25 MPG with a 408 ??? Yup!!

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:14 AM

Here's the recipe:
Magnum heads with tight quench .030. Bowls opened up. Stock valve job.
Wiesco dished pistons
Mopar Performance M1 Dual plane intake
Roller cam Compcams #20-000-9 506 lift 216 intake 224 exhaust duration.
Mopar orange box. 340 HP manifolds with a TTI 2 1/2 inch exhaust system.
Distributor that I recurved for timing all in at 2000 RPM.
This is a big one: Thermoquad 850 carb. Best carb I've tried and I've tried them all.
700R4 Chevy trany with converter lockup. But any overdrive trans would work.
3.23 8 3/4 rear end
Aluminum radiator with electric fans. Fans don't operate at anything over 40 MPH so you gain at least 1 MPG with that mod.

Posted By: DaytonaTurbo

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:22 AM

What speed are you driving at to get that mpg? With that rear gear and overdrive, you must be keeping the rpm very low...

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:25 AM

What is your (measured) CR and what gas?

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:26 AM

Running 65 to 70 MPH. At 70 I'm turning about 1800 RPM. I'm running a 28 inch tire too. 275/60 -15

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:32 AM

Calculated CR is 10.5 to one. Dynamic effective compression is 8.5 to one. Cranking pressure was 155 PSI. I always run 87 octane but on this last gas mileage run I put in 91 octane. I really don't know if it made any difference.

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:34 AM

Thanks bro

Posted By: Grizzly

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:38 AM

You did it!

I'm going to be optimistic and say you will hit somewhere between 12.8 and 13.2 seconds in the quarter.

Now let's see....

Skinny tires, lower it, and 3.08's; sounds like 27mpg to me?

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 02:41 AM

If I gear any taller I'll be able to feel the individual power pulses on the highway! LOL!!

Posted By: ademon

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 03:29 AM

Is this your everyday driver

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 11:06 AM

It's an every day driver. Now I have to complete the project. The body (except for engine bay) is ugly and the interior is shot. It's kind of a sleeper except for the big tires. Dog dish hub caps. Nothing fancy.

Posted By: Mr.Yuck

Re: 25 MPG with a 408 ??? Yup!! - 10/19/09 12:10 PM

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.

Posted By: 375inStroke

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 12:11 AM

Quote:

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.

13.0 MPG?

Posted By: phantomx

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 12:51 AM

I'd be interested in the MPH when you run it. Sounds like a good street combo.
Travis..

Posted By: CJK440

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 01:01 AM

I'm assuming this was mostly, if not all highway??

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 01:07 AM

Quote:

I'd be interested in the MPH when you run it. Sounds like a good street combo.
Travis..

I'll be taking the Duster to the drags to see what it will do on Sat. I'll report back. Hope I don't blow it up!!

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 01:17 AM

Quote:

I'm assuming this was mostly, if not all highway??

All highway except for a little drag race with a mustang on the freeway. (guess who won?)

Posted By: cogen80

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 02:36 AM

damn whats that like a 2.30 gear ratio in OD with those gears and tires?

Posted By: phantomx

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 04:48 AM

I had a 360, O/D 833, and 3.23 gears in my 67 Barracuda. That car FLEW on the freeway, 100 mph @ 3K rpm

Spent most of my commute @ 2200 in the fast lane.
Travis..

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 11:59 AM

Quote:

damn whats that like a 2.30 gear ratio in OD with those gears and tires?

2.261 to be exact! Just rumbles along at 70 MPH.

