VETMANIAC

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?



[Modified by VETMANIAC, 10:50 PM 5/5/2002]

oger

That is the same problem I saw with a Demon on a dyno. There is a book on how to make the Demon work maybe it is an easy fix. The Demon was changed for another carb and the problems went away.

Chuck Harmon

Very interesting dyno sheets, thanks for sharing them! I first thought your 29 degree advance was a typo, but then saw you bumped timing to 36. I am running 39 degrees on my L88. If the carb is going rich on you in the upper ranges, are you sure the secondaries are opening all the way? If the carb has too strong a spring in the diaphragm, you are not allowing enough air to enter.

My guess is that if you leave the timing at least 36 - 39 degrees, run jets somewhere in the low 80's, and put in a lighter spring in your secondaries you will see even higher numbers than the already impressive ones you shared. This is the subject of the best bench racing wags! :cheers:

Chuck

Flareside

Vettemaniac, you just gotta love 400 ft/lb of torque at 1600 rpms at the wheels! That ain't no small block, now is it? :lol:

Thanks for the info, it will definitely help with the cam and head decisions for my 540.

Corey_68

Great numbers :cheers: Why did stop at below 5500rpms on the dyno? I know 540ci is a lot of iron to sling around, but most Big Blocks are able to spin to 6,000 rpms if not more. :confused:

Gotta love that torque! :yesnod:

VETMANIAC

Oger, Thanks for the tip on the Demon Tuning book. I really don't want to waste any serious money on a new carb so hopefully I can tune this properly. I plan to eventually switch to Fuel Injection.

Chuck Harmon, Thank you for the tip. I am sure Zwede and I will be returning to the dyno once he gets his car running again. I will try dropping the jet sizes further and upping the spring pressure on the secondary.

Flareside, I do love the lowend torque. Let me know how your project is coming along.

Corey68, I didn't run it 6000 in the first few runs because my tach is off at upper rpms. I thought I was at 5700 rpm. It doesn't make any more power past 5500 rpm though.

427Hotrod

Really surprises me it didn't like the increased timing more than it did. Those heads must have some pretty efficient chambers or the lean mixture was gettting it into borderline detonation. Mine likes 39* total. it picked up 25 crank Hp on the dyno moving from 36 to 39. Interesting.... I've tried more on the dyno too out to 42* and mine didn'tlike that either on pump gas!

The Demon ought to be able to bring into line. The initial lean spots may be from the pump at the low end. Did you find out what PV's are in it? Does it have one on the back side?

I usually work on the primary jets to get my cruising and driving working right and then use the PVCR's to tune the max power on that side of carb. You might be able to play with some PV'opening points but you are going to go through that rpm range so fast under load in the car I doubt you will notice too much power problems in real use.

Congrats on the new numbers. The new exhaust really helped it breathe. Big motors need lots of air... in and out!!


By the way, I looked at a new Edelbrock catalog and I don't see that old C-427 type intake in there. Back to the swap meets or just get someone to donate you a nice Team G. The old ones are relatively short and should fit under your L-88 hood fine.


Jim

VETMANIAC

Jim,
The chamber of the heads did appear to have a more efficient design than some of the other aluminum heads I have seen. I compared them to a set of Brodix that were at the machine shop and a set of Darts and there is more of the Heart shape design in these heads that is promoted for the small block Vortec and LS-Series heads. I think GM might have done a little homework on these before they turned Edelbrock loose to cast them.

I haven't checked the secodary side for a PV. I will try to do that this week and get back to you.

I agree with you on the exhaust. It is by far the biggest improvement I have made.

I also looked on Edelbrock's Website in their online catalog and I couldn't find anything like the Intake that you were describing to me. The only Dual plane I saw was an RPM Air Gap Rect. port. I will scrounge some Swap meets and see what I can find. Please keep an eye out in your neck of the woods if you happen to attend any Swap meets this summer. Fuel Injection probably won't happen this year, so I have still time to play around with the carb setup.

Keep me posted on the upgrade to your Vette's posterior and thanks for the input. :)

Nick

Bob Turner

Hi Nick,

Nice job on the motor as always. I haven't seen you post that often- you must be out driving! Well, my 454 is done at the machine shop and hope to be posting up some pics by the end of the week. I need to plan out how I am going to swap the 350 out.

My latest problem is that i have a rod knock noise coming out of my '87 tpi motor. It may be a cracked flexplate or at least that's what I am hoping for!

Anyway, it sounds like your car is done except for the fuel injection swap. I remember you mentioning that a while back.

Talk to you soon,

Bob :cheers:

VETMANIAC

Bob,
I am glad to hear that your motor is almost finished. What head and cam did you end up choosing for your Big Block?

My wife and I are expecting our first child very soon so I have been very busy. I managed to whittle the Honey Do list down some though and go play on the dyno with Markus last week. Keep us posted on your Big Block buildup.

Nick

Bob Turner

Thanks, Nick! And congratulations on your first child. You learn alot and have fun too. My wife is due next month with our second child, I am moving to Phoenix, AZ, changing jobs, I need to find time for the motor swap, etc, etc. So, alot is going on!!!

I went with a flat tappet Comp Cam XE274H (230/236 .552/.555 110 LSA) and stock 049 heads that are pocket ported with 2.19"/1.88" valves. Not bad for a first BB. I would love to do a 540 or a 572 down the road like yours.

I should have a posting on the new motor at the end of the week providing I get it back to the house!!

Are you going to post some pics of your new engine and car? I don't think I have seen your car yet!!

Anyway, good luck with the baby.

Bob :cheers:

VETMANIAC

Bob,

My wife is due next month also. Good luck with the move and yes I will try to post some pics of the car and engine bay.

Nick

groovyjay

Very impressive numbers. If I understood right between the lines you're going for EFI in the future, what kind of unit have you been thinking of? :cheers:

VETMANIAC

groovyjay,

I do plan on going to Fuel Injection at a later date. I am currently planning on the Holley Commander 950 MPI system with the race upgrade. Zwede has had some luck with it and he is very familiar with tuning it. It shouldn't take as long to tune it with his help.