Another slow 340

[340 swinger]

So are you saying you run a 15.08 with the above combo?

You are barley running faster than a low compression, small valve, stock 73 340.

I had two separate misfire problems, first was my 72 340 swinger. It worked good up to about 4800 rpm then started breaking down. Turned out to be a bad coil. Second was on my 70 408 4 speed swinger, the problem was when the previous owner had it, (real good friend of mine). It wouldn't dial up more than 5000 rpm. He had changed everything including disconnect the wire harness and reconnecting each item one at a time and still wouldn't dial up. It turned out being the pick up coil in the distributor. Everyone told us that this pick up served one purpose and one purpose only, to start the car. This info was proven wrong. As soon as it was changed (from an old rusty distributor on the shop floor) the thing dialed up to 7000 for a joke and been doing so ever since.

 

[340dart.812]

just my 2 cents you mentioned the things that are slowing it down the spin and the miss if you put the 28 in drag radials you mentioned on you can run a 4.56 rear ratio that should give you a 1.65-1.75 60 ft time and that would compliment your cam and intake combo and take care of the spin you can shift at 6500 but you might go thru the traps at like 6700 or even more. Put the msd box on it and get a tach with a shift light and something I tried with the timing on my car was to wire in a msd retard box like for nos and retard the timing 3 degrees in drive gear and lock the timing and set it as high as it will crank up with(and not ping) but retarding the timing in third gear picked my car up 2 tenths Im running
360 30 over
1.88 port matched j heads
kb flattops zero deck 10.25 comp
eddy performer the smallest one with 318 sized ports matched to heads
crane powermax camIntake Duration at 050 inch Lift 222
Exhaust Duration at 050 inch Lift 234
Duration at 050 inch Lift 222 int./234 exh.
Advertised Intake Duration 278
Advertised Exhaust Duration 290
Advertised Duration 278 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.467 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.494 in.
Valve Lift with Factory Rocker Arm Ratio 0.467 int./0.494 exh. lift
Lobe Separation (degrees) 114
malory led dist locked at 28
march underdrive pulleys
elec fan
Im running 12.60 at 105 with 4.56 gears and no spin at all thats a 1.74 60 ft a couple other small things dont forget a carb spacer and way more converter if its a strip only Im running a turbo j 4400 converter built for a motor with alot more power and less gear and it stalls at around 3600 and I love it for even my small combo just gotta run a trans cooler dont touch your engine combo other than maybe the carb body to a 750 and just play with the jets
so I say leave the motor except for the carb
go to a 4.56 gear (its an 8 3/4 you can swap back to the 3.23 in 30 minutes to cruise)
go as big as you can stand on the converter
put the big drag radial on it
set the timing
and Im guessing you have a low 12 high 11 second car at sea level if not quicker
keep us posted what you do and what it runs

 

[waggin]

yep,get a box that wasnt built for a street motor,a convertor and lose the dinasour camshaft and put springs to go with the new cam and lifters......yea,the airplane gears gotta go toooooooooo

get rid of that orange box and go with the crome one i think youl get rid of the mis fire in the higher rpm range.

 

[Duster346]

Duster346, Any Updates???

Thanks for asking, and thanks to all of you for your great input.

I put the MSD 6AL on the car, and it still had a miss or pop at higher RPM. Still no tach yet, but I suspect a weak valve spring. To reiterate, the motor sat on the stand for 10 years, with the valves open .. oops.

I got the 9.5" converter from Lenny @ Ultimate Converter Concepts, but I haven't put it in the car yet. Unfortunately, our season is just about done here, and I wasn't able to make it out to the track with it.

After the Leadfoot Rally I originally wanted to start drag racing the car, but it appears as though we will race it again in the 2010 Leadfoot Rally. With that said, we have to keep the highway gears for now (1600 mile drive required as part of the race).

 

[Longgone]

It sounds like a pair of slicks with long shocks, a pinion snubber, and clamping the front segment of the leaf springs would go a long way. You`re probably losing almost a second spinning the tires for 80 feet.

