chev 4-7 firing order change

[doug schriener]

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]

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

[FireSale]

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]

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]

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]

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.

[MR DERBY CITY]

I changed the plug wires for the 4 -7 firing order years ago. The ole wagon ran rougher than hell and would barely drive onto the trailer....

[Bill Grubbs]

MJ, your problem was changing just the plug wires...you also have to change the sparkplugs.

Speaking of firing order... We did have a problem the first time we tried to dyno a set of Elston Tri-y's. They would not fit as the dyno cradle was too wide. The dyno operator said no problem we'll just swap sides and turn them upside down, like a boat header. I told him I did not think it would work.

Well...it did not work. In fact it did not work so well that the engine would not even start!!!

[SSDiv6]

There is more than swapping the camshaft and spark plug wires involved in the firing order swap.
Many times the engine will not pick up power due to the intake type used, dual plane versus single plane and it may require a change on the location of each header tube at the collector.

Here is a good article that addresses the subject:

https://www.enginelabs.com/engine-te...r-your-engine/

[Pedigo Perf]

Originally Posted by Bill Grubbs

MJ, your problem was changing just the plug wires...you also have to change the sparkplugs.

Speaking of firing order... We did have a problem the first time we tried to dyno a set of Elston Tri-y's. They would not fit as the dyno cradle was too wide. The dyno operator said no problem we'll just swap sides and turn them upside down, like a boat header. I told him I did not think it would work.

Well...it did not work. In fact it did not work so well that the engine would not even start!!!

For the record, that was NOT me!