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 12:26 PM

Quote:

Here's the recipe:
Magnum heads with tight quench .030. Bowls opened up. Stock valve job.
Wiesco dished pistons
Mopar Performance M1 Dual plane intake
Roller cam Compcams #20-000-9 506 lift 216 intake 224 exhaust duration.
Mopar orange box. 340 HP manifolds with a TTI 2 1/2 inch exhaust system.
Distributor that I recurved for timing all in at 2000 RPM.
This is a big one: Thermoquad 850 carb. Best carb I've tried and I've tried them all.
700R4 Chevy trany with converter lockup. But any overdrive trans would work.
3.23 8 3/4 rear end
Aluminum radiator with electric fans. Fans don't operate at anything over 40 MPH so you gain at least 1 MPG with that mod.

one question: are you running an adapter for the t-quad on the M1 dual plane, or is it capable of bolting up a spread bore?

some thoughts on the combo, it sounds like a real fun street combo, you could probably get a fair amount more power (~20-25HP & TQ) without sacraficing fuel economy (maybe even help a bit) going to headers.

you're leaving power on the table with the stock valve job in the magnum heads. it's undersized from the factory, and there's gains to be had to opening it and the pushrod pinch up (probably ~40-50HP)....would be interesting to see the power/economy difference with some lightly massaged EQ 318 (hughes "iron ram") heads or RHS heads

from what I've heard the M1 leaves something to be desired as far as performance, that it's essentially no better flow wise than a stock piece. would be interesting to try an LD340 modified to fit the t-quad....that might net you another 15-20HP....

I've thought that comp cam (XR265HR) would make a nice street cam for a small block....it must idle pretty much near stock with 408 cubes under it.

best I've managed so far with my 318 is 18mpg...combo is stock short block, home massaged magnum heads, reground cam by bullet cams, 259/259 adv, 208/208@.050, .316" lobe lift, .506" @ valve, headers, 3" single exhaust, RPM air gap, eddie 1406.

tranny is an A500, rear gears are 3.55, tires are 27" tall...car is a 5th ave, 3950lbs w/o me. I think my carb is what's holding my mileage back now...I haven't done an all highway/freeway trip, I'm guessing it'd hit 20.

Posted By: cogen80

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 02:48 PM

Quote:

Quote:

damn whats that like a 2.30 gear ratio in OD with those gears and tires?

2.261 to be exact! Just rumbles along at 70 MPH.

i guess the 408 with a 3.23 is still pretty peppy around town right?

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 03:37 PM

probably, especially considering the 700R4 has a 3.09:1 first gear, so overall first gear is effectively like a 727 with a 4.10.

my setup, with an A500 (2.74 first gear, .69 OD) and 3.55's is like a 727 with 3.91's in first, and a 2.45 rear in OD...

Posted By: cogen80

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 03:42 PM

Quote:

probably, especially considering the 700R4 has a 3.09:1 first gear, so overall first gear is effectively like a 727 with a 4.10.

my setup, with an A500 (2.74 first gear, .69 OD) and 3.55's is like a 727 with 3.91's in first, and a 2.45 rear in OD...

good point. i forgot about that. at first it sounds like a waste until you really look at the trans and gears.. not bad.

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 04:02 PM

Quote:

Hey Patrick, I do have an adapter on my M1. It's a square bore manifold. I know I left at least 50HP on the table but I wanted a stock idle with some hit to it. I debated having a three angle valve job but just ended up having the bowls hogged out and doing a nice bowl blend. This experiment was to try to make the engine as efficient as possible with high performance as a secondary goal. I know I'll want more power in the future. I have a new crosswinds manifold I might try out. If you are not running a thermoquad I can almost guaranty you'll get 2 to 3 MPG better gas mileage with one. They are just outstanding at atomizing the fuel at small throttle openings.

I followed this article by dulcich porting my mag heads....looking at his results, the bowl doesn't look like much of a restriction, the undersized valve job and especially the pushrod pinch seemed to me to make the biggest difference.

one thing with the air gap/crosswind, it's taller than stock (I presume the M1 is a low rise (stock height) intake if you can fit a stock air cleaner with an adapter). right now I have about 1/2" between my stock air cleaner and hood in my M body with an RPM air gap. you will probably be better served with an LD340, as they can be modded to use a spread bore carb without an adapter, and are about the same height as an Air gap (it's essentially the precursor to the eddie RPM manifold).

