Rough running 351W
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From: Miami, FL.
Rough running 351W
Still trying to tune my engine after some modifications. Cannot seem to get a steady, consistantly running engine and was wondering if sparkplugs may have something to do with it.
Should the factory recommended sparkplugs be used with the mods below and, if not, anyone know what would be the correct plug?
'86 351w w/125000? miles (about 150 on all cylinders on compression test, 22HG on "running engine" vacuum test), Edelbrock 2181 power package (#2181 intake, #2182 cam, #1406 carb. w/electric choke spliced into wiring harness' correct color-coded wire), #7811 timing set, MSD 6A ignition, headers w/dual exh.
TIA for any help, advice
Munrow
Should the factory recommended sparkplugs be used with the mods below and, if not, anyone know what would be the correct plug?
'86 351w w/125000? miles (about 150 on all cylinders on compression test, 22HG on "running engine" vacuum test), Edelbrock 2181 power package (#2181 intake, #2182 cam, #1406 carb. w/electric choke spliced into wiring harness' correct color-coded wire), #7811 timing set, MSD 6A ignition, headers w/dual exh.
TIA for any help, advice
Munrow
Last edited by munrow; Mar 31, 2005 at 05:28 AM. Reason: add more
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Motorcarft are fine but I suggest next time try regular Autolite plugs, cheap and hard to kill. You'll need a bigger than stock plug gap with the MSD too. Think I set mine to .065 last. You may have fouled a plug or 2.
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From: Miami, FL.
Checked all plugs, replaced one with a cracked insulator, re-gapped all to .060, replaced two plug wires that looked a little shakey.
Took the top off the Edel. carb. Floats and jets perfect, no residues, etc.
Could not get the d#&n thing to idle correctly, or, not surge greatly when put into drive or reverse with the brake on until I switched the dizzy vacuum connection from full to timed. Don't understand that because it was doing pretty good on full vacuum.
Started it (it's warmed to normal temp from screwing with it), idle was at steady 1000 RPM, put it in drive and rpm dropped to steady 750 RPM. Took it for a drive and, except for needing a timing tweak to fit timed vacuum, it ran just fine. Any ideas what happened?
Thanks for any advise/help.
Took the top off the Edel. carb. Floats and jets perfect, no residues, etc.
Could not get the d#&n thing to idle correctly, or, not surge greatly when put into drive or reverse with the brake on until I switched the dizzy vacuum connection from full to timed. Don't understand that because it was doing pretty good on full vacuum.
Started it (it's warmed to normal temp from screwing with it), idle was at steady 1000 RPM, put it in drive and rpm dropped to steady 750 RPM. Took it for a drive and, except for needing a timing tweak to fit timed vacuum, it ran just fine. Any ideas what happened?
Thanks for any advise/help.
Last edited by munrow; Apr 7, 2005 at 03:09 PM.
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The MSD makes much more spark and any bad wires or cheap cap will show up more readily. I use Standard Ignition 'Blue Streak' Cap & rotor and KEM wires, expensive but you get what you pay for. Use dielectric grease on all the wire ends too. It should be running full vacuum advance as I recall. If your curve the distributor get all the advance in by 3000 rpm.
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I have a 87-351W in my F250; last year for carbed Windsor. I found I had too much advance and the curve was too fast (too much advance, too early in the RPM range). The engine ran okay but pinged and rattled going uphill or with a load. The timed vacuum port off the carb was a better choice for me; full manifold vacuum advanced the timing way too early!
Which distributor are you using? Any idea of the total vacuum advance for the 351W?
The duraspark-II distributor that came out was set to 36* (18*plate X 2) plus 6* static for a total of 42* ; sounds way too much!
Good luck!
Which distributor are you using? Any idea of the total vacuum advance for the 351W?
The duraspark-II distributor that came out was set to 36* (18*plate X 2) plus 6* static for a total of 42* ; sounds way too much!
Good luck!
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From: Miami, FL.
