Single or Dual Pattern Cam

-
318 will run, I'm wanting to get better performance from my 318. I've had a lot of good suggestions on the cam. I thought that since you have a 318 I'd ask you what cam you recommend. Compression ratio 9.40:1, speedmaster cylinder heads with 170cc intake runner's, 1.88" intake valve's and 1.600"exhaust valve's, comp valve job and back cut the valve's. Intake, edelbrock performer rpm, carb 650 edelbrock. Headers 1 5/8" long tubes. Ignition, stock mopar with a gm 4 pin module and matching coil. Gear ratio, 3.55. I haven't bought anything yet as I'm trying to put together a good combination.
 
318's are idiot proof... just like slants.
More people have trouble tuning 360's is what I see the most.
You could build one even with a lobotomized. You don't need special advice.
Fyi Speedmasters dont have 1.88 valves.

Nothing changed...call a cam grinder is what you should do and stop asking youtubers who port with "socket templates" and use "butt dynos" for cam advice.
That's all great for experimenting on your own junk if you cant afford to pay a professional..but we have already established a correct way to do things to get optimal results that are measured and proven by something other than buttcheeks.

Get serious and educate yourself...or be prepared for a fruitless venture navigated by "so n so's work shed...brought to you by a 12 pack and and a bad idea".


Anyone remember that kook who's line was "give it the juice" or some ****...where all he did was tighten the kickdown cable on folks tired ram transmissions ...lol.. they're were like "damn this runs good" because it would shift higher than 2800 rpm and with some feeling....right before burning up the next month. Its rough out there... be careful what you read or who you follow. Chances are.. you can learn all the good they offer from a book in an hr or less with nothing broken or ruined in the end.
 
I've been reading what I can find on torque cams. What I can't understand is if a wide lsa is not good for torque than why does the cam manufacturers list their torque cams with a 110*-112* lsa?. If I run speedmaster cylinder heads with 170cc intake runner's and 2.02"intake/1.600" valve's with a comp valve job and back cut the valve's and have the bowl area cleaned up, would those cylinder heads hurt midrange torque and power? Also would a single pattern cam be a good idea? Or would 5.2 magnum heads be a better choice, that is if I can find them for a la intake manifold bolt pattern? Somebody recommended a Howard's cam that has 255* / 261*, 208* / 214*@ 0.050" and it has a lsa of 110* would this cam work with a 9.40:1 cr without having to back off the timing? I'm trying to do as much research as I can but there's a lot on cams that I don't know about, thanks for your help and patience.
 
The first thing to consider are your performance goals. Do you want to run 14s in the quarter? 13s ? 12s ? 11s ? Even if you never intend on taking your car to the track , it should be a consideration. If you rode in a friends performance car and decided that was fast enough for you, then find out what that particular car runs and work towards that goal. Examples: If a late eighties 5.0 Mustang is fast enough for you, then you might be satisfied with a 14 second car. If a Hellcat Challenger is not fast enough for you , then you are going to need a 10 second car. I'm pretty sure you are not looking for 10 second performance , but you may get bored with 14 second performance very quickly. 14s are cheap and easy with a 318. My Duster has a stock 75,000 mile 318. It ran fine and had good oil pressure. I added a 272 454 Summit cam, Comp 901 springs, LD4B intake , 650 DP and headers. I did a quick bowl port on the heads. The car has a stock converter and a 3.23 sure grip. I took it to the track last month for the first time and ran 14.39 at 96. Not especially impressive , but probably pretty typical results for a budget combo. The intake and carb I bought used years ago and the cam/lifters were $99 on a black Friday sale. Plans for next spring are more seat time, some tuning and a converter change. Your question about choosing a cam for torque: Even if you are able to build a great deal of torque relative to its displacement , it's still just a 318. It's not a 440 . It's not going to have neck snapping torque at 2000 rpm no matter what you do. To go fast with a small displacement engine without boost or N2O , you need RPM. You are going to have to consider how much converter you are willing to go with before you choose a cam. If you are married to your stock 1800-2000 stall converter , any cam much beyond 215 at .050 is probably going to feel soggy on the bottom. Throw a 3500 stall in it and you can install a cam that will really take advantage of the SM heads.
 