to all the people questioning "why?" well, some of us like to drive our cars a lot. I pulled my old 360 combo and sold it, it worked very well for what it was, pushing my porky M body to keep up with a 5.7L LX car, but with my existing OD tranny and rear gear could manage a best of 15 MPG in my daily commute (about 60/40 hwy/cty). I built up my roller cammed 318, and on the butt dyno it feels as strong as my old 360 combo, while having 4" more vaccuum at idle (it has a very stockish idle now, which I like), and increasing my mileage 20% (up to 18 in my commute).

power and economy are not mutually exclusive. look at the Z06 vette-- 505HP out of a [Email]218@050[/Email] hydraulic cam, and over 20mpg highway, or my friend's SRT8 300C--high 12's out of a 4200 lb car, that manages ~22mpg highway.

what's available for a t-quad as far as choke options? are they all the well style, or can you find some with an electric choke? I've thought about switching my airgap/600 eddie to an LD340/tquad or qjet combo, figuring I wouldn't lose performance, but perhaps gain economy. of course, I've got about 80% of the parts to convert my car to MPI, just don't have the time to sort it all out.

I think you could help both power and economy with headers. another thought I've had for economy and power was high compression, short timing cam with wide LSA, high flowing heads, and use water injection to suppress detonation.

something like ported RHS magnum heads, flat top pistons, tight quench (would be about 11.5:1), a single pattern cam with maybe 2-4 degrees more intake .050 duration than yours, but ~.540 lift on a 112 or 114 LSA installed at 108,
headers, LD340, and t-quad with water injection....I'd expect it to be in the 470-500 HP range, with a peak just north of 5000 RPM, mondo TORK! mild idle, and something that could squeak out over 20 mpg on a highway trip.

Posted By: Fury Fan

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 04:03 PM

Quote:

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.

Quote:

putting a 2.261 gear in a muscle car that you spent all kinds of $$$ building a 408 storker is like neutering your prize race horse because you want him to live longer.... if you wanted MPG's you could have just rebuilt a 318 and used a 2bbl throttle body.

Dang, Swingin', why you gotta rain on his parade?

It's his daily driver. The guy built a combo with a good sweetspot

he should be congratulated, not ridiculed.

Go put 4.88s in everything you own and poke your fuel tank with an icepick so you can use as much gas as you see fit.

Posted By: Mr.Yuck

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 04:14 PM

Quote:

Quote:

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.

Quote:

putting a 2.261 gear in a muscle car that you spent all kinds of $$$ building a 408 storker is like neutering your prize race horse because you want him to live longer.... if you wanted MPG's you could have just rebuilt a 318 and used a 2bbl throttle body.

Dang, Swingin', why you gotta rain on his parade? It's his daily driver. The guy built a combo with a good sweetspot he should be congratulated, not ridiculed.

Go put 4.88s in everything you own and poke your fuel tank with an icepick so you can use as much gas as you see fit.

hahaha no, not to rain but why build a 408 if you want mpg's? go buy a car that gets good gas milage.

Posted By: Jerry

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 05:08 PM

let me know when your ready to switch over to efi. get a tunnel ram bottom on there with a custom top and some nice atomizing injectors and you could probably see another 2-3 mpg with alot of tuning and a wideband. with the efi you can really dial in what your engine needs, plus you can adjust your timing based on what your engine needs.

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 05:14 PM

Quote:

let me know when your ready to switch over to efi. get a tunnel ram bottom on there with a custom top and some nice atomizing injectors and you could probably see another 2-3 mpg with alot of tuning and a wideband. with the efi you can really dial in what your engine needs, plus you can adjust your timing based on what your engine needs.

Jerry, you don't know how much I'd like to do a FAST EZ fuel injection set up. It would be awesome! It's so darn expensive though. Got any low buck set ups for a buddy?

I already use a LM-1 for tuning

Posted By: Jerry

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 05:20 PM

yeah, i do the intake conversions and can set you up with a megasquirt controller. best bang for the buck efi system out there. tuning wise all the efi systems are similar. on setup, you just need to build a harness for the megasquirt.

Posted By: DaytonaTurbo

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 06:17 PM

That low first gear must really do wonders for helping getting things moving off the line. I bet it's making a lot of difference to your launch with those 3.23's. 3.23's with a 727 1st gear would be pretty weak in comparisin IMO.

