340 Cam Comparison

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gzig5

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I'm hoping to get my 340 back together this fall for install next year when the body is ready. I'm mulling over my cam options. This will be an interim motor while I work on a 416 stroker. I have an XL275HL

Duration at 050 inch Lift: 231 int./237 exh,
Lift 0.525 int./0.525 exh. @1.5 ratio
Advertised Duration:275 int./287 exh.,
110 lobe separation

that would probably work pretty well but I would rather have a solid lifter cam. Thinking about the MP 284 .528 cam. It's got more duration but is equal int/exh.

P4120653
Duration at 050 inch Lift:241/241
Lift .528/.528 @1.5 ratio
Advertised Duration:284/284
112 lobe separation

My main concern is if that MP cam will push the torque/HP peaks up and how the 112 lobe separation affects it all vs the 110 of the other cam. I'm not going to be drag racing much at all, but will be doing auto-x/road course so low/mid range torque are important. Decent street manners are required too. I don't want to have to slip the clutch at 3000rpm to get it moving. I noticed in one list of MP cams that the oval track cams seem to have a narrower separation compared to most of the drag race oriented cams.
Mopar - Mechanical Camshafts FOR "A" Engines
The rest of the combo. ~3600lbs, 3.55 gear, 4spd with 2.66 first gear, stock bore '71 340 with fresh hone, new rings/bearings and stock pistons .025 above deck. ProMAXX 171 heads that flow peak of ~250cfm at .500-.600" lift, RPM Air Gap, 273 rockers or more lift with PRW 1.6 rocker, 750-850cfm carb, Hooker 1 3/4" headers, 2.5" full exhaust. I'll pick a head gasket to get .035-.040" quench on the 63cc closed chamber heads.
 
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Better the head flow, more Lsa and single pattern cam. I would go with the XL cam and maybe even 1 5/8 headers. You might even want to step back to a cam with duration in the 220’s.

remember these are just my personal opinions.
 
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That's interesting because I got a recommendation from Mike Jones that has even more duration 244/252, .365/.364" lift, @108 center for pretty close to the same potential combination. I will be first to admit that I don't fully understand how the different parameters affect performance and drive-ability, so I am trying to learn. I'm willing to try a couple combos to dial it in but hope to start in the general ballpark. For this interim motor though, you may be correct in less being more. But looking for feedback from someone that's run this or similar cam as to how it behaves. Hate to "leave too much on the table".
 
The lower the LSA, 110-108-106…. Tend to offer more low end torque. Rougher idle
The higher the LSA, 110-112-114….. tend to offer more top end HP. Smoother idle, need more compression to make up for the low end.

The better the head flows and the better the balance between in and out ports, the less of a split duration cam is needed. If you have good flowing heads, a large split is a power looser. Just the reverse if you’re heads are stock iron or just do not have a good flow balance between in and out ports. A single pattern cam is a power looser.

Not to sound like a jerk, but there is always a better cam. No matter what you choose, you can always get a better one. Ask 10 cam grinders there opinion and get 10 different answers.
 
I run a cam similar to the Jones grind on my 408 except mine has more lift .
Low end is not super torquey .

My 5.9 in the Cuda has a 221/229 on a 112 with .480s lift (.510 w 1.6 ratio rockers) and is a torque monster .
 
I'm a big fan of the 528. I WISH I could find one for a slant 6. They flat out work.
 
mbaird said:
I run a cam similar to the Jones grind on my 408 except mine has more lift .
Low end is not super torquey .

My 5.9 in the Cuda has a 221/229 on a 112 with .480s lift (.510 w 1.6 ratio rockers) and is a torque monster .
Click to expand...
Cranking cylinder pressure (CCP) is usually a good indicator of low end torque.
Have you measured the CCP on your 5.9?
 
mbaird said:
I have not ... but I should .
Click to expand...
I for one would be interested to know. I am thinking of a 416 build in the future and the million dollar question is "what cam do I use"
Sorry for stepping on the OP's thread.
Me bad
 