Dan,
Wider LSA was the thinking for low rpm [ tq ] cams. Like many things, with more knowledge over time, things have changed....
Some examples:
- piston rings are now thinner
- when our boat anchors were built, the thinking was to place the spark plug near the int valve so that the plug was cooled by the incoming charge; it was then discovered that the hot area near the exh valve caused pre-ign, so modern heads have the plug closer to the exh valve to initiate the flame front in that area first.
- thinner engine oil with tighter clearances are used today on perf engines, compared with wider clearances & thicker oil of yesteryear.

Crower was probably the most advanced & innovative of the cam grinders back in the day & their Mileage-Plus & Baja Torque master cams were ground on 110 LSA, not 112-114 like other companies. These were mileage/tq cams & were SP.

If you want tq, use a SP cam. DP increases overlap which generally helps top end at the expense of bottom end.
 
Bewy said:
Dan,
Wider LSA was the thinking for low rpm [ tq ] cams. Like many things, with more knowledge over time, things have changed....
Some examples:
- piston rings are now thinner
- when our boat anchors were built, the thinking was to place the spark plug near the int valve so that the plug was cooled by the incoming charge; it was then discovered that the hot area near the exh valve caused pre-ign, so modern heads have the plug closer to the exh valve to initiate the flame front in that area first.
- thinner engine oil with tighter clearances are used today on perf engines, compared with wider clearances & thicker oil of yesteryear.

Crower was probably the most advanced & innovative of the cam grinders back in the day & their Mileage-Plus & Baja Torque master cams were ground on 110 LSA, not 112-114 like other companies. These were mileage/tq cams & were SP.

If you want tq, use a SP cam. DP increases overlap which generally helps top end at the expense of bottom end.
Click to expand...
Even if I use the factory heads you think that a SP cam would be okay? What about the crower beast cams, are they any good?
 
If you have a good exhaust ports like most aftermarket headsI feel there's no real advantage to a split pattern camshaft. Actually I've seen a trend in tightening up the exhaust side lobe separation in a lot of new race performance cam grinds and circle track grinds. A split pattern is only trying to compensate for a week exhaust side. It was a hot subject and many were convinced that a split pattern was more modern and would produce more power, marketing jumped on that and produced a lot of new split patterns because people were buying them or should I say buying it. Jmo
 
It's really quite simple.
With a given pair of lobes;
When you decrease the LSA, you are moving the lobes together, so the first thing you will notice is that the overlap increases.
Simultaneously the durations of compression plus extraction also increase.
Going from 114LSa to 108 is 6*.
Overlap increases double of that so 12*.
Compression Plus extraction also increases 12*. Now; you can split these extra degrees between the two, almost any way you want to.
What you end up with is;
1) because of the earlier-closing intake valve, the low-rpm cylinder pressure rises, resulting in more low-rpm torque.
2) because the extraction degrees have been increased, this allows more time to transfer force from the piston tops to the crank to the flywheel, and theoretically she should get more torque, and better fuel mileage
3) the increased overlap, increases absolute power over the nose, at a slightly lower rpm, with a more rapid fall-off after the peak, but steals some fuel economy especially at lower rpms.
4) All in all, with the tighter LSA, you get a torquey engine with a narrow powerband, suitable for the Regular A833, and better able to put up with hiway gears.

