For those who changed from EFI to Carbuerator

[BarryTurano]

I got rid of my EFI system a while back. Put on a Quadra Jet. Put in a HEI Distributor. I was still having issues with bogging. Kept changing plugs finding some were fouled with fuel. Finally realized that the EFI pressurizes the fuel to a fine mist. Where as the carb does not. I went to a hotter plug that seems to have solved the problem. Put in NGK 2238 TR5 V-Power Plug. So far so good. Full rpm's where before I could not, would bog down after running for a while I would need to come off the throttle, then it would catch up. But I could not add throttle because it would bog again. Does not happen now. So by going to a carb go to a hotter plug.

 

[G_Hipster]

So your running the carb with the high pressure efi fuel pump? and it's flooding?

 

[Scott Danforth]

I got rid of my EFI system a while back. Put on a Quadra Jet. Put in a HEI Distributor. I was still having issues with bogging. Kept changing plugs finding some were fouled with fuel. Finally realized that the EFI pressurizes the fuel to a fine mist. Where as the carb does not. I went to a hotter plug that seems to have solved the problem. Put in NGK 2238 TR5 V-Power Plug. So far so good. Full rpm's where before I could not, would bog down after running for a while I would need to come off the throttle, then it would catch up. But I could not add throttle because it would bog again. Does not happen now. So by going to a carb go to a hotter plug.

You have something else going on. shouldnt need a hotter plug on a carb.

also, HEI distributors are not SAE J1171 marine rated with the exception of DUI. if your using a GM HEI unit, you just created an ignition source for a really big "BOOM"!

 

[BarryTurano]

The fuel pump was changed to a marine 7 psi fuel pump. The 15 psi pump was disconnected and bypassed. The distributor is Davis Unified Ignition for marine use, from Summit Racing. Sorry I should have put that information in before.

 

[RobertThoreson]

I feel you have a carb problem that you covered up with hotter plugs.

 

[wrvond]

So you were experiencing bogging issues then changed from EFI to carb, correct?

 

[BarryTurano]

Yes this has been going on for about 3 years. Have replaced the entire fuel system carb, pump filters fuel lines, anti siphon valves. On the ignition side went to HEI distributor then changed that to a Davis Unified Ignition. Each step would get a little better. Than it would revert back. Kept changing plugs but putting in the same plugs as the EFI system. Did a bunch of reading asked lots of questions then a light went on in my brain. That the EFI atomizes fuel more so then a carb. So why not try the hotter plugs. Put them in and so far it is working. If you look back under my name you will see a long sad drawn out history. The entire motor other than the block has been redone. Compression is good each cylinder is within 4 pounds of each other leak down test passed with no issues. The motor itself is a 1999 5.0 with 758 hours as of today. Fuel tanks have been emptied and cleaned. To put it mildly it has been a long road. I think that I see the light at the end of the tunnel and for once it is not an oncoming train. Later on this week it's supposed to be around 70. So I will make another offshore run again as a test and catch some fish.

 

[bruceb58]

What plugs were in there before? The plugs you have in there now are actually the exact heat range equivalent of the AC plug that your engine is supposed to come with.

 

[G_Hipster]

What plugs were in there before? The plugs you have in there now are actually the exact heat range equivalent of the AC plug that your engine is supposed to come with.

oh boy, if that isn't a reminder to check the basics

 

[JustJason]

Finally realized that the EFI pressurizes the fuel to a fine mist. Where as the carb does not.

That is simply not true. Flow test one some time, you'll see.

​All going to a hotter plug does is raise your combustion chamber temperatures. Raise them to much and you are going to run into pre-ignition/detonations issues, especially if your fuel quality is not primo. If you press your luck, you are going to be looking for a new engine. Your better bet is to run the exact spark plug your engine manufacture recommends and look elsewhere for your bog issue.

 

[BarryTurano]

What plugs were in there before? The plugs you have in there now are actually the exact heat range equivalent of the AC plug that your engine is supposed to come with.

Not really sure all I know is that these plugs are 1 step hotter than what was in there. I would not be surprised if I had the wrong plugs all along. If you are saying that these are the correct plugs then my problem started long ago with the parts changer that originally started this project.

 

[BarryTurano]

That is simply not true. Flow test one some time, you'll see.

​All going to a hotter plug does is raise your combustion chamber temperatures. Raise them to much and you are going to run into pre-ignition/detonations issues, especially if your fuel quality is not primo. If you press your luck, you are going to be looking for a new engine. Your better bet is to run the exact spark plug your engine manufacture recommends and look elsewhere for your bog issue.

All I have ever used is 87 octane non ethanol fuel. I have not experienced pre-ignition or run on. From what I have just read these are probably the correct plugs. Or at least I hope so. Fingers are crossed only some more time will tell.

 

[bruceb58]

All going to a hotter plug does is raise your combustion chamber temperatures.

If you look at the plug he has in there now, he has the correct plug.

Who knows, he may have also had too short of a plug in there before since he has Vortec heads.

BTW, the heat range of the sparkplug has a minimal affect on cylinder combustion temperature. It will cause detonation like you said though if it's too hot of a plug.

 

[Scott Danforth]

If you look at the plug he has in there now, he has the correct plug.

Who knows, he may have also had too short of a plug in there before since he has Vortec heads.

too short of a plug has happened on many people with vortec heads

 

[Dave-R]

I wonder if this could be a timing issue? On a lot of the newer engines, there are no timing marks. When you got rid of the EFI , you obviously changed a lot of things. There are a lot of ways to time the ignition but only one right way. Not sure if you need a shunt on the distributor or what. With the mods you have made. That is where I would start. P.S.S. If you have an old timing light, like I do. There were no degree marks on the balancer. I had to figure out the degrees BTDC I needed to give me 6 deg. About 5/8". Read the I boats timing procedure Don wrote, has helped me alot. Dave-R

 

[bruceb58]

There were no degree marks on the balancer. I had to figure out the degrees BTDC I needed to give me 6 deg. About 5/8". Read the I boats timing procedure Don wrote, has helped me alot. Dave-R

Easier just to buy timing tape or an advance style timing light. That's also useful to determine what your total advance is.

 

[Dave-R]

You know Bruce you are exactly right. That also gives me a new tool that I absolutely have to have. Now if the Admiral will approve. Dave-R

 

[Scott Danforth]

timing tape is about $5

 

[bruceb58]

If you do go for a new timing light, these are awesome. Measures dwell too if you happen to have a points engine still. Measures RPM so you now have something to verify your boat's tach to.

https://www.amazon.com/INNOVA-5568-...ie=UTF8&qid=1484163550&sr=8-2&keywords=timing

 

[Dave-R]

That is a nice timing light: Every time I need a new tool, the wife cannot believe I don't already have it. I think I can find a place to hide it the shop. Thanks Bruce.
Dave-R