Hi guys
I have an AMC 401 in my Jeep CJ and it is getting about 9 MPG around town. It runs between 2000-2400 RPM around town. Engine is stock with a ring and bearing job back in the 90’s. It has a Torker single plane intake and a 650 Holley DP. I modified the carb 20 yrs ago for a big cammed sbc. I can’t remember what all I did to it.
I want to improve the MPG. The most obvious I suppose is a new carb - thinking a 750 DP Brawler. My question is - would a Performer RPM dual plane improve MPG over the Torker?
I’d like to get MPG up to around 12-15 if possible.
Thanks, Tom
AMC 401 Intake Manifold MPG
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mag2555
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Re: AMC 401 Intake Manifold MPG
Here’s the info you ask about right from the source, Edelbrock!
For your needs in your stated average power band to me the Standard performer is the way to go, not the RPM model.
The performer series love a 1” spacer and with your cid even a 780 carb will add top end without making for loss of drivability,
For your needs in your stated average power band to me the Standard performer is the way to go, not the RPM model.
The performer series love a 1” spacer and with your cid even a 780 carb will add top end without making for loss of drivability,
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Re: AMC 401 Intake Manifold MPG
Yes, the Torker was not Edelbrock's best effort. Agree with mag2555, the standard Performer dual plane would be the way to improve MPG.
No, if you want MPG, a double pumper would be the last choice. For the MPG-per-dollar on a stock 401" AMC, the loss-leader 600 CFM Edelbrock would be the way to go.
Bottom line - don't put a performance intake and carb on an otherwise stock engine; your 9 MPG is what's happening.
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mag2555
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Re: AMC 401 Intake Manifold MPG
Also being rebuilt back in the 90s I would do a compression test to see where you at because 9 mpg is way off for a stock motor, I would expect that out of a motor with Cam of 235 @ .050 intake duration, not a stock one assuming the tune is in the ball park!
This makes me have concerns that you timing chain is well stretched and retarding your timing.
This change happens slowly over time until one day you find yourself where your at!
This makes me have concerns that you timing chain is well stretched and retarding your timing.
This change happens slowly over time until one day you find yourself where your at!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: AMC 401 Intake Manifold MPG
Stock AMC intake.. Mod the plenum and add a carb adapter to mount a pre 75 4mv type GM QJet. Keep the plenum fully divided but blend mod for a better transition.
Carb adapter shound be divided too..
Check the diz curve and vacuum advance.
You could try adding a full plenum divided to the torker.
Also put a Q jet on thar.. Make sure the torker is getting
plenum heat. A cold manifold will decrease MPG.
As said check the cylinder compression, camshaft and timing chain..
Carb adapter shound be divided too..
Check the diz curve and vacuum advance.
You could try adding a full plenum divided to the torker.
Also put a Q jet on thar.. Make sure the torker is getting
plenum heat. A cold manifold will decrease MPG.
As said check the cylinder compression, camshaft and timing chain..
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Walter R. Malik
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Re: AMC 401 Intake Manifold MPG
I think a dual-plane "Performer" would help a bunch; especially with carburetor meant for economy.
The older, (no longer available new), Holley "Z" series intake was made just for good economy and it did what it was meant to do.
With its shrunken ports it was not a horsepower intake manifold.
They were gone only after a few years ... this was in the 80's and early 90's..
If you can find one ... the part number is 300-31.
The older, (no longer available new), Holley "Z" series intake was made just for good economy and it did what it was meant to do.
With its shrunken ports it was not a horsepower intake manifold.
They were gone only after a few years ... this was in the 80's and early 90's..
If you can find one ... the part number is 300-31.
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Re: AMC 401 Intake Manifold MPG
Guys - Thanks for the input. It seems obvious that a dual plane is the right intake, but I didn’t know how much it might improve MPG. I suppose it will be more efficient in my RPM range and therefore take less fuel to make power there.
I did a compression check and was surprised that two cylinders are only 90 psi! The high cylinders are 140. This engine seems to run “good”, but it looks like it’s time for a full rebuild... it will need bored I’m sure. This is the point where I will argue with my wife that I “need” Edelbrock heads to improve the gas mileage!
I did a compression check and was surprised that two cylinders are only 90 psi! The high cylinders are 140. This engine seems to run “good”, but it looks like it’s time for a full rebuild... it will need bored I’m sure. This is the point where I will argue with my wife that I “need” Edelbrock heads to improve the gas mileage!
Re: AMC 401 Intake Manifold MPG
The Torker plenum divider can be intergrated with the carb spacer.4 hole type if keeping the 650 or also common 4 hole type Qjet adapter if willing to go to a gas mizer QJet.
Make the plenum divider plate out of thick sturdy aluminum plate with tabs to attach to the carb spacer with cut slots.
Are there smaller chamber AMC cylinder heads (290,304,343,360 cid) that can bolt on, swap on the raise the CR? Replacing the tired 401 Kelvinator with a basicly healthy other smaller cid AMC V8 is a alternative to rebuilding.
A 305 chev V8 swap might be just cheaper all around.
The holley 650 can be re-calibrated for better mileage, especially with a divided plenum..
If the 401 is cammed get a short duration cam for it.
215° or LESS @.050" less is better (less cam less cid, less carb) for overall MPG.
Make the plenum divider plate out of thick sturdy aluminum plate with tabs to attach to the carb spacer with cut slots.
Are there smaller chamber AMC cylinder heads (290,304,343,360 cid) that can bolt on, swap on the raise the CR? Replacing the tired 401 Kelvinator with a basicly healthy other smaller cid AMC V8 is a alternative to rebuilding.
A 305 chev V8 swap might be just cheaper all around.
The holley 650 can be re-calibrated for better mileage, especially with a divided plenum..
If the 401 is cammed get a short duration cam for it.
215° or LESS @.050" less is better (less cam less cid, less carb) for overall MPG.
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mag2555
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Re: AMC 401 Intake Manifold MPG
Yes, only 90 psi is very bad, but so is 140!
That’s why I mentioned the timing chain as I would be expecting 160s on the good cylinders otherwise,
Don’t be so fast to jump on the aftermarket aluminum head bigger port band wagon for what your looking to do and get out of the vehicle.
In stock form at .500” lift those heads flow enough ( 216 cfm) to make 400 hp , if you step up to a 2.08” valve which I have done during valve job and then do the average intake and exh weekend bowl blend mod , then that out come of 240 cfm@ .500” lift should net you 460 hp.
This bigger valve in the chamber will also gain you back some 2 CCs to pick up the compression as a side benefit!
This work besides the Torque and Hp gain will pick up a ton of throttle response !
Don’t go with a 305 Chevy no matter how easy the swap, as you will be very disappointed with the reduction in torque !
Have you ever driven one of those suck ass V6 Chevy Blazers?
Well the 305 stuffed into that weight vehicle is not much better, and the weight of yours is on par with that!
The 401 is a great motor so don’t ditch it!
That’s why I mentioned the timing chain as I would be expecting 160s on the good cylinders otherwise,
Don’t be so fast to jump on the aftermarket aluminum head bigger port band wagon for what your looking to do and get out of the vehicle.
In stock form at .500” lift those heads flow enough ( 216 cfm) to make 400 hp , if you step up to a 2.08” valve which I have done during valve job and then do the average intake and exh weekend bowl blend mod , then that out come of 240 cfm@ .500” lift should net you 460 hp.
This bigger valve in the chamber will also gain you back some 2 CCs to pick up the compression as a side benefit!
This work besides the Torque and Hp gain will pick up a ton of throttle response !
Don’t go with a 305 Chevy no matter how easy the swap, as you will be very disappointed with the reduction in torque !
Have you ever driven one of those suck ass V6 Chevy Blazers?
Well the 305 stuffed into that weight vehicle is not much better, and the weight of yours is on par with that!
The 401 is a great motor so don’t ditch it!
You can cut a man's tongue from his mouth, but that does not mean he’s a liar, it just shows that you fear the truth he might speak about you!
Re: AMC 401 Intake Manifold MPG
A modern aluminum V6 with EFI would be a great upgrade.
Say the V6 out of a wrecked Challenger, Auto trans and all.
Say the V6 out of a wrecked Challenger, Auto trans and all.
Re: AMC 401 Intake Manifold MPG
I have a stock AMC 360 in my CJ7 with a T18. 373 gears, 32” tire.
Edelbrock Performer intake, Eddy 1406 600 CFM vacuum, 1 5/8” headers, GM style HEI
Great torque and decent power to 4500 RPM.
Gas mileage isn’t great but trips are short, stop and go style driving. The dual plane and HEI were nice upgrades. Tune the vacuum advance can for best cruise advance will help MPG. Mine likes a short centrifugal curve. 16 initial, 18 mechanical for 34 total. I add 12 more degrees vacuum advance running off manifold vacuum.
Edelbrock Performer intake, Eddy 1406 600 CFM vacuum, 1 5/8” headers, GM style HEI
Great torque and decent power to 4500 RPM.
Gas mileage isn’t great but trips are short, stop and go style driving. The dual plane and HEI were nice upgrades. Tune the vacuum advance can for best cruise advance will help MPG. Mine likes a short centrifugal curve. 16 initial, 18 mechanical for 34 total. I add 12 more degrees vacuum advance running off manifold vacuum.
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Dan Timberlake
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Re: AMC 401 Intake Manifold MPG
SAE paper 720124 "Design. Refinement of Induction and Exhaust Systems Using Steady-State Flow
Bench Techniques" by American Motors is lots of fun.
There are some suggestions about how to simultaneously improve flow performance AND improve mixture quality with the "corner" in the intake where the vertical carb bore meets the carb plenum.
Bench Techniques" by American Motors is lots of fun.
There are some suggestions about how to simultaneously improve flow performance AND improve mixture quality with the "corner" in the intake where the vertical carb bore meets the carb plenum.
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