So I have been looking at different camshafts to put into my 340, turns out I have more questions now then when I started!

So Im pretty sure I understand the importance of duration, BUT I do not understand about the "lift"

I know the lift effects the ramp speed, but I dont want the lifter to "ski jump" off the cam

This is a street car and I do not need over 100% of volumetric efficiency like a race car.

*?* Should I have more lift in the Intake or Exhaust valve...or equal. I found a camshaft with 530/530?? *And what is too much lift with factory style rockers??

This may be a really dumb question but I only want to buy a camshaft once lol


Thanks again in advance guys!!

If you guys are ever in Michigan, free beer at my house

 

Why make things hard go with a mopar performance 'purple' cam and just be done with it.

 

Hey Duster !
The age old problem with Camshafts, is the more you learn, the more questions you will undoubtedly acquire, from the new-found knowledge answering each question.
Everything, about a Camshaft single event, affects every other event, whether it be Lift, Duration, Lobe Seperation, Installed Centerline, Ramp Speeds, etc., etc.
No matter,
Duration, is the amount of degrees of Crankshaft duration the valve is open.
It can be measured in degrees @ .050" tappet lift, or "seat to seat".
Lift, is the amount the camshaft "lifts" the Valve, which typically lift is power because the more the valve opens, again, "typically" the more Air/Fuel will flow for a bigger boom pushing on the piston.
All Camshafts will come with a reccomended Valve Spring, or "requirement" based upon Spring Pressure, Rate, installed height, etc., to keep the lifter in contact with the camlobe across it's reccomended rpm range.

Choosing a Camshaft for your "wee-40" should be based upon many factors, suffice to say, gearing, compression, tire diameter, intake, etc., etc., are all factors.
Rule # 1, Do not "overcam" your 340.

Might be some good basics reading over here
http://www.jegs.com/s/tech-articles/...Specifications

 

@Moparbob,

That was a great article, Thanks for that! I will definitely go with the smaller lift! Im really glad I asked this question.

You guys from this forum have taught me more about engines in a month then I knew most of my life.

~In your opinion, what is better for street application, more intake lift then exhaust...or vis versa

And with the Mopar "purple" cams, I would like a camshaft with a little more lift. Like in the 500 area. I havent found a mopar purple one above 480. But have certainly considered it!

 

what was the stock cam in the 1968 340? i do know the auto formula S cam was a little smaller than the 4 speed cam. i think the 4 speed cam was only in 1968, i think.

 

More exhaust lift and or duration is usually designed for a head that needs some help on the exhaust side relative to intake flow.

The "purple cam", comps 268H, and some others were created with an abundance of data ( head flow, piston / valve & retainer to guide clearance etc... They are good cams that allow the end user to stab them in and run them with little mods. And they work.


My advice: Copy a build from a buddy, a builder or a decent magazine. There are many article out there with data on exactly what parts do what. The 340 has been done thousands of time. An airgap, 750 carb, headers, 224/230 .48 ( i think) cam and spring nets a plus 90HP. With good tuning a little more.

 

http://www.mopar.com/assets/pdf/perf...mall_Block.pdf

p4120233 503 lift? or P4529317 533 lift?

 

I agree with jacilynn stay with the Mopar purple shafts. these cams are engineered and designed to give the best performance in Mopars. They have a great hp curve and are ground to out perform the competition. I've had nothing but good luck with these cams and more wins then I can tell you. I won my points class with a 72 Charger 340 against all kinds of big blocks. By the way a 480 lift cam with a 280 duration will have a rough idle. So be careful if you plan to drive this car on the street. Dont over cam a street engine. Also anything over 500 lift you should check your valve clearance...

 

Here is some more reading: http://www.hughesengines.com/TechArt...lattappets.php

 

IMO,
Back in the day...
The factory 340 268/276 Camshaft was tough to beat, great balancing act between driveability, versatility and all around good power that fit a wide variety of driving styles.
You could beat ém like a "Red Headed Stepchild" when you were mad at it, and drive it back & forth to work goin "easy" Monday mornings with a hangover.
Nowadays....
I'd take a look at the CompCams "resto" 340 Cam for the same versatility, albeit with 40 years later updated ramps
or,
if more power is wanted, the tried and true 274H from Comp is also a proven runner.

Nothing wrong with the Mopar purple grinds either, they work well, albeit they do give a very little away these days, as they are getting long in the tooth techwise. No matter, we ain't re-inventing the wheel, they do work.

SB Mopars with Iron Heads, either WITH or without Headers like a little help on the Exhaust side, generally 6-10 Degrees, although many smaller sticks tackle this by using a tighter 110 lsa and stay symetrical(same) events for BOTH Intake & Exhaust.

Hey Duster...
Whats the application ? Car ? Trans ? rear gear ? Tire Diameter ? Headers or no ? As much info as possible and maybe we can come up with something to reccomend.

 

when it comes to street stuff, i like the comp camps applications. for my 318, i went with the 256h - mild enough and yet waaaay stronger than stock, especially in low-down torque. that 268 will probably be right up your alley though, with a 340. it's a great cam.

 

Thanks for all of the quick responses!!
I will go into the intended use and my plans for this engine.

Sunday cruiser and occasional car show. Has 727 trans with a 8 3/4 rear" 3.55" I am throwing a 4inch stroke down its throat with a .30 bore.

I DO want good idle, I do not plan on going over 5500 rpm. Unless provoked lol

I am putting on a RPM Performer intake "2 plane" on it. The plan is porting the J heads but I JUST found a deal on Craigslist today for some eddy heads that have the work done to them already.

9.7ish:1 compression, dished D cup forged pistons, pump gas...Mabye a 2500 stall??any ideas

~Talked to an engine builder today and he said he gets his cams ground in S.C with around 230 duration and 600 Lift, said it give good idle and pulls vacuum. Is this not going to fit my engine idea??

THIS IS NOT GOING TO BE A RACE CAR lol maybe a couple passes a year

Thanks again guys, I really do appreciate all the help!
~Sean

 

Stroke is a totally different monster when it comes to camshaft selection for an engine...... Those are all too small unless you are towing a Chevy!!!!!

 

I would say it sounds like that 256h is JUST what you are after. Check out the specs, it's a cool cam.

 

nice cam great lift
Voo-Doo
Advertised Duration (Int/Exh): 256/262
Duration @ .050 (Int/Exh): 213/220
Gross Valve Lift (Int/Exh): .454/.475
LSA/ICL: 112/108
Valve Lash (Int/Exh): Hyd/Hyd
RPM Range: 1000-5500
Includes: Cam Only

The lift in this cam versus the purple 272-455 is remarkable... Look how new cam tec. comes along after decades.
this was the last mopar cam i used

 

All the posts above were "dead nuts" accurate IMO. Everyone has a favorite and has had success with different vendor..

HOWEVER.. You slipped in that it will have a 4" stroke. That changes the game.

Do want all your power in before 5500 rpm?

 

Well said, I'm with PK here.

 

Yes I would like all the power to be before or around 6k if thats good. I dont believe that going over 6k is totally necessary or practial for street use.

thanks