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Author Topic:   Motor Missing
HarrisMod#30
Member
posted September 08, 2003 09:01 PM
Had one act similar once - cam was walking back and forth changing the timing radically. The cam stop had fallen out of the water pump.
Probably not your solution, but just an idea.


tim62
Member
posted September 08, 2003 10:54 PM
You said that you changed the Ignition switch. Did you change the ignition wire while you were at it. I had the same problem and had a wire breaking down. Run a straight wire from a hot source of power to your ignition for temporary use and see if it helps.


xx RACER 96
Member
posted September 09, 2003 02:59 AM
We had one that was doing a lot of missing / spitting - turned out one of the plugs got a hairline crack right where the insulating porcelin went into the metal base - only when the crack got big enough was it obvious.... Couldn't find that miss for several weeks!


HarrisMod#30
Member
posted September 09, 2003 11:34 AM
Does it seem to be a fuel problem or ignition? I'd take a closer look at the fuel pump. I had the same thing happen to me. My big motor would hick-up exiting the corner and down the straights, but the little one did fine. It turned out the fuel pump just couldn't quite meet the demand of the bigger motor. If you move more air through the engine you've got to put more fuel in.
I'm assuming you have a fuel pressure gauge in the dash, and it might read just fine, but there is a fundamental difference between pressure and amount. You might not be getting all the fuel you think you are. Sharp bends or kinks in your fuel line can lead to this too.
The carb might be a place to look too. I've had carb troubles and replaced a bad one with what I've thought was a good one only to lead me down the wrong road to fixing the problem. Is your carb guy reputable? Many so-called mods can actually destroy a good carb out of the box.


HarrisMod#30
Member
posted September 09, 2003 02:08 PM
I would be concerned with the #8 inlet line. I think a #10 would be better. I also had a very similar issue with a motor and found out the cam gear was chewed up and the timing was changing. Only thing the distributor gear showed the same signs and I would think you would have seen this.



xx RACER 96
Member
posted September 10, 2003 01:41 AM
My Two cents worth?
You are either running out of fuel, or your valves are floating.
Look at the plugs right after a race!
Running out of fuel will give them the lean burnt whitish look. Sometimes the electrode will turn blue, as if it's been in a fire.

Floating valves will leave them a little darker.

Using fuel at that rate, you might need more pressure from the pump, to keep the volumn up.

HarrisMod#30
Member
posted September 12, 2003 04:47 PM
i would start at looking under the vavle covers ......look all the rockers over and see if they are rubbing the retainers ....and also bump the engine over with the covers off to see if there is coil bind ....also check to see if your retainers are hitting your valve guides ,also pay close attention to the rockers to make sure that they are hitting the valve stem correctly ......look for bent push rods .......i hope this helps


HarrisMod#30
Member
posted September 17, 2003 04:40 PM
Motor went on the dyno and it still missed and wouldnt turn over 7200 rpm,rules out our stuff, now the motor builder can deal with it, ill keep you guys updated!


HarrisMod#30
Member
posted September 17, 2003 07:40 PM
He found a clip or somthing on the valve seat that was broke and causing a valve not to close all the way..hes putting it back together and well see.


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