340 cam change

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AZ-Nick

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Since I have NO idea or clue what cam is in my 340, and if I have to take it apart just to determine what it is, I might as well think about making a cam change. The motor has X heads and adjustable rocker arms, look like the 273 hp cast iron units. I don’t know if the current cam is hydraulic or mechanical but I am guessing it is a hydraulic.
Sounds like an early type small hemi grind.
Trans- 727
Stall - don’t know I will change if needed
373 or 391 gear
Edelb RPM intake
AVS2 650 can change but I would like to use it.
X heads
TTI headers
I am in my 70’s so I am pretty sure I am Not racing the car.
What would you buy, Flat or Hydraulic?
Lumpy is good.
I like stump pulling set you back in the seat.
Which grind ?
I am waiting for delivery on a compression gauge.
I know I will get many answers.
Thanks
 
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How is your car running now? Is there anything you don’t like about it?

One thing to think about if it’s running good, you may want to let it be and enjoy it.
 
coloradohill said:
How is your car running now? Is there anything you don’t like about it?

One thing to think about if it’s running good, you may want to let it be and enjoy it.
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It runs ok but I have had many stock 440’s in B bodies that pull much harder so I know something is not right and I think it is the cam.
 
I remember back in the 70’s the mopar 484 and the 509 were the cams to get. But I would think nowadays there has to be a much better design in a cam to get.
 
I understand what you’re saying. I had a friend back in the 70’s and his sister’s boyfriend had a 68 340 Dart.
That thing would break the tires loose going down the road 30-40 mph. I remember.
I was only 14 or so. These days I have to wonder if it was an open differential or, was it that bad of a car? Not sure.

There a lot of very knowledgeable engine builders on this forum. I’m sure they will chime in.
Have fun with it!
 
Nick, if lumpy is on your list, go with the Hughes Whiplash cam. They sound great and they can perform well, too. Kills two birds with one stone and no guesswork.
 
You probably were asking about solid or hydraulic cams, you mentioned flat or hydraulic.
I have never tried this cam from hughes but if your 340 has the stock six pack cam, hughes makes a replacement that is of similar specs and supposedly out performs it.

Screenshot_20240827_214227_Chrome.jpg
 
Although I am hesitant to recommend anything flat tappet anymore after suffering my first flat tappet cam failure.
I might have to dip my toe into the roller world
 
4eighteener said:
You probably were asking about solid or hydraulic cams, you mentioned flat or hydraulic.
I have never tried this cam from hughes but if your 340 has the stock six pack cam, hughes makes a replacement that is of similar specs and supposedly out performs it.

View attachment 1716295683No
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No such thing as a sbm 6 pack cam
They all had the same cam except the 68 340 4spd cam
 
4eighteener said:
You probably were asking about solid or hydraulic cams, you mentioned flat or hydraulic.
I have never tried this cam from hughes but if your 340 has the stock six pack cam, hughes makes a replacement that is of similar specs and supposedly out performs it.

View attachment 1716295683
Click to expand...
that pencils out to .513/.525

which... sure, why not?
 
you can check the cam with a degree wheel and a dial indicator in the car.

i'd say with just a dial indicator to suss out the lift you could likely ascertain the rest of the grind or close enough to make an educated guess.

have a closer look at them rockers they may be crane or isky. they all look very similar.

and yeah, i think there are many better options over the old 509/484 grind.
 
I would do some more checking before blaming the cam for lack of performance. Dragging brakes will hurt performance.....& a new cam will not fix that.
 
Bewy said:
I would do some more checking before blaming the cam for lack of performance. Dragging brakes will hurt performance.....& a new cam will not fix that.
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or compression...

i fully agree, more in depth analysis before jumping straight to a cam.

for all we know if could have some wild *** cam in there with mid compression and a crap tune. hell, even a bad tune could make it a dog.
 
