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  #16 (permalink)  
Old 09-29-2009, 10:23 PM
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Quote:
Originally Posted by Greg T
Techinspector1 has the right idea. The problem here is that everyone is assuming way too much and being much more critical than is necessary.

First, if I could determine the valve timing events from the info provided by Howards I would have done so. All they give me is lift, dur, and LSA. Now, I don't claim to know a hell of a lot about cam timing, but I do know that the intake valve can close just about anywhere and still maintain these given fugures.

The cam I choose is not critical to a build because it is going into a fairly stock 350 with ehaders, 416 heads and 175 psi cranking pressure. Yes, that is all I know about the engine. The only reason I am changing the cam is because I have a bad lifter that intermittently collapses. So, as long as I am changing the cam and lifters I may as well put something in there that will give me some grunt. The reason I want an early closing intake is preserve the cylinder pressure. I know enough to know that a 34* or 35* intake closing will give me more torque and streetability than a 46* closing and the tighter LSA will give me some good low end torque. I have found THIS ISKY , and THIS CROWER . The Crower would be installed at 4* advanced to get near my desired closing point. I have a found a couple from Howards but they don't include this info. Thats why I asked.

Thanx very much, Techispector1, for the wealth of info.
Greg, if you don't know where you're starting from, it's difficult to know where you're going. If I were in your position, I would mount a degree wheel and dial indicator and find out exactly where the intake closes on your present cam. I have a solid bar of steel cut to Chevy lifter bore size on one end and Ford lifter bore size on the other end. The bar is 8" long and squared off smoothly on the faces. I use it in place of a tappet when checking timing events instead of a solid lifter. If you turn the block so that the tappet bore is vertical, there is enough weight from the bar that it will ride the lobe well and give you credible readings on your dial indicator. The other reason to use it is so that the length will get you up past the deck so you can easily mount your indicator.

Once you know the timing on the cam that is in the motor now, you will be able to make an intelligent decision on which way you want to go. Doesn't make any difference whether the present cam is installed straight up, advanced or retarded. Just read the numbers off the degree wheel and write them down. That's what the motor is seeing. It doesn't care where the centerline is, it just know that is opens and closes the valves subject to the present centerline, whatever it is.

So, when choosing the replacement camshaft, you can replicate the timing events you now have going on or change them according to what you think the motor will tolerate. You can order a cam with custom events or an off the shelf unit and install it wherever you want to alter the events you currently have in the motor.

But, like I said, I would find out where I am first.

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  #17 (permalink)  
Old 09-30-2009, 06:26 AM
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Thats an idea. It is just a stock-type parts store rebuilt motor with very smooth idle. But i will slap a degree wheel on just to make sure. I'm not wanting to go radical because the 416 heads don't flow anyway. And, it's just a daily driver S10.
Thanx!!
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  #18 (permalink)  
Old 09-30-2009, 02:29 PM
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Quote:
Originally Posted by techinspector1
Please explain in detail how this is possible. I am always interested in learning new methods.

I have a camshaft that has 240 degrees duration @0.050" with a lobe separation angle of 112 degrees and the lobes are symetrical from opening to closing flanks. What are the timing events, based on your statement here???
Timing points are 8 and 52 52 and 8 when installed straight up. 112-112
in open -in close exhaust open - ex close
From that its pretty easy to see how the tiing points will shift if you were to say advance the cam in the motor by 4deg

timing points with 4 deg of advance 12 and 48 56 and 4
in open -in close ex open ex close
Lonbe centers shift to 108in-116ex when the cam is advanced 4deg
Not that hard.

The isky cam you are looking at will in all probability check at 4 deg advance in the motor even thou the cam card timing specs indicate that the cam is "straight up" (its up to you to check this). The intake closeing point will likely be 31 deg instead of 35. This is why you must degree the cam if you want accurate valve timing.
The crower cam is quite a bit bigger duration than the isky cam is.
Why can you not determine the valve event timing of the howards cams.
All the info is there for you. just calc it out based on the cam going in sraight up. Then look atthe effect of moving the cam ahead 4deg (typical of most off the shelf street cams) or by what ever amoun to fo advance you choose. 2-4-6-8-10
You are not tied to any particular cam phaseing (advance or retard or straight up install) (even if the cam card timing calls for x and Y timing points) You can adjust the installed cam position yourself to good effect, once you have determined its true installed .050" valve event timing (with all tolerences included) by "degreeeing it". Degree it in. If it don't have the amount of cam advance you want,move it. You can advance a cam yourself to good effect up to about 8 deg either way from "straight up"

To determine the 4 valve events of a camshaft take the intake duration @.050 and divide by 2. subtract the LSA. That is your intake opening point.

