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440 struggles past 4,000 rpm #2670754
06/27/19 03:29 PM
06/27/19 03:29 PM
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California, U.S.A.
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Torquemonster440 Offline OP
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Torquemonster440  Offline OP
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Hey all,

I recently upgraded from my big valve 906's to some Promaxx big block aluminum heads. I upgraded to a set of Comp beehive springs and the appropriate locks and retainers. I also upgraded my Distributor cap to a HEI style terminal type. Along with new plug wires and rotor. I also made the distributor shaft "collar" mod to help stabilize my timing. I jetted my carb (Holley850dp annular booster) up 4 sizes on both sides anticipating the better airflow.

Now, to my issue, when I take it out to romp on it, it pulls hard to about 4k and kinda just holds there.. no misfire, so surging, it does not fall on its face like its fuel starvation, I've already crossed that bridge (while running my 906's) and upgraded to 3/8" line from the pickup forward and I run a QFT 120 GPH mechanical pump.

I verified my fuel pressure does not drop below 6 psi at any time, I ran a gauge up to my windshield. Cranking pressure is 155-160 psi on all cylinders. My timing is set at 37° all in by 1600 rpm. No vacuum advance. I tried 34° first ,but 37° feels better. I am getting full throttle, both sets of butterflies open completely with the pedal depressed. The plugs do look pretty lean, I may need to step up another 4 sizes. Also, that annular carb had 82's on the primary side and 78's on the secondary side when I bought it. Does that sound right? Either way, it ran great with my 906's on there. There is still a power valve on the secondary side. I did adjust the secondary float level too while I had the intake and carb off, because it used to flood from time to time. When I drained the secondary float bowl to remove the intake I noticed some small flecks of aluminum in the fuel, I suspect from cutting the new hard lines I had Installed. I checked the float adjustment after taking it for the first test drive and it looks ok.. just a tiny dribble out the sight hole while the car is idiling.

I took two different people with me for test drives, both say it pulls like a "freight train".. but it should definitely RPM better in my opinion.
Any ideas or input is appreciated. I'm pretty stumped..

Last edited by Torquemonster440; 06/27/19 03:39 PM.

1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2670764
06/27/19 03:55 PM
06/27/19 03:55 PM
Joined: Feb 2005
Posts: 15,218
PA.
pittsburghracer Offline
"Little"John
pittsburghracer  Offline
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PA.
Do you still have the old cap and rotor sitting there. If so throw it on but just for the heck of it check to make sure the wires are on right


1970 Duster
Edelbrock headed 408
6.143@110.85 mph
9.73@135.05 mph shifting at 6700 RPM
422 Indy headed small block
5.982@112.56 mph
9.42@138.27

Livin and lovin life one day at a time




Re: 440 struggles past 4,000 rpm [Re: pittsburghracer] #2670773
06/27/19 04:12 PM
06/27/19 04:12 PM
Joined: Jan 2003
Posts: 12,812
So. Burlington, Vt.
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fast68plymouth Offline
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fast68plymouth  Offline
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So. Burlington, Vt.
What cam, springs, rockers, pushrods?

Spring installed height?

Verified the pushrods aren’t rubbing on the heads?

If it does the same thing in all gears....... I doubt it’s fuel related.


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: 440 struggles past 4,000 rpm [Re: pittsburghracer] #2670776
06/27/19 04:23 PM
06/27/19 04:23 PM
Joined: May 2014
Posts: 117
California, U.S.A.
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Torquemonster440 Offline OP
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The wires are on correct, I have fire in all 8 holes. I might give the old cap and rotor a shot for the heck of it tho.


1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: fast68plymouth] #2670783
06/27/19 04:45 PM
06/27/19 04:45 PM
Joined: May 2014
Posts: 117
California, U.S.A.
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Torquemonster440 Offline OP
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The cam is the .528 solid purple shaft. 1.5 ratio Crane ductile rockers. 5/16" Crower push rods. The pushrods did rub slightly, I used one .015 " spacer shim on each side to achieve clearance next to the intake runners.The springs are Comp 26918-16 , recomended by Comp. 1.8" installed height. Where I exercised some judgement on my part, was to use two .030" shims under each spring to increase my seat pressure from 125 lbs closed to 147 lbs closed. I now know this is not the correct way to achieve more seat pressure. But,by my math of 1.8" installed height -.502 net valve lift, -.060 shim height and a coil bind height of 1.10" I'm still left with .138" clearance from coil bind. I'm really hoping those shims are not my problem. I have visually confirmed that the springs are not close to binding as well.


