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Opeler
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4 Posts
Discussion Starter · #1 ·
Hi guys...haven't posted in a while but i need some help. I had the GT at school doing a lot of work on it. I redid the engine a bit...new rings and gaskets...previous owner had done a bunch of work to it already. Anyways...school is over and it's sitting at home but for some reason it's only running on two cylinders. This is the first engine rebuild i've ever done and would like some pointers on where to start diagnosing this. I've already checked the plugs...got good spark and everything....i can smell gas on the plugs. I lined up the timing mark and everything. I have no idea how to tune a carburator but i'm thinking it's not that because the back two cylinders run...just the front two don't. Anyways...if anyone can give me some pointers on where to start that would be great.

Thanks
Brandon
 

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Member
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648 Posts
recheck your valve adjustments...if you over tightendown the rocker, then the valves won't close. It happened recently to someone else on the list.
Best of luck!
Jc
 

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Opeler
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101 Posts
do a compression test on the cylinders ,,, remember ,, suck, compress, bang, and blow....

suck: intake valve opens as piston moves down, and fuel & air is sucked in. compression: intake valve closes as piston move up & compress fuel/air.
bang: spark plug fires fuel/air. at tdc.
blow: as piston moves up it pushes exhaust out..

in short sounds like you have a valve open.
 

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boomerang opeler
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5,648 Posts
have a good look at the timing as they are a funny setup on these beasties ,
its very easy to have the plug wires crossed and have 2 right and 2 wrong ,like if you have the rotation (wrong way is counter clockwise i think )so say 1 and 4 would run but 2 and 3 would not
 

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Opeler
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4 Posts
Discussion Starter · #5 ·
i've done a compression test and all cylinders have good compression...90-100 psi...plug wires are right too...checked the manual for that one many times. The cylinders that aren't firing are 1 and 2...3 and 4 fire just fine. When i take the plugs out...cyl 1&2 are perfectly clean and new...3&4 have soot on them.
 

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Member
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1,735 Posts
90 to 100 lbs. is low for this eng. 130 to 150 is the range you should look for . If plugs are clean and dry then valves may not be opening , or major
vacuum leaks . Check your vacuum with a gauge next. Hope this gives
you a starting place :D
 

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Member
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199 Posts
i had a similar problem to this when i rebuild my motor. I skipped a tooth on the cam gear. witch made cly 3 and 4 not fire. Also my dizzy was 180 degs out causing it give lower compression numbers :eek:
 

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Registered
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2,733 Posts
Yeah, recheck cam timing, valve lash, and ignition timing. But first study up on how to time all this, understand it in your head before you pull the valve cover. It is strange, but once you really understand it, you are good to go.
The little flyer from OGTS that comes with engine parts tells it like it is in layman's terms, although I read it once and said "huh?" and read it again and again, looked at the pictures, looked at 'em again, and then it made sense. Don't be in a hurry. When you finally "get it" you can do it in your sleep.
 
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