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Discussion Starter · #1 ·
Something I’m really stuck on is this miss my stang has. Any rpm above 1200 it has an intermittent miss. I’ve replaced every thing from the carb to the ignition. Replaced intake gaskets and check all vacuum hoses. The only thing I can think of is a sticky valve. I did a compression test and a vacuum test not finding the problem.
The results on the vacuum test were a slight drop (3 in of vacuum) on the gage followed by a miss.
And with the compression test it was #1 164 psi, #2 164, #3 160, #4 168, #5 162, #6 167, #7 168, and #8 169. Is this good? What is my compression ratio?

This is starting to p*ss me off. Can’t go any ware without it shaking my teeth out!


<font size=-1>[ This Message was edited by: tricky on 5/13/02 11:05am ]</font>
 

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I dont know for sure about the miss, but I had a buddy that had a similar problem, and it turned out to be a bad power brake booster. The diaphragm was leaking and caused a slight vacuum leak, and it misfired on one cyinder just off idle. The idle circuit in the carb was rich enough to compensate, but as soon as the power valve and the main jet took over, the miss would come back. Also, the compression PSI readings wont tell your compression ratio. There are too many variables, cam timing, overlap, bore/stroke...etc. A 10:1 compression motor can have 250 psi of compression, and a 15:1 motor can have as little as 120 psi, depending on cam selection. Hope this helps a little.
 

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Discussion Starter · #3 ·
I will by pass the booster and see what happens. This one strumpet me! When I opened the secondary and brought the rpm up it was smooth.
 

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Discussion Starter · #4 ·
It’s not the booster. It seams like the higher the rpm the bigger the miss. The engine drops a few rpm also.
 

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check that all your vaccum ports that arent in use are plugged. check the PCV. also, disconnect the vaccum hose to the vacuum advance on your distributor and plug the port which is came off of (usually on the carb) then take it for a drive and see if the miss is gone. make sure to plug the ports however when you disconnect the vacuum advance or else the test is useless. if it makes a difference, then your vacuum advance needs adjusting.
 

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Discussion Starter · #6 ·
dave65FB
Tried ill that


<font size=-1>[ This Message was edited by: tricky on 5/14/02 10:22am ]</font>
 

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Discussion Starter · #9 ·
I still cant find the problem. Still has the miss and now my 66 stang is doing the same thing. Any idea?
 

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Is it running lean? I had a similar issue with mine when I went down in jet size in the primary thinking it was rich but turned out to be lean, increased jet size and it quit missing and felt some power gains.

I am sure you checked timeing, but maybe your advance is not coming in or something, or coming in to much for some reason.

Dont know all the details of your motor or situation, but could your cam timing be advanced or retarded, when I did my 85 gt the first time I put on the timeing chain wrong, in affect had the cam advanced.

Just some thoughts. Good luck
 

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Discussion Starter · #11 ·
Found my miss. Spent $230 on a new Edlbrock carb and no that was not the problem. Ran like sh*t halfway home. Stopped to get gas and thought I would turn the timing down a little. Ended up cranking it way up and unplugging the vacuum advance and ran perfect the rest of the way home. 230 bucks later.

See my other post.
 
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