The things that makes the bottom end soft are a low Dynamic compression ratio,and/or a late closing intake valve which traps less of the inducted mixture at lower rpms . Once the rpm gets up, inertia takes over and the late closing intake is no longer a factor.
Low cranking cylinder pressure can be low because of several factors. Forgetting ring and valve problems, the obvious things are; a large chamber volume compared to the swept volume, and a late closing intake; and/or a modest swept volume to start with.
The 340, at low-rpm, is already slightly handicapped by it's modest swept volume of 696.36 cc per cylinder, and it's short effective stroke when a late-closing big-duration cam is chosen. This all goes away at high rpm, so with an automatic and a hi-stall, you can get away with modest cylinder pressure.
But on the street, with a 2.66 low manual-trans, no TC, and 3.55s, @3600 pounds, that will get very old very quickly. So yes; with a big cam you will be slipping the clutch like an old 5.0Mustang. But what's worse to me, is with an 700 rpm idle, the slowest you can drive with 27" tires is about 5.9mph. And that's if the 340 makes enough power to pull itself smoothly down there.
I like your cam choice, but be prepared to spend some time on the tune. I would run a small double-pumper when on the street.
 
512Stroker said:
I for one would be interested to know. I am thinking of a 416 build in the future and the million dollar question is "what cam do I use"
Sorry for stepping on the OP's thread.
Me bad
Click to expand...

I will try to get that done tomorrow.
This cam is a Oregon Cams regrind hyd roller with 1.6 magnum rockers on IMM ported EQs. I have some 1.7 Harland Sharps on the way that will be an interesting experiment.
 
AJ/FormS said:
The things that makes the bottom end soft are a low Dynamic compression ratio,and/or a late closing intake valve which traps less of the inducted mixture at lower rpms . Once the rpm gets up, inertia takes over and the late closing intake is no longer a factor.
Low cranking cylinder pressure can be low because of several factors. Forgetting ring and valve problems, the obvious things are; a large chamber volume compared to the swept volume, and a late closing intake; and/or a modest swept volume to start with.
The 340, at low-rpm, is already slightly handicapped by it's modest swept volume of 696.36 cc per cylinder, and it's short effective stroke when a late-closing big-duration cam is chosen. This all goes away at high rpm, so with an automatic and a hi-stall, you can get away with modest cylinder pressure.
But on the street, with a 2.66 low manual-trans, no TC, and 3.55s, @3600 pounds, that will get very old very quickly. So yes; with a big cam you will be slipping the clutch like an old 5.0Mustang. But what's worse to me, is with an 700 rpm idle, the slowest you can drive with 27" tires is about 5.9mph. And that's if the 340 makes enough power to pull itself smoothly down there.
I like your cam choice, but be prepared to spend some time on the tune. I would run a small double-pumper when on the street.
Click to expand...
A/J that is a great explanation on cylinder pressure's
But Im from MO so I need more.
When you refer to intake valve closure what range of degrees ABDC would you consider too late? Thus causing low cylinder pressures at low rpm's?
 
AJ/FormS said:
The things that makes the bottom end soft are a low Dynamic compression ratio,and/or a late closing intake valve which traps less of the inducted mixture at lower rpms . Once the rpm gets up, inertia takes over and the late closing intake is no longer a factor.
Low cranking cylinder pressure can be low because of several factors. Forgetting ring and valve problems, the obvious things are; a large chamber volume compared to the swept volume, and a late closing intake; and/or a modest swept volume to start with.
The 340, at low-rpm, is already slightly handicapped by it's modest swept volume of 696.36 cc per cylinder, and it's short effective stroke when a late-closing big-duration cam is chosen. This all goes away at high rpm, so with an automatic and a hi-stall, you can get away with modest cylinder pressure.
But on the street, with a 2.66 low manual-trans, no TC, and 3.55s, @3600 pounds, that will get very old very quickly. So yes; with a big cam you will be slipping the clutch like an old 5.0Mustang. But what's worse to me, is with an 700 rpm idle, the slowest you can drive with 27" tires is about 5.9mph. And that's if the 340 makes enough power to pull itself smoothly down there.
I like your cam choice, but be prepared to spend some time on the tune. I would run a small double-pumper when on the street.
Click to expand...
Have you ever taken a cranking pressure test with a stock camshaft and measured it again after installing a late closing, large duration camshaft.
 
