300 dieseling
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300 dieseling
So I just purchased a 81 f100 with the 300 and I couldn't resist the offy intake and to bolt up a carb I had laying around.
So it's got a 600 cfm edel (1406) leaned out about 6% in both modes (jets and rods) and it runs good, but not perfect. It also, sadly, dieseling pretty badly now.
I've ran some seafoam through it and it helped a bit, but I'm at a loss.
Spark plugs are a good color, I don't think I'm too lean.
Just wanted to see if anyone out there had same setup and similar problems
I am also trying to pick a motor worth building, but I cant decide between 351w or a FE motor, if anyone has any suggestions.
Thanks
So it's got a 600 cfm edel (1406) leaned out about 6% in both modes (jets and rods) and it runs good, but not perfect. It also, sadly, dieseling pretty badly now.
I've ran some seafoam through it and it helped a bit, but I'm at a loss.
Spark plugs are a good color, I don't think I'm too lean.
Just wanted to see if anyone out there had same setup and similar problems
I am also trying to pick a motor worth building, but I cant decide between 351w or a FE motor, if anyone has any suggestions.
Thanks
Tuned
Joined: Jun 2003
Posts: 307
Likes: 1
From: South Florida
They had the same problems when they leaned out engines back in the early 70's to pass emissions.
They retarded the timing drastically at idle (ported vacuum) plus setting back the mechanical timing. They also used anti dieseling solenoids to make sure the throttle plates were completely closed at shutdown.
When an engine runs lean it runs hotter and any sharp object or piece of carbon can be hot enough to fire fuel vapor without the plug being fired.
Start by checking for vacuum leaks, making sure your dist advance is connected to manifold vacuum, try advancing the timing a bit and make sure the throttle plates are closed as much as possible for idle.
BTW, it's really hard to fine tune plug readings if you're using E10 gas.
They retarded the timing drastically at idle (ported vacuum) plus setting back the mechanical timing. They also used anti dieseling solenoids to make sure the throttle plates were completely closed at shutdown.
When an engine runs lean it runs hotter and any sharp object or piece of carbon can be hot enough to fire fuel vapor without the plug being fired.
Start by checking for vacuum leaks, making sure your dist advance is connected to manifold vacuum, try advancing the timing a bit and make sure the throttle plates are closed as much as possible for idle.
BTW, it's really hard to fine tune plug readings if you're using E10 gas.
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I've ran through most of that already, but I will sure look again. Nothin a can of brake clean can't find.
With the factory settings on the 600 it was quite rich. Do you think I could have leaned out too much? I can drop in old rods but I think that only changes higher rpm a/f mixture. Instill have the old jets and if anyone thinks it may be that I will re jet it again.
The advance is attached to a "tuned" port on the carb. Would taking it off the intake be better?
Thanks again.
With the factory settings on the 600 it was quite rich. Do you think I could have leaned out too much? I can drop in old rods but I think that only changes higher rpm a/f mixture. Instill have the old jets and if anyone thinks it may be that I will re jet it again.
The advance is attached to a "tuned" port on the carb. Would taking it off the intake be better?
Thanks again.
Tuned
Joined: Jun 2003
Posts: 307
Likes: 1
From: South Florida
Yes, try it on a full vacuum port or directly into the intake manifold.
Try resetting your throttle plate and idle adjustments.
Make sure the secondaries are fully closed and not binding.
Colder plugs can help too.
You can also use water instead of the seafoam to decarbon the top end.
Google for some directions on that.
Try resetting your throttle plate and idle adjustments.
Make sure the secondaries are fully closed and not binding.
Colder plugs can help too.
You can also use water instead of the seafoam to decarbon the top end.
Google for some directions on that.
Post Fiend
Joined: Dec 2007
Posts: 8,521
Likes: 16
From: Lost
Dieseling is frequently caused by having the idle RPM just a bit too high. What is it idling at?
As for engine to build, I'm a huge fan of the FE. Got a rather healthy FE in the 74 F100.
