Thinking about this Howard’s cam

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If you give me your compression ratio, rod length, bore, stroke, where peak torque occurs and your shift rpm I’ll run the numbers I use and we can see what we get.
 
Newbomb Turk said:
If you give me your compression ratio, rod length, bore, stroke, where peak torque occurs and your shift rpm I’ll run the numbers I use and we can see what we get.
Click to expand...
12.3 compression, 6.123 rod, 4 inch stroke, 4.08 bore.
Peak torque, not sure but with current cam I would guess 4800-5k ish.
Shift at 65 ish
 
B3422w5 said:
12.3 compression, 6.123 rod, 4 inch stroke, 4.08 bore.
Peak torque, not sure but with current cam I would guess 4800-5k ish.
Shift at 65 ish
Click to expand...


Just so in clear, you want to keep peak torque at 4800-5k or do you want to raise that up some???
 
Newbomb Turk said:
Just so in clear, you want to keep peak torque at 4800-5k or do you want to raise that up some???
Click to expand...

I doubt I will raise the convertor flash up from where it currently is( 4900-5000)
So, the motor is going to live between 5000-6500-6600 99% of the time.
The heads flow extremely well up to 650 lift, my current cam doesn’t open the valve enough to take all the advantage of that.
This extra duration I am thinking will make the car not hit any harder out of the gate, which isn’t a bad thing with the. 8.75 rear
 
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Here’s what I get with your numbers:

270/286 @ .050
109/106
.645/.620

The better the bore to stroke ratio, and the higher the rod to stroke ratio the less split it calls for.

For a 340 for example it calls out a single pattern cam most of the time.

So the 16 degree exhaust split doesn’t surprise me.
 
Newbomb Turk said:
Here’s what I get with your numbers:

270/286 @ .050
109/106
.645/.620

The better the bore to stroke ratio, and the higher the rod to stroke ratio the less split it calls for.

For a 340 for example it calls out a single pattern cam most of the time.

So the 16 degree exhaust split doesn’t surprise me.
Click to expand...
Wow. Interesting. Never heard of that big of a split before.
I am a big believer in a narrower LSA for a heavy car( mine is 3330 with me)
That cam seems “ big” to me lol
 
B3422w5 said:
Wow. Interesting. Never heard of that big of a split before.
I am a big believer in a narrower LSA for a heavy car( mine is 3330 with me)
That cam seems “ big” to me lol
Click to expand...

It is pretty close on the intake duration but the extra 12 on the exhaust doesn’t surprise me any more. Especially with geometry like your engine has.

I ran some rough numbers for the 385 inch deal I’ll eventually build and it called out a 16 degree split.

My WAG is the extra exhaust duration is to open the exhaust sooner to help with pumping losses.

I need to compare the cam you’re looking at and my numbers a bit closer.
 
Here are the timing numbers I get.

Howard’s:

EVO: 67 BTDC
ECL: 110 BTDC
EVC: 27 ATDC
IVO: 32 BTDC
ICL: 102 ATDC
IVC: 56 ABDC

268/274 106/102

My numbers:

EVO: 75 BBDC
EVL: 112 BTDC
EVC: 31 ATDC
IVO: 29 BTDC
ICL: 106 ATDC
IVC: 61 ABDC

270/286 109/106

Looking at the numbers, and like I see a lot most of the extra 12 degrees of exhaust duration of which went to Exhaust Valve Opening. So it opens the exhaust valve 8 degrees sooner. That’s 75% of the extra duration added to the opening side.

That is because (my opinion or better yet my WAG) with the geometry you have the engine wants to reduce pumping losses with that earlier opening.

Without the extra exhaust duration if you tried to open the exhaust valve 8 degrees sooner you’d also close it earlier and that hurts overlap.

Equally interesting is with only two more degrees of intake duration it opens the intake valve 3 degrees later but closes the valve 5 degrees later.

Crap I forgot to calculate overlap. I’ll do that next.

Also interesting is the Howard’s cam with its 4 degrees of advance doesn’t center the overlap triangle.

My numbers with 3 degrees advance centers the overlap triangle.

I’ll run the overlap numbers.
 
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Newbomb Turk said:
Here are the timing numbers I get.

Howard’s:

EVO: 67 BTDC
ECL: 110 BTDC
EVC: 27 ATDC
IVO: 32 BTDC
ICL: 102 ATDC
IVC: 56 ABDC

268/270 106/102

My numbers:

EVO: 75 BBDC
EVL: 112 BTDC
EVC: 31 ATDC
IVO: 29 BTDC
ICL: 106 ATDC
IVC: 61 ABDC

270/286 109/106

Looking at the numbers, and like I see a lot most of the extra 12 degrees of exhaust duration 75% of which went to Exhaust Valve Opening. So an extra 8 degrees on the exhaust opening side.

Equally interesting is with only two more degrees of intake duration it opens the intake valve 3 degrees later but closes the valve 5 degrees later.

Crap I forgot to calculate overlap. I’ll do that next.

Also interesting is the Howard’s cam with its 4 degrees of advance doesn’t center the overlap triangle.

My numbers with 3 degrees advance centers the overlap triangle.

I’ll run the overlap numbers.
Click to expand...

Is that a typo?
The Howard’s advertised numbers at 50 are 268/274
You have 268/270 above
Btw, I appreciate your info, it’s very enlightening!! :thumbsup:
 
B3422w5 said:
Is that a typo?
The Howard’s advertised numbers at 50 are 268/274
You have 268/270 above
Btw, I appreciate your info, it’s very enlightening!! :thumbsup:
Click to expand...

