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Discussion Starter #1
Hey all. New to the site.

So i'm stumped as to what to do.
I recently put an Edelbrock 4x4 Victor Jr. on my 350. After that install, I threw on a rebuilt 600 cfm Holley. While I was cranking it with the new parts installed, I had a pretty **** loud backfire come out the exhaust. Keep in mind the engine was running perfect (ish) with my old stock cast iron intake and old Carter carb. By perfect (ish) I mean the secondaries were needing work and no fuel ever came out of them.

So back to the point, I have spark on all 8 cylinders, timing is set, new Holley is working, new plugs/wires all around, yet no ignition on cylinders 2&4. I also have what looks like a coolant leak somewhere now from my passenger tailpipe. I have true dual exhaust so I know its coming from the 2,4,6,8 side of the block. This didn't start untill after the backfire.

So I'm here to check and see what opinions I can get. I'm guessing, and hoping, It is a bad head gasket. So far I think I have no compression in those cylinders, I still need to rent a compression tester.


By the way, the intake was passed down to me. I have no idea if it had any problems. I looked over it before I installed it and saw nothing meaning trouble. I sprayed starting fluid around the base of the intake, no idle pickup/change. Remember I have true dual exhaust.

Thanks guys.
 

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Discussion Starter #2
Forgot to mention, but NO water in oil from what I can see, and oil smells like fuel.
 

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First toss up...head gasket. Why rent a compression gage, they are not that expensive?

There is really no point in trying to diagnose with out compression readings. JP
 

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Discussion Starter #5
What I mean by no ignition, is the cylinder is not firing.
 

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Discussion Starter #6
Yea your right. I will buy one rather than renting. When I get it and use it, I'll let you know the results.
 

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Pull the valve/rocker cover on that side & inspect the valve springs/ rocker arms etc. I've seen broken rockers, push rod up through a rocker etc.
If you have the cover off. pull the power wire off of the distributor cap to kill the spark, and have a helper turn the engine to see if the rockers are working normal etc.
You need to start someplace, along with a comp test etc...
If those two spark plugs are quite clean looking, you may have coolant getting into those cylinders, from head gasket failure, or, leaking intake gasket at a coolant passage...
Since the intake is what you just installed, suspect a problem there...
 

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Discussion Starter #9
I just replaced plugs and wires. They are still brand new. I'll rip the intake off again to double check, and do what you suggested about the rockers. Thanks for the reply man
 

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Discussion Starter #10
Yes it backfired, but that was before this problem started.
 

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I wonder if the intake failed to seal, coolant leaked into the cylinders. it hydrolocked and blew the head gasket. Think you should focus on the coolant in the exhaust. That has to be fixed.
 

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Discussion Starter #12
I don't remember it having enough force while cranking it for something like that. It may be a possibility thought. Thanks for your thought.
 

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Sounds about rite and the odd fire side provided the power
even if not completely closed valves on 2-4 if they were full of coolant...

Takes a lot longer to try and move a cylinder full of water than one full of air.
Could be bent valves
 

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welcome Ryan

x2 coolant in the exhaust is the big problem..

check the spark plugs and compression, or a cooling system pressure test,, that should tell you whats up..
probly the head gasket between 2 and 4..

:texas:
 

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Discussion Starter #16
Thanks for the replies guys. I'm going to start with a compression test. Then move on to looking under the valve covers and see what they are like. I'll let everyone know.
 

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I'm leaning towards the head gasket being bad, the two adjacent cylinders aren't firing......because of a lack of compression? Where is the compression bleeding off to.....the water jacket. Is the radiator boiling over, or is it going out the tailpipe?
Buy a compression gauge, you need one.
 

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It's really easy. Spark, gas, compression. Check spark, stick your finger in the end of the plug wire, turn engine over, if you hit the ground and start convulsions, you got your spark. If the other cylinders are operating, high probability you are getting gas to those two. Now, it IS possible you may have left a couple of your socks stuffed into the intake manifold, that might stop the flow of gas on those two. Don't laugh. Especially since you have a different manifold.
That leaves compression, right? Well, unplug the main feed wire to the distributor, take out those plugs in those cylinders, have someone crank the engine, stick your finger in the hole, it will blow your finger out. No compression gauge needed. Of course, the gauge is a bit cleaner.
In review, for all gas engines, including your lawnmower, it's spark, gas compression. :biggrin:
 

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Is it possible some antifreeze got into the cylinders during the intake swap, and what you are seeing is just residual? or is this an ongoing thing? Lots of possibilities, I would at least pull the valve cover, and take a look, and then the redneck compression check. If it passes those tests, then move on to suspect the head gasket. Unless it is a lot of coolant in the cylinder it should still fire them.
 
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