Lets look at the Mopar 268/276/114 cam.
In at split overlap, the numbers are;
268intake/276exhaust/114LSA/ Ica of 66*/and
44* overlap, 114compression/106extraction
Ok lets tighten those same lobes up to 108, and I get;
268intake/276exhaust/108LSA/ Ica of 60*/and
56* overlap, 120Compression/112extraction

Here you can see the 6+6 degrees on each side of the lobes, yielding 12* more overlap, and plus 6* each to compression and extraction.
Now; 114* of extraction is quite a lot; excessive perhaps for a city car. IMO 108 would be lots, so then, you could trade 4* of extraction away, to compression, by retiming the cam.
But 120Compression +4more=124* which may be excessive for a high-compression engine, possibly putting it into detonation.
As to the overlap, this only works with headers and a free-flowing exhaust. An increase of 12* is a lot! about the same as 1.5 cam sizes in the 110LSA group, so you can expect to really feel the surge.

So, then, again; it's all in the combo.
If yur stuck with an automatic, the 108 cam has a fairly narrow power band, not at all suited to the WIDE 1-2 shift of the TF trans,(1.45/2.45= .592)
but better suited to that of the A833;(1.92/2.66=.722).
Some of that, to all of that, mismatch, can be side-stepped with a higher stall.
Ok so if you don't know about powerband requirement;
If you have a cam that wants to be shifted at 5500 rpm. And you are using a TF trans, then, when you out-shift First at 5500, the rpm will fall to 5500 x .592= 3256, therefore your powerband requirement is from 3256 to 5500=2244rpm. So your engine for this combo, needs some grunt at that 3256 to pull up the average-power from there to shift-rpm.
Whereas;
If you have an A833, the 1-2 rpm drop is to 5500 x .722=3971, therefore a powerband requirement of from 3971 to 5500=1529 which is just 68% of what the auto needs.
To be able to use the 108cam, in a competitive fashion to the 114cam , in the auto-combo, your auto would need a higher stall, to put the rpm to a similar 3971 rpm.
This is the simple solution, not the only solution.

As to single versus dual;
The dual pattern allows you to move the installed centerline away from split overlap without affecting the usefulness of the overlap very much, AND in street sizes, increases extraction for more torque and better fuel economy
Lets revisit that 340 cam but put the intake lobe on the exhaust side as well; I get
268/268/114LSA/Ica of 64* in at +4 (4* advanced), and
40* overlap/116Compression/108extraction.
Compare this to;
44* overlap, 114compression/106extraction from above
With the single-pattern, we gained 2* each compression and extraction, but lost 4* of overlap, and furthermore, overlap is now split 24/16 instead of on split overlap of 20/20.
Lets tighten it up to 108;
268/268/108LSA/Ica of 56* Advanced 6*, and
52* of overlap/124*compression/ 112 extraction.
As you can see, the numbers are a lil messed up.
However; the 124* of compression could really help a low-compression engine. and
the 112* of extraction is guaranteed to help with making torque. and hi-way fuel-economy, even around-town economy. but
overlap is now split 32/20 instead of 26/26, which is a bizarre bias towards the intake side.
So IDK. IMO at this cam-size, I don't see any advantage of an SP cam.
 
Last edited:
TTT
AJ/FormS said:
It's really quite simple.
With a given pair of lobes;
When you decrease the LSA, you are moving the lobes together, so the first thing you will notice is that the overlap increases.
Simultaneously the durations of compression plus extraction also increase.
Going from 114LSa to 108 is 6*.
Overlap increases double of that so 12*.
Compression Plus extraction also increases 12*. Now; you can split these extra degrees between the two, almost any way you want to.
What you end up with is;
1) because of the earlier-closing intake valve, the low-rpm cylinder pressure rises, resulting in more low-rpm torque.
2) because the extraction degrees have been increased, this allows more time to transfer force from the piston tops to the crank to the flywheel, and theoretically she should get more torque, and better fuel mileage
3) the increased overlap, increases absolute power over the nose, at a slightly lower rpm, with a more rapid fall-off after the peak, but steals some fuel economy especially at lower rpms.
4) All in all, with the tighter LSA, you get a torquey engine with a narrow powerband, suitable for the Regular A833, and better able to put up with hiway gears.

