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Cam Syncro / firing order questions


Nightbiker07

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OK. SO. I ditched the stock explorer cam and went with a comp cams xtreme energy cam. The cam is 4 degrees advanced, and when using the cam sync tool, the syncro is pointed slightly off to the passenger side when it is lined up (as opposed to straight ahead with a stock cam).

This would mean that the computer is seeing the cam at zero degrees, when in fact the cam is already moving valve train parts. Would I simply leave it like this, or do I have to manually advance the syncro so the PCM is in sync with the cam? Or would that be dealt with in the SCT tuning work that has been done?


Second half of the question. This cam was listed on Comp Cams website as a good H.O. Replacement cam. I have heard the H.O. uses a different firing order than the standard explorer engine. Would the firing order also be changed with the tune, or would I have to manually swap plug wires around on the coil packs and injectors?
I have never been quite clear on how the same crank can have two different firing orders by just changing the cam
 
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ummduh

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All i can help with is that the xplorer does in fact use the h.o. firing order.

there are really only a few firing orders for a cross plane crankshaft v8. Fun fact, the small block chevy, when corrected for the differences, uses the same firing order as the 302HO&351W.

I assume there is some type of proper way to install and sync the cam sensor, there's no way you can just drop it in and call it good with where it falls. I'd suggest looking that up.

edit: http://www.explorerforum.com/forums/index.php?threads/camshaft-position-sensor-replacement-a-bit-of-discussion.89670/
 
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RonD

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Crank rotates TWO full turns for each one full turn of Cam, that is what makes it a 4-stroke engine, 4 strokes of a piston is needed for 1 complete cycle, which means crank rotates twice and Cam rotates once

In a multi-cylinder engine two pistons are at TDC(top dead center) at the same time, this balances the engine, the Cam/valves decide which cylinder is on compression stroke or exhaust stroke TDC
So firing order can be changed by changing the Cam/valve timing but only between those two cylinders that share TDC

302 firing order
1-5-4-2-6-3-7-8

If you split this and put 1 below the other
1-5-4-2-
6-3-7-8
You now have the match pairs that share TDC
1 and 6
5 and 3
4 and 7
2 and 8

HO firing order
1-3-7-2-6-5-4-8

1-3-7-2-
6-5-4-8

1 and 6
3 and 5
7 and 4
2 and 8

You can see 3 and 5 are reversed in the order and 7 and 4

This is because the Cam was changed to open these valves in a different order
No change to the matched pairs so crank is the same

Putting in a Cam with longer open time for the valves doesn't change the firing order
 
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Nightbiker07

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RonD said:
You now have the match pairs that share TDC
1 and 6
5 and 3
4 and 7
2 and 8
Click to expand...
This is the part I wasnt grasping, I was thinking every cylinder came to TDC at a different time. Since two cylinders share TDC, it makes perfect sense how they could be reversed :beer:
 

Nightbiker07

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ummduh said:
All i can help with is that the xplorer does in fact use the h.o. firing order.

there are really only a few firing orders for a cross plane crankshaft v8. Fun fact, the small block chevy, when corrected for the differences, uses the same firing order as the 302HO&351W.

I assume there is some type of proper way to install and sync the cam sensor, there's no way you can just drop it in and call it good with where it falls. I'd suggest looking that up.

edit: http://www.explorerforum.com/forums/index.php?threads/camshaft-position-sensor-replacement-a-bit-of-discussion.89670/
Click to expand...
cam sync is installed according to the directions using the alignment tool. With the stock cam, the sync points straight forward, with this cam, it is slightly pointed to the side a couple degrees. I assume this is due to the cam being advanced 4 degrees over a stock cam.
 
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