For the thermoquad, member DEMONSIZZLER sells a divorced electric choke assy similar to what the newer edelbrock carbs run. It's adjustable and bolts to the carb, not the intake.

I find the thermoquad does deliver good mileage, however I've found it to give interesting results on the wideband o2. With the easily adjustable primary metering rod tree, it's not hard to tweak it to get your a/f's in the range you want them to be.

What kind of idle a/f's are you getting with your thermoquad? I've found mine loves to idle lean when the motor is up to temp.

FWIW I've got a megasquirt system nearly ready to go for mine as well. I really wanted to get it in the car this year, but between having R&R'd my motor for an overhaul and my transmission dying a slow death I just did not have the time to get around to it.

I bought my stuff a couple years ago already, but at the time I bought a MS-2 and a prefabbed harness from diyautotune.com I could have made the harness myself, but with the prefabbed one basically you just have to attach your sensor connectors and run the wires to where you want them. Looks like it'll save a lot of time, mess and thinking.

Posted By: QuickDodge

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 06:22 PM

Very impressive mileage figures! I'd love to have a car like that for regular driving.

Overdrive transmissions are a great idea. Much more comfortable highway cruising. Old school folks can say what they want, but some newer components are better!

I had an M-body years ago that came from the factory with a 2.2? ratio rear end. With a 3 speed 904, 998 or something like that it was a dog on take off. I never drove it on the highway, but a lot of M-body owners claim they can get 20+mpg with the 2.2 and 2.45 axle ratios.

For what it's worth, some Camaro's came with an overall gear ratio of just under 2 to 1. With a 408 and a fairly light weight car, you could probably pull these kinds of gears. I doubt it would make much difference in gas mileage. If you happen to have an unused higher gear axle laying around and want to experiment.....I'd be interested in the results!!

Have you kept a record of average fuel consumption?

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 06:32 PM

Quote:

Very impressive mileage figures! I'd love to have a car like that for regular driving.

Overdrive transmissions are a great idea. Much more comfortable highway cruising. Old school folks can say what they want, but some newer components are better!

I had an M-body years ago that came from the factory with a 2.2? ratio rear end. With a 3 speed 904, 998 or something like that it was a dog on take off. I never drove it on the highway, but a lot of M-body owners claim they can get 20+mpg with the 2.2 and 2.45 axle ratios.

For what it's worth, some Camaro's came with an overall gear ratio of just under 2 to 1. With a 408 and a fairly light weight car, you could probably pull these kinds of gears. I doubt it would make much difference in gas mileage. If you happen to have an unused higher gear axle laying around and want to experiment.....I'd be interested in the results!!

Have you kept a record of average fuel consumption?

best I got stock with my 5th ave (2.2 rear gear) was 25mpg at a constant 75-80mph going across michigan on a warm summer day. more typical was 23.

my 5th with the 360 and loose converter with the 2.2 wasn't too bad on takeoff, was a little soft, but it was a beast from about a 15-20mph roll....

FWIW GmachinedartGT (I think that's his handle) has a stroker small block with a solid roller, he runs 26" tires, a 2.94 gear, and a 904. IIRC he gets ~17-18mpg running at freeway speeds, and can still click off low 12 second quarters...not bad considering his tire/wheel package and suspension is set up for handling, not drag.

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 06:43 PM

Quote:

Quote:

let me know when your ready to switch over to efi. get a tunnel ram bottom on there with a custom top and some nice atomizing injectors and you could probably see another 2-3 mpg with alot of tuning and a wideband. with the efi you can really dial in what your engine needs, plus you can adjust your timing based on what your engine needs.

Jerry, you don't know how much I'd like to do a FAST EZ fuel injection set up. It would be awesome! It's so darn expensive though. Got any low buck set ups for a buddy?
I already use a LM-1 for tuning

I don't think the FAST EZ system is sophisticated enough to make it worthwhile, it's still a TBI system, so you have potential wet flow fuel distribution issues. it doesn't control timing. if you're serious about EFI, I'd go full multiport. batch vs. sequential is much less of an issue.

for your setup, I like jerry's idea of a tunnel ram base, build a plenumn and use a mustang, LS1, 5.7 hemi, etc style throttle body at the front or side. ford motorsports 30lb/hr injectors should feed your mill, and would be easy to come by on ebay or craigslist.

