Cam Firing Order

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oris williams

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Clinton Ms
I hope Brian can help me with this. This is all I have for spec sheet. Cylinders 4 and 7 are not heating up properly.

B613C11D-D148-443E-A713-83852AC011B4.png
 
Could be any number of things. The firing order ground in to the cam being probably last on a long list. What are we working on and what have you done for diagnosis so far?
 
Ritter XR block with Molnar crank and rods. 9.20 deck with Indy 360-1 heads. I’ve done compression test/198 psi. Pulled plug and grounded to check for firing/changed wire and plug to verify if wire and plug were ok. All this checks out. Have not done leak down as of yet. Did I miss something?
 
oris williams said:
Ritter XR block with Molnar crank and rods. 9.20 deck with Indy 360-1 heads. I’ve done compression test/198 psi. Pulled plug and grounded to check for firing/changed wire and plug to verify if wire and plug were ok. All this checks out. Have not done leak down as of yet. Did I miss something?
Click to expand...
What happens if you run the rpm up to like 12-1300 for 30 seconds or so? Do those cylinders wake up?
 
Your cam card is hard to read I cant make out valve lash, what’s the lash set to?
 
After checking all the vitals I decided to finally do a leakdown test. Leaked at 5.6%. So looks like rings are sealed. Cam card showed standard firing order. Swapped cylinders 7 and 4 plug wires and guess what! Hitting on all 8 now! Cam is cut for 4/7 swap. So relieved. Thanks you guys for all the help with my issue
 
Wow. I’m very surprised by that. But, I’m happy you got it figured out.
 
8001A866-576D-4344-88AB-CAE9BF4E6062.png

Doesn’t it say on the last line of your cam card right there ^^^^
FIRING ORDER- STD
That’s a big screw up from a cam company and I’d be sure to let them know.
 
Exactly! I’ve owned several cams and never had that problem….but this is my first 50mm roller and my first 48 deg block also.
 
Hello, Oris. So what kind of increase are you looking at with the 4/7 swap? Thanks John
 
Not really looking for a big increase but I do hope it helps with harmonics above 7000 rpm. Not sure of shift point yet but should be around 7800-8000
 
Engine masters did a firing order comparo with the 4/7 swap on a potent bbc. I think they found 2 hp. Certainly was less than ten, is my memory.
 
The 4-7 swap has more to do with moving the load on the mains than making power.
 
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