HawkRod is doing the 2023 Hot Rod Power Tour!

[RGAZ]

Hawk,

Good to see you on Day one. The 73 Duster overheated badly near Augusta and the water pump seized on me, so I called in my rescue ride. Had a great time through the first couple days, but the 6 hour parade out of Atlanta was rough on the old Slant 6. Definitely doing next year. Here is my ride....

Good to see you again!
RGAZ

 

[qkcuda]

Hawk

I just looked at the dyno sheet more closely and noticed peak power was at 4500-4700 rpm. I know from the engine dyno that peak power was somewhere between 5000 -5500 rpm, and that was before the Edelbrock cylinder heads and stronger valve springs. Did they limit the max engine speed on the pull?

 

[HawkRod]

If only you knew someone with a dyno in their backyard. Hmmmmm.

I kinda forgot you have one (jealous!). I'd love to "keep money in the family". I guess the hardest part would be getting there...

Hawk......... next time down, you can take my 440 with you

Right now, I am working on Barry's 440. It will get the same treatment as mine from a build perspective, but a milder cam. It will have Mopar stage 6 aluminum heads, so it will have some grunt too!

Hawk,

Good to see you on Day one. The 73 Duster overheated badly near Augusta and the water pump seized on me, so I called in my rescue ride. Had a great time through the first couple days, but the 6 hour parade out of Atlanta was rough on the old Slant 6. Definitely doing next year. Here is my ride....

Good to see you again!
RGAZ

View attachment 1482009

Sorry to hear about your water pump. Yes, the stop and go driving, especially in the heat, was hard on these old cars. Unfortunately, there were a number of casualties; sorry yours was one of them.
By the way, the picture of your car really doesn't do it justice - there is no significant rust on your car - pretty amazing for an old car!

Hawk

I just looked at the dyno sheet more closely and noticed peak power was at 4500-4700 rpm. I know from the engine dyno that peak power was somewhere between 5000 -5500 rpm, and that was before the Edelbrock cylinder heads and stronger valve springs. Did they limit the max engine speed on the pull?

Good question, and the short answer is I don't know. My engine speed was not limited on the dyno, but there was no reason to wind it up even higher since both power and torque were dropping off after 5000 RPM. (In some of my early runs, I was letting off the gas too quickly as I was inexperienced. But the later ones I did rev it more.)
I can't imagine that the aluminum heads would cause this - if anything, they should increase the RPM capability with their better breathing.

Maybe it's the restrictions in the exhaust and/or throttle body? I have 1 7/8" primary tube headers. If I recall correctly, yours were 2.0"?

Is it tuning?

Something else?

 

[Nxcoupe]

I kinda forgot you have one (jealous!). I'd love to "keep money in the family". I guess the hardest part would be getting there...


Right now, I am working on Barry's 440. It will get the same treatment as mine from a build perspective, but a milder cam. It will have Mopar stage 6 aluminum heads, so it will have some grunt too!


Sorry to hear about your water pump. Yes, the stop and go driving, especially in the heat, was hard on these old cars. Unfortunately, there were a number of casualties; sorry yours was one of them.
By the way, the picture of your car really doesn't do it justice - there is no significant rust on your car - pretty amazing for an old car!


Good question, and the short answer is I don't know. My engine speed was not limited on the dyno, but there was no reason to wind it up even higher since both power and torque were dropping off after 5000 RPM. (In some of my early runs, I was letting off the gas too quickly as I was inexperienced. But the later ones I did rev it more.)
I can't imagine that the aluminum heads would cause this - if anything, they should increase the RPM capability with their better breathing.

Maybe it's the restrictions in the exhaust and/or throttle body? I have 1 7/8" primary tube headers. If I recall correctly, yours were 2.0"?

Is it tuning?

Something else?

You are retired and you just drove, what, 1100 miles? This is a hop, skip and a jump from you. Lol.

Also, on engine dyno you were open headers, this will extend the hp and torque range over corked exhaust, provided the engine needs the breathing room. Sounds like your's does.

 

[qkcuda]

No, I ran a 750 carb and 1 3/4 headers. I always thought the valve springs were too light on the iron heads when we dynoed it, causing power to drop off after 5000 rpm. I later changed to the beehive springs which I then switched over to the Edelbrock heads. It seemed to make power to higher rpm at the track after the head and spring swap.

 

[HawkRod]

You are retired and you just drove, what, 1100 miles? This is a hop, skip and a jump from you. Lol.

Also, on engine dyno upu were open headers, this will extend the hp and rorque range over corked exhaust, provided the engine needs the breathing room. Sounds like your's does.

Haha. 2,200 miles actually Now I'm about at my limit for what I'm allowed based on my insurance. If we are lucky, the Power Tour next year will head up towards your area - or, maybe I trailer it to cut down on miles. I might try to take you up on stopping by. Might make a good FBBO thread too to wring the most we can (reasonably) while keeping its street manners.

I agree that I think my engine could use more breathing. I'd bet open 2.0" primary tube headers would provide a different result. Of course, that's not so good to drive on the street!

No, I ran a 750 carb and 1 3/4 headers. I always thought the valve springs were too light on the iron heads when we dynoed it, causing power to drop off after 5000 rpm. I later changed to the beehive springs which I then switched over to the Edelbrock heads. It seemed to make power to higher rpm at the track after the head and spring swap.

Interesting. I have no idea then what may be different. main thing I can think of is the exhaust???

