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ET Prediction vs Consistency #700778
05/17/10 06:38 PM
05/17/10 06:38 PM
Joined: Jan 2009
Posts: 52
Bakersfield, CA
MarkKirby Offline OP
member
MarkKirby  Offline OP
member

Joined: Jan 2009
Posts: 52
Bakersfield, CA
Ok so here's the problem......well to some it's not considered a problem.

This weekend I made 9 passes with the ET never varying more than .006 the entire day. A dream day from the standpoint of consistency, which is not unusual for this combo. Everybody says I should not complain and be thankful the car is so freakin consistent. R/Ts were all .00X-.01X so it was a good day by going to the money window as well.

So what's the problem????? The problem is....the weather varied about 1000' feet during the day. This car should have slowed down at least 2-3 hundredths(if properly tuned).....but it didn't. Carb builder says I'm way lean but LM-1 disagrees at 12.5-13.0. Engine builder says quit whining and keep winning. I still think something is wrong. Any ideas?

416 SB at 13.5:1
Holley 950HP Jetted at 84/86
No PV....Idle a little on the rich side perhaps
575hp @6500...550tq @4700
Protrans 904
A-1 8" converter @5500....launch at 4600
5.13 Dana
3300lb loaded A-Body, 4-link
Overtired at 16 x 33 x 15 GY
ET 10.649 to 10.657 at 124.74(every pass same mph)
DA between 2150 and 3172

What do you think????


Mark & Nancy Kirby 1971 Plymouth Duster The Grape Ape 10.20 @129mph 1.32 60'
Re: ET Prediction vs Consistency [Re: MarkKirby] #700779
05/17/10 06:47 PM
05/17/10 06:47 PM
Joined: Nov 2009
Posts: 2,177
ill
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dennismopar73 Offline
top fuel
dennismopar73  Offline
top fuel
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Posts: 2,177
ill
well yes id say something wrong
dont think you have given enough info
because if i was building small blocks
and car that weighs as much as youres
i want to rebuild it exactly as youres
and lose some wieght get her down 2800
maybe put a 1050 dom on it

Re: ET Prediction vs Consistency [Re: MarkKirby] #700780
05/17/10 06:53 PM
05/17/10 06:53 PM
Joined: Jun 2003
Posts: 52,972
Romeo MI
MR_P_BODY Offline
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MR_P_BODY  Offline
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Posts: 52,972
Romeo MI
When a engine is lean they do stay very consistent
so it could be the A/F ratio reading is wrong... to
close to the end of the collector can cause this...I
dont like it lean and just move the dial to compensate... JMO

Post deleted by Defbob [Re: MR_P_BODY] #700781
05/17/10 08:01 PM
05/17/10 08:01 PM

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Re: ET Prediction vs Consistency #700782
05/17/10 08:10 PM
05/17/10 08:10 PM
Joined: Jan 2009
Posts: 52
Bakersfield, CA
MarkKirby Offline OP
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MarkKirby  Offline OP
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Joined: Jan 2009
Posts: 52
Bakersfield, CA
I never shut down in the lights. Can't get to neutral and I think this is too hard on tranny. I quit using this test years ago.

The plugs look a little fat to me with tan porcelain and a couple threads darkened on the body of the plug.


Mark & Nancy Kirby 1971 Plymouth Duster The Grape Ape 10.20 @129mph 1.32 60'
Re: ET Prediction vs Consistency [Re: MarkKirby] #700783
05/17/10 08:13 PM
05/17/10 08:13 PM
Joined: Jan 2003
Posts: 5,488
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,488
SoCal
Quote:

Ok so here's the problem......well to some it's not considered a problem.

This weekend I made 9 passes with the ET never varying more than .006 the entire day. A dream day from the standpoint of consistency, which is not unusual for this combo. Everybody says I should not complain and be thankful the car is so freakin consistent. R/Ts were all .00X-.01X so it was a good day by going to the money window as well.

So what's the problem????? The problem is....the weather varied about 1000' feet during the day. This car should have slowed down at least 2-3 hundredths(if properly tuned).....but it didn't. Carb builder says I'm way lean but LM-1 disagrees at 12.5-13.0. Engine builder says quit whining and keep winning. I still think something is wrong. Any ideas?

416 SB at 13.5:1
Holley 950HP Jetted at 84/86
No PV....Idle a little on the rich side perhaps
575hp @6500...550tq @4700
Protrans 904
A-1 8" converter @5500....launch at 4600
5.13 Dana
3300lb loaded A-Body, 4-link
Overtired at 16 x 33 x 15 GY
ET 10.649 to 10.657 at 124.74(every pass same mph)
DA between 2150 and 3172

What do you think????




Are you still running that cam you had in it when we dyno'd it?
13.5 is alot of compression with OEM heads! I think there's at least .2 in the cam itself.
And what intake, the victor? Any spacer?
I ran my little 360 with a 950HP and 87 jets square. So yeah your a little lean IMO.
Really, you should have a 1050 on there. It will still be consistent, and I guarantee it won't be lean (unless you purposely jet it down alot).

Brian


Brian Hafliger
Re: ET Prediction vs Consistency [Re: Brian Hafliger] #700784
05/17/10 08:23 PM
05/17/10 08:23 PM
Joined: Jan 2003
Posts: 5,488
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,488
SoCal
Another thing I noticed Mark is your MPH...I ran 126-127mph and only had 560HP with 3350lbs.
Either the dyno HP is not matching the e.t. or there is a problem with the car.
What kind of 60ft. does it normally do?


