Degreed My 340 Camshaft Today

[cookietruck]

I don't know how to interpret these charts, but I entered some data and here is what was generated:

View attachment 1716429598

View attachment 1716429599

Makes sense. You are installed 0* advanced while the cam card is calling for 4*.
Use the 4* advance setting in your timing set. Remeasure. Check that the intake valve events match the cam card.
I would also check intake and exhaust lobe centerlines.

 

[1MeanA]

According to the info listed from KrazyCuda on other threads, this Oregon cam is ground like this:

Lobe separation 114
Lobe centerline intake 110
Lobe centerline exhaust 118

Which means it’s got 4 degrees advance built in. What does your Oregon cam sheet say? I don’t know about that 118 number.

 

[crackedback]

Which means it’s got 4 degrees advance built in. What does your Oregon cam sheet say? I don’t know about that 118 number.

The intake cl and exh cl added, divide by two = the LSA number. Cam math

If this cam was 112 IC, exh would be 116

 

[dibbons]

I never saw a sheet with the camshaft so I can only quote what Krazy has posted here and there.

 

[Bewy]

With re-ground cams, you are limited by how much you can change the LSA from the original LSA of the cam...because the metal has already been removed. Doing so will result in a very small lobe

 

[dibbons]

Update: Rv'd a message from Oregon Cams:

"When you degree the cam in you should set the intake at 108 intake center line if you can. A degree either way won’t matter."

 

[Bewy]

'A degree either way won't matter'. Very good advice from Oregon. The nonsense I see on this & other forums about degreeing in a cam to some mythical centre line...when the cam has never been run to get a baseline. As D. Vizard says, only when the optimal cam specs have been selected will moving the cam make a significant difference.

 

[1MeanA]

I can't find my cam sheet but I dug this up as I had saved it:

#2120

221/227 @ .050”, 276/286 adv, .438”/.456” lift, 114 sep


Per the 68 Plymouth service manual, the factory specs are:

276/284 dur, .444"/.453" lift

Int op = 26° BTC
Int cl = 70° ABC
Exh op = 78° BBC
Exh cl = 26° ATC

From calculations:

Intake centerline = 112° ATC
Exhaust centerline = 116 BTC
Lobe separation = 114°


This is the grind we have been using that is supposed to be the cam you are inquiring about. We made this master from a cam that a customer supplied us that was supposed to be the factory Mopar cam. We have made quite a lot of them. We can do a regrind for $79 on your core or make a new one for $179.

Thanks

Ken
1-800-539-9165
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[dibbons]

Which means it’s got 4 degrees advance built in. What does your Oregon cam sheet say? I don’t know about that 118 number.

I never saw a sheet with the camshaft so I can only quote what Krazy has posted here and there.

From calculations:

Intake centerline = 112° ATC
Exhaust centerline = 116 BTC
Lobe separation = 114°

OK. Now I just wonder what "from calculations:" refers to? The factory camshaft or the Oregon Camshaft.

 

[dibbons]

Update: Some more measuring today

Intake center line 68 + 160 = 228 / 2 = 114
Exhaust center line 67 + 159 = 226 / 2 = 113

Cam lobe separation angle (LSA) 114 + 113 / 2 = 113.5

My Cloyes crank gear has provisions for either four degrees retard or advance. I will probably try the advance slot next.

 

[1MeanA]

OK. Now I just wonder what "from calculations:" refers to? The factory camshaft or the Oregon Camshaft.

Per the note from Oregon they copied an original '68 340 4 speed cam

 

[dibbons]

Update: Advanced the camshaft four degrees today and re-measured:

Intake center line 91.5 + 130 = 221.5 / 2 = 110.75
Exhaust center line 72 + 163.5 = 235.5 / 2 = 117.75

Cam lobe separation (LSA) 110.75 + 117.75 = 228.5 / 2 = 114.25

 

[cookietruck]

Update: Advanced the camshaft four degrees today and re-measured:

Intake center line 91.5 + 130 = 221.5 / 2 = 110.75
Exhaust center line 72 + 163.5 = 235.5 / 2 = 117.75

Cam lobe separation (LSA) 110.75 + 117.75 = 228.5 / 2 = 114.25

Did that make the intake valve events match the cam card?

 

[crackedback]

RUN IT!

 

[dibbons]

Updated Measurements after having advanced camshaft four degrees:

 

[cookietruck]

Within 1* on the intake valve events right? Seems great.

 

[lilcuda]

Post #5. The engine cycle is 720*. So the exh valve is on the seat for more than half the duration [ 348* ] of the cycle.

720/2=360

 

[dibbons]

Update: These are the final piston to valve clearances measured with a dial indicator and Felpro head gasket torqued to 40 ft.lbs that measured .055" (1.5 mm) after the above torque. First figure straight up installation followed by the four degree advanced installation. The advance decreased intake clearance and increased exhaust clearance.

Exhaust

15 BTDC .203 n/a
10 BTDC .192 .208
5 BTDC .194 .211
TDC .205 .229

Intake

TDC .300 .190
5 ATDC .225 .195
10 ATDC .220 .202
15 ATDC .240 n/a

 

[1MeanA]

I didn't remember bothering to check piston to valve clearance with that cam.

 

[dibbons]

I didn't remember bothering to check piston to valve clearance with that cam.

For this 340 stock-like application not necessary to be too concerned with valve clearance. However, after break-in this same camshaft will be used in my 305 project (de-stroked 340) in which we have installed TRW domed pistons (L2322F see foto) which rate up to 13:1 compression with 239 psi (using stock 3.31 stroke, 63cc chambers, .039 gasket, .407 dome @ 10.7 cc, .017 above deck). Of course, by way of de-stroking, we will be losing between one and two full points of compression.

According to calculator: using 2.96 stroke (with 6.298 rod length), .030 over, 73cc chambers, .039 gasket, .017 above deck, we find 10.43 to 1 compression. Dynamic compression using intake close @ 68 we find 7.98 to 1 with 163 psi. Intake close @ 60 we find 8.49 to 1 with 176 psi.