I dynoed my car with Zwede last Friday and I got some interesting results. I will try to post the dyno graphs below. Just in case the graphs don't display I will sum up the results Below.
The car has the following:
540 C.I. using Merlin II Block
GM Signature Series Rectangular Port Aluminum Heads, 2.25 IN 1.88 EX, Mild Port Work
Cam, 232/238 @ .50, .585 IN .595 EX Lift on a 110 Lobe Sep.
Intake, GM Hi Rise Dual Plane, Mild Port Work
Carburetor, Demon 850 Vacuum Secondaries
Headers, Hooker Super Comp 1-7/8's
Tranny, 5-speed TKO
Rear, Stock 3:08 gears

I saw some strange things with the fuel curve and I am looking for help on how to correct it.

Dyno Run 1, Max Power = 446.12, Max Torque = 530.87, Primaries 84, Sec. 93, Timing = 29 Degs. Total. Air to Fuel Ratio is below 12.5 from 2000rpm to 3200 rpm and falls below 11.25 from 3400rpm to 5400 rpm.


Dyno Run 2, Jets are at 82 and 90. Max Power =447.8, Max Torque = 548. Air to Fuel Ratio is between 11.9 and 12.9 from 2000rpm to 3200rpm and falls below 12 from 3500rpm to 5500 with a low of 11.4 4700 rpm.



Dyno Run 3, Jets are at 82 and 87. Max Power = 455, Max Torque = 536. Engine is getting pretty warm now.



Dyno Run 4, No Air Cleaner



Dyno Run 5, Timing at 36.



Dyno Run 6, Open Exhaust. Power = 460 Torque = 570. I have Cut-Outs just before the rear wheels.



The graph shows that this run was very lean. A/F was above 14 from 2000 to 4000 and above 13.4 at 5500.

I am looking for help on how to smooth out the Fuel Curve on my Demon 850 VS carb. I have some nasty bumps in the A/F graph that I would like to get rid of. I did notice that I had too much play in my Accelerator Pump on the Primary Bowl during all of these runs. I discovered this problem the next day. This may account for the some of the Roller Coaster behavior of the graphs below 3000rpm. Any other ideas?

 

:cheers:

 

Thanks John,

As you can see from the A/F graphs I still have much tweaking to do to the Demon. I did enjoy the dyno sessions and I look forward to going back. Hopefully there will be further improvement.

Nick

 

Gotta love that flat torque curve!! Big blocks are :cool: Wish I could help you with the AF, I don't know squat about those Demons (we're using injection). Definitely something funky going on. Might be worth getting a master tuner for a day once everything is ready...

 

Thanks Merlin,

I don't know of any Master Carb Tuners in the area that I can drag to the dyno with me, so I guess I will have keep tweaking it myself. I do have some things to try next time I dyno.

So what is left to do before you strap yours to the dyno? Are you getting all of the paint and body finished before final tuning or are they tuning now? By the way, I loved that video you posted with the jet blowing the truck off of the tarmac and into the water. I can't imagine that the truck flying into the water was part of the plan. I would expect that the EPA would have a cow with a running truck getting dumped into the water like that.

Good luck with your project and keep us updated.

 

I don't know much about the Demon line of Vac second carbs. But in your normal mech seconds like my 825 CFM Race Demon. Your can change the discharge boosters to tailor the fuel curve. The power valve cuircut might also be off and you can change it's flow rates.

I'd also say that it's asking for more cam. Maybe retard the cam 2-4 degrees and see if it likes it.

The squirters are just a one shot deal when you first go to WOT so that would only explain the start of the run.


[Modified by gkull, 12:42 PM 5/8/2002]

 

gkull,

Thanks for the reply. I agree that the accelerator pump clearance adjustment is only going to help the first part of the graph if at all. I have a lot of work to do to fix the whole thing. I recently ordered the How to Tune Your Demon book so maybe I can get some clarification on what things to try on the VS model. If you have the Race Demon Series then I know there are more parts that are removeable on yours. The Race Demons allow for Ultimate adjustment. Keep the tips coming. I am writing everything down into a "To Try" list for when we return to the Dyno. I will keep everyone updated on my progress and what I learn about the carb as I go.

Nick

 

Your way beyond me! :crazy: I had such a hard time just fitting a small block with raised ports and big valve covers. In fact - just in the in and out fittings the pan didn't clear the steering ram and the valve covers couldn't come off to adjust my rockers.

