Two dead holes. What am I missing?
Thread Starter
Instructor
Joined: Sep 2021
Posts: 103
Likes: 29
From: Fort Worth, Tx.
Two dead holes. What am I missing?
My car came with a early HEI distributor and a junk assembly line rebuilt Quadrajet. I wanted to have tach working, be able to put the shielding back on, and not have to prime the carb to start it.
So I bought new small cap electronic distributor, high output coil, wires, plugs, and new replacement Holley spreadbore.
Other than falling on it's face on taking off from a dead stop. It ran good with no misfire before repairs. It now has a bad miss. Doing a cylinder balance determined cylinders 5, and 8 are the problem. Plug 5 is clean. Compression is 170. Test plug wire and it was open. I figured must have gotten two bad wires in the set. I replaced both wires. No change. Both are still dead. On dual plane intake 5 and 8 are on same runner. I would think if problem was lean misfire the front cylinders on that side would also be lean. But all the other cylinders are fairly even. What am I missing. Vacuum gauge is steady in the green. No indication of valve or timing issue.
So I bought new small cap electronic distributor, high output coil, wires, plugs, and new replacement Holley spreadbore.
Other than falling on it's face on taking off from a dead stop. It ran good with no misfire before repairs. It now has a bad miss. Doing a cylinder balance determined cylinders 5, and 8 are the problem. Plug 5 is clean. Compression is 170. Test plug wire and it was open. I figured must have gotten two bad wires in the set. I replaced both wires. No change. Both are still dead. On dual plane intake 5 and 8 are on same runner. I would think if problem was lean misfire the front cylinders on that side would also be lean. But all the other cylinders are fairly even. What am I missing. Vacuum gauge is steady in the green. No indication of valve or timing issue.
Burning Brakes
Joined: Jan 2003
Posts: 961
Likes: 275
From: Frederick MD
My car came with a early HEI distributor and a junk assembly line rebuilt Quadrajet. I wanted to have tach working, be able to put the shielding back on, and not have to prime the carb to start it.
So I bought new small cap electronic distributor, high output coil, wires, plugs, and new replacement Holley spreadbore.
Other than falling on its face on taking off from a dead stop. It ran good with no misfire before repairs. It now has a bad miss. Doing a cylinder balance determined cylinders 5, and 8 are the problem. Plug 5 is clean. Compression is 170. Test plug wire and it was open. I figured must have gotten two bad wires in the set. I replaced both wires. No change. Both are still dead. On dual plane intake 5 and 8 are on same runner. I would think if problem was lean misfire the front cylinders on that side would also be lean. But all the other cylinders are fairly even. What am I missing. Vacuum gauge is steady in the green. No indication of valve or timing issue.
So I bought new small cap electronic distributor, high output coil, wires, plugs, and new replacement Holley spreadbore.
Other than falling on its face on taking off from a dead stop. It ran good with no misfire before repairs. It now has a bad miss. Doing a cylinder balance determined cylinders 5, and 8 are the problem. Plug 5 is clean. Compression is 170. Test plug wire and it was open. I figured must have gotten two bad wires in the set. I replaced both wires. No change. Both are still dead. On dual plane intake 5 and 8 are on same runner. I would think if problem was lean misfire the front cylinders on that side would also be lean. But all the other cylinders are fairly even. What am I missing. Vacuum gauge is steady in the green. No indication of valve or timing issue.
I would get a spark checker or spare plug and just hard ground the plug outside the chamber and start the car and watch both 5 and 8. See if you have no spark or intermittent spark.
Thread Starter
Instructor
Joined: Sep 2021
Posts: 103
Likes: 29
From: Fort Worth, Tx.
Ok, first off which distributor did you purchase? Big difference in the quality of various distributors and a dizzy is one of those parts that’s gotta be right. What I do find interesting is that 5 and 8 are 180 degrees opposite of one another in the firing order. Perhaps it’s just a coincidence but I wonder if you’re not getting a trigger signal from the dizzy pickup to fire off those two cylinders.
I would get a spark checker or spare plug and just hard ground the plug outside the chamber and start the car and watch both 5 and 8. See if you have no spark or intermittent spark.
I would get a spark checker or spare plug and just hard ground the plug outside the chamber and start the car and watch both 5 and 8. See if you have no spark or intermittent spark.
Is my vette stock?? HAHA
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From: Im not allowed to tell you
2020 C3 of the Year Finalist - Modified
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Somebody had this issue a month or so ago. They had a vacuum line hooked up to the last intake runner and it was causing it to not get a fuel mxture back there. Did you change any hoses
Last edited by Rescue Rogers; Jul 18, 2023 at 03:46 PM.
Thread Starter
Instructor
Joined: Sep 2021
Posts: 103
Likes: 29
From: Fort Worth, Tx.
No power brakes. Plugging the main source on manifold solved problem. So the leak is in dash or wipers. Those are the only changes I made. The wipers were disconnected, and dash didn't work right. The canister was bypassed. It still is. After getting wipers working the door would open then shut when started. There is one hose open on wiper door switch but I thought it is a vent. I couldn't find where it went in diagram.
