340 cam change

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AJ/FormS said:
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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Funny you mention that story/experience, I am getting ready to do something similar since i wiped a lobe last week. I hope it works as positive as yours did!
 
4eighteener said:
Funny you mention that story/experience, I am getting ready to do something similar since i wiped a lobe last week. I hope it works as positive as yours did!
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Watch for pistons hitting the head, or valves crashing pistons; measure measure measure. I got lucky that all the parts played nice together.
And above all, calculate your predicted Cylinder Pressure/ Dynamic C/R, before you torque the heads on ......... especially if running iron heads. With a stroker, you can very quickly get into pressure problems when downsizing.
All the best to you.
 
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.
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I looked for the Lunati 268 cam specs but couldn’t find anything on it on their website.
 
fyi, when edelbrock bought up lunati (who was already owned by comp) they basically nixed a whole segment of the catalog. my *guess* is that they are just blowing out what stock might remain while only producing chevy and ford stuff because the market isn't there for mopar.

summit doesn't even list lunati on their pull down menu any longer
 
That's why I recommended having something ground similar to the Comp 268. The Lunati specs a dual valve spring which normally needs machining on the heads. The Comp grind would use the inexpensive 901 spring which is a drop in.
 
RustyRatRod said:
That's why I recommended having something ground similar to the Comp 268. The Lunati specs a dual valve spring which normally needs machining on the heads. The Comp grind would use the inexpensive 901 spring which is a drop in.
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I like that idea, much better.
 
RustyRatRod said:
That's why I recommended having something ground similar to the Comp 268. The Lunati specs a dual valve spring which normally needs machining on the heads. The Comp grind would use the inexpensive 901 spring which is a drop in.
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But from what I’ve read there are issues with either the Comp cam or was it the lifter??? Or am I wrong?
 
AZ-Nick said:
But from what I’ve read there are issues with either the Comp cam or was it the lifter??? Or am I wrong?
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I didn't say get the Comp cam. I said in my post way up there somewhere ^^^^^ to let Ken at Oregon Cam grind you one. He has a 268 grind and will grind it on your core. But that suggestion got buried in all the hoorah.
 
What I would do is get the stock replacement 340 springs. There have been people who had trouble with the 901 springs hitting the rocker arms, including me on a 360 I built several years ago. Get those and remember to, when you regrind a cam, you will probably need longer pushrods. That's no big deal. They are cheap and easy to measure for. We can walk you through it if you go that way.
 
AZ-Nick said:
But from what I’ve read there are issues with either the Comp cam or was it the lifter??? Or am I wrong?
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Here you go. Look at grind #1179. That's their version of the 268. The grind numbers are all the way in the left side.

Hydraulic Camshaft Specifications

cam and camshaft specifications
oregoncamshaft.com
 
Also what about lifters, what brand to get?
Is Rhoda’s Lifters brand still available and are they still good?
 
well...with the info you don't know it's like going to the doctor and saying "i've got a pain"
With 22 initial and 38 total and no detonation sounds like low compression. If that is the
case none of the cams suggested will provide " Stump Pullin"
Low compression will require low duration with decent lift.
You need to supply the guys with more info
 
ir3333 said:
well...with the info you don't know it's like going to the doctor and saying "i've got a pain"
With 22 initial and 38 total and no detonation sounds like low compression. If that is the
case none of the cams suggested will provide " Stump Pullin"
Low compression will require low duration with decent lift.
You need to supply the guys with more info
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I agree with you 100%.
As I said, I needed to change the timing quite a bit to get it to run good.
And I would be NUTS to purchase another cam and pieces without knowing what cam, engine compression and valve train is installed at this time. I am only gathering everyone’s opinions and suggestions at this time and I will decide when I am satisfied that with my findings.
 
I am in the same boat as the OP. I have the stock 340 automatic cam in my car and would love to upgrade it. But the car runs fine and doesn’t leak any coolant or oil. So changing to a different cam could open up a can of worms never mind the fact the downside of the current lifter/cam issues.
 
When my time comes , probably this winter Im taking Rusty's advice... 1968 340-4 speed cam from Oregon Cam..
 
I ran a mopar 280 474 cam and changed to the lunati 703 and gained nothing. Then I went to a Hughes solid 237 242 @50 537 542 lift and gained 2.5 tenths. Car was a 68 dart 3550lbs. 9.6 comp. Rpm, 750, headers, 3.55s and 2400 stall. Ran 13.2 and 12.90s with the Hughes cam.
 
Your result does not surprise me. The solid lifter cam actually has less 050 duration. 8-10* less duration, depending on the lash of the Hughes cam. What is the LSA of the Hughes cam?
 
All this talk about cam yet the OP wants a little more pull. Just my opinion, but OP needs to check compression and if ok why not look at a gear change- does it have 3:23 or something else. And exhaust- does it have stock mufflers or? Those are fast and low cost mods. If cam then I agree with RustyRatRod.
 
AZ-Nick said:
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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I had a 340 resto cam in my 318 and did not like it so I swapped it out with a Comp Cam XE250. Nice mild street cam real nice torque down low.
If your cam is hydraulic make sure your oil has zinc.
 
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