Engine not doing well on the dyno, second dyno run better

[nicanor]

I had the car on the dyno and its only making 260 hp and 350 tq and when shut down, the engine deisels. We changed out the distributor and also put in a Flame Thrower Peritronix (sp?). I had a Holley 770 on the car and took it off and installed a 670 Holley.

The last dyno on the car results are 293 hp and 401 tq after installing the 670 Holley.

I did put 440 heads (452) on the car and a healthy cam, 4 speed.

Camshaft Technical Details
Intake Valve Lift 1.5
Exhaust Valve Lift 1.5 .518"
.518"

Intake Valve Lift 1.6
Exhaust Valve Lift 1.6 .552"
.552"

Intake Duration at .050"
Exhaust Duration at .050" 229°
242°

Lobe Separation Angle 107º

Intake Opening at .050"
Exhaust Opening at .050" 10.5° BTC
51° BBC

Intake Closing at .050"
Exhaust Closing at .050" 38.5° ABC
11° ATC

Min. Suggested Cylinder PSI

Sweet Spot RPM 1800-5200

Any suggestions why the hp/tq is so low at the wheels and the car desiels? I want the car to look stock though.

Thanks,
Barry

 

[4spd69RR]

Re: Engine not doing well on the dyno, second dyno run bette

I had a similar problem with my old runner with the desieling. I also had a 750 holley on it. I change the holley because the base was warped. I also had a leak around my intake. Now I was not dyno testing my engine, the issue I stating may not be the total problem you are facing. However I change the carb to a edlebrock and install new gaskets for the intake. My problem went away.

 

[moparchris]

Re: Engine not doing well on the dyno, second dyno run bette

The dieseling is a basic tune up problem. The throttle is open too much or the timing is too retarded. The "low" HP and TQ numbers aren't so low. 290 hp will power a 3000 pound car to 105 mph trap speeds in the quarter with an automatic. I have said it before many times that dyno numbers are just that dyno numbers. A Holley 670 is too small for your engine. I dont know why you pulled the 770 to put a 670 and expect more hp. When the 770 is tuned right it will blow that 670 off the map. Will the car go faster? Well thats what a drag strip is for. If your following the direction of the dyno operator, its time to find a new place to dyno your car. When I go to the dyno I do all my own tuning. I read up on what items are on my car and I prepare by getting the needed parts to tune it then I go to the dyno shop and do all my own tuning. It is amazing what you will learn about your own car, which will help you in the future when you have a tuning problem. BTW my money is on the 770 being faster at the dragstrip.

 

[69hemibeep]

Re: Engine not doing well on the dyno, second dyno run bette

Dyno #s at the wheels are lower than at the flywheel I hope your not comparing with those #s

 

[mcmopar]

Re: Engine not doing well on the dyno, second dyno run bette

The dieseling is a basic tune up problem. The throttle is open too much or the timing is too retarded. The "low" HP and TQ numbers aren't so low. 290 hp will power a 3000 pound car to 105 mph trap speeds in the quarter with an automatic. I have said it before many times that dyno numbers are just that dyno numbers. A Holley 670 is too small for your engine. I dont know why you pulled the 770 to put a 670 and expect more hp. When the 770 is tuned right it will blow that 670 off the map. Will the car go faster? Well thats what a drag strip is for. If your following the direction of the dyno operator, its time to find a new place to dyno your car. When I go to the dyno I do all my own tuning. I read up on what items are on my car and I prepare by getting the needed parts to tune it then I go to the dyno shop and do all my own tuning. It is amazing what you will learn about your own car, which will help you in the future when you have a tuning problem. BTW my money is on the 770 being faster at the dragstrip.

:yeathat:

 

[nicanor]

Re: Engine dyno results included question results

The dyno results have the hp of 291 max at 4000 rpms and a max tq of 401 at 2750 rpms. That just doesn't seem right.

Thanks,
Barry

 

[george68hemirr]

Re: Engine not doing well on the dyno, second dyno run bette

Dyno #s at the wheels are lower than at the flywheel I hope your not comparing with those #s

what is it bobbie.......12% less.....right??

 

[69hemibeep]

Re: Engine not doing well on the dyno, second dyno run bette

Dyno #s at the wheels are lower than at the flywheel I hope your not comparing with those #s

what is it bobbie.......12% less.....right??

Kind of a rule of thumb is 15-20% the automatics make it higher but there are so many factors like the drag in the diff and oil weight tires torque converter I have heard as high as 28% difference. Now when comparing factory HP to today's results the equation used for figuring HP on a Dyno has change two times that I know of so its apples and oranges. Get it tuned and I think you will be happy.

 

[george68hemirr]

Re: Engine not doing well on the dyno, second dyno run bette

and take it to the drags and see what the real numbers are :jester:

 

[moparchris]

Re: Engine dyno results included question results

The dyno results have the hp of 291 max at 4000 rpms and a max tq of 401 at 2750 rpms. That just doesn't seem right.

Thanks,
Barry

4000 is way too low. You need to find out what is holding it back. There are a miriad of problems that could be limiting the RPM potential. Remember dynos measure torque, period. The computer go through a matrix of mathematic equations to arrive at a HP number which is a function of torque and RPM, one without the other makes for low hp numbers.

 

[SomeCarGuy]

Re: Engine not doing well on the dyno, second dyno run bette

I would suggest doing one change at a time. Now you don't know what helped. i would bet you put in a good distributor and that is where you picked up.

That new carb is wrong and probaly hurt you a good bit. The 770 needs to be tuned. If they can give you A/F ratios, that would be a great help.