 

[Don Frelier]

Like this:

 

[qkcuda]

Hawk, I watched an episode of Roadkill Garage last night where they were trying to make the Crop Duster more street friendly, with a goal of still running 11.50's so that they did not need to install a roll bar. The engine was a 383 based stroker putting out 548 flywheel horsepower. They changed out the 4.10 gears for 3.23's, replaced the 850 race carb with a 750 DP, and added a full 3 inch exhaust system. The car ended up running mid 11's at 119 mph. It was interesting to me because that's just about exactly what my car ran with 3.55 gears, a 750 DP and a full 2 1/2 inch exhaust. Likewise I did not want to go faster because of the roll bar requirement. Both cars used drag radials. I figure the Duster was a few hundred pounds lighter than the fastback Cuda, so that accounts for the extra horsepower.

 

[HawkRod]

Hawk, I watched an episode of Roadkill Garage last night where they were trying to make the Crop Duster more street friendly, with a goal of still running 11.50's so that they did not need to install a roll bar. The engine was a 383 based stroker putting out 548 flywheel horsepower. They changed out the 4.10 gears for 3.23's, replaced the 850 race carb with a 750 DP, and added a full 3 inch exhaust system. The car ended up running mid 11's at 119 mph. It was interesting to me because that's just about exactly what my car ran with 3.55 gears, a 750 DP and a full 2 1/2 inch exhaust. Likewise I did not want to go faster because of the roll bar requirement. Both cars used drag radials. I figure the Duster was a few hundred pounds lighter than the fastback Cuda, so that accounts for the extra horsepower.

Interesting. Obviously, my 70 Road Runner is heavier than your Cuda, but otherwise I have a very similar drivetrain. I have a 3.55 rear and a 2 1/2" exhaust. I have to go back and see what the CFM rating is of my F.A.S.T. throttle body, but I'm pretty sure it is north of 800 CFM.

My father-in-law was really curious looking at the dyno results. He is baffled as to why power started dropping off just below 5000 RPM. He said that engine, as built, should pull higher than that. I think a key will be to find why power dropped off. This engine is making 675 lb ft of torque, so it stands to reason it should be over 547 horsepower. There is probably something that is causing the power drop off above 5000 RPM. Exhaust restriction? Ignition issue? Fuel issue? Who knows. I wasn't "with it" enough to think clearly when I did the dyno pulls. If I had been smart, I would have taken a video of my F.A.ST. screen that shows all the engine parameters when I did the pulls. This may have shown me some information to help further "tune" it.

Having said all that, my father-in-law calls my car the "Torque-monster". The car drives absolutely awesome and so some of this just becomes bragging rights with numbers. But I do want to address the high end drop off at some point. I am convinced this engine has more in it, and if I can get that without sacrificing the drivability, I am all in!

 

[qkcuda]

I used to shift it at 5000 rpm when it had iron heads and the the lighter valve springs. I later found out that due to the increased mass of the hydraulic roller lifters, you had to increase the spring rate to keep the valvetrain under control. After the change to the Edelbrock heads with the beehive springs it would run quicker shifting at 5500 rpm, and really didn't gain or loose any time shifting at 6000. Personally I would suspect an issue with the chassis dyno above 5000 rpm rather than an actual drop off in power. Let's blame it on the tires spinning!

 

[HawkRod]

Let's blame it on the tires spinning!

I LIKE the way you think!!!

 

[steved033]

Interesting. Obviously, my 70 Road Runner is heavier than your Cuda, but otherwise I have a very similar drivetrain. I have a 3.55 rear and a 2 1/2" exhaust. I have to go back and see what the CFM rating is of my F.A.S.T. throttle body, but I'm pretty sure it is north of 800 CFM.

My father-in-law was really curious looking at the dyno results. He is baffled as to why power started dropping off just below 5000 RPM. He said that engine, as built, should pull higher than that. I think a key will be to find why power dropped off. This engine is making 675 lb ft of torque, so it stands to reason it should be over 547 horsepower. There is probably something that is causing the power drop off above 5000 RPM. Exhaust restriction? Ignition issue? Fuel issue? Who knows. I wasn't "with it" enough to think clearly when I did the dyno pulls. If I had been smart, I would have taken a video of my F.A.ST. screen that shows all the engine parameters when I did the pulls. This may have shown me some information to help further "tune" it.

Having said all that, my father-in-law calls my car the "Torque-monster". The car drives absolutely awesome and so some of this just becomes bragging rights with numbers. But I do want to address the high end drop off at some point. I am convinced this engine has more in it, and if I can get that without sacrificing the drivability, I am all in!

I'd be interested to see your results. I FINALLY got my GTX possibly sorted out from a WOT/fuel pressure issue where I ran a separate B+ from the battery to the fuel pump relay becasue the FAST factory wiring wasn't up to the task of running everything off the single B+ in.

 

[HawkRod]

I'd be interested to see your results. I FINALLY got my GTX possibly sorted out from a WOT/fuel pressure issue where I ran a separate B+ from the battery to the fuel pump relay becasue the FAST factory wiring wasn't up to the task of running everything off the single B+ in.

View attachment 1526467

Thanks for the note. What you mentioned is an interesting possibility and one that I definitely think could be possible culprit. I haven't yet had a chance to work through this on my car (after all, it drives awesome and I have had other priorities). Having said that, I'm hoping I can make the trek to see @Nxcoupe some time late in the year or early next year and see if I can buy some dyno time so he can help me sort out what is going on.

I promise I WILL update this thread and/or start another to discuss what I find once I get to this. Hopefully within 6 months from now...

 

[Nxcoupe]

Thanks for the note. What you mentioned is an interesting possibility and one that I definitely think could be possible culprit. I haven't yet had a chance to work through this on my car (after all, it drives awesome and I have had other priorities). Having said that, I'm hoping I can make the trek to see @Nxcoupe some time late in the year or early next year and see if I can buy some dyno time so he can help me sort out what is going on.

I promise I WILL update this thread and/or start another to discuss what I find once I get to this. Hopefully within 6 months from now...

To quote Tony Beets:'Let's make this happening!'