Take the intake opening point you just calculated:
Add 180, and then subtract the intake duration @.050. This is the intake closing point. You now know the intake opening point and closing point of the cam when installed "straight up"

Repeat using the exhaust duration @.050" and the same LSA

EG: 240@.050" single pattern cam ( duration is the same on both in and ex lobes.)... 112 LSA

240/2-112 = 8 8+180-240= 52 8 and 52

EG 255 @.050" 108LSA

255/2-108= 19.5 19.5+180-255= 55.5

timing is 19.5 open 55.5 close
advance this 255cam w/108 LSA by 6deg the intake timing will be 25.5 and 49.5

the exhaust timing will shift to 61.5 and 13.5

Lobe centers shift to 102in and 114ex when this single pattern 255 cam 108LSA is advanced by 6 deg

eg#2
cam is:
224-234 @.050 106 LSA advanced 3 deg

timing points are
9open and 35 close intake

46open and 8close exhaust

Lobe centers are 103in and 109ex

If you move theis same cam retarded by 4deg from "straight up" (106-106)
the centers shift to 110in-102ex
timing points re now 2 and 42 in
39 and 15 ex

same cam installed "straight up" instead of "advanced 3 deg"
the timing moves to 6 and 38 in
43 and 11 ex

Works the same for any cam as long as you know the duration @.050 of both the intake and exhaust and the LSA of the cam.
You can calculate the "straight up" timing points and see the effect on those timing points by moving the cam by what ever amount advanced or retarded makes you happy.

The cam card timing points are for checking. The amount of cam advance or retard expressed by the cam card in and exhaust .050" timing points .. is not carved in stone. It is a suggestion.
Nothing is stopping you from adjusting the cam installed position a bit more advanced or a bit retarded from where its is , to get the effect you are looking for.
Its not hard to do once you know where the cam is in the motor.

Which Howards cams (part numbers) are you considering using that you cannot determine the valve timeing of that cam, when installed "straight up" and what it will be with a bit of dialed in "advance" or "retard"?

Last edited by F-BIRD'88; 09-30-2009 at 03:32 PM.
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  #19 (permalink)  
Old 09-30-2009, 05:24 PM
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Quote:
Originally Posted by techinspector1
Please explain in detail how this is possible. I am always interested in learning new methods.

I have a camshaft that has 240 degrees duration @0.050" with a lobe separation angle of 112 degrees and the lobes are symetrical from opening to closing flanks. What are the timing events, based on your statement here???

Oh, and just so you and the rest of the lads here know, there is no difference afforded by whether the opening and closing flanks of a lobe are symetrical or asymetrical. That part of the lobe profile has nothing to do with the opening and closing points ground into the lobe at the time of manufacture. An asymetrical lobe is used to jerk the valve open quickly and return it to its seat more gently to help prevent valve bounce on the seat. A lobe can be ground symetrically or asymetrically and still have the same opening and closing points.

symmetrical lobes can affect it because it changes where the CL's are at, do you mark the centers at the lobe peak or split the difference on the .004" numbers, the .001" numbers, the .050" numbers or the .200" numbers- all of them will give you a different centerline on the same lobe profile if it is assymetrical, and even cam manufacturers disagree on the best method.
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  #20 (permalink)  
Old 09-30-2009, 05:59 PM
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Am looking at the following:

Chev SB (Hydraulic)
Lift: .449/.449
Adv. Duration: 290/290
Duration @ .050": 224/224
Lobe Center: 108
Hot Street, 4bbl. & Headers Recommended


And:

Chev SB 262-400
Application: Max Torque
RPM Range: 1700-5700
Lift w/1.5 Rockers: .470/.470
Adv. Duration: 284/284
Duration @ .050": 220/220
Lobe Sep. Angle: 108
Recommended Valve Springs: 98214



But I wanted to kow how the intake closing coinsides with the Isky and the Crower.
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  #21 (permalink)  
Old 09-30-2009, 10:43 PM
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Okay, one more question. Let's say the cam card shows an intake closing of 35* at .050. But the cam card also says 4* advanced. Does this 35* fugure mean the 4* advance is already accounted for, or if i install the cam normally without an offset key will it close at 31*? In other words, are the valve events posted on the card using straight up or 4* advanced timing?
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  #22 (permalink)  
Old 10-01-2009, 03:40 AM
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Quote:
Originally Posted by Greg T
Okay, one more question. Let's say the cam card shows an intake closing of 35* at .050. But the cam card also says 4* advanced. Does this 35* fugure mean the 4* advance is already accounted for, or if i install the cam normally without an offset key will it close at 31*? In other words, are the valve events posted on the card using straight up or 4* advanced timing?
Most of the time on street cams the cam company makes the cam with 4 or 5deg or 6 degrees of advance dialed in. and the cam card timing numbers reflect this. the most common being 4 degrees.