Yup, I fat fingered that so I fixed it.

As for overlap, and BTW Howards used a .904 lobe for that cam which is good but their cam with its LSA has 87 degrees of overlap. That is seat to seat overlap.

I went to the Howards lobe list and found a 270 and a 286 lobe that are .904 lobes so that's an equal point and those big exhaust numbers still get you only 88 degrees of overlap.

That's because the went to a 109 LSA to keep the engine from drowning in overlap.

Very interesting I think.
 
I know of 4 cams that are running( have run)
on Bloomer heads FWIW.
My 260/264 solid( 565 lift)
259/264 roller (640 ish lift)
263/270 roller. ( 640 ish lift)
268/274 roller. ( 640 ish lift)
Mine is the dog of the bunch, but it should run 130 pretty easily in decent air based on what it ran few weeks ago in terrible air(128+)
 
Newbomb Turk said:
Yup, I fat fingered that so I fixed it.

As for overlap, and BTW Howards used a .904 lobe for that cam which is good but their cam with its LSA has 87 degrees of overlap. That is seat to seat overlap.

I went to the Howards lobe list and found a 270 and a 286 lobe that are .904 lobes so that's an equal point and those big exhaust numbers still get you only 88 degrees of overlap.

That's because the went to a 109 LSA to keep the engine from drowning in overlap.

Very interesting I think.
Click to expand...

I didn’t know that was a 904 lobe. Kinda scares me. I think my current cam is 875
Where are you finding that?
I have their 260/264 565/565 on a 106
 
B3422w5 said:
I didn’t know that was a 904 lobe. Kinda scares me. I think my current cam is 875
Where are you finding that?
I have their 260/264 565/565 on a 106
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If you google Howard’s lobe list you can pull up a PDF list of their lobes.

I started in the .875 lobe list and it wasn’t there so I thought damn they used .842 lobes for that cam.

But nope, they weren’t there. They are in the .904 section.
 
Newbomb Turk said:
If you google Howard’s lobe list you can pull up a PDF list of their lobes.

I started in the .875 lobe list and it wasn’t there so I thought damn they used .842 lobes for that cam.

But nope, they weren’t there. They are in the .904 section.
Click to expand...
:rolleyes: Yikes
 
B3422w5 said:
Didn’t notice this grind in the past. Think it would pick the car up significantly.
Right about what I think the motor would most like, without going to a roller and the extra costs associated with that.

Mechanical Flat Tappet Camshaft; 1964 - 2003 Chrysler 273, 340, 360 4000 to 7600 Howards Cams 710782-06 | Howards Cams
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Hey Don! IMO the cam the engine would want to fit your ?new? goals is going to be bigger...and i'm sure there's another tenth there. This new cam is likely not going to show it's potential until the converter gets loosened. I'd definitely gage its intensity to the one being used currently. As has been mentioned, you might venture into other manufacturers lobes. And don't be afraid to guess wrong by 3-4 degrees duration either. A lot of exhaust lobe profiles are more gradual so the split in numbers typically is negated by .200" lift. Hate to say it but likely new springs, and of course the crossing of fingers during the 'run-in' process would have me nervous. Any time you push the intensity and rpm and increase loads on a 59* motor ...it makes me nervous. I'm not comfortable arm-chairing a new profile in consideration of those issues but on theory alone the bottom cam you listed using the Bloomer heads looked good to me, and yes I know it's a roller. If that is now contemplated, then with an oem block not bushed, typically the cam lobe lifts are capped about .420" to keep the oil gallery covered.
 
ValiantS said:
Hey Don! IMO the cam the engine would want to fit your ?new? goals is going to be bigger...and i'm sure there's another tenth there. This new cam is likely not going to show it's potential until the converter gets loosened. I'd definitely gage its intensity to the one being used currently. As has been mentioned, you might venture into other manufacturers lobes. And don't be afraid to guess wrong by 3-4 degrees duration either. A lot of exhaust lobe profiles are more gradual so the split in numbers typically is negated by .200" lift. Hate to say it but likely new springs, and of course the crossing of fingers during the 'run-in' process would have me nervous. Any time you push the intensity and rpm and increase loads on a 59* motor ...it makes me nervous. I'm not comfortable arm-chairing a new profile in consideration of those issues but on theory alone the bottom cam you listed using the Bloomer heads looked good to me, and yes I know it's a roller. If that is now contemplated, then with an oem block not bushed, typically the cam lobe lifts are capped about .420" to keep the oil gallery covered.
Click to expand...

All good advice!
My block is bushed
 
I’m no expert on anything but I agree 100% with ValiantS that the car will need more converter to see the max gain especially with the bigger camshaft. What is the current camshaft in the car? If I missed it on the post I apologize.
 
71Demon528 said:
I’m no expert on anything but I agree 100% with ValiantS that the car will need more converter to see the max gain especially with the bigger camshaft. What is the current camshaft in the car? If I missed it on the post I apologize.
Click to expand...

260/264 565/565 solid

Have pretty much decided if I swap cams, I will go to a roller. Don’t want to risk something bigger going flat staying solid.
Maybe this cam…Vert will work with it

Howards Cam Mechanical Roller Camshaft; 1964 - 2003 Chrysler 273, 340, 360 3800 to 7600 712123-06
 
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