Engine Vibratrion

5ive.oh · Sep 18, 2006

New 306 shortblock just fired up for the first time and it has a bad RPM vibration. i have changed the balancer and it made no diff at all. The vibration is still there even with the belt off and no accessories running. It does get a bit better if I remove the bottom pulley. Think maybe the engine builder screwed something up when it was being put together? The pulley doesn't seem to wobble when I have it running.

JChalfan · Sep 18, 2006

Have you checked all the basics, like making sure all the plugs and injectors are firing? If all that stuff is good, I'd talk to the guy who built the engine.

Jeff

5ive.oh · Sep 18, 2006

I'm having issues with #7 plug on these GT40P heads. My header doesn't clear the plug on that side real well I've already had three plugs break on me. I'm running carbed no fuel injection here.

JChalfan · Sep 18, 2006

5ive.oh said:
I'm having issues with #7 plug on these GT40P heads. My header doesn't clear the plug on that side real well I've already had three plugs break on me. I'm running carbed no fuel injection here.

If your #7 plug is cracked and you didn't notice it, that could cause it to not fire and make the engine run rough.

At what RPM's does it run rough? My experience is that if 1 cylinder is not firing, it will usually shake the worst around 2000-2500 RPM.

Also, if you are using adjustable rockers, are you sure they are adjusted correctly?

Jeff

5ive.oh · Sep 18, 2006

Non Adjustable rockers. If I pull the wire off the distributor it still runs the same so I am thinking my issue is there. When I pulled the plug it wasn't cracked but it was wet with fuel. I changed the wire and it still runs the same. There is spark arcing from the distributor when I pull the wire. It shakes bad at about 3k RPM. One thing after another with this car.....

JChalfan · Sep 18, 2006

5ive.oh said:
Non Adjustable rockers. If I pull the wire off the distributor it still runs the same so I am thinking my issue is there. When I pulled the plug it wasn't cracked but it was wet with fuel. I changed the wire and it still runs the same. There is spark arcing from the distributor when I pull the wire. It shakes bad at about 3k RPM. One thing after another with this car.....

It definitely sounds to me like that #7 plug isn't firing. That would explain it being wet with fuel, running the same when you pull it off the dizzy, and vibration around 3k.

What I have had happen before is a plug will get a very small crack in the porcelain insulator, right by the base of the plug. The spark jumps through this crack and grounds out without having ever fired the plug. But you would still get the arcing from the dizzy when you pull the wire.

I've never had GT40P heads, but I understand they have plug fitment problems if you aren't using the correct headers. When you installed that plug, did you use a spark plug socket which had the rubber insulator removed from inside the socket? I've broken and cracked a few plugs by using a socket with that insulator removed, and lots of times you won't even know the plug has been cracked.

Maybe it's possible to get a shorter plug that would work for now?

Good luck, I'm sure you'll get it figured out. I'm really suspicious of that #7 plug.

Jeff

5ive.oh · Sep 18, 2006

Thanks man, it's definately that damn plug. I tried shorter plugs but the threads are not deep enough to reach in to the plug hole. The header pushes against the plug. I have dimpled the header a bit to remedy this but to no avail. Damn money pit........

JChalfan · Sep 18, 2006

5ive.oh said:
Thanks man, it's definately that damn plug. I tried shorter plugs but the threads are not deep enough to reach in to the plug hole. The header pushes against the plug. I have dimpled the header a bit to remedy this but to no avail. Damn money pit........

No prob, happy to help. Just buy a set of headers that work with the GT-40P's, and then sell your old set to recover some of the $$$. Once you get it all up and running right, I'm sure you'll be real happy with your new engine.

I've heard that the ford racing GT40P headers aren't the only ones that will work with the P heads. I beleive one or more of the aftermarket shortys offer enough clearance. Ask around on here, you should be able to figure out which ones.

Jeff

JChalfan · Sep 18, 2006

Holy crap, I just found this article about what one guy did to fix the problem:

http://www.fullsizebronco.com/forum/showthread.php?p=986548

That guy has a lot of free time on his hands! Impressive work.

I'm not recommending doing that at all, I just thought you'd get a kick out of it.

Jeff

5ive.oh · Sep 18, 2006

Holy crap! I don't have that much invested in the headers to got through all that. I guess BBK makes some LT's that clear, I have a set of LT's on it now and want to stick with them.

BTW:Your not going to try and sell me a camshaft now are you?

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