Strange happenings at the Dyno

[GunMetal]

   So I took the Charger to a chassis dyno today and had some weird things happen.
 1) First run- start out in 1st gear.....Power steering belt rolls over on top of the pulley.
        The A/F ratio is about 15.5-16.0 thru most of the run.

 2) Second run- start out in 2nd gear....A/F still 15.5-16.0 thru most of the run (I think the PS belt jumps also)

 3) Third run- start in 3rd....A/F down to 12.25-13.0 (my own A/F meter in the car shows this typically when I   drive).  The radiator overflow starts shooting out water. Stop the engine and notice the PS belt off the pulleys but   out of the way and both the belts for the AC have rolled over as well!

Can anyone tell me why the A/F ratio would be so lean in 1st and 2nd gears, but fine (I assume) in 3rd?

 Now for the results: 398hp @ 5300rpm and 416lb-ft @ 4100rpm!
That's rwhp & rwtq without dialing in ign, carb etc.

Engine spec to follow.

[GunMetal]

  Engine specs:
   400 stroked to 470ci
   9.5:1 comp.
   Forged crank, rods, pistons
   Hydraulic roller Erson cam w/ 1.6 roller rockers-- .584 lift
   Eddy ootb 84cc alum heads
   Quickfuel SS-750-AN dbl pumper ootb
   TTI 1 7/8" primary headers, 3"  X-pipe exhaust system, and Dynomax Ultraflo's
   MSD box and distrib. set at 18* btdc, 36* btdc by 2800? (iirc)
   
  Trans:
   727 w/ 4gear planetary(iirc)
   bolt in sprag
   3000 stall converter

  Rear:
   8 1/4 w/ 3.91 sure grip -Auburn cone style
   I have 8 3/4 w/ 3 other center sections on the list to be rebuilt.

  This is in my '73 SE.

   Am I missing any important info? 

[firefighter3931]

Those are good numbers 

Not sure what to make of the lean a/f but it could be a software issue with the dyno 

As long as the plugs look good and your onboard a/f instruumentation are not showing lean i wouldn't sweat it 



Ron

[GunMetal]

Thanks Ron, that will let me sleep better tonight. I'll figure out the belt issue eventually.

[frederick]

This caught my eye:
Quickfuel SS-750-AN dbl pumper ootb
I've got the same carb.....
Recommend you check it out, mine had 70 IAB, 31HSAB and one 88 secondary jet,.
The card said it should have 71IAB, 33HSAB and 2 82 secondary main jets.
Luckily found out about it before bolting it on, the dealer was helpfull and sent out the correct parts immediately.

I've heard of another with the same problems, seems like QF has some assembly trouble.


I did some tests with the 70IAB and 31HSAB, -pig rich everywhere, 12.3AFR while cruising.
The 71IAB and 33HSAB did improve things, now it's 14.0 cruising.
The idle AFR isn't very smooth yet, so I am considering moving the IFRs.
I haven't tested WOT jet, so I can't comment on that.


For record the SS-750-AN should have:
68 Primary Mains
82 Secondary Mains
71 IAB
33 HSAB
31 Shooters
0.033 IFR
0.060 PVCR
6.5 PV
110 Needle and seat


Almost forgot, I've got it on top of a Stealth headed 383.

On the strange AFR readings in the two lower gears, have the checked the fuel pressure and the float height?

[GunMetal]

  Uh oh! Maybe I better plan on pulling this thing apart and verifying the spec card. Thanks for the heads up.
I noticed that my card shows a 68 prim main jet, as yours is a 66, may explain why I'm rich. I kinda figured I'd have to do some adjusting with the carb, but assumed the card would be correct. I've never had a Holley type carb before, but knew the Eddy carb that was on this had to go! (couldn't put the purple Proform on, Quickfuel just looked better).  PM me as things progress on your dial-in, I'll do the same. It may take a bit of time for me to get at this. The " honey-do" grows daily.      Steve

[resq302]

  Uh oh! Maybe I better plan on pulling this thing apart and verifying the spec card. Thanks for the heads up.
I noticed that my card shows a 68 prim main jet, as yours is a 66, may explain why I'm rich. I kinda figured I'd have to do some adjusting with the carb, but assumed the card would be correct. I've never had a Holley type carb before, but knew the Eddy carb that was on this had to go! (couldn't put the purple Proform on, Quickfuel just looked better).  PM me as things progress on your dial-in, I'll do the same. It may take a bit of time for me to get at this. The " honey-do" grows daily.      Steve

I wish mine grew daily!  I think mine gets bigger by the hour!

[firefighter3931]

As a rule of thumb ; annular boosters tend to run rich(er) vs a downleg style booster. 

If anything, your initial dyno results were showing lean in the lower gears. 

On engines that produce a lot of manifold vacuum an annular isn't necessarily the best way to go, inmo.

