Cruise friendly low 12's with a 340 Dart

-
W

watchdoc

Well-Known Member
Joined
Oct 20, 2008
Messages
121
Reaction score
63
Location
Greenville, NC
Hey Everyone, after years of bracket racing my dart, I'm doing more cruising and car shows now so my goal is a pump gas cruiser that runs low 12's.

Here's my current setup

71 Dart Swinger
73 340 cast crank engine
stock J heads
clutch fan and 180 Tstat
stock 340 manifold
Weind action plus 8007 dual plane intake
Purple shaft 284/484 cam
Holley 3310 750 (70 primaries #5 powervalve, 10" vacuum at 750rpm)

727, 8 3/4, 3.23 suregrip 489 case
GER 11" converter 1500 stall/1800 flash (i don't like it),
BFG drag radials

Anyway, the car runs 13.9-14.0 and gets 10-12mpg. i would like to run low 12's and get 15-16mpg with a more cruise friendly converter.

So far, i figure i need headers (TTI or Dougs), a different converter (suggestions welcomed), and maybe the Eddy 850 carb with the small primaries and giant secondaries.

I wanna keep the 3.23's for cruising BTW.
 
Low 12's and high mileage really do not go together well. This is a bigger problem with small blocks. A tad more so with a short stroke 340/318. Stroking the engine is an excellent soulution to easy power to move the car well, less effort.

I think they best way to go about getting this dual purpose machine into a higher mileage area would be an overdrive trans and a set of 4.30 gears which pan out at about a 2.96 in over drive.
Or 4.56's that feel like 3.14's in overdrive.

The Edelbrock spreadbore carb IMO is a good idea. They have a version of the Quadrajet. It's hard to ignore brand new, but, if your anygood with tinkering, the T-Q is offered in 800 & 850 sizes, are cheap by compare, easy to rebuild and take to a few mods very well. Very tuneable if your willing to sort out rods and jets. I have bent up AFB rods to suite. There 3/4 inch to long for a T-Q, but with the simple bend, the veriaty sores through the roof.

Further info can be had here; http://thermoquads.com/
You tell'em I sent you over from here for help. "Dave" the owner/builder is a good man.

Your goal is not an easy one to do.
 
Also, i'm running the mopar Chrome box, taylor wires, and bosch platinum plugs.

Looks like i'm gonna get a Dynamic 9.5" converter as pers shaun.

Still haven't decided on headers but I'm leaning towards TTI's.

Still contemplating the carb and instake setup. Also considering having my J heads ported.

Keep the ideas coming. Of course, I'd like to keep this as low buck as possible.
 
Well, don't port the J heads just yet. You can run 12's on unported J heads with a 340. The extra arm of the stroker would need more port volume, but I think it would be workable towards your goal of mileage while still having enuff to power the car into the 12's.

IF you have the coin for tti's, I'd do it.

I like the idea of a spreadbore carb myself, but to each his own. The tiny T-Q primarys (Or QJ's) will help in the mileage diraction. It may be marginal, but if you keep up with all the little things, it will add up.

If you didn't mind the cost of a roller, I'd say go roller for mileage help since it's rolling over the lobe instead of sliding on iol. But the price difference is huge.

For mileage, try a multi spark box. This is the one area I find them superior to the MoPar boxs. Otherwise, theres no difference.

Intakes can be a funny thing in a build like this. For a single plane intake, I'd look no further than the MoPar M-1. The RPM is the dual plane of choice, but doesn't fit a spreadbore unless an adapter plate is used. Adding height. Can your hood line handle it? Spacers are generaly 3/4 inch.
 
i would Sugest a 2500 stall 11" converter 391/410 gears 28" tire MSD ign.tti headers 2.1/2" exaust. 100 Shot NOS you will be fine
 
Don, 3.91's and 4.10's aren't exactly cruise friendly. A 518 would solve this but i really didn't want to cut the car.

N20 would certainly do the trick but I would prefer the N/A route.

The stroker kit sounds interesting but pricey.

I hadn't really considered a multispark ignition so that's an option.