Posted By: QuickDodge

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 06:56 PM

Reasons I like this Duster:

1. Dusters are nice looking cars. A LOT BETTER looking than any gas sipping Honda Accord!

2. With a 408, automatic and 3.23 gears it should run respectably on the drag strip. (and out run the Honda!)

3. A-bodies can be set up to handle and corner VERY well.

4. It cost a lot less than a new car that's not even half as cool.

5. At 25 mpg, a normal guy on an average budget can afford to actually drive it everywhere and enjoy it!! Antique cars in the garage are ok, but the real fun is in driving them!

Posted By: Fury Fan

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 08:30 PM

Quote:

FWIW I've got a megasquirt system nearly ready to go for mine as well. I really wanted to get it in the car this year... but I just did not have the time to get around to it. I bought my stuff a couple years ago already...

Misery loves company! I've got 2 MS units sitting on the shelf, for at least 9 months, and only need time to get it done. Just need a round tuit!

It would sure be nice to find some more Mopar guys running Megasquirt (and a local guy would be a Godsend!)

Posted By: cogen80

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 09:49 PM

Quote:

FWIW GmachinedartGT (I think that's his handle) has a stroker small block with a solid roller, he runs 26" tires, a 2.94 gear, and a 904. IIRC he gets ~17-18mpg running at freeway speeds, and can still click off low 12 second quarters...not bad considering his tire/wheel package and suspension is set up for handling, not drag.

i thought he said he went 12.7 and gets like 13 mpg.

Posted By: DaytonaTurbo

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 11:01 PM

Quote:

Quote:

FWIW I've got a megasquirt system nearly ready to go for mine as well. I really wanted to get it in the car this year... but I just did not have the time to get around to it. I bought my stuff a couple years ago already...

Misery loves company! I've got 2 MS units sitting on the shelf, for at least 9 months, and only need time to get it done. Just need a round tuit!

It would sure be nice to find some more Mopar guys running Megasquirt (and a local guy would be a Godsend!)

Well maybe we'll get around to ours at the same time.

Over the winter I at least want to finish assembling the MS unit, drill/mount my fuel rails and get some of the plumbing started so at least I'll be good to go next spring.

Posted By: DynoDave

Re: 25 MPG with a 408 ??? Yup!! - 10/22/09 11:49 PM

Quote:

Quote:

why build a 408 to run 13.5? Who care about mpg...make it run right and you might be able to pull a 13.0.

Quote:

putting a 2.261 gear in a muscle car that you spent all kinds of $$$ building a 408 storker is like neutering your prize race horse because you want him to live longer.... if you wanted MPG's you could have just rebuilt a 318 and used a 2bbl throttle body.

Dang, Swingin', why you gotta rain on his parade? It's his daily driver. The guy built a combo with a good sweetspot he should be congratulated, not ridiculed.

Go put 4.88s in everything you own and poke your fuel tank with an icepick so you can use as much gas as you see fit.

Thank you.

Sounds like a great combo dmerc!

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 12:20 AM

Quote:

IS THERE A TUNNEL RAM INTAKE THAT BOLTS UP TO MAGNUM HEADS?? Sorry about the caps.

AFAIK the pattern is the same as any SB so I'd think a SB tunnel ram would fit.

Posted By: stumpy

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 02:32 AM

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 02:35 AM

I deleted it just as you were posting. Didn't know if my sense of humor would be appreciated or not

Posted By: DJVCuda

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 02:45 AM

Quote:

Quote:

IS THERE A TUNNEL RAM INTAKE THAT BOLTS UP TO MAGNUM HEADS?? Sorry about the caps.

