300 miss
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300 miss
I have a '71 f-100 with the 300-6. It has a newer rebuilt head with port work and a 3 angle valve job. I also have the comp cams 260h with the clifford intake and holley 390. I have it running and it runs well but has a slight miss. I have the float level set and idle mixture screws. The timing is on i believe. It has new plugs and wires and a rotor. I need to get a new cap. Any ideas what this could be? Thanks
Tuned
Joined: Jan 2006
Posts: 290
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I would look at the dizzy cap for build up on the contact post. My I6 would not even start a few months ago untill I took the trusty pocket knife to scrap the crud off the 6 post inside the cap. Check for sparks in the dark if the cap cleaning does not help. With your upgrade you might want to upgrade your spark supply.
Tuned
Joined: Jan 2006
Posts: 290
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Does it miss when the engine is at idle, or does it miss when you mash the skinney pedel? Miss at idle I would look for electrical probmems. If you have, what I call a bog or flat spot when you give it gas, look for carb problems. The Holley 390 has many ways to be tweeked. Don't mess with the carb if you don't have to at this point. It might be time update your coil to match your other mods.
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the miss is at idle mostly and when you bring the engine up off idle and hold it it misses. Mostly at idle. What should i upgrade with the ignition. I have the dual advance dizzy that id like to get rid of for a single advance one (pre smog). I have some type of electronic ignition that gets rid of the points i dont think its pextronics or whatever. what should i upgrade to?
Tuned
Joined: Jan 2006
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DANA60, See what Harte3 is running on his 83 300 I6 for spark supply in this post? That looks like a hot setup. Recurved DSII, Mallory Ect....
Another way to go is a local guy rebuilds vacuum advanced dizzys with GM coils and GM HEI modules with mounting hardware. All I need to do was to supply a hot wire to his assy. Smam dunk for a little over $150 a year ago. Because my I6 does not spin up to the moon I was told I did not have to spend maga-bucks for spark supply. I have the Clifford intake w/ the 390 Holly and EFI exhaust. The rest is plain Jane rebuild, built for the long run. Oregon Iginition Supply 503.931.5978
Another way to go is a local guy rebuilds vacuum advanced dizzys with GM coils and GM HEI modules with mounting hardware. All I need to do was to supply a hot wire to his assy. Smam dunk for a little over $150 a year ago. Because my I6 does not spin up to the moon I was told I did not have to spend maga-bucks for spark supply. I have the Clifford intake w/ the 390 Holly and EFI exhaust. The rest is plain Jane rebuild, built for the long run. Oregon Iginition Supply 503.931.5978
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I put a new msd blaster coil on but it still has the same problem. I tried timing it with both sets of timing marks and i can bring the mark into the scale but it runs worse. Also when i bring the timing mark into the timing scale the vacuum drops. When i tune timing for max vacuum it runs smoother. Im stumped
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Postmaster
Joined: Dec 2006
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From: Spokane, WA
gofastforless.com is well worth reading for ideas on inexpensive ignition upgrades like using the GM HEI stuff. BTW, I added the Mallory box, MSD coil and Taylor wires before I had the engine rebuild done...that made a significant difference in performance on the old engine...I am a true believer now on ignition upgrades.
Last edited by Harte3; Apr 15, 2007 at 09:22 PM.
