Carb Upgrade
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New User
Joined: Aug 2019
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From: Longmont, CO
Carb Upgrade
I recently got married to a 1978 F150 Supercab 2wd with a 400 6.6. It has been suggested to swap the original carb out for an Edelbrock 1406 and an HEI ignition system to make the old girl feel like youngster again. The carb is a pricy item and the truck has a bit of rust. The question is: Is it worth it? BTW, I am new to this forum and doing my own engine work, although I do know which end of the wrench to use.
Hotshot
Joined: May 2003
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From: south louisiana
If that 400 is completely stock, no, you won't do anything here. You at least need a cam upgrade first. I've done one with a Summit p/n 5200 cam but kept the stock 2 bbl intake and topped it with a Holley 500 cfm 2 bbl carb, exhausted through long tube headers and the difference was night & day. That 4 bbl and intake alone won't change a thing.
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New User
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From: Longmont, CO
Thanks for the reply Baddad. This sounds like some cud I gotta chew on. Right now the truck is working as a farm truck, but I sure would like to get some more sprint on the highway.
Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
There is quite a lot of performance left on the table in a stock ignition distributor, especially with a pickup truck, which were designed to haul very heavy loads. The advance curve is very slow and "lazy", due to the heavy springs on the centrifugal advance weights. So for example an OEM Ford truck engine might not reach full ignition advance till something like 4000 RPM or more.
If you get into the distributor and play with the "curve" a bit and bump this to 2500 or 3000, that is a very low to no cost way to improve both performance and economy. Lots of people will tend to bolt all kinds of expensive aftermarket hardware on their engine, but ignore the distributor and the timing curve.
If you get into the distributor and play with the "curve" a bit and bump this to 2500 or 3000, that is a very low to no cost way to improve both performance and economy. Lots of people will tend to bolt all kinds of expensive aftermarket hardware on their engine, but ignore the distributor and the timing curve.
Hotshot
Joined: May 2003
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From: south louisiana
Along the lines of what Tedster mentioned, have you tried bumping the initial timing up yet ? The factory 1970's setting of 6*BTC is extremely lazy. Bump it to 12*BTC and see the difference.
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From: Longmont, CO
Thanks Tedster & Baddad for the replies. Even though I am not from Scotland, I am always for keeping the money in my pocket. Timing advance is the next step. Anything else I should know about this maneuver?
Post Fiend
Joined: Apr 2002
Posts: 19,311
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From: Waterloo, Iowa
Yes, it's more complicated than just simply giving the distributor a clockwise twist and locking it down. If you do a Gurgle Search on "distributor curving" there should be a gazillion websites, YT videos and the rest of it popping up to give some real nuts and bolts "how to" stuff. It isn't particularly difficult, though Ford distributors make it moreso than it needs to be to get at the innards under the breaker plate. And it's a cut and try thing - adjust, reinstall, measure, go test drive. Etc.
Basically it's using the engine itself as a distributor machine, which were common back in the day. There are still a few guys out there that do this. Maybe under $100 still, plus shipping. It's worth doing one way or another, and you'll thank yourself everytime you drive it.
Basically it's using the engine itself as a distributor machine, which were common back in the day. There are still a few guys out there that do this. Maybe under $100 still, plus shipping. It's worth doing one way or another, and you'll thank yourself everytime you drive it.
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Who gave you the 1406 recommendation? Those carbs were terrible when Carter made them and they are still terrible now. Get a carb with annular boosters, one of the best carbs for the price that has that is the Summit 600cfm carb. It's based on the old Holley design and is a very easy to tune carb.
Hotshot
Joined: May 2003
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From: south louisiana
If you're not satisfied with the results, then try recurving the distributor.
Post Fiend
Joined: Apr 2002
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From: Waterloo, Iowa
No, but then that isn't what we're talking about, which was my point.
What he really wants to do is map out the existing curve. Because, after several decades there's no way to actually know for certain what's been installed, swapped out, neglected, broken, or is defective.
Even if (or, especially if) everything is working according to Hoyle and is barebones stock Ford pickup truck OEM equipment he will be, no doubt, much happier with the performance by recurving the rate of advance. That was my point. Sorry for any confusion.
If you're not satisfied with the results, then try recurving the distributor.
Even if (or, especially if) everything is working according to Hoyle and is barebones stock Ford pickup truck OEM equipment he will be, no doubt, much happier with the performance by recurving the rate of advance. That was my point. Sorry for any confusion.
Hotshot
Joined: May 2003
Posts: 11,141
Likes: 25
From: south louisiana
No, but then that isn't what we're talking about, which was my point.
No, that's what you were talking about. This is an open forum. It's not your private forum.
What he really wants to do is map out the existing curve. Because, after several decades there's no way to actually know for certain what's been installed, swapped out, neglected, broken, or is defective.
Even if (or, especially if) everything is working according to Hoyle and is barebones stock Ford pickup truck OEM equipment he will be, no doubt, much happier with the performance by recurving the rate of advance. That was my point. Sorry for any confusion.
No, that's what you were talking about. This is an open forum. It's not your private forum.
What he really wants to do is map out the existing curve. Because, after several decades there's no way to actually know for certain what's been installed, swapped out, neglected, broken, or is defective.
Even if (or, especially if) everything is working according to Hoyle and is barebones stock Ford pickup truck OEM equipment he will be, no doubt, much happier with the performance by recurving the rate of advance. That was my point. Sorry for any confusion.
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From: Longmont, CO
Thanks to all for your wise counsel. You guys are talking graduate school material here, but unfortunately I'm still in elementary school so I thinks is best to start with a basic tune-up. That way I can learn my way around a small part of the engine bay, again. I have to confess I once rebuilt the stock carburetor on my '70 Nova only to find out its useful life had already come to an end. Hopefully my future questions won't make you lose the will to live. Thanks again.
Post Fiend
Joined: Apr 2002
Posts: 19,311
Likes: 97
From: Waterloo, Iowa
You're doing fine, just read as much as you can get your hands on about basic carb theory, selection, setup, tuning operation. It's all available, a wealth of information online in the form of factory documentation, pretty much all of it for free. Eventually, you won't have to ask for advice (or see threads derailed or sidetracked by people with ... ego issues)
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New User
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From: Longmont, CO
Hey thanks for the reply. I am just winding my way through stuck plugs, balky rotors and bent distributor clips. It is as you say youtube is my new best friend. Although sometime it takes watching a bunch of different videos to get the idea because ,any of the guys doing these are not following the same procedure. All in all it feels great to get a measure of control over things.
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