78 400 HEI Conversion question
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Junior User
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From: Southern California
78 400 HEI Conversion question
So I am converting my 400 to an HEI setup. I know there will be some who don't like it, but I personally like the setup and I think it is cleaner having everything in one package.
I found TDC and pulled the old distributor, got the new HEI dropped in and wired up for 12V when the key is on. It fired right up and runs but it sounds terrible, almost anemic. It is chugging like a train.
I double checked the voltage to the coil and it is 15.2 vdc when the truck is running. I double checked everything that I can think of but it still runs terrible. Anybody that can share any experience or advise is appreciated.
Thanks
I found TDC and pulled the old distributor, got the new HEI dropped in and wired up for 12V when the key is on. It fired right up and runs but it sounds terrible, almost anemic. It is chugging like a train.
I double checked the voltage to the coil and it is 15.2 vdc when the truck is running. I double checked everything that I can think of but it still runs terrible. Anybody that can share any experience or advise is appreciated.
Thanks
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Junior User
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From: Southern California
I am not 100% sure. Same plugs & wires that were good before. Runs very strange, almost sounds like a train. Sounds like what I would think it would if it were running on 4 cylinders. It stumbles terribly and sputters or dies when I try to give it gas. I will try to get a video posted up if I can figure out how to.
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From: Southern California
Yeah I double and triple checked that. That's exactly what I originally thought when it initially started. I was sure I had a couple wires crossed.
Logistics Pro
Joined: May 2010
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From: Regina, Saskatchewan
You're sure the balancer read "0" AND the piston was a TDC? You might have had the balancer correct at "0", but that doesn't mean the #1 piston was at TDC. Not accusing of wrongdoing, but I've made this mistake before when checking valve stem clearances -> thought I was at TDC when I actually needed another full revolution of the crank to reach TDC.
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Junior User
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From: Southern California
You're sure the balancer read "0" AND the piston was a TDC? You might have had the balancer correct at "0", but that doesn't mean the #1 piston was at TDC. Not accusing of wrongdoing, but I've made this mistake before when checking valve stem clearances -> thought I was at TDC when I actually needed another full revolution of the crank to reach TDC.
I think my best bet at this point is to start over and make 100% sure I am at TDC. Just a little difficult because I am doing it by myself and hard to do everything at once.
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Mountain Pass
Joined: Dec 2017
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From: Nevada
Do you need to switch plugs and wires when you convert to HEI? Seems like I read somewhere that HEI systems recommended high suppression wires and at a minimum re gapped plugs.
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Mountain Pass
Joined: Dec 2017
Posts: 126
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From: Nevada
According to Holley Sniper Hyperspark instructions a “solid core plug wire should not be used”. They recommend a high quality, helically wound suppression wire such as MSD. With the plugs they recommend opening them up in .005 increments and repeatedly testing them until the engine is running smooth. Good luck.
Lead Driver
Joined: Jul 2017
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From: San Jose, CA
If you did not actually verify the timing AFTER it was running, then you're just going on pure luck. Installing a distributor where it was before is not exact. Doing so with a completely different distributor design just makes it less exact.
Definitely put a timing light on it and see where it is.
Or if you don't have a light handy, simply advance the timing to see if it gets better or worse. You can't hurt timing, and it can always go back to where you had it if it just gets worse by playing around.
Paul
Definitely put a timing light on it and see where it is.
Or if you don't have a light handy, simply advance the timing to see if it gets better or worse. You can't hurt timing, and it can always go back to where you had it if it just gets worse by playing around.
Paul
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Junior User
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From: Southern California
That was what I was looking into as well. From what I have found so far, the plug gaps can be opened up a bit but not mandatory. I can't find anything regarding the wires. It previously had a Pertronix Flame Thrower distributor so the wires plugged right in no problem, but maybe they are not what's recommended? They are ACCEL High Temp Radio Suppresion Core 8mm wires.
Thread Starter
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Junior User
Joined: Nov 2015
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From: Southern California
If you did not actually verify the timing AFTER it was running, then you're just going on pure luck. Installing a distributor where it was before is not exact. Doing so with a completely different distributor design just makes it less exact.
Definitely put a timing light on it and see where it is.
Or if you don't have a light handy, simply advance the timing to see if it gets better or worse. You can't hurt timing, and it can always go back to where you had it if it just gets worse by playing around.
Paul
Definitely put a timing light on it and see where it is.
Or if you don't have a light handy, simply advance the timing to see if it gets better or worse. You can't hurt timing, and it can always go back to where you had it if it just gets worse by playing around.
Paul
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Junior User
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From: Southern California
It was missing or hesitant when driving and accelerating and it was getting worse and worse, it would spit and pop through the carb if I would try to get on the gas, but it started and idled great.
Since it has a brand new carburetor, my uneducated guess was that it had to be spark related and...since I like the looks and performance of an HEI, I figured I might as well switch if I was going to replace anyway.
I am going to clean up my wiring in the morning and take it for a test drive to see if the new HEI solved my problems, if not then I will have a nice Pertronix Flame Thrower distributor for sale real soon...
Since it has a brand new carburetor, my uneducated guess was that it had to be spark related and...since I like the looks and performance of an HEI, I figured I might as well switch if I was going to replace anyway.
I am going to clean up my wiring in the morning and take it for a test drive to see if the new HEI solved my problems, if not then I will have a nice Pertronix Flame Thrower distributor for sale real soon...