Stock stroke 340 with flat tappet and J heads

Need more power in my Dart. Have a fresh 340 shortblock with TRW flat tops, and a factory steel crank. Have a ported set of J heads with 2.02 intake valves and 1.68 exhaust valves. Would like to go 12.00 or better using a flat tappet cam and these heads. I also have an M1 single plane or an LD340 that I can use.
Car is: 1967 Dart GT. currently has a 340 in it. 4 speed, 4.30 Dana 60. Exhaust is TTI 1-5/8 to 1-3/4 step headers with full 3" out to the back bumper. 28"x14.50" Hoosier Quick Time Pros.
Suggest me a cam, valvesprings, carburetor, etc to put this thing at a 12 flat or better with the above shortblock and heads.
My thoughts are that this is definitely possible, even with less than 10 to 1 compression. My old 340 in my AAR with 9.7 to 1 compression, factory TA heads with factory rockers that were less that 1.5 ratio measured, factory six barrel, and a MP .509 cam went mid 12s, with a best of 12.35, and I ran it for years.

Even at stock weight..Bullet/Ultradyne nf60 intake lobe, nf57 exhaust lobe. 108ish split.

any more?

MP .557" cam.

The old combo in my Duster was pretty similar to what you describe - with the .557" cam and 1.5 rockers, stock stroke, unported W2s with TRW pistons, Edelbrock Vitor, 750 DP carb, TTi 1 5/8 step headers with full exhaust, 4.30 gear it went a best of 11.97. Car weighed around 3,200 - full interior, no roll bar, flat steel hood. 275 drag radial and FMVB 904. Shifted at 7,200.

Where's the car at now? You're in the ballpark now. The M1 has too much plenum for your motor. I'd play with the carb, timing and suspension and you are there. A stock eliminator auto 340 runs under 10.50. That's a hard task. You just some good tuning.

The 340 that is in it now runs 13.20's. I put it in about 25 years ago, has a very mismatched cam for the combo. I want to put the fresh shortblock in, and want to try to take advantage of a more modern cam profile, etc.

Then your best bet is to pick up the phone and call Jim at Racer Brown, or Cam Motion, or Dwayne Porter and have them spec you a cam.

It's the same money.


FWIW, in a 73 A body, with an all stock 340 except for a .480 lift MP cam, Strip Dominator, 5204 hooker headers and 3.23 gears the car ran consistent 12.80's.

A 4.56 gear and some tuning the car eventually went 12.40's at over 109 and was out of cam at 1000 feet.

1969, 340 swinger,
All stock driver car, no lightening, 69 340, stock untouched x heads, stock short block besides stock replacement .030 trw's, I put a .557 cam in it, strip dominator, 750dp, floated what I had for valve springs at 1000ft. Went 12.01@110.01, had 4.88s with a 28x9, 727. Put that motor together when I was 16yrs old.
Couple yrs later I put w2s on that exact short block and cam and went 11.17@118.
That stuff ran ok for the knowledge I had back then, circa late 90s early 2000s.
The cam could have def been improved looking back, no torque..........

If you haven't degree the cam that is in the motor do that first, if it is ground on a 106 LSA and is installed at 107 or more on the intake lobe advance it to 101 to 103 intake lobe center and see how your current parts like that
SB with the stock short stroke don't have much bottom end so you have to correct that first
What does are car 60 ft. times now?

1971 Demon, unsure of weight, but full interior and all steel body panels.
340 + .030", TRW flattops (10:1), mildly bowl ported J heads
Strip Dominator intake, 750 holley DP, 1 5/8" headers, 3" flowmasters
solid FT Comp cam, .508" lift, 246 at .050" duration, 108 LSA...going from memory, cam card is at home
low gear set 904, 8" converter
4.86 gear 8.75 rear, 28x10.5 slicks, SS springs

Ran 7.40s in the 1/8...11.70s or so in the 1/4. Very successful bracket car.

I had a 10:1 340 with ported 2.05 valves X heads. It had a 243@.050 hydraulic cam, 3800 converter, 3.91s and it went a best of 11.98@114 through a full exhaust system.

One of the best mods was changing to the larger intake valve. This was in the late 90s but if I remember correctly it picked up about .3 from the larger intake valve.

Stock piston weight: 720 grams
Stock pin weight: 160? grams
Stock connecting rods: 758 grams

Typical sftermarket HP stuff:
Piston weight: 500 grams
Pin weight: 120 grams
Connecting rods: 650 grams

As the car accelerates, the engine also accelerates its rotation. Accelerating the heavier rods, pins and rods eats some of the power that could be used to accelerate the car.

R.

IMO, the main success/failure part of this equation with regards to the "12.00" is the 4 speed.

If the car isn't set up well enough to leave at 5k plus, and hook, and not break stuff..... The 12.00 is going to be a tough task.

This is where I find most 4 speed street/strip combos come up short compared to their automatic/high stall equivalents.

This was an old combo that ran 11.82 40 years or so.
Street legal 1972 Duster (340)
.030 Direct Connection pistons
cleaned up stock rods (upgraded bolts) and crank
cleaned up 2.02 heads
590 lift solid cam
port o Sonic intake
850 Holley carb
4.88 gears
4 speed
super stock springs
cage,frame connectors,only fiberglass was a heavy 6 pac hood.

In today's world throw a good set of radial tires on it and a set of ProMaxx or Sidewinder heads and you would be FLYING.


My old Duster at Keystone 001 by John Cadamore, on Flickr

I agree. At a minimum you need to be able to tune the clutch. Which means some sort of adjustable pressure plate and a sintered iron disc. Then you have to understand what you are doing.

Also a 2 step is just about mandatory if you really want to make it run. As much as I did it...a 2 step would have made my life much easier. You can control launch RPM exactly and move the RPM up or down as the situation dictates.

The clutch and flywheel are responsible for most of the breakage. High plate loads and heavy flywheels best the hell out of the tires and break parts.

Were those domed?

The OP could just make another thread:

"stock stroke 340 street/strip 12.00 4 speed combos"

I should have mentioned my example is a stick. On M&H DOT tires. At that time it had a non adjustable pressure plate with a sintered iron disc.

Now it has an adjustable pressure plate.

Hopefully I can make some passes in 2018 and post results.

Yes they were (domed). We didn't have many affordable piston choices back then when boring the block. Times have certainly changed for the better.

I always LOVED the Comp grind that was 255 @ 050 540 lift on a 106 That tight LSA makes it launch like a maniac I always installed at 103 for 1/8th maybe 105 if all quarter that cam is EASY on parts and never quits
You really need to sink spring pockets or use valves with keeper groove moved up 050 or Something so you can get installed ht you need--
I like a 106 for small blocks