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Mwjones

Mwjones

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I have a 1969 340 that is internally stock. I have a 8 3/4" rear end with 3.23 with a Dr Diff posi, A new Holley EFI, Hooker headers and MSD with an electronic distributor. With that she is just not very fast. My question is what would add more power, a cam or new heads? or would both be best? Any advice would be appreciated.
 
Mwjones said:
I have a 1969 340 that is internally stock. I have a 8 3/4" rear end with 3.23 with a Dr Diff posi, A new Holley EFI, Hooker headers and MSD with an electronic distributor. With that she is just not very fast. My question is what would add more power, a cam or new heads? or would both be best? Any advice would be appreciated.
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You should 100% verify the tune. Do you let the EFI control timing? Most times I see this on the forum and people end up regretting doing that. Do you know what kind of timing curve it has? That would be the first thing I would check.
 
"Not very fast" is pretty subjective. Do you have a reference? 0-60, 1/8 or 1/4 times, etc etc?

One thing I recommend is one of the performance meters like G-tech which can give you acceleration informantion

After that the basics, see above

Run a compression and leak down test.

Then tuneup. Timing. Play with A/F ratio. You have a display which gives you that?

What are tire diameter? Consider lower rear gear

Auto? Consider a stall converter.
 
"Not very fast"? Compared to what?
A stock 340 is a solid low 14 second car. Tune it and throw some gears at it and it's low 13 sec. or better.
And that is with points ignition, a carburetor, and exhaust manifolds.
If yours is not performing at least on a par with that, you've got other issues that throwing more parts at isn't going to solve. As the previous posters said, check your tune.
Remember, EFI is not going to perform better than a well-sorted carb. Drivability may improve, but AFR is AFR regardless of what mechanism is delivering it. MSD may be flashy, but any improvement on a stocker is dubious at best. The headers are only a slight improvement over the quite-good factory Hipo manifolds on an otherwise stock motor. You basically have a stock motor with some expensive toys on it.
New heads? Your cam, while quite good for a street cam; is not even taking full advantage of your stock X heads at this point. Upgrading the heads will serve no purpose other than to lighten your wallet, until the rest of your combination calls for it.
As said, triple check your tune, then go for gears and/or a convertor (if an automatic). Then sort the suspension and get it to hook.
 
RustyRatRod said:
You should 100% verify the tune. Do you let the EFI control timing? Most times I see this on the forum and people end up regretting doing that. Do you know what kind of timing curve it has? That would be the first thing I would check.
Click to expand...
Rusty is correct. The default timing table in the Sniper is really basic. Like only three steps in the timing. You need to build a good table to to make it work.

We install a bunch of these in my shop. Currently have a 340 '72 Barracuda now that I'll be tuning this week. The basic fuel and timing table will get it going, but it all needs to be tuned.
 
speed cost, how fast can you afford to go??? been said for years! you have spent some money but not really anything thats going to make more or better power than your 340 came new! after your headers what you got for exhaust?? cam converter and gears would be what id do, then if ya want more, intake and heads, maybe a stroker kit,..its a slippery slope,..the farther you slide the more it'll cost, but the faster it should go....cheapest way is to know where you want to end up, and do that,..buy once, cry once!!
 
Before I opened up the engine, I'd find a set of 3.91 or 4.10 gears. That'll perk up a 340.
 
We put a 340 with a 471 lift cam in a car. This engine ran like a house on fire in the car it came out of , 69 Swinger .The car we put it in was a pig. took it to the track it went 14.98. This car wouldn't spin factory bias ply spare tires without mashing the throttle and rocking the brakes. We put 410 gears in the car still a pig.

We the pulled the trans and put a cheap GER 3500 stall converter in the car. He could sit at a stop with 275x15 tires and melt them just stabbing the throttle with 355 gears. Took the car to Island Dragway the car ran 1360's. It was a 72 Charger Rally 340 auto.

