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Discussion Starter #1
I currently have a 545 with out-of-the-box SCJ heads, 10.5:1 Probe pistons, 2 inch long tube headers, 2600 stall, 5200lb Bronco, Holley 870 vac sec carb, and a Comp Cams (XE284H .584 / .588 - 240I and 246E @ .050). Running a Stealth intake. I have 3" exhuast with 3" magna flows - total lenght of exhaust system is less than 5ft.

My issues is that the engine seems very under powered for what its is. I've had smaller displacement engines with samller cams that feel like they could stomp this one into the ground.

Any ideas and why it might seem weak?
 

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There could be a lot of reasons. How about a dyno sheet so we can see what it's doing?
 

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My issues is that the engine seems very under powered for what its is. I've had smaller displacement engines with samller cams that feel like they could stomp this one into the ground.
Perception is one thing, actual performance data is another. Has this thing been tuned at all? Dyno? Drag strip? A/F ratio? You have to know where you are to figure out where you need to go.

As stated gears and tires can be a big game changer too. 44's with 3.00 gears aren't going to impress anyone.
 

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From past observations, the carb, intake and camshaft are not well suited to one another.
The cam is probably the biggest culprit; it's certainly big enough for that 2,600 RPM converter just not the right balance.

How is this engine intended to get used...?
 

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Discussion Starter #7
Thanks all for the help. I've spoke to a local speed shop and they will not even look at it until I get rid of the 870 avenger carb; I'm looking for an 850 or bigger double pumper now.

I'm stuck with the cam for now as it's part of the 1 year warranty I got; it;s the biggest one my builder would warranty for the full yr. I plan on changing it in a year.

Gear ratio = 4.10
Tire size = 315/75/16 or 35"
C6 trans with wide ratio kit

Intened use is my local daily driver but I want it to go like all hell as well.

Sorry no dyno sheets at this time.
 

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Discussion Starter #9
I agree Critters - but do you think that could be entire problem? I've had less motor with 4:10 and 40" tires that pulled harder and spun way easier than this 545.
 

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Sounds like your combination isn't working together, too much cam. With 545 inches that carb probably isn't enough and that intake may be killing you too!
 

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Discussion Starter #11
To much cam? Really? Either way I'm stuck with the cam for a year. What do you suggest? RMCOMPRandy said the carb intake and cam are NOT well matched. Any suggestions on which intake and carb I should switch to?.

FYI - the motor will not see more than 6100 rpms if that makes any diff.
 

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Talk to Randy and get an intake and carb that is more suited to your cam profile and your heads.
 

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Thanks all for the help. I've spoke to a local speed shop and they will not even look at it until I get rid of the 870 avenger carb; I'm looking for an 850 or bigger double pumper now.

I'm stuck with the cam for now as it's part of the 1 year warranty I got; it;s the biggest one my builder would warranty for the full yr. I plan on changing it in a year.

Gear ratio = 4.10
Tire size = 315/75/16 or 35"
C6 trans with wide ratio kit

Intened use is my local daily driver but I want it to go like all hell as well.

Sorry no dyno sheets at this time.
The point is that the intake lobe on that cam is probably to big for the 2,600 RPM Stall converter; (to much duration and not enough lift).
The rest is probably livable, (though not a perfect match), IF the converter and gearing matched the camshaft.

EDIT: If you have a 9 position timing set, you may get some help by advancing the cam timing another 4 degrees; (if the intake notch in the piston will accept it).
 

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LOL this sounds stupid but a mopar guy I work with put a set of flowmasters on backwards on his 440 thing was so gutless would not turn over 3,200 and ran like crap.... I think your issue is def carb and intake related.
 

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Did your builder GARAUNTEE a hp figure with this engine? Why does the local speed shop have a problem with the Avenger. The Avenger is basically a 3310 with the options that you would have to buy seperatetly. How long do you have left of the one year? How many miles and does everything seem koscher other than the lack of power? Was this all over the shelf build or was any special things done to it?
 

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Couple of questions and suggestions:

1) What is your timing set at, initial and total, and at what rpm is all the timing in at?

2) When you are stating a lack of power, what exactly do you mean? Can you fry the tires from a stand-still without having to brake-stand or any other tricks? Or, does it run out of steam at a certain rpm?

3) Where do you need the most power, rpm wise?

4) Have you spent any time tuning the carb, such as, installing lighter springs for the secondaries?

5) Have you checked that you're getting full secondary opening on the carb?

6) Install a vacuum gauge, and give us the reading when idling, cruising, and at WOT.

7) What size air cleaner do you have on it? Is it sucking in hot under the hood air?

Something is wrong, and I suspect it has to do with the tuning. Even with such a "small" carb, you can make over 500 hp. The small carb starts to hurt hp at higher rpms, but at lower rpms, it should be just fine.

As far as throttle response goes, I was never able to get the same "crispness" that a double-pumper Holley gives from either a Holley vacuum secondary or Edelbrock carb, from home tuning.

Hope that helps,

Dave
 

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Discussion Starter #17 (Edited)
bigblok86ranger
No HP guarantees. Speed shop said the've had to many tunning issues with the avenger series carbs. It's taken me almost 3 months to get the engine installed, so I have 9 months on the warranty. Roughly about 100 miles on the engine now; there is no milage restriction on the warranty. The build was pretty much right off the shelf.

fireballferkey
I could easily put some mufflers on backwards as well. Good thing this build has straight through Magna Flows.


DJOHAGIN
1) 18 initial, 34 total - all in by 2500
2) Its slugish at the bottom - frying tires, yes but just barley. I talked to Hughes converters yesterday and they said that I should not go to the next converted as it will be an 11" instead of a 12". They said with the weight of the truck this would be an issue. No sure if the converter has anything to do with it; I'm current runnig a Hughes 2500.
3)down low (but of course 1500-6200 would be great:D) I have no plans to rev higher than 6200; rev limit will be set at 6k
4)Yes, I have the weakest spring in there now. The transision seems ok with no hesitaion. I actually was thinking they weren't opening.
5)No - How do I do this?
6)at idle its 13-15 and bounces the hole time. I will get the other readings to nite.
7)14"x5" I have not reinstalled the hood yet.

I'm not super thrilled with the vac sec myself but thought it would be good considering the weight (5200lbs). I talked to holley and the said my ruff idle could be becuase I have the primarys open to far and not actaully using the idle circut. They suggest craking the secoundaris open a half turn and reseting my idle mixture and curb idle. They also said to see if I have vacum at the port vacum while idling; if so this would be a good indication that I'm not using the idle circut.

Thanks All.
 

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"6)at idle its 13-15 and bounce the hole time. I will get the other readings to nite"

Your vacuum needle is bouncing? It should be smooth as silk. If it's bouncing, you're losing compression somewhere. Probably need to adjust the rockers?

Unless that's something a really radical cam would do?
 

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Discussion Starter #19
1FSTCAT
I have a small oil leak at the back of the intake and will be pulling tonight. I planned to go ahead and check/adjust the rockers at that time. Holley mentioned the bouncing vacum and boucning idle could becuase I'm not actaully using the idle circut to idle. They're also the one that told me use the 870 avenger. What's your thoughts?
 

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4.10 gear is great for a 32" tire, not 35's

35" with a 4.10 diff is the equivalent of stock tires (30") geared 3.41. Factor in the extra weight (as much as double the stock tire) and it will punch a big hole in the available power.

To match the effective gearing of a stock 30" tire with 3.73 rear gears, a pretty standard setup, 35" tires would reguire a 4.35 gears to make driveline speeds the same (to make the speedo read correct, in other words).

Brad
 
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