512Stroker said:
A/J that is a great explanation on cylinder pressure's
But Im from MO so I need more.
When you refer to intake valve closure what range of degrees ABDC would you consider too late? Thus causing low cylinder pressures at low rpm's?
Click to expand...

That all depends on static compression. Mine for example, has a static of 10.1:1, dynamic of 7.99 and cranking pressure is 175 PSI even with an IVC of 70 degrees.

Change the static to 8:1 and that makes the dynamic fall and eats up a TON of cylinder pressure. So it's all relative.
 
Both of your suggested camshafts are very good hot 340 cams for a street / strip the comp being a little bit bigger because of lash consideration. Both cams are a little large for a 355 gear ratio in my opinion but will work well. Both cams need a minimum of 10 to 1 compression. I'm not a fan of the higher 112 LSA on the new Mopar grinds they should have left it alone at 106 but I'm a four-speed guy.
 
fishmens67 said:
Have you ever taken a cranking pressure test with a stock camshaft and measured it again after installing a late closing, large duration camshaft.
Click to expand...
Yes and no
I have had three cams in my 367; the 292/292/108; the 270/276/110; and the current 276/286/110
With each one I back-calculated the Scr to achieve about the same cylinder pressure, with the new Ica. So my Scr for the first cam was 11.3, with the second it was 10.7 and with the last it is 10.95. The pressure variation between them was only about 3 to 5 psi, and that was probably due to my changing the installed centerline, after the calcs were done, on account of I'm not anal enough to move a cam 2 degrees, from where it drops in, lol, especially when I already have 180psi or more . I mean if I only had 150psi, and could get 3 more psi for 2 degrees well ya, I'm going for the 3psi.
With the 292* cam I moved it three times, not to get more pressure cuz it had lots, but to move the power around a bit. and finally, to get a lil more power extraction out of it, in a misguided bid for fuel-economy. Forget it with the 292!
I can tell you that I did not like the street combination of the 292* cam and 3.55s with a 2.66 lowgear. The power-peak did not arrive until ~5500/46 mph in first gear, and it liked to be shifted way higher than you might imagine; top of first was 6000/50mph, but I usually carried that out a lot deeper. 7200 was 60mph......
I know the 3.55s were all wrong for that cam, but 3.55s was all that I wanted to run.
I pulled that cam a couple of months later, in favor of the 270/276/110; then I was a happy happy guy. The 270 made tons more low-rpm torque, a fatter midrange, still revved to 7200 albeit with less power. But since both cams spun the tires to past the speed limit, I didn't miss the lost power. That wouldn't come until the third cam went in.
I can also tell you that I will never go back to a low-pressure engine. Even my 2.5liter OrlandoDD is pushing over 200psi; what a sweetheart. Ok well the 6-speed helps,lol.
 
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In response to me being a 318 hater;
The biggest reason to start with a 360
is because it falls together at 10.7Scr with no machining; read cheap. No decking costs. no head milling, no intake shaving. Just boring. The machining costs that can be saved, together with not having to do a valve job on 30year old heads, can be put towards OOTB 63cc closed-chamber alloy-heads; and with the alloys, can be run an easy 20 or 30 more psi.
For me it was a natural. What I wouldn't know in 1999 was how powerful 185plus psi would feel. The scuttlebutt at the time was 9.5Scr was all you could run, and nobody was talking Dcr or psi, and there were no Dcr calculators at the time. So I had to figure it all out long-hand with hi-school math. Little did I know that 185psi would run WOT on 87E10 with full-timing.

Do you know;
what you have to do, to a 318 with a performance cam, to get it up to 185psi? With a middle of the road Ica of 64* and at 930 ft elevation where I live, it will take a Dcr of 9.0, and an Scr of 11.3
The thing of it is, to make 11.3Scr, the Total chamber volume has to be, at 3.94 bore, 64.3c........... Good luck with that. To use the .039FelPros, Everything will have to be machined.
I don't hate 318s; I'm a realist.
Does a 318 need 185 psi?
Well, no......
But I can practically guarantee you that if you ever get a chance to drive one, you will never go back to 150 psi; which is what you would have to do, to run open-chamber iron heads on 87E10 with full Power-Timing.
To run 150 psi with a 64*Ica and iron heads, the Scr would need to be 9.7, and the Total chamber volume would need to be ~75cc. yeah, good luck with that. There are no cheap parts that I know of, that fall together anywhere near that, adequate for a cam that sports an Ica of 64*...
I don't hate 318s; I'm a realist.
Do you need to run an Ica of 64*?
Well no, but
that's about what's on the 340 cam that everybody brags on.............. which I won't ever again stick in a 318.
64* is middle of the road;
54* is smallish for modest power with fuel economy, and
74* is flippin' huge for a streeter.
 