Where do guys think I'd end up with just the TTI's, big eddy carb, and a dyno tune?
 
I,m running the3310 holley on my stroked 340(372)450hp dynoed 4speed,4.10 gear.Ran 12.8 at 108mph 1.8 60ft.Feep the carb. and put money into other goodies.Gears and tires,pinion snubber,headders will all bring your times down.Good luck and play safe!
 
Just to toss out another angle, run 4.10 gears with your 727 and put a gearvenders OD unit on it. That will drop it to a 3.20 for the highway. Not terribly low buck, but meets all the other criteria.

This thread has me all inspired, as my set up will be quite similair( I took the OD unit off my F250) and I was wondering how it would run. Keep us posted on how it works with the combo you choose please!
 
I have the adjustable pinion snubber which works well when it hooks.

Gear vendors OD looks interesting but at nearly $3,000, it's out of my budget. For a casual cruiser, you'd never recoupe the expense. The 518 swap makes the most sense and is the cheapest route IMO but I just hate the idea of cutting my floorpan to make it fit.

Other people have mentioned a TBI setup or even swapping carbs for long cruises. I even thought of just disconnecting the secondaries for cruising and running the primaries pretty lean.

A couple of people have also mentioned dropping down to a 4.5 powervalve since I pull 10" of vacuum.

Keep the ideas coming!!
 
Other people have mentioned a TBI setup or even swapping carbs for long cruises. I even thought of just disconnecting the secondaries for cruising and running the primaries pretty lean
Click to expand...

TBI if aftermarket is OK and would help run the car perfect in a mileage search.
Disconnecting the secondarys is not a good idea since it is really your right foot that controls the carb. If you have a problem controling your foot, your not alone, but we don't cut our brains out to fix the foot problem.

The other O.D. trans option is a 904 OD. I can't remember the numbers. 518 is a 727 OD, the 904 is aaaaaaaaaaa, duhhhh um er ma duhhh


Hey, you don't have to cut the floor to put that one in is where I was going with this.

Gear Vendors, LOL and brack a lung on that one. 3 large G's for less of an overdrive. THPHHHHHHHHH on that. OK, so it handles a gazzillliiion HP OOTB. Who's going there? Or exceeding the 904OD? OR not building there 904 OD proper like?
 
Whoa, 3! G??? I love inflation. Bought mine for 1800 and change(jobber rate )5 yrs ago. Yea, they aren't the biggest drop, but Hey, I already got it!

I start looking for a OD auto too. (next car!)
 
The cheapest and easiest way to get OD is with a late A-833 4-speed overdrive manual. With a little work they can be almost as strong as the beefy 4-speeds of the muscle car years, and with stock ratios they have a high .73:1 ratio (you can also get a super-beefy OD 4-speed gearset from Passon, but that costs around $1500). Couple that with maybe 3.91 rear gears and it would be very street-friendly while also being quick (BUT it is a manual, that may not be your thing). For that engine you need to update the technology if you want to go fast while being economical, and for that you'll need some good-flowing heads with closed chambers and high compression (Magnums) along with a modern fast-ramp cam, good intake, and good headers. If you can't do that though, I'd say port your J heads (mildly) and get a Lunati VooDoo series, COMP Xtreme Energy series, or Hughes cam, maybe around .500" lift and 268-272* duration. Also get some good headers (others will recommend these) and a crossover for your exhaust (if you don't already have an H-pipe at least). You could also try an Edelbrock RPM dual-plane intake. I'm pretty sure these would get you into the low 13's, possibly the 12's.
 
I would get 3.55's, keep the carb, get the MSD, play with the timing advancing the initial to 20*-25* and limiting the total to where it runs best 30*-35* or so and run vac adv, get headers [don't have to be tti] , a 2 1/2 exhaust, and around 2200-24 stall.
 
can't beat a six pack for gas milage, also run an adjustable vacuum advance. i'd build atleast a 360, around 10.5-11:1 with aluminum heads (so you can get away with pump gas). make sure your piston/head setup will have good quench. probably a comp tight lash street roller (comp). that'll get you close, i'd probably build up a 518 w/ OD so you can run a 4:10 gear, that way you can still cruise. thats probably how i would go about it.
 