RustyRatRod said:
Oh just perfect for a mild street build.
:rofl:
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i mean with the 280 duration cams, 3500 stall converts and 4.56's everybody is running these days i'd say it's a touch on the lighter side of things!

but i'm sure that would run great in a 9:1 motor with stock-ish stall and 3.23's
 
junkyardhero said:
i mean with the 280 duration cams, 3500 stall converts and 4.56's everybody is running these days i'd say it's a touch on the lighter side of things!

but i'm sure that would run great in a 9:1 motor with stock-ish stall and 3.23's
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I would run something like what I posted OR the Lunati 268 grind. A touch high on the lift though, they like a dual spring with that one. Maybe get Ken Heard at Oregon to grind a Comp 268 clone.
 
What year 340? I would recurve that distributor if you haven’t already. My bros 340 didn’t come alive until we took 14 degrees of mechanical timing out and added more initial timing!
 
RustyRatRod said:
I would run something like what I posted OR the Lunati 268 grind. A touch high on the lift though, they like a dual spring with that one. Maybe get Ken Heard at Oregon to grind a Comp 268 clone.
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I like the Lunati 268 cam specs, it is a little higher in duration and a little lower in lift than the hughes cam. Probably more advantageous with the x heads. I think the compression ratio of a stock 340 (10.5?/year?) might eliminate the whiplash cam as an option, which hughes specs for lower compression engines in the 8 to 1 range.
Either of the other 2 cams would probably be better with power brakes.
I agree, more about the motor has to be determined before doing anything, especiallyreplacing the cam, especially with gambling with new cams and lifters.
EarliA had a good thread recently determining cam specs with the cam still in the engine, and the engine still in the car.
 
Slantsix64 said:
What year 340? I would recurve that distributor if you haven’t already. My bros 340 didn’t come alive until we took 14 degrees of mechanical timing out and added more initial timing!
Slantsix64 said:
What year 340? I would recurve that distributor if you haven’t already. My bros 340 didn’t come alive until we took 14 degrees of mechanical timing out and added more initial
Click to expand...
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The block is a 70 and the X heads are a 69. There was a stock 340 damper with no degree tape on it so I added a tape to it to check the timing. It also has a MSD6al and MSD Distributor. It was set at 22deg initial and 38deg in around 2800. I took the distributor out cleaned it up, ordered new springs, reset it up. I have it set at 18deg initial and 36deg in by 2200rpm.
 
4eighteener said:
I like the Lunati 268 cam specs, it is a little higher in duration and a little lower in lift than the hughes cam. Probably more advantageous with the x heads. I think the compression ratio of a stock 340 (10.5?/year?) might eliminate the whiplash cam as an option, which hughes specs for lower compression engines in the 8 to 1 range.
Either of the other 2 cams would probably be better with power brakes.
I agree, more about the motor has to be determined before doing anything, especiallyreplacing the cam, especially with gambling with new cams and lifters.
EarliA had a good thread recently determining cam specs with the cam still in the engine, and the engine still in the car.
Click to expand...
I’m waiting for delivery on a Compression gauge so I can get some numbers. Don’t get me wrong, the car runs good but I am sure there is a lot more that can be brought out.
I hate to tear it down but I can’t stand to not know what cam is in there.
 
junkyardhero said:
you can check the cam with a degree wheel and a dial indicator in the car.

i'd say with just a dial indicator to suss out the lift you could likely ascertain the rest of the grind or close enough to make an educated guess.

have a closer look at them rockers they may be crane or isky. they all look very similar.

and yeah, i think there are many better options over the old 509/484 grind.
Click to expand...
I agree, Before I purchase anything I will be checking the current cam as best as I can.
 
4eighteener said:
I think the compression ratio of a stock 340 (10.5?/year?) might eliminate the whiplash cam as an option,
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Those 340s mightabin 10.5 engines when blue-printed to NHRA specs back then,
But taking an original apart, and subbing in an 039FellPro, about a minute with a calculator will point to about 9.6 in the real world today.
BTW
I put a 318 cam into one of those back in the early 70s, and it was ferocious on the street in my 65 Valiant wagon. Oh, I forgot to mention that I installed 318 heads on it too, closed-chamber ones. I have no idea what the compression ratio was, I don't think I was even 20 years old at that time. I just bolted together what I was given. Man that was a combo!
I called it my Big-Bore 318, cuz it also had the 2barrel intake in it, lol. It was all 318 except the bore size and the Fenderwell headers.
 
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