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AJ
This thread is not about 318s or 360s. Appreciate the input but please try to stay on topic.

Btw.. when I measured compression on this motor before pulling it apart it averaged 180 psi with what appears to be a stock 340 cam and 2.02 J heads on my gauge. I’m putting 63 cc heads on so I think I’ll have plenty of compression potential.
 
gzig5 said:
That's interesting because I got a recommendation from Mike Jones that has even more duration 244/252, .365/.364" lift, @108 center for pretty close to the same potential combination. I will be first to admit that I don't fully understand how the different parameters affect performance and drive-ability, so I am trying to learn. I'm willing to try a couple combos to dial it in but hope to start in the general ballpark. For this interim motor though, you may be correct in less being more. But looking for feedback from someone that's run this or similar cam as to how it behaves. Hate to "leave too much on the table".
Click to expand...


the reason I suggested stepping back in duration is you stated decent street manners.
Mopar small block heads are not known for good flow numbers, push rod gets in the way of the intake port and the bolt boss get in the way of the exhaust port(only somewhat cause some of the best gains from porting an exhaust port come from the roof being modified and raised, hot air rises.). the reason you want less LSA is to help pull in a fresh charge of gas and air by pulling it in when the exhaust gets sucked out. less LSA= more overlap which the intake valve is open while the exhaust valve is open. this helps make up for a less than desirable flowing intake/exhaust ports. the increased the duration of the exhaust lobe of a dual pattern cam helps this as well. and yes all this will cost you some horsepower and compression as more LSA is less overlap and more compression. as for the 1 5/8 headers, they help with increased velocity and match the flow better in a less than desirable flowing head. cams and headers have to match the capabilities of your head. all out racing cams and heads work well with those bigger headers but run like crap on the street. just watch a stock class mopar drive thru the pits at an NHRA race with a 320 duration cheater cam. you would be cussing at every stop sign/stop light.

back in the day(1977) I ran a stock 340 dart with Direct Connections Street Hemi Grind camshaft. .471/.474 lift, 284 duration and 90 degrees overlap(smallish LSA). I'm guessing it was about 227 duration at .050 lift. It was designed to be used with stock stamped rocker arms and stock cast iron exhaust manifolds which I know you are not planning to use. It idled a bit rough but smoothed out soon after idle, had plenty of low end torque, pulled hard once it came into operating band and raised the upper rpm limit quite a bit. it was a blast to drive. alot of guys I have talked to are real happy with Hughes Engines cams they have and on FABO I hear alot of good things about Oregon Cam grinders, more modern lobes and cam profiles they both use.

don't worry about the shivvvy and furd dudes, you wont have any problems putting the smack down on them, I didn't. you will even look good up against the new modern muscle cars as well. dudes on Street Outlaws are always talking about too much horsepower and over powering the street. 700 horsepower is a lot of tire smoke on the street but real nice on a glued track.
 
RustyRatRod said:
That all depends on static compression. Mine for example, has a static of 10.1:1, dynamic of 7.99 and cranking pressure is 175 PSI even with an IVC of 70 degrees.

Change the static to 8:1 and that makes the dynamic fall and eats up a TON of cylinder pressure. So it's all relative.
Click to expand...
Mulling through threads.......Rob, you mentioned in my thread that 7.5 is the limit for DCR, yet you are at almost 8. Does this mean that you are running aluminum heads?
 
CFD244 said:
Based on the info I am getting. An XE262 won't work in a stock '70 340.
Click to expand...
you may need a spring upgrade but I don't see why the XE 262 wouldn't work. It's not a super aggressive lift so it should work IMO
 
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