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Dyno Dissappointment #2957991
08/27/21 12:48 PM
08/27/21 12:48 PM
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PA--USA
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70VERT Offline OP
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I've had a blast restoring my 70 Challenger Vert. Originally a 318/727 car I cloned it into a 440 RT/ 4 speed. Started with a 440 Truck engine out of a motor home, kept the cast crank, bored 15 thou over. had the heads totally rebuilt and taken down 50 thou, steel head gaskets, edelbrock performer intake, Hedman Headers. MSD dist, single wire Powermaster alt and Blaster coil. Just had it Dynoed at 304 HP at the wheels. Really disappointed ----- Thoughts?????. I know I can spend big bucks from here, but I was expected more at this point

Re: Dyno Dissappointment [Re: 70VERT] #2957997
08/27/21 01:15 PM
08/27/21 01:15 PM
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St.Pete,Florida
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lancer493 Offline
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I would say you need to provide more specific information here.Carb, cam timing and specs , actual compression ratio and cylinder head info come to mind. If you haven't tried to dial in the combination yet, maybe you missed on the tune up. What you are seeing there is probably not far from actual rear wheel horsepower of a stocker rebuild. More specifics are needed. It sounds like you are just getting started and need to make some adjustments ,one at time ,to get a direction. You may still have some left on the plate. Work the small stuff first , one at a time. Good luck, keep at it. Bill

Re: Dyno Dissappointment [Re: lancer493] #2958003
08/27/21 01:39 PM
08/27/21 01:39 PM
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70VERT Offline OP
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Missed a little here....thanks.............Installed a Hughes engine "whiplash" cam and at the time,used a cam timing wheel to check it.....o adjustment beyond the timing marks was required Worked Worked with Hughes Engines to have custom length push rods made also, (due to planing down the heads) Have a Holly 850 Street Avenger Carb on her. Dual 3" TTI exhaust system. Id like to see a little more HP, but unsure whats best

Re: Dyno Dissappointment [Re: 70VERT] #2958005
08/27/21 01:48 PM
08/27/21 01:48 PM
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Kalispell Mt.
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HotRodDave Offline
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Without knowing the exact cam specs I don't think the results are far off from what the combo should make, it's probably closer to 375 at the flywheel, some fine tuning may net a small handful of HP but not a ton. The next thing I would upgrade would be some bigger valves and decent amount of porting in the heads (or sidewinder or edelbrocks) and at least a performer RPM intake as the regular performer is barely any better than stock. Heads or intake upgrade alone would not net much as the other would still be the choke point, doing both together should wake it up.


I am not causing global warming, I am just trying to hold off a impending Ice Age!



Re: Dyno Dissappointment [Re: 70VERT] #2958006
08/27/21 01:51 PM
08/27/21 01:51 PM
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Cab_Burge Offline
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What RPM did it make peak HP and peak torque?
What was the weather that day?


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Dyno Dissappointment [Re: 70VERT] #2958007
08/27/21 01:51 PM
08/27/21 01:51 PM
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Rogue River, OR
Jeremiah Online work
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Originally Posted by 70VERT
I've had a blast restoring my 70 Challenger Vert. Originally a 318/727 car I cloned it into a 440 RT/ 4 speed. Started with a 440 Truck engine out of a motor home, kept the cast crank, bored 15 thou over. had the heads totally rebuilt and taken down 50 thou, steel head gaskets, edelbrock performer intake, Hedman Headers. MSD dist, single wire Powermaster alt and Blaster coil. Just had it Dynoed at 304 HP at the wheels. Really disappointed ----- Thoughts?????. I know I can spend big bucks from here, but I was expected more at this point



I have a similar 451 with 906's, performer, and stock big block a body exhaust manifolds. It makes right at 300hp to the wheels on a chassis dyno as it is driven off the street, heat soaked and all. Uncorking the 2.25" repro exhaust is work 20rwhp.

If you have a smaller cam (xe294h w/ 1.6's here) and headers compare to my manifolds I'd guess you might find 15-25 tops at the wheels. What RPM did you pull it to?

The 451 in my dart made a hair under 500hp/500tq on a realistic engine dyno with a Performer RPM and 1-7/8" dyno headers. I figured the manifolds -50hp, intake -15, full exhaust -25hp, factory magnum air cleaner -10hp and don't forget the accessory drives for a very believable 100hp loss at the flywheel. That leaves us with 400hp going into the clutch.

400x.80=320rwhp on a perfect day. Take a car driven in off the street (heat soaked) on an 85 deg. day and 300ish at the wheels isn't out of the ball park.