Lets look at the Mopar 268/276/114 cam.
In at split overlap, the numbers are;
268intake/276exhaust/114LSA/ Ica of 66*/and
44* overlap, 114compression/106extraction
Ok lets tighten those same lobes up to 108, and I get;
268intake/276exhaust/108LSA/ Ica of 60*/and
56* overlap, 120Compression/112extraction

Here you can see the 6+6 degrees on each side of the lobes, yielding 12* more overlap, and plus 6* each to compression and extraction.
Now; 114* of extraction is quite a lot; excessive perhaps for a city car. IMO 108 would be lots, so then, you could trade 4* of extraction away, to compression, by retiming the cam.
But 120Compression +4more=124* which may be excessive for a high-compression engine, possibly putting it into detonation.
As to the overlap, this only works with headers and a free-flowing exhaust. An increase of 12* is a lot! about the same as 1.5 cam sizes in the 110LSA group, so you can expect to really feel the surge.

So, then, again; it's all in the combo.
If yur stuck with an automatic, the 108 cam has a fairly narrow power band, not at all suited to the WIDE 1-2 shift of the TF trans,(1.45/2.45= .592)
but better suited to that of the A833;(1.92/2.66=.722).
Some of that, to all of that, mismatch, can be side-stepped with a higher stall.
Ok so if you don't know about powerband requirement;
If you have a cam that wants to be shifted at 5500 rpm. And you are using a TF trans, then, when you out-shift First at 5500, the rpm will fall to 5500 x .592= 3256, therefore your powerband requirement is from 3256 to 5500=2244rpm. So your engine for this combo, needs some grunt at that 3256 to pull up the average-power from there to shift-rpm.
Whereas;
If you have an A833, the 1-2 rpm drop is to 5500 x .722=3971, therefore a powerband requirement of from 3971 to 5500=1529 which is just 68% of what the auto needs.
To be able to use the 108cam, in a competitive fashion to the 114cam , in the auto-combo, your auto would need a higher stall, to put the rpm to a similar 3971 rpm.
This is the simple solution, not the only solution.

As to single versus dual;
The dual pattern allows you to move the installed centerline away from split overlap without affecting the usefulness of the overlap very much, AND in street sizes, increases extraction for more torque and better fuel economy
Lets revisit that 340 cam but put the intake lobe on the exhaust side as well; I get
268/268/114LSA/Ica of 64* in at +4 (4* advanced), and
40* overlap/116Compression/108extraction.
Compare this to;
44* overlap, 114compression/106extraction from above
With the single-pattern, we gained 2* each compression and extraction, but lost 4* of overlap, and furthermore, overlap is now split 24/16 instead of on split overlap of 20/20.
Lets tighten it up to 108;
268/268/108LSA/Ica of 56* Advanced 6*, and
52* of overlap/124*compression/ 112 extraction.
As you can see, the numbers are a lil messed up.
However; the 124* of compression could really help a low-compression engine. and
the 112* of extraction is guaranteed to help with making torque. and hi-way fuel-economy, even around-town economy. but
overlap is now split 32/20 instead of 26/26, which is a bizarre bias towards the intake side.
So IDK. IMO at this cam-size, I don't see any advantage of an SP cam.
Click to expand...
That was interesting reading for me. So, if I get a cam that has a 108*-110" LSA I should be okay? Now if I have to use factory heads will a SP cam be okay. I don't know if you read my earlier post but my intended use of the car is for cruising, no track time. I'm wanting to improve throttle response, low to midrange torque. Is there anything that I could do to the transmission to help acceleration, trans is a 904. I'm learning a lot on here.
 
Dan,
A trend today that was not there 20 yrs ago is using lower ratio rockers on the exh side, especially with DP cams. Is that a way of using a cheap DP shelf cam that has too much exh duration, & lower ratio rockers reduce lift & effective duration? Probably.

From Sig Erson of Erson cams,
'The cam with closer lobe centers will always produce more power in the midrange than a cam using the same profile & wide lobe center, & in many applications will produce more power all through the range depending on many variables such as the induction system, rod angularity & flow capacity of the ports.'
 
You must log in or register to reply here.
-

Back
Top