400 M Spec's
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
400 M Spec's
Just want to hear your all's advice on how my motor is tuned at the moment.
I'm new to the 400m so just just checking.
I have the idle set to 800 ish rpm
Timing set at 0 deg.
Just rebuilt the 2bbl carb, and have the idle mixtures screws set out to 3.5 turns.
Its running at about 18 19 hg on the vacuum gauge.
New oil with plugs and wires,cap and rotor and air filter, fuel filter.
Its really peppy at the moment gets up and goes pretty quick, no pinging or knocking.
It starts with one pump on the pedal and doesn't diesel.
I do have one question tho, on the sticker on the valve cover it says to time to 14 deg before.
What would be a good degree to help fuel mileage but keep power?
I'm new to the 400m so just just checking.
I have the idle set to 800 ish rpm
Timing set at 0 deg.
Just rebuilt the 2bbl carb, and have the idle mixtures screws set out to 3.5 turns.
Its running at about 18 19 hg on the vacuum gauge.
New oil with plugs and wires,cap and rotor and air filter, fuel filter.
Its really peppy at the moment gets up and goes pretty quick, no pinging or knocking.
It starts with one pump on the pedal and doesn't diesel.
I do have one question tho, on the sticker on the valve cover it says to time to 14 deg before.
What would be a good degree to help fuel mileage but keep power?
Laughing Gas
Joined: Jul 2002
Posts: 843
Likes: 1
From: USA
I have the idle set to 800 ish rpm
Timing set at 0 deg.
Just rebuilt the 2bbl carb, and have the idle mixtures screws set out to 3.5 turns.
Its running at about 18 19 hg on the vacuum gauge.
New oil with plugs and wires,cap and rotor and air filter, fuel filter.
Its really peppy at the moment gets up and goes pretty quick, no pinging or knocking.
It starts with one pump on the pedal and doesn't diesel.
I do have one question tho, on the sticker on the valve cover it says to time to 14 deg before.
What would be a good degree to help fuel mileage but keep power?
Timing set at 0 deg.
Just rebuilt the 2bbl carb, and have the idle mixtures screws set out to 3.5 turns.
Its running at about 18 19 hg on the vacuum gauge.
New oil with plugs and wires,cap and rotor and air filter, fuel filter.
Its really peppy at the moment gets up and goes pretty quick, no pinging or knocking.
It starts with one pump on the pedal and doesn't diesel.
I do have one question tho, on the sticker on the valve cover it says to time to 14 deg before.
What would be a good degree to help fuel mileage but keep power?
My engine always started quicker when it had a carb on it versus now that it is fuel injected. Only difference really though is I don't have to pump the pedal. I guess the sensors have to tell the computer what to do before it starts.
Thread Starter
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
I think i will jump her up to 12 degrees and go from there.
I was wondering why i couldn't get her to get any higher than 19 on the vacuum gauge, I'm looking forward to re-timing her and see how she reacts.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
You need some timing advance to allow the fuel/air mixture time to fully ignite, with it set at 0*, it's not fully ignited until the piston is halfway down the bore, you've lost half the available thrust. The higher the rpm, the more timing advance is needed to get the full thrust.
Thread Starter
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
You need some timing advance to allow the fuel/air mixture time to fully ignite, with it set at 0*, it's not fully ignited until the piston is halfway down the bore, you've lost half the available thrust. The higher the rpm, the more timing advance is needed to get the full thrust.
Will advancing the timing make it idle any different?
And will it help improve fuel mileage?
Thread Starter
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
OK double checked my timing again today, what i thought was 0 degrees was actually more in the 12 to 14 degrees mark.
When i first checked the timing all i could see by the yellow mark that's on the crank pulley was a 0, who ever marked the pulley made a huge mark.
So i cleaned the timing marks to where i can see, and sure enough its at about 12 degrees.
So i went to see if i could get any higher on the vacuum gauge.
Here is what i found out, when i screwed both mixture screws in all the way, the truck never died till i hit the throttle.
My question is, isn't that a sign of a bad power valve?
I can get it to the 20 hg mark, but with it idling at 1000rpm, which is to high.
At 850 ish it hangs around the 19 hg mark, course its only 21 degrees here today, so i don't know if that has anything to do with it.
When i first checked the timing all i could see by the yellow mark that's on the crank pulley was a 0, who ever marked the pulley made a huge mark.
So i cleaned the timing marks to where i can see, and sure enough its at about 12 degrees.
So i went to see if i could get any higher on the vacuum gauge.
Here is what i found out, when i screwed both mixture screws in all the way, the truck never died till i hit the throttle.
My question is, isn't that a sign of a bad power valve?
I can get it to the 20 hg mark, but with it idling at 1000rpm, which is to high.
At 850 ish it hangs around the 19 hg mark, course its only 21 degrees here today, so i don't know if that has anything to do with it.
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Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
You want it idled high enough in neutral so that it will still idle in gear when you shift it into gear and at the lowest rpm it will idle in gear. This is how I do it. I've never used a vacuum gauge to do it.
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Thread Starter
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
I think my choke isn't set right.
I been noticing while trying to tune it, the choke plate is about half open when the motor is fully warmed.
I would like to keep my rpms down during idle, helps with fuel.
I been noticing while trying to tune it, the choke plate is about half open when the motor is fully warmed.
I would like to keep my rpms down during idle, helps with fuel.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Just me, but the choke is the first thing I completely remove from a carb. Never seen one that actually worked as intended. I prefer to baby the throttle a few minutes (at most) instead of relying on something that's unreliable.
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Laughing Gas
Joined: Jan 2012
Posts: 1,106
Likes: 25
OK thanks for that bit, but id like to get it to work rather than junking it.
Back to my original question. When the mixture screws are in all the way and the truck continues to run, does that mean the power valve is bad?
I thought i read that somewhere on here but cant find any info on it now.
Back to my original question. When the mixture screws are in all the way and the truck continues to run, does that mean the power valve is bad?
I thought i read that somewhere on here but cant find any info on it now.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
Can't answer that. Never had a P/V go bad. Usually when the mixture screws are unresponsive, the throttle is open too far, exposing the transfer slots in the throttle bores, this puts the carb into the transition circuit, making the mixture screws unresponsive.
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