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Discussion Starter · #1 ·
ok
I've got the Predator Cam in the Cam card says 110 LSA
see here http://s22.photobucket.com/albums/b309/ToddZ/?action=view&current=img010.jpg

Cam in at 4 degrees advance at crank gear
per Proform Degree wheel instructions
1) Find TDC with stop
2) set dial indicator on retainer at max intake lift zero
3) rotate to .050" before and after max add both dimensions and divide by two.
First run
60 degrees before max Intake lift
140 degrees after max Intake lift
200/2=100 LSA right?

Change cam to straight up
1) Find TDC with stop
2) set dial indicator on retainer at max intake lift zero
3) rotate to .050" before and after max add both dimensions and divide by two.
First run
55 degrees before max Intake lift
130 degrees after max Intake lift
185/2=92.5 LSA right?
So why did LSA go down I thought removing advance would cause LSA to go to 104?

Cam back in at 4 degrees advance at crank gear
1) Find TDC with stop
2) set dial indicator on retainer at max intake lift zero
3) rotate to .050" before and after max add both dimensions and divide by two.
60 degrees before max Intake lift
140 degrees after max Intake lift
200/2=100 LSA right

So where do I go to get 110?

Todd
 

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Your statement “So why did LSA go down I thought removing advance would cause LSA to go to 104?” Your reference to LSA should be ILC.

LSA (Lobe Center Angle and in my opinion should only be read as Lobe Separation, omitting the word Angle to save confusion)is relative to the cam itself and does not change.

ILC (Intake Lobe Centerline) is relative to the cams position in relation to the crankshaft.

A cam with a 110 LSA installed straight up such that the ILC is 110 is neither advanced or retarded. 110 – 110 = 0 Degrees.

Manufactures say Cams with a 110 LSA must be installed with a ILC of 106 degrees to say that the cam has a built in 4 degree advance. Such that 110 – 106 = 4 degrees.

If you install a cam with the ILC at 104 degrees the cam would be installed 6 degrees advanced (110-104 = 6 degrees). This is a nice position to increase the Dynamic Stroke and DCR enhancing low and mid range torque.

If your getting and ILC of 100 then your cam is 10 degrees advanced (110 – 100 = 10 degrees). Too advance in my opinion.

NOTE: Always do a Piston to Valve measurement after degreeing the cam. Spray WD40 on the valves, mock #1 Cylinder Valve Train components using your choice of head gasket, place a .400” roll of plumber putty in an “X” pattern in the piston valve relief’s and turn the engine through one cycle. Use a razor blade to dissect the putty and measure the thickness. You can also use a very week valve spring and dial indicator.

Here’s a Link with a DCR Calculator – Have Fun :eek:))

http://www.empirenet.com/pkelley2/DynamicCR.html
 

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Discussion Starter · #3 ·
Ron;
I'm at the cam install point so install straight up then? No advance?

I've got the valvetrain figured out and with the 7.90 trick-flow pushrod the valve stem alignment is just a hair off center to intake side

The pistons are -.010 to -013 and I have the heads on with a set of mr. gasket premium headgaskets .028"
I can remove drivers cylinder head and clay model but can't I just dial indicate at closest point clearance left?
 

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I would b/c it will like to rpm anyway!!

And btw, did the cam card read 110/118?? B/c the second number didn't look like 110 is all. (More like 118)..

If so, it will be a 114/110 cam!!! Very much similar to the old 30-30 here too!

pdq67
 

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Todd: Huh! I take it's a SBC.

To give you advise on were and why to position a cam I would require some Info:

Kind of car and weight - Tranny - Gear ratio - size of tires - Intake and Exhaust

Eng Specs: Bore - Stroke - Rod length - Head cc - Piston Dome cc - Valve size.

What do you want to do with this car ?

Right now my only advice is to install the cam @ 106 degrees rather then straight up. I have no idea what your car is or what your using it for.

Considering the above info - Dynamic Stroke is relative to the cams ICL which determines DCR and relavent to the type of gas you plan to use.

I notice that cam is Solid Flat Tappet with an advertised 314 duration for Int & ext and .485 lift for Int & ext - sounds like the old 327 30-30 Cam. The lift is not over board but that duration requires allot of static compression to get the best performance out of that cam.

Fill me in with some info and I can give an opinion but you probably already have an idea where it's going - lol
 

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OK 11.0: Compression

Rod length 5.70”
64 cc Heads
10.6 CC Domes
4.0” Bore
3.0” Stroke
.028” thick Gasket
4.030 Gasket bore (Approx)
Piston to Deck .012”

Cam is 314 advertized duration for Int & Ext
LSA is 110 Int and what 118 Ext?
Lift .485 fir Intake & Ext

Entering this info into Kelley’s DCR Calculator I get the following DCR’s for the following Intake Lobe Center Lines ( ILC )

ILC of 110 = 7.02 DCR Dynamic stroke 1.8” Straight up
ILC of 106 = 7.36 DCR Dynamic stroke 1.9” Advanced 4 Degrees
ILC of 104 = 7.52 DRC Dynamic stroke 1.96” Advanced 6 Degrees

According to Patrick Kelley’s DCR instruction you should have a DCR between 7.5 and 8.2 for to days street driven engines; however, the 302 is definitely seems to be an exception and for the life of me can’t understand how it burns fuel efficiently – and it's evident that the 302 certainly does not have much power or torque on the bottom end - lol

I would choose the ILC of 104 Degrees thus advancing the cam 110 - 104 = 6 Degrees but I’m not an expert on the 302.

