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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Some light reading with questions about rough running issues
I’m back with more questions and observations
Got the timing light yesterday and was able to clean the balancer to be able to read the marks and rubbed some chalk in them for added visibility for my old eyes. It shows I’m running 38-40 BTC. Is this even possible? I can’t get anywhere before 25 without it stalling.
I have not been able to verify 0 = TDC yet but will hopefully when the wife gets back to bump it for me.
I used the vac gauge hooked to the back of the carb where the PCV valve is attached normally. Dist vacuum disconnected and other small port on carb is blocked off. The timing is set now at max vacuum. I’m at 15 on the vac gauge at 900 RPM’s idle
The truck is running rough still especially at low speed, like idling through the neighborhood it feels like it’s missing. Once I get on it, It seems to do ok and the throttle is responsive. The RPM’s fluctuate 20-25 up and down at least when idling and regardless of which wire I have the tester on.
Question- with the PCV hose unhooked from the back of the carb, The Idle goes way up is this normal?
Question- Does this seem like it could be dizzy or points related? Plug wires look ok, the strobe looks pretty even in intensity on each wire Dist cap looks ok. The dizzy where the points and condenser sit is a bit dirty but it seems to be functioning ok- I might get new points and condenser or a pertronix igniter to see if that makes any difference. Rotor looks ok, I cleaned the contact a bit Pulled #2 and #6 plugs, they don’t look bad, not black and oily and not white. Verified firing order is right for the HO 1,3,7,2,6,5,4,8 and plugs are on the cap counter clockwise. Plug wires are 7mm. New plugs gapped at .035
The motor is a 5.0 HO Roller from a mustang GT. Not rebuilt. The PO put a comp cam in it part number 35-420-8 grind 270hr Exhaust closes at 21ATDC and opens 69 BBDC Intake opens at 29 BTDC and closes 61 ABDC Hmmmmm.. 40-29=11 could it be he installed the cam wrong and TDC would actually be at the 29 mark…. I really grasping and have no idea if that’s even a realistic possibility
Edelbrock 1405 carb with offroad needles and seats, .095 primary and secondary jets and .065X47 rods. Fuel pressure at 5.5 psi
It’s running better, but not where it should be, It just feels rough running, I’ve never had a vehicle that had a cam upgrade so maybe some of what I am feeling is a lope.
Thanks for listening, if you have any idea on things to try, verify and what I might need to recheck I’m all ears.
Brett
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Sat Apr 30, 2011 12:37 pm |
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BFD305
Official CCB Member
Joined: Sun Oct 10, 2010 11:33 pm Posts: 231 Images: 5 Location: Greeley, CO
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Re: Some light reading with questions about rough running is
You need to check TDC, you could be a tooth off and need to set the timing that far off because of it. Does not sound like a points issue.
Is it possible that the outside of the balancer slipped on the hub of the balancer?
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Sat Apr 30, 2011 1:27 pm |
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Shawns Fords
Official CCB Member
Joined: Sat Oct 02, 2010 7:36 pm Posts: 779 Images: 0
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Re: Some light reading with questions about rough running is
I would definitely verify TDC is correct. A trick to do that on your own is to put the Crank pully right before and with #1 plug removed use a small pocket screwdriver to slide into the plug hole and as you hold the driver turn the crank with a ratchet with socket. you can feel the piston push the driver to the top. you wont drop it in there if it is long enough and thin enough.
I would also make sure the idle mixture screws are not in too far. Maybe back them out a turn or two and see if it smooths out.
you cant go wrong with a pertronix points replacement.
I have also seen the balancer/damper slip on the insulator.
you may also have a worn timing set as well.
A loose distributor drive gear.
Cant think of anything else right now.
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Sat Apr 30, 2011 2:16 pm |
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Viperwolf1
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Re: Some light reading with questions about rough running is
I bet your Bronco timing pointer is on the wrong side with the 50 oz mustang balancer. It's about a 40 degree difference. Verify with a piston stop then get some Mr Gasket timing tape to remark the balancer.
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Sat Apr 30, 2011 3:17 pm |
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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Re: Some light reading with questions about rough running is
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Sat Apr 30, 2011 3:51 pm |
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Viperwolf1
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Re: Some light reading with questions about rough running is
Yep. Mustang pointer was on pass side. If you subtract 40 from your reading you should be real close. You would want it to read somewhere around 50 BTDC with that pointer.
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Sat Apr 30, 2011 7:17 pm |
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Shawns Fords
Official CCB Member
Joined: Sat Oct 02, 2010 7:36 pm Posts: 779 Images: 0
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Re: Some light reading with questions about rough running is
That new timing light should be able to do that too.
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Sat Apr 30, 2011 7:30 pm |
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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Re: Some light reading with questions about rough running is
Quick Update.
TDC has the pointer on 24BTDC on the balancer. I'll get a tape and install it so it will read correctly. Going to be a few days before I can get back at this section. Might be tackling the rear quarter panel next:) or the doors.. or putting different seats in..
Lol. Brett
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Mon May 02, 2011 11:01 am |
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Viperwolf1
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Re: Some light reading with questions about rough running is
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Mon May 02, 2011 11:58 am |
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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Re: Some light reading with questions about rough running is
I checked it by placing a wooden dowel in the #1 cyl and cranked it until the it stopped coming out. The wife was holding it to make sure it had stopped completely. I'm using the pointer that's in place on the drivers side of the engine if I am facing the engine. I could be off by a degree perhaps depending on when she told me to stop but it should be pretty close. The rotor is pointing to plug 1 on the dist cap at this position as well.
I can do it again if this does not sound like the correct method to get TDC. Brett
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Mon May 02, 2011 12:22 pm |
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Viperwolf1
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Re: Some light reading with questions about rough running is
I would do it again with a piston stop. There's probably 10 degrees of crank movement at the top where the piston doesn't move.
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Mon May 02, 2011 5:52 pm |
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crawlercreations
Official CCB Member
Joined: Sat Nov 06, 2010 9:36 pm Posts: 1101 Location: Arvada
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Re: Some light reading with questions about rough running is
Please correct me if I am wrong but I believe I remember seeing somewhere that all of these issues arose after you changed a bunch of stuff on your carb? Offroad needle and seat and such? If it was running fine before the change then it is all in the carb as long as that is all you changed?
_________________ There is a fine line between "hobby" and "mental illness"
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Mon May 02, 2011 6:28 pm |
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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Re: Some light reading with questions about rough running is
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Mon May 02, 2011 6:49 pm |
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BNC04
Official CCB Member
Joined: Thu Jan 27, 2011 1:01 pm Posts: 350 Images: 0 Location: Longmont
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Re: Some light reading with questions about rough running is
_________________ 75 D44/ARB/Disc PS. 86 5.0 Carbed- NP-435 yukon rear. 4.11 3.5 Susp lift Rampage top
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Mon May 02, 2011 7:00 pm |
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