Dude, if he said a $3000 Gear Vendors OD setup was out of his budget, then I doubt even half the things I recommended would be affordable for him. Also, it's been pretty much proven that six packs (at least on SB's) are less efficient than a good 4-bbl/dual-plane intake.
 
toss that GER converter in the trash, Its garbage. A good converter will make a huge difference.

Low 12s out of a 340 and streetable is going to be hard to do. You need a 4" stroker crank.
 
I could afford more but the practical side of me sees the point of diminishing returns. You can buy alot of gas for $3,000 so I'm trying to use the engine I have with some bolt-ons and tuning to reach the goal.

I ordered the dynamic 9.5" converter yesterday. The crappy GER unit simply had to go regardless of this plan.
 
68 HEMI GTS said:
can't beat a six pack for gas milage, also run an adjustable vacuum advance. i'd build atleast a 360, around 10.5-11:1 with aluminum heads (so you can get away with pump gas).

i'd probably build up a 518 w/ OD so you can run a 4:10 gear, that way you can still cruise. thats probably how i would go about it.
Click to expand...

A 6pac is a great idea, but he has a budget that will not allow it.

The 360 is a great idea IMO. I did a zero deck pistoned 360 with Edelbrock heads. This is a great combo and the OOTB heads on this set up was dynamite. A decent sized cam ws used and it helped alot in the builds target.

If the OE poster can do this with a 4 inch crank......... It'll be a beautiful thing. The price difference in the build is really only the crank price and possible block clearance grinding. Worth it IMO.

68 HEMI GTS
I have a question for you. Have you put a 518 in an A body before?
I ask because I have seen the 904 O.D. version go in with the use of a hammer for minor clearances. How about the 518?
 
watchdoc, screw returns in terms of money, enjoyment is the key and nothing else should be sought. Otherwise, anything but a resto to perfection done all by yourself on the cheap is a loss and that is even a hard thing to do. Make money or increase worth effectivly and cheaply.
 
MOPEkidD-3 said:
Dude, if he said a $3000 Gear Vendors OD setup was out of his budget, then I doubt even half the things I recommended would be affordable for him. Also, it's been pretty much proven that six packs (at least on SB's) are less efficient than a good 4-bbl/dual-plane intake.
Click to expand...

i disagree with how a six pack can be less efficient that a four barrel set up on any street application. On an all out race motor, then yes i prefer multiple four barrels!! lol the nay sayers on six packs usually don't have a good understanding of carburation tuning. i went through this a few years ago on a street car i had. i got so tired of everybody telling be how great a single four barrel would run that i borrowed a few different intakes and carbs to try out. the six pack out ET'd and got way better milage than any dual plane or single plane intake i tried. but they are expensive and i understand that, for a novice carb tuner a single four barrel would be better. when you start talking about running low 12's and getting 15mpg, your gonna have to spend some money, and thats where i would spend mine. IMO

rumblefish360 i've never tried a 518 in an A-body, i was just thinking of a cheap way to have O.D.
 
I have considered a crate 360 or building a junk 360 with aluminum heads. I could sell my 340 and recoup alot of the costs I'm sure. I've also been told a 904 will net me a tenth or two and a lil beter mpg but I don't know if this is true or now. At this point, I'm gonna try the headers, converter, a dyno tune, and some new tires as my BFGs are worn out. I guess slicks for the track is another option.
 
Well, I personally dont think those goals can come together. Honestly, the best bet to get milage, and torque, and drivability, is a 4" stroke. A medium duty cam, and ported iron will do it. The last one cost about $4800 re-using what you can. Maybe sell the rest of the un-usable parts for some cash reserve. That's what I'd do. No way to get 16mpg, low 12s, and drivable out of a 340. It simply can't get the job done.
 
Some other engine suggestion? Personally, if I had a bunch of time and money, it would have a 2JZ swap in it and I would daily drive it with 800hp and a single turbo but I'm trying to stay mopar faithful
 
You must log in or register to reply here.
-

Back
Top