I would appreciate if other members could check my DCR Calculations and perhaps elaborate as I may be sticking my foot in my mouth here. :eek:))
 

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I will bet the cam is ground on 114 lobe separation angle. The 110 int. and 118 exh. is what you would have with the intake advanced 4 degrees. For each degree you advance the intake lobe centerline you will lose a degree for the exhaust lobe centerline.

The very most I would degree the cam would be to 108 intake lobe centerline. That would put the exhaust on 120.

If you degee the intake and determine the lobe center angle - degree the exhaust and determine the lobe center angle -then add both together and divide by 2 it should equal the lobe separation angle the cam was ground with. Example 110+118=228 divide by 2 =114 or advance it 2 more degrees is 108+120=228 divide by 2=114.

Sounds like the cam has 4 degrees advance ground into it. The only way to know for sure is to degree it. Do not add 4 more degress without knowing what you are starting with. I have never found more than 6 degrees advance to be beneficial, quite to the contrary, too much advance will hurt both power and torque.
 

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I reread the first post again. If you have the crank timing gear at 4 degrees advance you are in effect advancing the cam 8 degrees. Your calculations are exactly right.

Put the crank timing gear on the neutral postion and the cam should be at 110 on the intake lobe. This is assuming that 4 degrees advance is ground into the cam. This will be fine for your application.

The triangle or diamond should be the advanced postion on the gear- The box or square should be the retarded position and the circle should be the neutral postion on the gear. Is this the same as yours?
 

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I think your LSA is (110+118)/2=114, just like the 30-30. That cam card image is wrong. The line labeled "lobe separation" should say "lobe centerline". The 30-30 lobe centerlines are 112 and 116, a little different to get the same 114 LSA.
 

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You’re right that card is confusing and the old LS and LSA argument unfolds once more.

It reads Lobe Separation (Specific position of Lobe on Cam?) not Lobe Separation Angle as 110 Int and 118 Ext and to Degree and Install the Intake Lobe at 110.

Assuming 110 and 118 are the Int and Ext Positons, the LSA should be (110 + 118) /2 = 114 (marine LSA camshaft specs)

Degreeing and Installing the Intake Lobe at 110 effectively advances the cam 4 degrees (114 – 110 = 4) which is the Mfgr’s built in 4 degree advance.

Using Kelley DCR Calculator with a LSA of 114 and ILC of 110, I get the following:

ILC 110 = Dynamic Stroke of 1.78 and a 6.93 DCR -> Dam that’s LOW but I guess that’s how the 302 operates.

Say the Intake Lobe is installed at 106 Degrees effectively advancing the cam 8 Degrees.

ILC 106 = Dynamic Stroke of 1.88 and a 7.27 DCR (still below the 7.5 to 8.2 range)
This looks more efficient to me but as I say I’ve never built a 302 – 327’s I have.

FUN Huh :eek:))
 

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Remember, the little jewel is 11 to 1.

And this is why Isky's old Z-30 solid lifter cam ran so well in the smaller engines b/c it is 290/250, 108/108, .450" net lift on both valves w/ .030" lash like the old 30-30.

pdq67
 

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Discussion Starter · #16 ·
Ok
Heres a quick result at Straight up reading
http://i22.photobucket.com/albums/b309/ToddZ/Cam Swap/IMG_3144.jpg
Must of honked up TDC on run #2 at straight up

Changed cam to straight up
1) Find TDC with stop
2) set dial indicator on retainer at max intake lift zero
3) rotate to .050" before and after max add both dimensions and divide by two.
First run intake
69 degrees before max Intake lift
145 degrees after max Intake lift
214/2=107 LSA right?

Exhaust
80 degrees before max exh lift
160 degrees after max exh lift
240/2=120 LSA right?

Looks better
Now what do I check?

Todd
 

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I would just run it at 107 intake centerline. Check the Piston/valve clearance to make sure you have enough clearance. I will bet it is OK as is.

I am almost positive, along with most others, that this is a copy of the old 30-30 cam that was originally in your engine. If I had a Z/28 with the 302 I would run nothing else.

You could put the head on, doesn't have to be torqued down just tighten firm, install a pushrod, rocker and adjust the valve. Roll the engine through the cycle with the dial indicator on the valve end of the rocker. You can see the degree the valve begins to open and the degree it closes. You will have a very accurate degree number to use for your dynamic compression. I will bet it is close to 82 degrees after BDC.
 

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Discussion Starter · #19 ·
Ok Here are the timing events for valve opening and closing points.
Intake starts open at 34 degress before BDC
Intake closes at 108 degrees before TDC

Exhaust begins open at 100 degrees after TDC
Exhaust closes at 30 degrees after BDC

I'll check valve to piston after I install soft spring on #1 intake exhaust

Todd
 

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Do you have the regular valve springs on or light springs? If you have the springs you are going to run it is a little harder to check V/P clearance. If you have light springs you can get the degree wheel to 10 degrees BTDC and start pushing down on the intake valve (with a dial indicator measuring how much clearance you have) and continue to do that at 3-4 degree intervals until you get to 10 degrees ATDC. Chances are the closest point will be at about 6 degrees after TDC. You can tell when the dial indicator starts showing more clearance.

If you have the regular springs you will be running on you can set the valve at .030 and roll it through the cycle a couple of times, then recheck your clearance. Then measure close to .090 of blades in a feeler gauge. Get a breaker bar and socket and back the rocker arm nut off exactly 1 turn. Put the feeler gauge with the .090 of blades between the rocker and valve. Tighten the rocker nut up exactly 1 turn. Rotate the crank very slowly and carefully. If you have less than .090 clearance between the piston and valve the engine will lock up. If you have .090 or more it will rotate freely. This isn't very scientific but it works. You can do the same for the exhaust.
 
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