I'm a firm believer that you can make any carb work. they just take time and it's a learning curve. I ran a 750 vac sec Edelbrock for nearly ten years on a single plane.

That might be all your problem You have big heads and a small runner dual plane. You have to have intake ports that continually get smaller to the valve. Or else you get fuel separation. I tried a RPM and a Weiand Stealth on big heads and I could never get them to work right. With your big motor - like mine - once you have so much you don't even think about a few foot pounds at 2000 rpm.

How often is your motor ever near there? Unless I have mine in lockup 4th gear OD my 3500 stall is a blip away. I can rev it a 1000 rpm just idling down the street and not go any faster around town.

I went single plane 15 years ago on a 355 SBC and have never been happy in my experiments with dual planes. Just don't buy max rpm Victors. I have a Weiand Team_G for low throught my max rpm.


[Modified by gkull, 9:06 AM 5/9/2002]

 

Depending on what you want the motor to do I would look to a much bigger cam and a single plan intake, at least a Victor Jr (unless you have hood clearance issues) The cam you are running is a small cam for a 427, let alone a 540. I would think something in the range of at least 245 (better yet 255 or more) degrees of duration at .050 I think you will need more carb also.

Saying this I have no idea what you are wanting the motor to do, but judging from your post it looks like you are looking for more power.

 

Nick, what type of exhaust are you running? It doesn't look like it's holding you back too much.

-Joe

 

gkull,

I have been considering the switch to the Weiand Team G. I just have to be careful about hood clearance issues. I have an L-88 style hood, but I am pretty sure that a Victor Jr. won't fit.

69 N.O.X. Ratt,

I wan't the engine to have pretty good manners on the street. Even with this cam, it tends to buck and surge in first gear if I am just idling along at low speed. I think that the 110 Lobe Sep. may have more to do with that than the actual duration though. I plan on trying a wider lobe sep. on my next cam.

Flareside,
I have 1-7/8 inch primary tubes into a 3 inch collector. The headers are Hooker Super Comps. How is your project coming? What heads have you decided to go with?

 

What size pipes and mufflers?

 

I have 2-1/2" pipes all of the way back and 20" Dynomax Hemi Turbo Mufflers. I have cutouts just before the rear wheels. Have you decided on Cylinder Heads yet? I saw that someone on the forum was having issues with the raised Exhaust ports on a set of Canfields. It would be nice if the header manufacturers would build some sets for the new raised exhaust port heads. Did you finally give up on AFR? Are there heads still vapor ware or is anyone out there running them?

 

After lots of see-sawing, I went with Dart Pro-1 335cc CNC heads. They should be here sometime next week. Yep, the ports are .3" raised (the Canfield's are around .8"), so my Sawz-All and welder stand ready ;) I think the fact that there is no standard height for raised ports keeps the header manufacturers out of the game.

I went with the best head I could afford, because *I hope* they will make more power with less cam duration for better drivability. Most of the experts seem to agree here; buy heads over cams. I'm planning to start with a solid lifter cam instead of a roller. Maintenance is not an issue for me, but price and reliability are.

AFR is a distant memory :mad They repeatedly told me (every month when I called) that the heads would be available in 8 weeks. Every month since DECEMBER! I placed a deposit on them in January. Every time, it was "the casting will be here any day now, and then we'll start cranking them out". When I last spoke to them (April), they still didn't even have one final casting completed. I highly doubt that anyone will have them until August at the earliest. The delay didn't bother me nearly as much as the dishonesty and runaround. They are STILL saying the delay will be 8 weeks...


[Modified by Flareside, 8:13 AM 5/10/2002]

 

I just go back from vacation last night. So your getting rid of the 850 VS demon and your going double pumper of larger CFM? Years ago I installed a 600 Edl carb and a performer intake. Well with all my tuning I thought that it had to be the low cfm holding my 355 ci. back in the 1/4 mile. So I bought the Edelbrock 750 cfm. Well after much tuning it had multiple runs with the exact same 1/4 mile times as the 600. So the carb was not what was holding it back it was the wimpy intake. That's when I first went to single planes. Because I had the good heads, cam, and exhaust. The manifold was the restriction.

 

gkull,

The manifold may well be a restriction on this engine. I plan on changing one thing at time though, and analyzing the effect. If I pick up horsepower with the change to the 950HP then I will look at a Weiand Team G or an Edelbrock Victor Jr. Since my Secondaries aren't opening all of the way I want to try a carb that I can be certain the secondaries are going to open on. Thank you for your feedback and I will keep everyone posted on the changes that I make.