See what your car brake stalls at. Shouldn't be under 2800. If it is get a converter. You'll thank me for this advise
 
Professor Fate said:
"Not very fast"? Compared to what?
A stock 340 is a solid low 14 second car. Tune it and throw some gears at it and it's low 13 sec. or better.
And that is with points ignition, a carburetor, and exhaust manifolds.
If yours is not performing at least on a par with that, you've got other issues that throwing more parts at isn't going to solve. As the previous posters said, check your tune.
Remember, EFI is not going to perform better than a well-sorted carb. Drivability may improve, but AFR is AFR regardless of what mechanism is delivering it. MSD may be flashy, but any improvement on a stocker is dubious at best. The headers are only a slight improvement over the quite-good factory Hipo manifolds on an otherwise stock motor. You basically have a stock motor with some expensive toys on it.
New heads? Your cam, while quite good for a street cam; is not even taking full advantage of your stock X heads at this point. Upgrading the heads will serve no purpose other than to lighten your wallet, until the rest of your combination calls for it.
As said, triple check your tune, then go for gears and/or a convertor (if an automatic). Then sort the suspension and get it to hook.
Click to expand...
People say that a efi system is better for controlling the afr than a carburetor because of its ability to self tune, is this true or bs.
 
IMG_3216.jpeg
 
Both but!!!!!

Realize the cam will add power but the larger the duration the higher the operating rpm will be.

Also, if there is no cylinder head support to not only flow better but to also handle the higher lifts that are normally paired with bigger camshafts, the limited airflow will not allow the power to come flowing through.

I suggest purchasing a cam and cylinder heads to meet your goals. Don’t shoot for a facet HP by rather a time slip on the track even though you may never go. It’s easier for most of us to assemble a package of parts to meet a drag strip ET than anything else. Be prepared for a complete car package.
 
Dont happen very often but maybe twice in this thread.A slipping sprag in the converter,will turn a tork multiplyer into a fluid coupling.What appears to be stall speed,is not making any tork it’s just beating the oil to death.It can be hard for a layman to diagnose. A decent tranny guy will pick it up easily .If your tune checks out it may be worth your time to have it checked out.
 
Professor Fate said:
"Not very fast"? Compared to what?
A stock 340 is a solid low 14 second car. Tune it and throw some gears at it and it's low 13 sec. or better.
And that is with points ignition, a carburetor, and exhaust manifolds.
If yours is not performing at least on a par with that, you've got other issues that throwing more parts at isn't going to solve. As the previous posters said, check your tune.
Remember, EFI is not going to perform better than a well-sorted carb. Drivability may improve, but AFR is AFR regardless of what mechanism is delivering it. MSD may be flashy, but any improvement on a stocker is dubious at best. The headers are only a slight improvement over the quite-good factory Hipo manifolds on an otherwise stock motor. You basically have a stock motor with some expensive toys on it.
New heads? Your cam, while quite good for a street cam; is not even taking full advantage of your stock X heads at this point. Upgrading the heads will serve no purpose other than to lighten your wallet, until the rest of your combination calls for it.
As said, triple check your tune, then go for gears and/or a convertor (if an automatic). Then sort the suspension and get it to hook.
Click to expand...

Not quite true.
I took a stock 69 340 Dart in 1972, added headers , came factory with 3.55 gears, and went to the track.
14.23@ 99 mph
It wouldn’t have gained another whole second just by “ tuning”
They ran good with the factory settings.
And again, mine had headers, not exhaust manifolds
 
Very true. In the late '70s my bone stock 340/4spd./3.23 GTS was running 14.30s, dipped to 14.27 once- only mod was a recurved distributor, the AVS off of a 440, and F60 Firestones in back (and I hate to admit it, a pair of slapper bars). Later additions of Cyclone headers, LD340, Holley 780 and a set of 3.91s put me at 13.30s. Still with stock cam.
But don't take my word for it.
1967-1969 Dodge Dart GTS
1685735329202.png

 
Well it looks like another "drive by" thread.........the OP ever been back?
 
Professor Fate said:
Very true. In the late '70s my bone stock 340/4spd./3.23 GTS was running 14.30s, dipped to 14.27 once- only mod was a recurved distributor, the AVS off of a 440, and F60 Firestones in back (and I hate to admit it, a pair of slapper bars). Later additions of Cyclone headers, LD340, Holley 780 and a set of 3.91s put me at 13.30s. Still with stock cam.
But don't take my word for it.
1967-1969 Dodge Dart GTS
View attachment 1716097384
Click to expand...


I take your word for it. No doubt 60 series tires would have helped too.
just telling you what my 3 year old one ran back in 72.
just Driving it to the track and racing it.
 
Usually a complete ignition tune and dialing in the carburetor along with a good dual exhaust system, stall converter and a set of gears is all that's needed for street fun. If one has the funds a dyno tune will get awesome results. Also building the engine by pure stock drag racing rules can produce great results.
 
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