chev 4-7 firing order change

doug schriener · 11-17-2018, 12:18 AM

Hi-This may have been talked about here;if so indulge me-what is the purpose in changing the firing order? Is it because 5 and 7 fire close together? Does it make more power or show a difference in cooling? Thanks for all answers. Doug Schriener

1720 · 11-17-2018, 05:05 PM

http://garage.grumpysperformance.com...cam-swap.5508/

FireSale · 11-17-2018, 09:38 PM

Read the link. The same goes for using a 351 firing order on a 302 Ford where 7 and 8 fire in sequence. It can take some of the stress off the crank. You need to use a cam that matches the firing order, though. I tried just moving the wires and it wouldn't fire...

Adger Smith · 11-19-2018, 09:19 PM

Big Cu.In. Hi HP Chevy engines will usually kill the # 4 main if the firing order is not altered. It can also smooth some of the pulses out in the intake manifold, too. The first altered firing order cam I used came from Lunati back in the early 70's. Some guy named Chris told me I needed it.
Draw out the firing order across the intake plenum to see where the air goes as well as the power pulses hit the crank.

Ed Wright · 11-21-2018, 01:12 PM

When I was running (NOT driving!) a 410" "outlaw" dirt track sprint car in the '80s, the 4-7 firing order swap improved my bearing life. Did not test that on a dyno. All I had was a chassis dyno.

Mike Pearson · 11-21-2018, 04:09 PM

I have 3 engines. all have different firing orders. One is standard. one is 47 swap. One is 47-32 swap. All seem to run the same. don't see any real difference the way they run of idle. more of a gimmick in my opinion. all Bullet cams too.

11-17-2018, 12:18 AM	#1
doug schriener Junior Member Join Date: Oct 2003 Location: pennock,mn Posts: 83 Likes: 21 Liked 7 Times in 6 Posts	chev 4-7 firing order change Hi-This may have been talked about here;if so indulge me-what is the purpose in changing the firing order? Is it because 5 and 7 fire close together? Does it make more power or show a difference in cooling? Thanks for all answers. Doug Schriener

11-17-2018, 05:05 PM	#2
1720 Junior Member Join Date: Feb 2011 Location: Ontario, Canada Posts: 30 Likes: 202 Liked 2 Times in 1 Post	Re: chev 4-7 firing order change http://garage.grumpysperformance.com...cam-swap.5508/ __________________ RT - SS/X circa 1972. Talbot Racing Family

11-17-2018, 09:38 PM	#3
FireSale VIP Member Join Date: Feb 2014 Location: Lakewood Washington Posts: 1,407 Likes: 29 Liked 237 Times in 126 Posts	Re: chev 4-7 firing order change Read the link. The same goes for using a 351 firing order on a 302 Ford where 7 and 8 fire in sequence. It can take some of the stress off the crank. You need to use a cam that matches the firing order, though. I tried just moving the wires and it wouldn't fire... __________________ Dale Shearon 68 Mustang 6394

11-19-2018, 09:19 PM	#4
Adger Smith VIP Member Join Date: Dec 2001 Location: Texarkana Ark/TX Posts: 2,446 Likes: 575 Liked 880 Times in 311 Posts	Re: chev 4-7 firing order change Big Cu.In. Hi HP Chevy engines will usually kill the # 4 main if the firing order is not altered. It can also smooth some of the pulses out in the intake manifold, too. The first altered firing order cam I used came from Lunati back in the early 70's. Some guy named Chris told me I needed it. Draw out the firing order across the intake plenum to see where the air goes as well as the power pulses hit the crank. __________________ Adger Smith (Former SS)

11-21-2018, 01:12 PM	#5
Ed Wright Veteran Member Join Date: Mar 2005 Location: Sand Springs, OK Posts: 8,132 Likes: 896 Liked 390 Times in 170 Posts	Re: chev 4-7 firing order change When I was running (NOT driving!) a 410" "outlaw" dirt track sprint car in the '80s, the 4-7 firing order swap improved my bearing life. Did not test that on a dyno. All I had was a chassis dyno. __________________ Ed Wright 4156 SS/JA

11-21-2018, 04:09 PM	#6
Mike Pearson VIP Member Join Date: Mar 2007 Posts: 2,453 Likes: 616 Liked 1,939 Times in 583 Posts	Re: chev 4-7 firing order change I have 3 engines. all have different firing orders. One is standard. one is 47 swap. One is 47-32 swap. All seem to run the same. don't see any real difference the way they run of idle. more of a gimmick in my opinion. all Bullet cams too. __________________ Mike Pearson 2485 SS