Dyno Day

[Weccemah]

Finished my engine dyno yesterday. I have a 400ci sbc with a 750 speed demon with 64p and 76s jets vac sec, Edelbrock performer rpm intake, AFR 180cc eliminators, Lunati 282/282 231/231@.050 .571" lift on a 108 lsa, MSD hei, 10.3:1 c/r with 200psi cranking pressure. Timing set @ 31 total.

It made 425hp and 462ft/lbs on its best run, tried more timing on 92 octane to 34 and power fell off, tried less to 28 and power fell off, EGTs were 1200-1400 degrees and the afr was 11:1 in the left bank and 14:1 in the right bank.

I feel this wasent a good test day and there is more on the table.

Any thoughts?

 

[Indycars]

With those components and that much difference in air fuel ratio between the banks of the engine, I would certainly agree with you. There's more to be had, something seems to be amiss. What kind of lifters are you using with the cam, flat or roller??? I'll be interested to see what you get, if you go back for another dyno test. Grumpvette can speak from experience, so lets see what he has to say.

BTW, you attachments are too small to read at 145 x 160. They should be somewhere around 1024x768, if you can upload them again in a larger resolution, it would certainly help.

 

[Weccemah]

They are hydraulic roller lifters on a roller cam

 

[Weccemah]

This is the rest

 

[grumpyvette]

ok
FIRST, congrats on building a rather nice street/strip combo, I'm sure you'll enjoy
you've obviously designed the engine combo to produce good low and mid rpm torque which, on a street car is usually the smart route, to go.

looking over the comments and the spread sheet info from the dyno you obviously need to get the fuel/air ratio to match on both banks as that's bound to result in more power and ideally you'll want that ratio to be at about 12.5:1, peak potential power is usually found at near that 12.5:1 f/a ratio, (TUNING the carbs f/a ratio to THE RICHER end of the potential torque peak(12.5-13.5 A/F RATIO), tends to delay detonation issues) LOOK AT THE F/A RATIO CHART
you've most likely got an additional extra 20 plus hp once its been tuned correctly,and don,t forget that a low restriction exhaust with tuned headers helps
THIS MAY HELP
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next, Id point out that your engines max torque peak generally closely follows the cylinder fill efficiency, as the rpms increase, and falls off as the ports limit the cylinders ability to fully fill.
those cylinder head ports are a bit small to easily reach the displacements full potential, thats one reason the torque tends to peak at about 4200rpm, on that combo,now obviously cam timing, intake design, and exhaust scavenging, can be tuned to change, or move that peak to some degree, but the ports cross sectional area will remain a significant restriction at some point in the power curve, to understand whats going on Id suggest reading thru the links below and the sub links

http://www.rbracing-rsr.com/runnertorquecalc.html

http://www.bgsoflex.com/intakeln.html

http://www.wallaceracing.com/max-rpm2.php

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[Weccemah]

It is for a street car, and thank you.
It was built for street use and the peak power and torque ended up being exactly where I wanted: torque around 4000 rpm and hp above 5500 but below 6000
I was just expecting higher #s in the same rpm range. I suppose I should be happy that my first real build(meaning I decided every measurement) was a success. Plus its not in the car yet, so I havent actually FELT the difference from the 327. Thanks for all the good info and links that you've posted for me and everyone else. The info was a major player in what I ended up building. Took me ~14 months in research alone!
Thanks again Grumpy!

 

[grumpyvette]

Im always glad to help where I can, and its nice to see someone RESEARCHING the combo vs just looking for "deals" on an almost random selection of components, assembling them and only THEN wondering why things are not working as intended.
as you obviously prove a little research and taking your time during the planing and assembly tends to get better results, now you just need to sort out the tuning issues

 

[Weccemah]

I think what I'm gonna do is when I get it in the car, I'm taking it to a chassis dyno and finishing tuning it. The consensus with everyone I've talked to is that the engine dyno was not properly set up and/or operated. Plus it will be alot cheaper!

I have to figure out why the left bank of cylinders reads 12:1 afr and the right reads 14.5:1 Any ideas?

 

[grumpyvette]

...

I have to figure out why the left bank of cylinders reads 12:1 a/f ratio and the right reads 14.5:1 Any ideas?

when you get a distinct bank to bank variation in f/a ratios theres usually either a passage, or jet in the carb that's partly clogged or theres a vacuum leak some place, obviously you'll want to make sure theres no vacuum leaks first,you'll want to stagger jet the carb, to compensate for an intake with distribution issues
I generally start with all jets the same, lets say #78 in your case, and a # 5.5 power valve, then I use an infrared temp gun and reading plugs to get all the plugs reading correctly by swapping jets and power valves until I get the correct plug look and uniform exhaust temps

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[Weccemah]

Update:

I have had the motor in the car for a few weeks now. What a fun motor!! Ran great for a few days, then when I started to tune the carb a little, the motor started to run like crap. Re-checked the timing before this too, and when I did, it was at 22* initial timing. I had bumped the distributor at some point, and when I put it back to 31* total like on the dyno, it did NOT like that either. After a lot of messing around, it seemed to want more fuel, and also had a stumble whenever I pushed the pedal down quick, even though the spark plugs were sooty. So long story short, I ended up changing the timing to 16/36*, mixture screws from 3/4 turn out to 3 turns out, squirter from a 31 to a 37, pump cam to the #2 hole, opened the butterflys up a bit at idle with an adjustment on the speed demon, and eventually settled on 72/73 jets in the primarys and 82/83s in the secondaries. Ran great that day, then the next day it was popping in the exhaust, so I turned the mixture screws back to 1 turn out, and now it runs great again. Not even a stumble when I smash the pedal at any speed. I think I got it now :|
I also called barry grant and they said that I had the wrong carb for my car and that it should be a mechanical secondary. I only drive on the street though. It does have a muncie and 4.11 gears with 26" tire, 4120 lb car, I thought I should have a vac secondary though :? .

 

[Weccemah]

UPDATE 2:

Well my driving season is over for this year. I had a great time with the new motor in the car! I did get it on a chassis dyno a couple weeks ago though

After all the carb tweaking I did in my previous post, I had it 95% dialed in for my motor. All I did on the dyno is change timing back to 31* where it did its best. It is STILL running lean on the low and mid rpm range with 13.5:1 from 4500-5700 and 14:1-16:1 before that, but I like the idea of being lean down low for part throttle cruise. I made four runs and all were on 91 octane with either 34* or 31* total timing.

I dont have the dyno sheets scanned yet, but when I do, I'll post'em here. Anyways my new #s are a best of 392.8rwhp @5700 and 424.2 rwtq @3700-3800ish.
I was at 400rwtq or above from 2700-4300rpm. Lots of tire spinning on the road.

We did a 15% driveline loss calculation and it came out to be 462bhp and 499ft-lbs tq. Fully installed with the hood down for test!

Next spring I'm going to go back with an air-gap, coated manifold and bigger carb jets and see what it does then.

 

[Weccemah]

Here are the graphs: