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  #16 (permalink)  
Old 07-01-2013, 06:38 PM
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Is your carb. inclosed under a hood or are you drawing fresh air through a scoop or other means? Idling if under a hood it will be drawing in hot air caused from engine temperature and that can make it run real rich!!! Till you run it hard and it clears up and then it idles and gets into a rich cycle again?

Jester

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  #17 (permalink)  
Old 07-01-2013, 06:48 PM
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Originally Posted by painted jester View Post
Is your carb. inclosed under a hood or are you drawing fresh air through a scoop or other means? Idling if under a hood it will be drawing in hot air caused from engine temperature and that can make it run real rich!!! Till you run it hard and it clears up and then it idles and gets into a rich cycle again?

Jester
It does the same thing even with the hood open, if I go out and pound it, then come home, pop the hood, let it idle a bit, and viola....
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  #18 (permalink)  
Old 07-01-2013, 07:59 PM
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Quote:
timing is 24* initial, 34* total, all in by 2800rpm
Vacuum advance is limited to 10* using a manifold source.
If you have 10 degrees vac adv from a manifold vacuum source, plus 24 initial, you should be seeing 34 degrees at idle.

My point to this was 34 degrees (if that's what you're seeing) is enough timing at idle and there's little/no need to mess w/adding initial to clear things up because that cam isn't radical enough to justify more than 34 degrees initial.
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Old 07-01-2013, 09:48 PM
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Originally Posted by cobalt327 View Post
If you have 10 degrees vac adv from a manifold vacuum source, plus 24 initial, you should be seeing 34 degrees at idle.

My point to this was 34 degrees (if that's what you're seeing) is enough timing at idle and there's little/no need to mess w/adding initial to clear things up because that cam isn't radical enough to justify more than 34 degrees initial.
That's exactly what its set up for. And at idle, with vacuum I'm at 34*. The only reason I have to mess with the timing now is whatever was limiting it to a 10* curve isn't anymore lol. Today it was 40+ at 3000rpm and kept climbing with rpm. So its going to have to come out. Would like to solve the idle issue first.
Anything mechanical that I could be missing? Not just tune? For it to be as Smokey and stinky it seems like the Carb would have to be real messed up which being brand new I'm hoping it isn't.
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  #20 (permalink)  
Old 07-02-2013, 07:35 AM
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Originally Posted by bygddy View Post
Hey guys, so went to the track last night,
Truck ran good, went a best of 12.98 @ 117
Zero hook on radials, walking it past the 60ft
Consistant 13 teens most of the night, MPH ranged from 115-118 as a high
Guys there with traction running mid 11's at the same MPH.
Its running fine in every way except at idle.
Its not "rich" but shows very poor combustion, it smokes and its not black, its just unburned fuel.
A little bit when your on it, but lots at idle.
383
Vortec heads (mild porting)
Performer rpm cam.
488/520, 234/244@0.50
Air gap rpm intake
Quick fuel 650 dp
Stock jetting, 4.5pv
Long tubes.
Msd dist HEI style with external blaster 2 coil
Msg 6a box
Summit wires.
Holley blue pump
Holley reg
Fuel pressure at 5psi
Floats at bottom of sight glass.
4 corner idle, all screws roughly 1 turn out.

That's all I can think of. Any suggestions?
Edit, timing is 24* initial, 34* total, all in by 2800rpm
Vacuum advance is limited to 10* using a manifold source.
I had much the same problem with 2x4's. Found two factory defects in the front one on the 3rd time I tore it down and inspected it with a 6 and 10x magnifying glass. Can you borrow a carb just to try out? Try another timing light also. I've gotten weird readings with a lose or dirty pickup on the wire. ( a little elec cleaner or starting fluid) MSD says to not use an advance light although my old snap-on advance usually works ok. Air bleeds on the carb good n clean? Improved my ET n 60' by leaving the line a lot easier than I was. Dropped about a second off ET n 60'.
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  #21 (permalink)  
Old 07-02-2013, 09:52 AM
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Get a Eatons or a Auburn posi, before the spool breaks the rear end/axles.
The 7.5 is fine with a posi set up correctly and wheel hop is avoided (caltracs)