AFAIK the pattern is the same as any SB so I'd think a SB tunnel ram would fit.

you could redrill a t-ram...

i bet my eddy street ram would be a good candidate

FWIW - I have 3.23's and a 26" tall tire, running 3400 @ 75 and get a best oof 16 and average of 14 ( playing with it ) with my t-ram and mild 360 - on the 300 mile round trip to Carlisle every year..

I also run 12.56 in the quarter.

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 02:50 AM

I alway thought a TR would be unstreetable but there was a good thread a ways back & people shared that they are in fact VERY streetable w very little work & the visual appeal has gotta be good (or even a stub stack on a single carb sticking thru the hood).

Posted By: HotRodDave

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 03:54 AM

Quote:

Quote:

IS THERE A TUNNEL RAM INTAKE THAT BOLTS UP TO MAGNUM HEADS?? Sorry about the caps.

AFAIK the pattern is the same as any SB so I'd think a SB tunnel ram would fit.

Magnum intake bolts go straight up and down unlike the ones on an LA that go in almost straight into the intake face of the head. I -frequently re-drill the heads to use the LA intakes, the other way around looks sloppy.

Posted By: hotlines

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 04:17 AM

I'm have a W2 head 340 roller motor with low compression in my 64 Signet and could sure use an OD, I have a built 700R4 sitting in my shop. Where exactly can I get the conversion stuff needed to pull this off. Thank you in advance

Posted By: DaytonaTurbo

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 04:53 AM

I know wilcap sells the adapter plates to make it work. Does jw sell an ultrabell that'll fit a 700R4?

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 10:47 AM

Quote:

I'm have a W2 head 340 roller motor with low compression in my 64 Signet and could sure use an OD, I have a built 700R4 sitting in my shop. Where exactly can I get the conversion stuff needed to pull this off. Thank you in advance

Several ways to do it but I used a plate from Wilcap. The rest you have to fab up yourself.

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 10:56 AM

Quote:

Reasons I like this Duster:

1. Dusters are nice looking cars. A LOT BETTER looking than any gas sipping Honda Accord!

2. With a 408, automatic and 3.23 gears it should run respectably on the drag strip. (and out run the Honda!)

3. A-bodies can be set up to handle and corner VERY well.

4. It cost a lot less than a new car that's not even half as cool.

5. At 25 mpg, a normal guy on an average budget can afford to actually drive it everywhere and enjoy it!! Antique cars in the garage are ok, but the real fun is in driving them!

Thanks quickdodge, you hit the nail on the head. it's a blast to drive this car everywhere. I haven't run a mixed driving check yet but I expect it to deliver 20 MPG in town if I baby it.(hard to do ya know!) I should be listing some quarter mile times on Saturday if all goes well.

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 11:27 AM

Quote:

IS THERE A TUNNEL RAM INTAKE THAT BOLTS UP TO MAGNUM HEADS?? Sorry about the caps.

yes....if you redrill them to LA pattern

Posted By: CJK440

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 12:13 PM

Quote:

Quote:

I'm assuming this was mostly, if not all highway??

All highway except for a little drag race with a mustang on the freeway. (guess who won?)

I'd be interested in how the car does around the town. Thats where the T-quad will really shine. Steady RPM on the highway, you probably wont see much mpg diff with any other carb if A/F ratio is the same. But from stop light to stop light, the tiny primaries will be better suited.

How it will work with the tranny & rear ratios will be interesting.

Posted By: Dodgem

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 06:19 PM

curious as to why you did not run 34 with 11 vacuum added on to achive the same cruise advance but have a little more WOT for more performance???

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 06:45 PM

Everything I have read says that the more efficient combustion chamber of the magnum heads needs less advance. This also helps lower pumping loss at cruise. When I take it to the track I'll play with the timing to see if i can squeeze a little more out of it.

Posted By: Fury Fan

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 07:21 PM

The more efficient the chamber and port design, the less time you need for combustion (meaning, less ign advance), the less negative torque that will be created, and the less heat that will be lost to the cooling system.

All adds up to more fuel efficiency.

Posted By: Rapid340

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 07:28 PM

The less timing required, the more efficient the combustion system (heads, chamber, piston, ignition).