 

[1wild&crazyguy]

just my 2 cents you mentioned the things that are slowing it down the spin and the miss if you put the 28 in drag radials you mentioned on you can run a 4.56 rear ratio that should give you a 1.65-1.75 60 ft time and that would compliment your cam and intake combo and take care of the spin you can shift at 6500 but you might go thru the traps at like 6700 or even more. Put the msd box on it and get a tach with a shift light and something I tried with the timing on my car was to wire in a msd retard box like for nos and retard the timing 3 degrees in drive gear and lock the timing and set it as high as it will crank up with(and not ping) but retarding the timing in third gear picked my car up 2 tenths Im running
360 30 over
1.88 port matched j heads
kb flattops zero deck 10.25 comp
eddy performer the smallest one with 318 sized ports matched to heads
crane powermax camIntake Duration at 050 inch Lift 222
Exhaust Duration at 050 inch Lift 234
Duration at 050 inch Lift 222 int./234 exh.
Advertised Intake Duration 278
Advertised Exhaust Duration 290
Advertised Duration 278 int./290 exh.
Intake Valve Lift with Factory Rocker Arm Ratio 0.467 in.
Exhaust Valve Lift with Factory Rocker Arm Ratio 0.494 in.
Valve Lift with Factory Rocker Arm Ratio 0.467 int./0.494 exh. lift
Lobe Separation (degrees) 114
malory led dist locked at 28
march underdrive pulleys
elec fan
Im running 12.60 at 105 with 4.56 gears and no spin at all thats a 1.74 60 ft a couple other small things dont forget a carb spacer and way more converter if its a strip only Im running a turbo j 4400 converter built for a motor with alot more power and less gear and it stalls at around 3600 and I love it for even my small combo just gotta run a trans cooler dont touch your engine combo other than maybe the carb body to a 750 and just play with the jets
so I say leave the motor except for the carb
go to a 4.56 gear (its an 8 3/4 you can swap back to the 3.23 in 30 minutes to cruise)
go as big as you can stand on the converter
put the big drag radial on it
set the timing
and Im guessing you have a low 12 high 11 second car at sea level if not quicker
keep us posted what you do and what it runs

get some octane and raise the timing to 30*-32*. jmo

 

[Cheapstreet]

check to make sure your timing isnt going way up at high rpm.
and giving you detination.

pop a 4.30 gear in it... and some slicks
and say hello to high 12's
pretty much the way it is right now.....

 

[cuda66273]

Door #1
Get rid of the orange box, it's retarding the timing 8* starting at 3200 RPM and by 5200 it's fully retarded. The chome and gold aren't much better especially if your street driving the car. You've got the MSD so use it.

Think about that main body on the carb....replace a decent Holley main body designed for the Carb with a Chinese copy....think about it. Have you cleaned the carb...10 years of sitting it's bound to have issues. Rebuild $150.00

Throw a set of Caltracs on it, it's like adding 2" of tire. $339.00

Change the valve springs $80 - $130.00

Get the distributor recurved correctly. $69.00

Look at the Stewart Warner programable digital tach and shift combo, small simple and deadly accurate $149.00

I assume your referring to the Holley or Carter 120 mechanical pump, check your fuel pressure, if it's been sitting for 10 years the diaphram is probably stretched out or rock hard, a simple fuel pressure test will tell you, should be at 6 PSI. Whether it's good or not you need to drill out the 1/4 NPT inlets and outlets to 3/8 NPT and put the proper sized fittings in it if you want it to flow anywhere close the advertised 120 GPH. Inadaquate fuel flow will cause that high speed miss 2 Fittings $10.00 or less.

Door#2
Get more power to the ground, add the Caltracs Mono-Leaf and their front and rear shocks. $600.00

Gears at least 3.91 even better would be 4.10/30 depends on how much street driving you want to do. $250.00?

Convertor-Dynamic 3500-3800 $395.00

It's all pretty simple, it just takes money.


Door #3
Email me direct and I'll email you a FREE copy of our 47 page book "Tuning to Win" it may help guide you through your tune-up and show you what to look for.