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mopar head

mopar head

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Would some of you Tech`ies, explain what I have in laymans terms. I left it up to my machinest to choose this cam. It was an Auto car, now 4spd. What would be a better alternitive? Some future day I want my 340 to be all it can be on 93. Street machine, 3.23 rear, Edl. airgap, holley 770 VS. tti headers and 2.5" system. Car runs like a scalded dog now, IMO, but if their`s room for improvement? Or just leave it and enjoy? Thanks, Grant

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Sure, the highlited parts mean;

320 is the lift ON the cam and the 480 is the lift at the valve. 320 X 1.5 = .480.
Cam timing @ .004 is the advertised timing. When the valve lifts .004, they start looking at the degree wheel on how long it stays open. Not the same as duration @ .050. That's when the valve opens up .050 and then they look at the degree wheel for how long it stays open.

The max RPM is where power will drop off enuff to call the cm useless after that point... in general. This is the bracketed RPM use of this cam. Valve float is the danger point in laymans terms. Zero power.
 
That cam will work. Who makes it? I am going to be puting a Comp 274 cam in my 340 that is going to be the same build as yours but with mabby some eddy heads. Or a Comp 275 high lift would be better. They did not make that one when I got my cam or I would of picked that one my self. I think the next size up mabby it is 28? Some thing? Is getting a little big.
 
Thanks rumble, The engine has a nice little lope to it but would this grind be considered , compared to stock, about the same, or considered a higher lift or longer duration cam? I guessing the latter?
 
Burntorange70 said:
That cam will work. Who makes it? I am going to be puting a Comp 274 cam in my 340 that is going to be the same build as yours but with mabby some eddy heads. Or a Comp 275 high lift would be better. They did not make that one when I got my cam or I would of picked that one my self. I think the next size up mabby it is 28? Some thing? Is getting a little big.
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Hey Burnt, It`s a Crane. This engine was built in "02"
 
mopar head said:
Thanks rumble, The engine has a nice little lope to it but would this grind be considered , compared to stock, about the same, or considered a higher lift or longer duration cam? I guessing the latter?
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Yes, the latter since it has alot more duration and lift than the stock cam.

This cam is something I'd consider labeling... something like a;

Street machine cam or high Performance street grind, light (Very) bracket cam.

I'd leave it in there and not worry to much about anything. Changing out cams until you find what works best for you or the combo is a expensive route and could go on for a long time.

The word of, "You should have gotten *** cam" OR you could have done better with a *** cam" will never end since that is an opinion and there like butt holes, everywhere and some really reak!!!!!!
 
Thanks, So little longer duration than stock, but theres conflicting #` from Chiltons to an old advertisement, funny? Or maybe I`m decifering wrong. Thanks fellas, I just did`nt want to sound like an Idiot when people ask, and always do, what kinda cam ya got in it? And 9 out of 10 times they ask, gotta 440 in it? I`ve always told them a little longer duration than stock. LOL

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Also be aware that there is a short run manual trans cam used in 1968 only. I beileve that was slightly more aggresive than the stock 340 cam. Though, the numbers I read in the advertisment are rather large, I have never seen anything that said that cam was used.

Mopar offered only two split duration cams for the small blocks for many years and only recently added a upgraded version of that cam. It was the 340 cam.
Now theres 3 split duration S/B cams. Non that large until you get into the "Super Gas " bracket racing cam which was a Comp Cam that is still offered. That's not that cam in the advertisement by far.
 

Not to sound like an idiot, but what's the equation to figure out duration at .050?? Like lets say my cam says 312 duration in the catalog, what would it be at .050??
 
wigsplitter74 said:
Not to sound like an idiot, but what's the equation to figure out duration at .050?? Like lets say my cam says 312 duration in the catalog, what would it be at .050??
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I don't think there's any absolute correlation between the two. The lobe profile can vary between .004/.006 and .050 tappet lift by quite a bit depending on design.
 
DoctorX is right. There is no formula for this since each cam company will rate there cams differently. Not only that, but they will rate each of there own cams differently.

Let me give you an example with Comp Cams, though, there not the only one to do this, actually, they all do this;

Hyd cams are given there advertised duration when the valve lifts at .004
Crane will do it at .006 while another brand will do it at .008.
(Just for example)

There mechanical street cams will be rated at yet another amount of tappet lift and the race grinds yet another.


Duration @ .050 is a constant. The rating of the can doesn't begin until there .050 lift. This make all the cams look smaller but keeps them all equal in there rating as when they begin to open and finally close.

Theres more to cams than meets the eyes and it does get involved.
 
doktor_x said:
I don't think there's any absolute correlation between the two. The lobe profile can vary between .004/.006 and .050 tappet lift by quite a bit depending on design.
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Oh, ok. I guess what I've been wondering is how come if I look at a cam in Jegs it says Adv. Duration, but look ath the same cam in Summit and it says Duration at .050. I'm just wondering how they are figuring it, I thank you for your input.
 
wigsplitter74 said:
Oh, ok. I guess what I've been wondering is how come if I look at a cam in Jegs it says Adv. Duration, but look ath the same cam in Summit and it says Duration at .050. I'm just wondering how they are figuring it, I thank you for your input.
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It's like rumblefish360 said... the duration @ .050 tappet lift has become a standard point of reference. The advertised duration figures vary from manufacturer to manufacturer and sometimes between tappet styles within each manufacturer's catalog. Comparing figures @ .050 will give a more accurate idea of meaningful valve timing action.

For example: I ran one years ago that was something like 306° adv. but the .050 was 222°. The advertised duration was taken at .004 or something. Another manufacturer may state the measurement @ .008 and show adv. duration as 280° or so. It leaves a lot of room for guesswork.

I may have confused the issue further, but I'm still in a fog this morning. 8-)

Edit to add: If a retailer doesn't show numbers @ .050, I'll usually dig up the information at the manufacturer's website or in a catalog (if I have it).
 
Looks good to me Doc.

MoPar sez to multiply there advertised duration by .850 for there @ .050 number. Take some time out to compare these figures to other cam grinders .050 figures.

The only thing I don't like about the Purple cams is there a single duration cam while most cams being sold today are a split, more exhaust than intake. This help balance out the flow since the exhaust is normaly weaker in flow and could use more duration.

Once you port the head, proper porting will not need a split duration cam or less of a split.

Stock heads can use 10 - 12 degrees depending on the head flow. Ported heads use less while seriously ported heads use even less and so on and so on. There is a point of overkill. That also why you don't see monster exhaust durations.
 
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