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 07:43 PM

my mild 318 (combo listed above) seems to like 32 or so degrees of total advance for best power and economy. I'm using a 17 degree vac advance can on the dizzy, for a total of 49 degrees of cruise advance.

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 07:48 PM

I wonder what will make more power? 87 octane with a little timing pulled out or 91 octane with a couple degrees more timing advance??

Posted By: RapidRobert

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 08:49 PM

Quote:

I wonder what will make more power? 87 octane with a little timing pulled out or 91 octane with a couple degrees more timing advance??

Posted By: racincuda

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 09:59 PM

Posted By: HotRodDave

Re: 25 MPG with a 408 ??? Yup!! - 10/23/09 11:25 PM

Depends on if what the engine needs. Normally in my experiance the magnum heads work best 32-34 mechanical advance. When I had my 318 mpg motor it really ran better with a very short mechanical advance and a short vaccume advance. If I remember the sweet spot for mechanical was 18 initial and 32 total. The shortest vaccume advance can I found was 8.5 and it did the best, I think it would have really liked a couple less total degrees. Once I got it all tuned right it ran the same on 87 octane as 93 and neither one wanted more advance. I am now at 3000 ft elevation so that lowered my preasure a hair.

Posted By: ThermoQuad

Re: 25 MPG with a 408 ??? Yup!! - 10/24/09 04:36 AM

Great work

I wonder if a six pak would do even better. I am glad to see someone put some thought into having a fast [but old] car & gas mileage just like new tupperware can... [Tupperware refers to a corvette-plastic container with an airtight lid...]

Have you put synthetic fluid in the diff??? Anything synthetic for lubricants will help raise the mileage as well.

I have a very strong 416 six pak in an E body with overdrive that got 16 mpg going to & from Carlisle 180 miles each way. Speed was 55-70 mph mostly on cruise control. I'd show the naysayers my log book for the car but that's classified info.

Posted By: Magnum

Re: 25 MPG with a 408 ??? Yup!! - 10/25/09 11:49 AM

Quote:

putting a 2.261 gear in a muscle car that you spent all kinds of $$$ building a 408 storker is like neutering your prize race horse because you want him to live longer.... if you wanted MPG's you could have just rebuilt a 318 and used a 2bbl throttle body.

I love the idea of cubes and tall gears. GM did it with the previous generation Camaros. 5.7L with a 0.50 overdrive. 25-30 mpg and 13 second quarters.

Small engines can't be run down the highway with tall overdrives. Most 4 cyl cars are above 3000rpm on the highway.

Plus a 318 and a 2 barrel would be gutless compared to Dmercs combo. Power and mileage, that's a goal worth chasing.

Quote:

curious as to why you did not run 34 with 11 vacuum added on to achive the same cruise advance but have a little more WOT for more performance???

Magnums engines will not take advance like the LA headed engines. I've run my best times in my 5.9 Magnum at 30 deg total.

Great work Dmerc. Your 408 has surpassed my best MPG of 23. With some similarities. I'm also Magnum headed but with stock cubes, 360. Also overdriven but with 5 speed manual and 3.55's.
In a truck plagued with poor aerodynamics but as you I also firmly believe in vacuum advance. I run 18 vacuum on top of my 30 mechanical for a total of 48.

Keep us posted on your 1/4 mile results. I predict you will have no problems surpassing 14's.

Posted By: dmerc

Re: 25 MPG with a 408 ??? Yup!! - 10/25/09 05:11 PM

Thanks Magnum. I did go to the track yesterday and it did not go well. Car would launch flood out die. did it twice. I think the choke pull off is the culprit. It also functions to slow the opening of the secondary air valve. I've taken the choke pull off... off. This only happens at the drags when I really hammer it quickly.(in front of hundreds of people!) I'll know next week. I'm going to try again!!!

Posted By: Skeptic

Re: 25 MPG with a 408 ??? Yup!! - 10/23/12 09:52 PM

Shameless

with hopes for some updates

Posted By: patrick

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 01:00 PM

dmerc's last post was over a year ago...you might be waiting a while

Posted By: Rug_Trucker

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 01:06 PM

Posted By: 63stabamatic

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 02:17 PM

Sounds like a great combo! Looks like you're really on top of this project, but I have to ask. Is your odometer/speedometer calibrated?