Isky cams cam cards show the timing as "straight up" according to the numbers.
But the last isky cam I installed went in with 4 deg of advance when I degreeed it. So I didn't need to adjust it.
108 LSA 104 intake c/L 112 ex C/L

The bottom line is you have to check. And if it matters to you you will check the installed timing and correct it, or move it to suite your build.

Were you able to calculate the timing points of the Howards cams using the simple calculator math I outlined?
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  #23 (permalink)  
Old 10-01-2009, 08:53 AM
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I havent had the time to calculate anything since I spent most of the day yesterday in the ER. But, you're saying that the isky's timing card already reflects the 0* advance. So, in other words, just installing the can as directed by isky using the existing marks should be correct. Or. close to it depending on tolerances. I will check it, I'm just trying to clarify. Some cam cards make note that the cam is 4* advanced and I didn't know if the card timing frelected that or, if I installed using their timing marks the valve events would not coincide with the cards events. Does that make sense?

On a second note, the Crower I'm looking at says intake close at 37* but says nothing about advance. Should I advance that one 4* to get my targeted 35* . See, this is not a build. It's just a simple cam swap cuz I have a lifert collapsing in a stock rebuilt 350.

Last edited by Greg T; 10-01-2009 at 09:00 AM.
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  #24 (permalink)  
Old 10-01-2009, 07:16 PM
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Quote:
Originally Posted by Greg T
I havent had the time to calculate anything since I spent most of the day yesterday in the ER. But, you're saying that the isky's timing card already reflects the 0* advance. So, in other words, just installing the can as directed by isky using the existing marks should be correct. Or. close to it depending on tolerances. I will check it, I'm just trying to clarify. Some cam cards make note that the cam is 4* advanced and I didn't know if the card timing frelected that or, if I installed using their timing marks the valve events would not coincide with the cards events. Does that make sense?

On a second note, the Crower I'm looking at says intake close at 37* but says nothing about advance. Should I advance that one 4* to get my targeted 35* . See, this is not a build. It's just a simple cam swap cuz I have a lifert collapsing in a stock rebuilt 350.
You need to look at the tming cards. The crower cam is a 108 LSA. The card clearly states that the valve timing on the card reflects this cam installed at 104 intake C/L
That is 4 degrees advanced. If it closes at 37 when in at 104 in C/L and you want 35 then move it 2 more degrees, not 4. (after checking it first)
When you do move it and additional 2deg it will be in on a 102in C/L and therefore will be 6 advanced.


The isky cam card shows the timing as straight up ansd the card says 0 deg advance. But it may very well check differently (about more 4deg advanced from the card).

Use cam gear offset bushings and a cam bolt locking plate to adjust the cam advance in the motor as required.

Chev SB (Hydraulic)
Lift: .449/.449
Adv. Duration: 290/290
Duration @ .050": 224/224
Lobe Center: 108
Hot Street, 4bbl. & Headers Recommended


this cam needs to be 5deg advanced for a 35deg in closing point


And:

Chev SB 262-400
Application: Max Torque
RPM Range: 1700-5700
Lift w/1.5 Rockers: .470/.470
Adv. Duration: 284/284
Duration @ .050": 220/220
Lobe Sep. Angle: 108
Recommended Valve Springs: 98214


this cam would need to be 3deg advanced for a 35deg in closing point.

Last edited by F-BIRD'88; 10-01-2009 at 08:04 PM.
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  #25 (permalink)  
Old 10-01-2009, 10:33 PM
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Because I skipped over all the back and forth about cam degreeing, I am not sure if anyone has answered your question about Howards quality....I have used their stuff and it is on par with any of the Big Name valvetrain components out there. Usually the price is better but the quality is very very good. (if not excellant)
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  #26 (permalink)  
Old 10-02-2009, 02:15 PM
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Well, that's really why I was looking at them to begin with. I know, roughly, what I want to throw in there for the time being and found it hard to swallow Isky's pricing. This cam will probably only be in service for a year or so as I am planning on making a drag truck of this S10. I just need it to be dependable until I get everything I need to do the project. Right now it is my daily driver and since I need to replace a lifter I thought I would just give it a little more snot and a tougher sounding exhaust note while I had it apart. I may just grab the Howards based purely on price alone. As long as I can get thru the break in process I should be fine. I don't even plan on changing springs for this motor.
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  #27 (permalink)  
Old 10-04-2009, 12:28 PM
How fast is fast enough?
 
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for price alone builds its hard to beat Elgin. They have a pretty decent selection and good reputation too.
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