The 351W can make serious power too. Either engine type can be stroked to well over 400 CID, for some serious torque, but the FE doesn't need any special prep to allow for the longer crank throws.
In the end, it comes down to what your goal is, and what you plan to put the engine into.
Towing and low end torque, the FE wins. Mild cam and 9-10:1 CR in a 390, you're there. 400+ lb/ft at 2500 is quite common, but 4500-5000 is about all it'll turn before starting to drop off drastically. 427/428 can reach higher RPM while still making power, but they aren't easy to locate.
Higher RPM power, the 351W is easier to get there. Lots easier to find the needed pieces for the 351W to support higher RPM blasts.
As for engine to build, I'm a huge fan of the FE. Got a rather healthy FE in the 74 F100.
The 351W can make serious power too. Either engine type can be stroked to well over 400 CID, for some serious torque, but the FE doesn't need any special prep to allow for the longer crank throws.
In the end, it comes down to what your goal is, and what you plan to put the engine into.
Towing and low end torque, the FE wins. Mild cam and 9-10:1 CR in a 390, you're there. 400+ lb/ft at 2500 is quite common, but 4500-5000 is about all it'll turn before starting to drop off drastically. 427/428 can reach higher RPM while still making power, but they aren't easy to locate.
Higher RPM power, the 351W is easier to get there. Lots easier to find the needed pieces for the 351W to support higher RPM blasts.
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Yes, try it on a full vacuum port or directly into the intake manifold.
Try resetting your throttle plate and idle adjustments.
Make sure the secondaries are fully closed and not binding.
Colder plugs can help too.
You can also use water instead of the seafoam to decarbon the top end.
Google for some directions on that.
Try resetting your throttle plate and idle adjustments.
Make sure the secondaries are fully closed and not binding.
Colder plugs can help too.
You can also use water instead of the seafoam to decarbon the top end.
Google for some directions on that.
I have run down and reset my idle air adjustment screws a few times, and without a tach, I have no idea what rpm I'm running at, but I am shooting for just in-between highest possible idle with just screws and lowest sustainable idle with screws, maybe just a little closer to the latter.
It's a relatively new carb, so its pretty free moving, but I will definitely watch that a bit closer.
Any recommendations on plugs?
Thanks again.
Originally Posted by Rogue_Wulff
Dieseling is frequently caused by having the idle RPM just a bit too high. What is it idling at?
As for engine to build, I'm a huge fan of the FE. Got a rather healthy FE in the 74 F100.
The 351W can make serious power too. Either engine type can be stroked to well over 400 CID, for some serious torque, but the FE doesn't need any special prep to allow for the longer crank throws.
In the end, it comes down to what your goal is, and what you plan to put the engine into.
Towing and low end torque, the FE wins. Mild cam and 9-10:1 CR in a 390, you're there. 400+ lb/ft at 2500 is quite common, but 4500-5000 is about all it'll turn before starting to drop off drastically. 427/428 can reach higher RPM while still making power, but they aren't easy to locate.
Higher RPM power, the 351W is easier to get there. Lots easier to find the needed pieces for the 351W to support higher RPM blasts.
As for engine to build, I'm a huge fan of the FE. Got a rather healthy FE in the 74 F100.
The 351W can make serious power too. Either engine type can be stroked to well over 400 CID, for some serious torque, but the FE doesn't need any special prep to allow for the longer crank throws.
In the end, it comes down to what your goal is, and what you plan to put the engine into.
Towing and low end torque, the FE wins. Mild cam and 9-10:1 CR in a 390, you're there. 400+ lb/ft at 2500 is quite common, but 4500-5000 is about all it'll turn before starting to drop off drastically. 427/428 can reach higher RPM while still making power, but they aren't easy to locate.
Higher RPM power, the 351W is easier to get there. Lots easier to find the needed pieces for the 351W to support higher RPM blasts.
Thanks on the motor ideas. I have always wanted to build a FE motor up, but it seems the parts price will make the FE motor much more costly.
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