Posted By: Skeptic

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 05:51 PM

Quote:

dmerc's last post was over a year ago...you might be waiting a while

Oh well

interesting thread anyways.

Posted By: Kern Dog

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 06:07 PM

Way to go, Dmerc.

These great cars do NOT have to be "single purpose" machines. Efficiency crosses many lines and a clean running engine can be fast and fuel efficient.
Late model cars are compromises of the big 3 factors: Emissions, economy and performance. YOUR efforts are in line with the OEMs, and it should be congratulated. Nice work.
My car will never see 25 mpg even driving downhill with 90 series tires and the trans in neutral. I do plan on improving the combination to maximize mpgs, but there are some points to which I will not concede. I will not modify the exterior, change the tires or switch to a smaller engine. The T-Quad carb could be the single most effective modification to improve mpgs. Your efforts are paying off, and posting them here will certainly help others reach their goals.
Thank you.

Posted By: Hooligan

Re: 25 MPG with a 408 ??? Yup!! - 10/24/12 10:06 PM

Hey! Does a high volume oil pump have an adverse affect on the MPG's, as opposed to a stock oil pump???!

Posted By: Dakota_Don

Re: 25 MPG with a 408 ??? Yup!! - 10/25/12 02:52 AM

i would say yes to the high vol oil pump.. a stock pump is fine for the street

good job on the mpg, i wanna do the same with my 318 dart..

Posted By: Dodgem

Re: 25 MPG with a 408 ??? Yup!! - 10/25/12 02:53 PM

It's More to do with pressure. the high volume pumps tent to build more pressure and building pressure takes power so some parasitic loss! all ads up.
But for safety at RPM a like a high volume pump with and light or adjustable releif spring so you can set your max pressure at say 65 not 110 but it still has the volume when called for.

this is with 1/2 15/40 and 1/2 5W 50 motor was cool
http://www.youtube.com/watch?v=kmvZNkBHfUU&feature=plcp

this was on enital start up this summer went to 68 I think dead cold.
Course the alt quit just as I mentioned it wireing issue took ot the regulator all fixed now.
http://www.youtube.com/watch?v=YvhENA8svJY&feature=plcp

Posted By: Jerry

Re: 25 MPG with a 408 ??? Yup!! - 10/25/12 04:08 PM

it has to do with volume as well you can't build pressure if your bearings are sloppy and leaking all over. if you have tight bearings then no need for a high volume pump. hydraulic horespower is calculated by hhp=pressure*flow/constant.

therefore both components are equally important when figuring parasitic loss. if you don't need a high volume pump don't use it.

Posted By: dOrk !

Re: 25 MPG with a 408 ??? Yup!! - 08/27/20 11:42 PM

Did someone say larryLOVEits 408 was getting 25 plus ?

With THAT FACT and his installation of those greyvvelore seats ...

I’ll bounce my offer up aNutter 1k$

Posted By: Fat_Mike

Re: 25 MPG with a 408 ??? Yup!! - 08/28/20 04:19 AM

Originally Posted by Doc Fiberglass

Did someone say larryLOVEits 408 was getting 25 plus ?

With THAT FACT and his installation of those greyvvelore seats ...

I’ll bounce my offer up aNutter 1k$

Hey Bro! Not sure what brought this up tonight, but 8 years ago was "in the past." Dudes don't talk about that stuff...

Posted By: dOrk !

Re: 25 MPG with a 408 ??? Yup!! - 08/28/20 04:25 AM

AM ... FM ... I saw someone viewing the topic and decided to post...

Dudes don’t talk about what ?

Posted By: TC@HP2

Re: 25 MPG with a 408 ??? Yup!! - 08/28/20 01:14 PM

I used to get high teens with the 440 in my 3/4 ton crew cab. Yeah, its entirely possible to hit 20s in a car.

Congrats!

25 MPG with a 408 ??? Yup!!