start for initial timing would be about 15
 
1967 I agree with you on the ignition issue above 4300 Rpms

However

More initial timing isn’t going to change what’s happening after 4300 Rpms when he is at 35 Total already

5 initial , that’s 30 mechanical , so a 15 degree number T in the distributor

Change it to 15 initial plus 30 mechanical = Not good

Now if he had a off idle issue , yes


Anyways


34-36 Total Timing after 2500 Rpms is just fine

Another degree or two isn’t going to add 200 HP


Sounds more like a MSD ignition box problem or coil

Did you have the Carb apart or rejet at all ?
 
I did not jet the carb yet. I just got it all together and was fighting some odds and ends before the event.

Proform distributor, electrical pickup (0.010 air gap between the reluctor and pickup) , msd 6AL with the rev limit set to 5500, and an Acell Super coil. No ballast resistor(bypassed by 2 10g wires twisted together and crimped together on each end to form a larger wire)

I have a jet kit and was thinking of jumping 4 jet sizes up from what it is in it now.

I have really pretty decent drive around after I changed the accelerator pump cam I have no real stumble.

It has an old Holly Red pump with 1/4" nipple to 3/8 lines all the way to the pump. Now I know when you dbl the dia of a hose you actually triple the vol it can flow. But I'm not running out of fuel, because my AFR never leans out.

Should I dial more time into it? New distributor?
 
I’m not a fan of proform parts at all, if it was me I’d be looking at replacing that dizzy.
 
That is what was In it when I got the car so I kept it. Do you think the 35 total is ok though? I know that is what my mud truck likes with it's 350 but there is a lot of difference between an 86 square body stock motor and this 440
 
You're miss 100+ HP. You're problem is not in fine tuning carb jets and ignition timing
 
That's part of the " something isn't right " I don't think the dyno guys where able to set it up right for my car. That is a wild dyno curve.

The motor was just built completely, cam was degreed all new parts except the crank( oem forged) and LY rods the rest was all assembled. The car torques up hard and pulls, smokes the tires even on a roll with 3.55 gears.
 
justavillain said:
That's part of the " something isn't right " I don't think the dyno guys where able to set it up right for my car. That is a wild dyno curve.

The motor was just built completely, cam was degreed all new parts except the crank( oem forged) and LY rods the rest was all assembled. The car torques up hard and pulls, smokes the tires even on a roll with 3.55 gears.
Click to expand...

Maybe its the dyno. Take it to a track. Track results don't lie.
 
Assuming you have a MSD 6AL, just an idea but check your cylinder select loops on your ignition box.
Perhaps the MSD thinks you have a 6 cylinder then your rev limiter would be lower than expected for example 5,500 X (6/8) = 4,125.
Not exactly where your problem showed up but something to rule out.
 
The 2 full loops are there. That was a good idea to check it out though.

I have plans on switching to a different msd box and dizzy as soon as I can get the funds replenished( rebuilding 2 engines in less than 2 years takes it out of your bank acct!)
 
You appear to have good torque. HP is torque x rpm / 5252. No rpm = no HP
Fix the higher rpm break down and you'll fix the HP number. My bet is electrical.
Doug
 
Dont most dynos read as rear wheel horse power? and then it usally is only a percentage of actual engine hp
 
Proper springs correctly installed? Or possibly lifter/lash/preload if ignition doesn't fix it.
 
mopar73dge said:
Dont most dynos read as rear wheel horse power? and then it usally is only a percentage of actual engine hp
Click to expand...
This is correct but at 250 to the wheels with that setup (something isn't right)
350-400 to wheels I'd still be trying to figure out where I'm loosing power !
 
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