so im at the shop talking to my buddies ,and the subject of doing a 4-7 swap came up. I honestly never heard of such a thing . but you live and learn. so my question is; what is it? why would anyone want to do this? benefits? my curiousness makes me want to learn more about it . anyone care to enlighten me?

 

It started with the LS1 engines. GM changed up the firing order, why is up to speculation as I don't believe that GM made any announcements as to why. Cylinders # 2 & 3 were also swapped in the firing order.

One reason stated by folks is that it smooths the power pulses on the crank shaft. Which may be true with how the trigger wheel is set up along with the misfire detection scheme.

When installing a 4/7 swapped cam into a SBC need to remember to also swap those two spark plug wires.

RBob.

 

I run a 4/7 swap camshaft in my race engine. If it wasn't for the extra cost of a 4/7 I'd say go ahead and get one. For a street engine, there's no real benefit to buy one.

The 4/7 cam just changes the firing order by swapping cylinders 4/7 around. Instead of 18436572, it's 18736542. It takes away the imbalance from cylinders 5 and 7 firing right after each other but then moves it to 4 and 2.

If you had identical camshafts but one was standard firing order and the other was a 4/7 swap and you did dyno testing, you wouldn't see any difference. It's suppose to change the harmonics on the crankshaft to run a bit smoother.

 

4 and 7 are on opposite sides of the firing order. Instead of 18436572, you get a cam ground 18736542, and swap the spark plug wires to match. 5 & 7 are adjacent and they steal airflow from each other (single plane), but you end up in the same boat with 4 & 2.

Someone else will have to add more comment on the benefits. Or you can Google.

 

The plug wires on my distributor cap don't go crisscrossing now with the 4/7 cam.

 

4/7 swap camshaft have been around a long time. It is a old pro stock trick that will increase horse power only a small amount in certain applications. Ford used it in the 351 windsor and 5.0 HO engines.