The 1st & 2nd gear lean acceleration numbers might be fuel delivery related. Do you have a fuel pressure guage mounted ? What fuel pump are you using ?

I've seen a low pressure issue create a lean condition before but that was while the car was moving ; the G-forces were pushing fuel backwards as the car accelerated. This would not be an issue on a chassis dyno where the car is sitting stationary. 



Ron

[GunMetal]

My manifold vacuum runs around 12" @ idle. I don't have power brakes until I drive a bit and deccel.

I have 2 liquid filled gauges mounted in the fuel system; 1 -shows pressure after the mechanical pump,
      2 - shows pressure after the regulator and filter at carb fuel feed split. I'm regulated to 6.5psi.

    Interesting thought regarding acceleration leaning out the carb. On a side note, although I haven't opened the carb, when I adjusted the float level the passenger side shows level across the center of the sight glasses, but the driver side is slightly higher . I do plan to take this to a Dyno operator who is more familiar with carburetted engines, specifically Holley type dbl pumps, but this one was close, reasonable, and I just finished the bulk of the build. I just wanted to see a baseline and get a rough idea what I was making.
  I plan to pull v/cs and look over the valve train. Pull the plugs and inspect. Verify TDC on timing tape, and re verify the ign. Now that I have all this access to the plugs with my TTIs it will be much easier. 

[firefighter3931]

The 6.5psi is fine.  Of course with the guage location you can't see what the pressure looks like during a WOT blast going down the road. Those liquid filled guages are inaccurate which can be a problem.....heat will cause false readings (liquid heats up).

I'm assuming you have a 120gph Mechanical ? What size fuel line ?

The float level is fine ; QF and PF want the bowls 1/2-3/4 in the sight glass while Holley says at the bottom of the sight hole. 

I agree further testing is needed to dial in the carb but you can also do a plug reading. Just bring it up to redline and shut the engine off immediately. Pull a plug and see what it's showing. 



Ron

[GunMetal]

I will have to run a line from the regulated side to an observable gauge and do a WOT blast. Been wanting to do that, but just hadn't got to it yet. I'm running the stock 5/16" fuel lines until I can get the new sending unit in. I've read here where there are people racing with 5/16" lines with much more hp than I so I wasn't too concerned. I'm not sure what the mechanical pump is rated at, but I thought is was an up graded unit when I replaced it. I have run out a fused power line to the back of the car for an eventual electric pump install. I bought a Holley "red" w/ filter on ebay a couple of years ago,then read you recommend the Mallory unit. I'll probably up grade to that when when I attack the tank/sender.
   When I pull the plugs this w/e I'll do the redline trick first. I'll report back with my findings.   Thanks for the help Ron!

[frederick]

 Uh oh! Maybe I better plan on pulling this thing apart and verifying the spec card. Thanks for the heads up.
I noticed that my card shows a 68 prim main jet, as yours is a 66, may explain why I'm rich. I kinda figured I'd have to do some adjusting with the carb, but assumed the card would be correct. I've never had a Holley type carb before, but knew the Eddy carb that was on this had to go! (couldn't put the purple Proform on, Quickfuel just looked better).  PM me as things progress on your dial-in, I'll do the same. It may take a bit of time for me to get at this. The " honey-do" grows daily.     Steve

I'm very sorry, I misread the card, mine says 68 for the Primary Main Jet also. (I've corrected the mistake in my post)
Triple checked the rest of the specs I listed and they're OK.

I'll make a new thread on how I'm progressing with the dial-in.

I had an Edelbrock carb on it, too!
But I like this carb much more, and it's easier to tune IMO.

p.s. Have you seen this thread on moparts:
http://board.moparts.org/ubbthreads/showflat.php?Cat=0&Number=6495361&page=5&fpart=all&vc=1

[GunMetal]

  Wow, incredible thread! Thanks Frederick. Had to take a few sessions with it to aborb what I could. I hope I have the patience and perserverence to see my tune to that level. I look forward to your dial-in post when it gets started, we'll compare notes.
  Looks like rain was predicted for this week end, we will see how all that works out.  Hope to have some info for you guys soon.  
   Modified-Got plugs!   Got carbon

[GunMetal]

Obviously running rich. Before pulling the plugs, I warmed the engine, then I ran it to 6000 in first gear, watching rpms and A/F. Happy to report no sign of excessive lean condition as noted in the beginning of the post.  I only did it for about 2-3 seconds,then pulled into the driveway. I then put it in park, ran it up again 2-3 seconds more and shut it off at speed. After letting it cool down I pulled the plugs. Reading the post Frederick linked I know I've got some work ahead of me,however by the time I'm done I should have even more power and better MPG!  Win/Win!

[elacruze]

The 6.5psi is fine.  Of course with the guage location you can't see what the pressure looks like during a WOT blast going down the road. Those liquid filled guages are inaccurate which can be a problem.....heat will cause false readings (liquid heats up).