Re: Dyno Dissappointment [Re: 70VERT] #2958009
08/27/21 01:59 PM
08/27/21 01:59 PM
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Keymar, MD
DusterKid Offline
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Sounds like a fairly stockish rebuild and they were only rated 375HP at the flywheel from factory I think. Figure in the drivetrain loss that's sounds about right for a stockish street car rebuild. Do you want more HP just for the number or do you want more power? For a street cruiser that sounds like a nice cruiser. Never understood building a 500+ HP for a street cruiser.

Re: Dyno Dissappointment [Re: Jeremiah] #2958010
08/27/21 02:01 PM
08/27/21 02:01 PM
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Tallmadge, Ohio
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Paul_B Offline
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Did you try any tuning? Adjustments such as ignition timing and carburetor (Fuel/Air Ratio) can make a big difference in power. On my hemi, adjustments to timing and changing jets in the carburetor helped me get 80+ more horsepower on the dyno. Not sure if you could see that much, but if you just have a bunch of parts bolted together, tuning would almost certainty help you find some hidden power.

Re: Dyno Dissappointment [Re: Jeremiah] #2958015
08/27/21 02:50 PM
08/27/21 02:50 PM
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440Jim Offline
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Originally Posted by Jeremiah
I have a similar 451 with 906's, performer, and stock big block a body exhaust manifolds. It makes right at 300hp to the wheels on a chassis dyno as it is driven off the street, heat soaked and all. Uncorking the 2.25" repro exhaust is work 20rwhp.

The 451 in my dart made a hair under 500hp/500tq on a realistic engine dyno with a Performer RPM and 1-7/8" dyno headers. I figured the manifolds -50hp, intake -15, full exhaust -25hp, factory magnum air cleaner -10hp and don't forget the accessory drives for a very believable 100hp loss at the flywheel. That leaves us with 400hp going into the clutch.

400x.80=320rwhp on a perfect day. Take a car driven in off the street (heat soaked) on an 85 deg. day and 300ish at the wheels isn't out of the ball park.

I like Jeremiah's post. Realistic, although approximate, numbers for various parts & factors.

Re: Dyno Dissappointment [Re: DusterKid] #2958019
08/27/21 03:06 PM
08/27/21 03:06 PM
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West Coast, USA
jbc426 Offline
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Originally Posted by DusterKid
...... Never understood building a 500+ HP for a street cruiser.


I totally agree with your sentiment. 500 hp is not nearly enough!

I find 650+ is approaching enough power, but I'm thinking 800hp is just about right. I'm limited due to running a stock 440 block, or I would have added a 150hp shot of N2O for use in second gear on up on my street/highway cruiser.


1970 Plymouth 'Cuda #'s 440-6(block in storage)currently 493" 6 pack, Shaker, 5 speed Passon, 4.10's
1968 Plymouth Barracuda Convertible 408 Magnum EFI with 4 speed automatic overdrive, 3800 stall lock-up converter and 4.30's (closest thing to an automatic 5 speed going)
Re: Dyno Dissappointment [Re: jbc426] #2958021
08/27/21 03:18 PM
08/27/21 03:18 PM
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crackedback Offline
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Cam is a lot larger than the stocker. With a good tune I'd expect it to make more than 400 at the flywheel with headers.

Don't know what the ignition timing is at idle, but it's likely going to want in the 16-20 range minimum. Might need a limiter bushing that MSD doesn't make as well.

Re: Dyno Dissappointment [Re: 70VERT] #2958022
08/27/21 03:25 PM
08/27/21 03:25 PM
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So. Burlington, Vt.
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The two things that stick out to me are:
- no mention of any head porting or oversized valves
- “Performer” manifold. If it’s the std Performer, not the Performer RPM there is some potential power left on the table there........ especially if the heads get reworked.
If the motor has stock heads with no porting and the std Performer, I can see where you’d have an under 400hp(at the crank) combo.

I find chassis dyno results can have an even bigger swing from facility to facility than engine dynos(and different engine dyno results can vary quite a bit).
So, without having something to compare to off that dyno...... your 304rwhp is just an arbitrary number to me.
Maybe the dyno service could give you some numbers from bone stock modern muscle to use as a comparison.

A pretty basic pump gas 440 with say...... 9.5cr, a mid-sized hyd cam, some mild head work to factory heads, headers, intake, carb, etc will be in the 425-450hp range at the crank.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: Dyno Dissappointment [Re: jbc426] #2958025
08/27/21 03:36 PM
08/27/21 03:36 PM
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St.Pete,Florida
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lancer493 Offline
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DusterKid makes a very good point. You've got a 70 Challenger CONVERTIBLE 440 4spd R/T. Quite a valuable and fun car. The motor sounds like a stump puller.Don't worry about the numbers. If it's fun to drive , do it! Its too valuable of a vehicle to end up around a tree. Spend some time tuning it and enjoy it. There's probably a bunch of us on here that would love to be cruising around and shifting gears in that car .Enjoy it. It's only numbers.
Bill

Re: Dyno Dissappointment [Re: lancer493] #2958055
08/27/21 05:38 PM
08/27/21 05:38 PM
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lewtot184 Offline
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generally people have unrealistic expectations from a chassis dyno. remember that a chassis dyno is driving the fan, water pump, alternator, mufflers, transmission, rear axle, wheels tires. for what i take on the build 304hp isn't bad. i think unrealistic chassis numbers stems from unrealistic engine dyno (magazine/internet stuff) numbers. the chassis dyno is the truth meter and people can't deal with it.

