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Old 09-16-2014, 06:37 AM
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Intake Question?

I recently put a set of GT40P heads and an Edelbrock Performer Intake (non-EGR) on my 351W. Now the #4 cylinder isn't firing.

I've checked compression in that cylinder, which is good (160PSI), performed a leak down check, swapped out plugs, plug wires, reclocked the distributor cap to make sure it wasn't a bad contact in the distributor, and it still doesn't fire.

Last night I noticed on the factory intake that there's a port on the left side of the carburetor mounting base, and also a stainless looking pan underneath the factory intake that this port seems to go to. I've attached two pictures for clarification.

Anyone know what this port/pan thing is? The Edelbrock intake doesn't have this and I was wondering if this was effecting my carburetion?
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Old 09-16-2014, 07:15 AM
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CantRepeat CantRepeat is online now
 
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Heat riser passage, shouldn't have anything to do with #4 not firing.

Are you getting spark and fuel to #4?
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Old 09-16-2014, 08:05 AM
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Old 09-16-2014, 10:06 AM
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Fuel should be the same to all cylinders, compression test proves lifters are working and that you didn't miss some plastic wrap on the intake manifold gasket for #4 port That just leaves spark. If the other cylinders are firing normally, then points/pickup, coil etc. all are in order leaving cap wire and plug as possible culprits.

Have you checked for spark at the #4 plug (remove plug, attach wire, ground plug and watch for while cranking)? If no spark, swap wires and plug with a known good cylinder. If still no spark then you have a bad distributor cap (internal crack or leakage path). What do the terminals inside the cap look like? It only takes a tiny bit of dust/moisture/scratch/etc. to screw with the spark path between the rotor and cap terminals.
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Old 09-16-2014, 07:51 PM
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Sounds like possibly a vacuum leak. I know its a silly question but you have looked at the intake runner for a vacuum port that is not capped or plugged right? Could be the intake gasket not sealing around the port and leaking from the underside. How about a pic of the intake installed?
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Old 09-16-2014, 08:55 PM
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Quote:
Originally Posted by whiskeyriver View Post
Sounds like possibly a vacuum leak. I know its a silly question but you have looked at the intake runner for a vacuum port that is not capped or plugged right? Could be the intake gasket not sealing around the port and leaking from the underside. How about a pic of the intake installed?
Whiskey,
That's the main thing I'm leaning towards right now. I used the Edelbrock Performer intake and it has a 3/8" vacuum port in the #4 intake runner (same cylinder that's cold). I teed into it with the fitting from my PCV in the valve cover. Before that fitting was plumbed into the carburetor spacer fitting. I took the spacer off when I put on the new intake.
I'm thinking that's my problem. I'm going to put the carb spacer back on, tee my PCV line back into that, then plug the #4 intake port and see how that works. Just haven't had a chance yet.

Any opinions?
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Old 09-16-2014, 09:01 PM
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Quote:
Originally Posted by Bellinghamster View Post
Have you checked for spark at the #4 plug (remove plug, attach wire, ground plug and watch for while cranking)? If no spark, swap wires and plug with a known good cylinder. If still no spark then you have a bad distributor cap (internal crack or leakage path). What do the terminals inside the cap look like? It only takes a tiny bit of dust/moisture/scratch/etc. to screw with the spark path between the rotor and cap terminals.
Spark is good on that cylinder. I've reclocked the distributor cap to see if it changed cylinders. It did not. I've switched plugs from other cylinders that were working, still no combustion....
Has to be fuel/vacuum related.
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Old 09-16-2014, 09:06 PM
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Originally Posted by CantRepeat View Post
Are you getting spark and fuel to #4?
Getting spark, not sure about fuel.
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Old 09-16-2014, 09:08 PM
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Quote:
Originally Posted by tockit View Post
Whiskey,
That's the main thing I'm leaning towards right now. I used the Edelbrock Performer intake and it has a 3/8" vacuum port in the #4 intake runner (same cylinder that's cold). I teed into it with the fitting from my PCV in the valve cover. Before that fitting was plumbed into the carburetor spacer fitting. I took the spacer off when I put on the new intake.
I'm thinking that's my problem. I'm going to put the carb spacer back on, tee my PCV line back into that, then plug the #4 intake port and see how that works. Just haven't had a chance yet.

Any opinions?
I think you are on track here.
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Old 09-16-2014, 09:12 PM
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I think you are on track here.
I sure hope so! Tired of fooling with this thing.
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