Ron

THREAD STEALER ALERT

Ron, what do you recommend for a permanently installed fuel pressure gauge? I need 0-50psi for my EFI, and I have a liquid filled $25 gauge currently.

[firefighter3931]

The 6.5psi is fine.  Of course with the guage location you can't see what the pressure looks like during a WOT blast going down the road. Those liquid filled guages are inaccurate which can be a problem.....heat will cause false readings (liquid heats up).

Ron

THREAD STEALER ALERT

Ron, what do you recommend for a permanently installed fuel pressure gauge? I need 0-50psi for my EFI, and I have a liquid filled $25 gauge currently.

Eric, is that guage mounted on the fuel feed line ? If so....go with a non liquid filled guage 

If you're wanting something inside the cab the best way to go is an electric Autometer setup but those are expensive. 


Ron

[elacruze]

The 6.5psi is fine.  Of course with the guage location you can't see what the pressure looks like during a WOT blast going down the road. Those liquid filled guages are inaccurate which can be a problem.....heat will cause false readings (liquid heats up).

Ron

THREAD STEALER ALERT

Ron, what do you recommend for a permanently installed fuel pressure gauge? I need 0-50psi for my EFI, and I have a liquid filled $25 gauge currently.

Eric, is that guage mounted on the fuel feed line ? If so....go with a non liquid filled guage 

If you're wanting something inside the cab the best way to go is an electric Autometer setup but those are expensive. 


Ron

It's mounted directly on the throttle body, in the pressure test port.

[firefighter3931]

Obviously running rich. Before pulling the plugs, I warmed the engine, then I ran it to 6000 in first gear, watching rpms and A/F. Happy to report no sign of excessive lean condition as noted in the beginning of the post.  I only did it for about 2-3 seconds,then pulled into the driveway. I then put it in park, ran it up again 2-3 seconds more and shut it off at speed. After letting it cool down I pulled the plugs. Reading the post Frederick linked I know I've got some work ahead of me,however by the time I'm done I should have even more power and better MPG!  Win/Win!

To accurately assess WOT jetting you need to bring the engine up to redline and kill it immediately. Basicly just run it in first and turn the key off and let it coast to a stop....then pull a plug. By allowing it to idle you have squewed the plug reading. 

It might be rich at idle yet close at WOT. 

The good news is that it's not lean so you know the jetting is close. I'd try it again as i suggested above and if the plugs look the same ; adjust the jets 2 sizes smaller on the primary and secondary circuits....then retest.

You're not that far off 


It doesn't hurt to squirt some carb cleaner in the bleeds just to make sure that they're clean. 


Ron

[firefighter3931]

It's mounted directly on the throttle body, in the pressure test port.

That will be a problem (heat)....I would swap in a non filled guage for better accuracy. 

You could test it out and note the pressure differences between cold and hot but don't be surprised to see a difference in cold static vs hot running fuel pressure readings 



Ron

[GunMetal]

I ran the engine up to 6000+ on the driveway in park for 2-3 seconds and turned the ign. off at speed. Will a no load run-up differ from an on-the-road run-up? The carb is brand new, but as we've seen ,junk can get into strange places. After cleaning the plugs and reinstalling, I'll fire it up and squirt the cleaner into the bleeds as well. Thanks!

[firefighter3931]

Will a no load run-up differ from an on-the-road run-up?

Definately.....the engine needs to be under load in order to get a proper plug reading. 

Sorry, i should have done a better job describing the procedure 

Just find a deserted strech of road that will alow you a low gear/full throttle pass and enough room to coast & shut down. The idea is to eliminate the idle circuit while doing the plug read. 


Ron

[GunMetal]

O.K. I can do that. I'll clean the plugs first for a more accurate reading.Raining now, going to have to wait

[GunMetal]

Decided my time is worth more than trying to clean those plugs so I bought new ones. What a difference in idle quality and A/F ratio.   Even though the old plugs were relatively new, they were in there with the Ebrock carb and it's extended choke time. I work fairly close to home and must have carboned up the plugs then. There may have also been a plug wire not fully engaged on a plug as well. The A/F looks to have picked up a full number. I will monitor this and do the high rpm stuff to see if things are better than I thought. I'll report back with the findings and move on to the next step.  Thanks for the help guys!  
      Steve

[firefighter3931]

Cool...good news Steve ! 

What plugs are you running in the E-head 470 ? I really like the NGK BCP-6ES with pump gas (10.0-11.0) compression and RPM cylinder heads. They stay cleaner, longer and the engine seems to fire much easier. 


Ron

[GunMetal]

Those are the plugs I use also. I had used the accel shorty header plugs, saw you recommended the NGK's and discovered the NGK's were actually shorter than the accels. Go figure!  I'm also wondering if the carbon bleeds off some of the spark to ground before it jumps the plug gap? Less spark, less complete burn, richer exhaust?
  I'll check things out, Thanks