Caltrac traction bars or fab your own similar. + ET streets
What is it with you and carbs? try the 750 you got.
check the HEI for a burned centerpost/cap
Good MPH = lots of power What is the 1/8th MPH?
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  #22 (permalink)  
Old 07-02-2013, 10:21 PM
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Originally Posted by F-BIRD'88 View Post
Get a Eatons or a Auburn posi, before the spool breaks the rear end/axles.
The 7.5 is fine with a posi set up correctly and wheel hop is avoided (caltracs)

Caltrac traction bars or fab your own similar. + ET streets
What is it with you and carbs? try the 750 you got.
check the HEI for a burned centerpost/cap
Good MPH = lots of power What is the 1/8th MPH?
8th was 8.56 @ 89.03
I have sht luck these days. The 750 summit had the same issue. That was why I bought the quick fuel Carb, and I hate vacuum secondaries.
The hei has an external post with a spark plug type connection then a coil wire to a blaster 2 coil.
What i do notice is all the plug wires have a whitesh yellowish stain at the boots where they plug into the dist cap, the coil wire is showing the same. I don't remember seeing this when I first got the truck.
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  #23 (permalink)  
Old 07-02-2013, 10:29 PM
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Originally Posted by Fang16 View Post
I had much the same problem with 2x4's. Found two factory defects in the front one on the 3rd time I tore it down and inspected it with a 6 and 10x magnifying glass. Can you borrow a carb just to try out? Try another timing light also. I've gotten weird readings with a lose or dirty pickup on the wire. ( a little elec cleaner or starting fluid) MSD says to not use an advance light although my old snap-on advance usually works ok. Air bleeds on the carb good n clean? Improved my ET n 60' by leaving the line a lot easier than I was. Dropped about a second off ET n 60'.
Carb is less then a week old, and the summit Carb I had on it was doing the same which is why I replaced it.
The timing light has me frustrated and maybe chasing my tail, my no name light read high, like 44* plus at idle,which made no sense. I borrowed a Blue Point digital light with every bell and whistle, it read fine the first time I tried it. Now, its "seems" to read fine, it reads 24* initial, which is exactly what the PO had the dist set for, and was limited to 34* total, and its was showing all in by 2800, now it still reads the same initial, but the mechanical doesn't stop, right up until 45* at 4000 rpm,. Truck doesn't ping, or act weird (smoking not withstanding) and pulls hard. So I'm wondering if I'm really chasing a false reading agin caused by the msb box
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  #24 (permalink)  
Old 07-03-2013, 06:55 AM
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Quote:
Originally Posted by bygddy View Post
Carb is less then a week old, and the summit Carb I had on it was doing the same which is why I replaced it.
The timing light has me frustrated and maybe chasing my tail, my no name light read high, like 44* plus at idle,which made no sense. I borrowed a Blue Point digital light with every bell and whistle, it read fine the first time I tried it. Now, its "seems" to read fine, it reads 24* initial, which is exactly what the PO had the dist set for, and was limited to 34* total, and its was showing all in by 2800, now it still reads the same initial, but the mechanical doesn't stop, right up until 45* at 4000 rpm,. Truck doesn't ping, or act weird (smoking not withstanding) and pulls hard. So I'm wondering if I'm really chasing a false reading agin caused by the msb box
I'm just gonna throw this out there: Check the dist for good ground, dist shaft for play, dist drive gear for wear. Also check all wiring going to the dist n box esp box positive n ground including engine grounding to frame. Could u maybe borrow a 6al? Loan u mine but I'm in Ar. Thinking carb isn't the problem as it's doing the same with two differant ones.
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