Brian Hafliger
Re: ET Prediction vs Consistency [Re: MarkKirby] #700785
05/17/10 08:48 PM
05/17/10 08:48 PM
Joined: Aug 2003
Posts: 43,882
Bend,OR USA
C
Cab_Burge Offline
I Win
Cab_Burge  Offline
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Posts: 43,882
Bend,OR USA
Is that carb. a 80496 or a 80496-1? The reason I'm asking is the staggered jetting your using versus the way they come from the factory I have had to adjust the idle mixture screws in as far as 1/4 turn out from bottomed out on some of those carbs on motors with big cams and single plane intakes to get a clean idle. As far as consistency as already mentioned a slightly lean mixture will not vary much in performance from just right on the density altitude to better or worse, don't tell any other racers that A fat mixture will slow down and pick up with the weather changes much more than a leaner mixture will


Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: ET Prediction vs Consistency [Re: MarkKirby] #700786
05/18/10 10:55 AM
05/18/10 10:55 AM
Joined: Feb 2009
Posts: 1,532
off the grid
340B5 Offline
pro stock
340B5  Offline
pro stock

Joined: Feb 2009
Posts: 1,532
off the grid
Is this that uncontrolable urge to go faster? Sounds like you could if you jet up, but the weatherman would have to be on point.


Yeah, it's got a smallblock.
Re: ET Prediction vs Consistency [Re: MarkKirby] #700787
05/18/10 11:44 AM
05/18/10 11:44 AM
Joined: Dec 2008
Posts: 184
Central Coast
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Plumcrazyracing Offline
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Posts: 184
Central Coast
Quote:

Ok so here's the problem......well to some it's not considered a problem.

This weekend I made 9 passes with the ET never varying more than .006 the entire day. A dream day from the standpoint of consistency, which is not unusual for this combo. Everybody says I should not complain and be thankful the car is so freakin consistent. R/Ts were all .00X-.01X so it was a good day by going to the money window as well.

So what's the problem????? The problem is....the weather varied about 1000' feet during the day. This car should have slowed down at least 2-3 hundredths(if properly tuned).....but it didn't. Carb builder says I'm way lean but LM-1 disagrees at 12.5-13.0. Engine builder says quit whining and keep winning. I still think something is wrong. Any ideas?

416 SB at 13.5:1
Holley 950HP Jetted at 84/86
No PV....Idle a little on the rich side perhaps
575hp @6500...550tq @4700
Protrans 904
A-1 8" converter @5500....launch at 4600
5.13 Dana
3300lb loaded A-Body, 4-link
Overtired at 16 x 33 x 15 GY
ET 10.649 to 10.657 at 124.74(every pass same mph)
DA between 2150 and 3172

What do you think????






Kirby, was this past weekend the first time out with the new combination?

If you ran this combination previously, how did the E.T. compare to previous DA's and track conditions.

What type of weather station? Has it been calibrated?

As far as weather, if the DA went up did you guys end up with a decent tail wind? (Notorious at famoso)

Last but not least, did your 60' drop off (and then pick back up on the top end) at all or was it consistent as well?

Steve

Oh yeah, Dave has a nice valve body with a clean neutral.

Re: ET Prediction vs Consistency [Re: Plumcrazyracing] #700788
05/18/10 02:59 PM
05/18/10 02:59 PM
Joined: Jan 2009
Posts: 52
Bakersfield, CA
MarkKirby Offline OP
member
MarkKirby  Offline OP
member

Joined: Jan 2009
Posts: 52
Bakersfield, CA
Wow! A lot of good thoughts here. Thanks for the help.

Brian

Yes it's the same cam. You have mentioned before that you think I can pickup with a cam change. What cam in particular are you thinking of. I currently have .627/.637 with 276/281 @50 in at 106. And yes, I installed the Super Victor which did not gain anything over the previous Offy Port O Sonic I have run for 20 years. Not one single HP! The Dominator is an interesting idea and one which I might try if I can find an adapter somewhere. I might just go ahead and jet the thing way up to see what happens. It's just that with an aggressive racing schedule we have so precious few TNT opportunities to woodshed these things. The MPH discrepancy is probably due to the big gear and tire(5.13 and 16x33). And yes, the 60' times also do not vary with weather.

Cab

I am prepared for the car slowing down and loss of consistency. I would trade consistency for predictability any day. No problems with idle it's clean and steady at about 1000rpm in gear.

340B5

No real urge to go any faster....just looking for predictability in the face of constantly changing weather conditions.

Steve

Where the heck have you been? I've been looking for you the last couple of races. This is not a new problem for me. Ever since I stopped predicting ET by the seat of my pants and started using sophisticated weather equipment the car has not followed the rules. I use an Alta Lab and Crew Chief Pro that are both good pieces and regularly calibrated so that's not the problem. I'm sure it's the car. Yes, we did get a bit of a tail wind that I think I factored in appropriately so I can't blame it on that. You need to get out there buddy...we miss you!

I'm just going to jet the thing higher than I would have expected to see what happens.


Mark & Nancy Kirby 1971 Plymouth Duster The Grape Ape 10.20 @129mph 1.32 60'
Re: ET Prediction vs Consistency [Re: MarkKirby] #700789
05/18/10 06:04 PM
05/18/10 06:04 PM
Joined: Jan 2003
Posts: 5,488
SoCal
Brian Hafliger Offline
master
Brian Hafliger  Offline
master

Joined: Jan 2003
Posts: 5,488
SoCal
That confirms my thoughts...you not moving enough air through that engine to use that intake! So once again, I believe the heads are letting you down in the HP dept.
But that's a different post!

I would start at 87's square. Also, you might pick up more than normal by going to the dominator with that bigger intake. You can only get so much flow out of a 950HP!


Brian Hafliger






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