Re: Dyno Dissappointment [Re: 70VERT] #2958074
08/27/21 07:00 PM
08/27/21 07:00 PM
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Bend,OR USA
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All chassis dyno give you the net reading (true HP to the rear wheels), not the gross reading like the factory uses on there adds to the flywheel. down
My last pump gas street car had a 517 C.I. 400 block stroker motor that made 612 HP at 5500 RPM and 644 Ft. Lbs. torque at 4500 RPM with a set of ported 906 heads with big valves with 9.25 to 1 compression ratio and big solid lifter roller cam on a DTS brand engine dyno with a low deck six pack set up tune to the max, that motor made right at 500 HP net at 5000 RPM peak with a 10 inch custom converter on a local chassis dyno, that is 19.4 % loss with 4.10 gears in the rear end shruggy
On your deal you may have more power in the engine that is not getting to the rear wheels because it is running out of fuel above 5000 RPM, been there done that whiney work scope
If I was you I would make sure that the motor is not going lean above 4500 RPM at wide open throttle in high gear, look at buying and using a good wide ban O2 exhaust system so you can see real time air fuel ration while driving twocents


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: Dyno Dissappointment [Re: 70VERT] #2958093
08/27/21 07:57 PM
08/27/21 07:57 PM
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Benton, IL.
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DaveRS23 Online rolleyes
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Late model motor home heads are a real cork with any cam at all. Lots of good suggestions above.

I only have one question; how far down in the hole are the pistons? Of better yet, what is your cranking compression?


Master, again and still
Re: Dyno Dissappointment [Re: Cab_Burge] #2958110
08/27/21 08:51 PM
08/27/21 08:51 PM
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Plymouth, MI
Blusmbl Online content
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Originally Posted by Cab_Burge
All chassis dyno give you the net reading (true HP to the rear wheels), not the gross reading like the factory uses on there adds to the flywheel. down


Sorta. Gross and net refer to the test conditions when they were originally rated- net is still a flywheel number, but it includes things like the alternator, the water pump, the fan, the full exhaust system with representative backpressure, etc.. The gross ratings were not realistic. Both of them will still be higher than the rear wheel horsepower number. Depending on manual vs. auto, or the type of converter, you could see losses in the vehicle anywhere from 12% to 22+%, below the net rating.

Dynos also have 2 correction factors - SAE and standard. SAE is also more representative of real world conditions. STD corrects to completely dry, 60* air, with a density altitude of near 0, so the STD number will always be higher than the SAE. SAE corrects to 77* air, a little lower barometer, and more reasonable humidity (it's closer to 2000' density altitude). This applies to both engine dynos and chassis dynos.


'18 Ford Raptor, random motorcycles, 1968 Plymouth Fury III - 11.37 @ 118
Re: Dyno Dissappointment [Re: DaveRS23] #2958154
08/28/21 12:14 AM
08/28/21 12:14 AM
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Originally Posted by DaveRS23
Late model motor home heads are a real cork with any cam at all. Lots of good suggestions above.

I only have one question; how far down in the hole are the pistons? Of better yet, what is your cranking compression?



Missed the motor home part, saw truck engine. DOH!!!!

Re: Dyno Dissappointment [Re: crackedback] #2958167
08/28/21 01:19 AM
08/28/21 01:19 AM
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Memphis
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pair of Edelbrock heads would wake this engine up I bet !


Take care,
Rick
68 Coronet R/T 440 & 68 Charger 528 Hemi,and 5 Challengers! 6 cyl, 318, 360, 383, 451
Re: Dyno Dissappointment [Re: HemiRick] #2958171
08/28/21 01:40 AM
08/28/21 01:40 AM
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California
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Without knowing your cam specs, I think 300ish RWHP is about right, that's about 380hp. 440's especially with stock heads are just not big HP makers. They don't make good dynamic compression (comparatively to other rod stroke combos) and the factory heads can't breathe.

I had a strong running 440 (.030 over) with flat tops, a Hughes solid flat tappet cam and Edelbrock performer heads with 1 7/8" headers. The engine made 360 RWHP (or 450HP). I also was disappointed but the 3700lb B body ran 11.90s @ 115mph.

Bottom line: 440s make a ton of torque and that's why they were feared on the street, they got things moving in a hurry.


1969 A12 Roadrunner
1970 Plymouth Cuda
1968 Dodge Dart
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