As to Netfly's last post, changed cap, rotor, wires. All plugs look acceptable for wear, etc. Am looking for a set of wires locally that I saw advertised online as being able to withstand temps. of 500 degrees. Keep getting oil out of the oil fill tube connection and it swells the wires when it hits them. I know I've got some blow-by going on but am still waiting for the funds to be able to rebuild the 351 in the garage. Want a stroker but will probably just go stock.
Still have the same problem on full vacuum. Was using rebuilt DurasparkII from AdvanceAutoParts. Got another one yesterday for $50 w/core so that I can play with the re-curving on the old one. Didn't want to mess with it then 'cause I've got two jobs to go to today. Would rather have it run rough and get the work done than to maybe screw something else up.
Gonna try just swapping dizzys this afternoon or tomorrow. Hopefully it will run like it did before. Still gonna have to set it for the proper curve. Worst that can happen is I can rule out the dizzy as the culprit.
Thanks for the info/tips,
Munrow
Still have the same problem on full vacuum. Was using rebuilt DurasparkII from AdvanceAutoParts. Got another one yesterday for $50 w/core so that I can play with the re-curving on the old one. Didn't want to mess with it then 'cause I've got two jobs to go to today. Would rather have it run rough and get the work done than to maybe screw something else up.
Gonna try just swapping dizzys this afternoon or tomorrow. Hopefully it will run like it did before. Still gonna have to set it for the proper curve. Worst that can happen is I can rule out the dizzy as the culprit.
Thanks for the info/tips,
Munrow
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From: airdrie canada
Originally Posted by TheWiz427
I've never run full vacum to a distributor! With full vacum the vacum advance is useless.
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From: Huntersville
I once had a rebuilt dura-spark that caused alot of timing problems. I finally figured out that the rebuilder had cranked the adjustable vacuum canister all the way in. As soon as vacuum hit it it would pull in all the vacuum advance it could.
Make sure if yours is adjustable that it's not turned all the way in.
here's a good article on timing.
http://fordmuscle.com/archives/2000/...ng/index.shtml
clint
Make sure if yours is adjustable that it's not turned all the way in.
here's a good article on timing.
http://fordmuscle.com/archives/2000/...ng/index.shtml
clint
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From: airdrie canada
351w
thanks to you and the wiz427, the edelbrocl manual that came with the carb says to hook up to the full vac port, seeing as i'm using this for a truck that pulls a 5800 lb trailer, the article says that best acceleration is comes when total advance is achieved before 2500 rpm, is this the same for torque, i'm not so worried about 0-60 but pulling power. thanks again, i'll try to set it up according to this article and test it again.
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From: Huntersville
I've seen them set up both ways but like the ported vacuum on mine. If it's on full vacuum you can set up the dist. accordingly and some say the engine will run cooler. I don't know. If it's set up full vacuum you will have to tune the vauum advance to where it's not pulling in too much at an idle.
I still like ported, that way at an idle all that's affecting the idle is the mechanical advance (if any) and the carb settings.
Make sure to check your vacuum advance and see if it's adjustable. It's either a 1/8 or 3/32 allen wrench inside the vacuum nipple. If I remember correctly backing it out reduces the vacuum advance amount.
Mine was all teh way in and pulling in about 50* of timing just off idle. yes it spark knocked. lol
clint
I still like ported, that way at an idle all that's affecting the idle is the mechanical advance (if any) and the carb settings.
Make sure to check your vacuum advance and see if it's adjustable. It's either a 1/8 or 3/32 allen wrench inside the vacuum nipple. If I remember correctly backing it out reduces the vacuum advance amount.
Mine was all teh way in and pulling in about 50* of timing just off idle. yes it spark knocked. lol
clint
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From: airdrie canada
351w
i changed the vac line to the timed port and reset the inital timing to 10 degrees btdc and noticed it ran a little rough so i guess i'd better get the new wires on, i took the truck out and put pedal to the metal, i must admit i was impressed. now i need to get the trailer attached and try the big hill, but i guess i'd better try to fiqure out the timing curve, and then see if i can get that to the specs in the article. anyway i'll keep you informed. 