1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2670794
06/27/19 05:15 PM
06/27/19 05:15 PM
Joined: Aug 2003
Posts: 34,491
Bend,OR USA
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Cab_Burge Offline
I Win
Cab_Burge  Offline
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If it does the same thing in every gear it is ignition caused twocents scope
Why did you change the jetting?

Last edited by Cab_Burge; 06/27/19 05:17 PM.

Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2670821
06/27/19 06:18 PM
06/27/19 06:18 PM
Joined: Jan 2003
Posts: 12,812
So. Burlington, Vt.
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fast68plymouth Offline
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My .02.......
I suspect it’s the wrong springs for the app.

Beehive springs rely on being run close to coil bind to reduce the onset of surge/harmonics........ you’re still .120 away.

Granted I would have expected it to go quite a bit higher than 4000 before the unhappiness started.

If you’re in 2nd gear, foot on the floor...... 4000-ish..... it’s doing what it’s doing...... does it recover instantly as soon as you shift to the next gear?

Does the ignition box have a rev limiter?
If so........ turn it all the way down to zero (off).

If you bring the motor up to like 3800 in neutral........ hold it there, and then increase the throttle.... will it go above 4000 cleanly?

What’s the carb part number?


68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123
Dealer for Comp Cams/Indy Heads
Re: 440 struggles past 4,000 rpm [Re: Cab_Burge] #2670828
06/27/19 06:26 PM
06/27/19 06:26 PM
Joined: Oct 2003
Posts: 3,810
South Park, Pa.
68LAR Offline
master
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South Park, Pa.
Originally Posted by Cab_Burge
If it does the same thing in every gear it is ignition caused twocents scope
Why did you change the jetting?


I agree. Plus the jetting is backwards. Larger jets should be in the secondary, not primary. My book says that an 850 AN should have 74's in the front and 86 in the back with no power valve in the back. I'd address this first. Then move on to the electrical part.


4 speed street legal. Best time 10.99 @ 124 mph on 93 octane pump gas @ 3926# total weight
Re: 440 struggles past 4,000 rpm [Re: 68LAR] #2670870
06/27/19 08:04 PM
06/27/19 08:04 PM
Joined: May 2014
Posts: 117
California, U.S.A.
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Torquemonster440 Offline OP
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Torquemonster440  Offline OP
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Originally Posted by 68LAR
Originally Posted by Cab_Burge
If it does the same thing in every gear it is ignition caused twocents scope
Why did you change the jetting?


I agree. Plus the jetting is backwards. Larger jets should be in the secondary, not primary. My book says that an 850 AN should have 74's in the front and 86 in the back with no power valve in the back. I'd address this first. Then move on to the electrical part.


Great info, I'll do that.. thank you.


1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2670893
06/27/19 08:57 PM
06/27/19 08:57 PM
Joined: Jan 2003
Posts: 1,950
central texas
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krautrock Offline
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central texas
you changed alot of things at once.

i believe some holley 850 annular carbs were baseline with a secondary PV, if so the jets should be the same all around...

maybe you have a problem with rotor phasing on the new dist cap you are using??

i would try the old ignition stuff. Also, what fast68plym said up there^^ but of course try the easier stuff first...

Re: 440 struggles past 4,000 rpm [Re: krautrock] #2670917
06/27/19 10:14 PM
06/27/19 10:14 PM
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Posts: 3,099
usa
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lewtot184 Offline
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going up "4 steps" on jetting could be a bunch; especially if your not figuring jet area; and using a carb with a sensitive booster. too fat kills power/rpm.

Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2670997
06/28/19 07:44 AM
06/28/19 07:44 AM
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Posts: 35,591
Lincoln Nebraska
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RapidRobert Offline
Circle Track
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Lincoln Nebraska
Quote
it ran great with my 906's on there. but it should definitely RPM better in my opinion.
The carb did fine with the 906's? what exactly does it do at 4K?


live every 24 hour block of time like it's your last day on earth
Re: 440 struggles past 4,000 rpm [Re: RapidRobert] #2671005
06/28/19 08:18 AM
06/28/19 08:18 AM
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Posts: 851
Texas, USA
ChrgrCuda Offline
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What diameter is the tube coming from the fuel tank sending unit? Is it 3/8 or 5/16 diameter? Also, check your fuel pump pushrod. Just had same issue on customers 440 GTX. The pushrod was wearing down.....


68 Cuda Notchback [Email]10.86@120[/Email] 69 Charger R/T 440/505 2009 Challenger SRT8
Re: 440 struggles past 4,000 rpm [Re: RapidRobert] #2671006
06/28/19 08:19 AM
06/28/19 08:19 AM
Joined: May 2014
Posts: 117
California, U.S.A.
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Torquemonster440 Offline OP
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Torquemonster440  Offline OP
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Originally Posted by RapidRobert
Quote
it ran great with my 906's on there. but it should definitely RPM better in my opinion.
The carb did fine with the 906's? what exactly does it do at 4K?


In high gear, it will climb to 4k easily.. then just kind of hold there.. it still feels like its pulling, but by that time I'm out of real esate and I have to get off the throttle. I do need to test some more.. rev it in neutral etc.. but, I'm busy till Saturday evening, I'll report back after I have more time to tinker with it. Thanks for the Input all.👍


1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2671015
06/28/19 09:17 AM
06/28/19 09:17 AM
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GTX MATT Offline
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Which 850 Annular carb is it? 9380?


Now I need to pin those needles, got to feel that heat Hear my motor screamin while I'm tearin up the street
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2671017
06/28/19 09:19 AM
06/28/19 09:19 AM
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Chicago, IL
TonyS451 Offline
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I know you found some metal flakes in the carb bowl, did you check your fuel filter as well? I know you said it holds steady fuel pressure, but worth a check.


2 kids and a dog
Re: 440 struggles past 4,000 rpm [Re: Torquemonster440] #2671021
06/28/19 09:36 AM
06/28/19 09:36 AM
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Posts: 677
New Hampshire, USA
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oldiron Offline
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You might try opening the exhaust. A baffle in muffler that came loose, or partially collapsed inner wrap on exhaust pipe will cause exactly that


66 Belvedere Vert, 4 Speed/Jerico, slowly, very slowly, getting faster - NA LD Wedge
New New Best: 10.56 @129
68 B'cuda 4 gear Jerico - Another New Best of 9.86 & Trying to slow up
https://www.youtube.com/watch?v=T4jDLKwd9Gs
Re: 440 struggles past 4,000 rpm [Re: TonyS451] #2671022
06/28/19 09:38 AM
06/28/19 09:38 AM
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SW Ohio
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cgall Offline
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You could temporarily rig an electric fuel pump to see if it's a fuel starvation/vapor lock issue.

Re: 440 struggles past 4,000 rpm [Re: ChrgrCuda] #2671026
06/28/19 09:55 AM
06/28/19 09:55 AM
Joined: May 2014
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California, U.S.A.
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Torquemonster440 Offline OP
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Torquemonster440  Offline OP
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Originally Posted by ChrgrCuda
What diameter is the tube coming from the fuel tank sending unit? Is it 3/8 or 5/16 diameter? Also, check your fuel pump pushrod. Just had same issue on customers 440 GTX. The pushrod was wearing down.....
mp

The pickup was upgraded to 3/8" inlet. The pushrod deal crossed my mind, but I have not checked yet. I also doubt it would maintain fuel pressure like it does with the push rod wearing down, but it's a fairly easy check.

Last edited by Torquemonster440; 06/28/19 10:05 AM.

1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
Re: 440 struggles past 4,000 rpm [Re: GTX MATT] #2671029
06/28/19 09:58 AM
06/28/19 09:58 AM
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California, U.S.A.
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Torquemonster440 Offline OP
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Originally Posted by GTX MATT
Which 850 Annular carb is it? 9380?


Yes, it's the 9380. And yeah I did follow up on Holley's website.. looks like it should of had 78's all the way around when new.


1966 Satellie.. 12.55 @107.75. 906 heads. 3780 lbs.
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