4/7 swap cam

[sj valley dave]

Just to clarify, we got this SB2.2 from Bill H used. He had built it for Mo Gordy in NC. I think that Mo requested the LS-1 firing order cam and Bill built it that way...The reason I just think it idles smooth, is that I know the HP this engine makes, I know approx the duration/lift this cam has and when I compare it to other rollers that we have had in the past it just seems to idle smoother and doesn't have that characteristic hard rump/rump...LOL No idea why, just figured that maybe the 18726543 firing order had something to do with it...Any other ideas TB or Perfconn? I was never sold on the 4/7 swap...how about the 4 cylinder swap? why would Chevy do it? Thanks for any replies..

[DANNY]

Lol ya I always wondered why the LS1 was diff too lol... I prob will never use one cus
Ill keep putting the plug wires in the regular chevy firing order lmao...

[perfconn]

When chevy came out with the LS engines they were completely redesigned including the firing order.Look at those little intake ports.Do you think the cathederal ports are better than the old style intake ports? I was at a chevy dealer the other day looking at the new Corvettes.All aluminum engine with dry sump,blower,titanium rods and its only rated at 638hp.Either its way under rated or its not very good.There are all steel 23degree wetsump round track engines that are way better than that.
The camshaft duration and overlap determines how smooth an engine is not the firing order.All firing orders in a V8 fire a cylinder every 90 degrees irregardless of the firing order.

[stockcar5]

I was at a chevy dealer the other day looking at the new Corvettes.All aluminum engine with dry sump,blower,titanium rods and its only rated at 638hp.Either its way under rated or its not very good.

or it was built to meet strict epa emissions guidelines....

there is way more to changing the firing order than the saleman is leading you on to. it will change crankshaft harmonics, main bearing loading, cooling system performance, and intake pulses. im sure there is more...

[go2fast]

We run a 4 7 3 2 swap 55mm cam on a 418 with 903 lifters. I thank it help a little on the tork we like it

[500BOMBER]

Waste of money.
If you don't change the cubic inches or the weight of the crank and rods or the camshaft profile or the rocker ratio or anything else about the engine,how can you expect to make more power by changing the firing order?
You are simply moving the 5-7 cylinders firing next to each other to the 4-2 cylinders firing next to each other.

Yep, Exactly!

[sj valley dave]

I was told last night by a metalurgical engineer that what he has surmised by talking with a few peeps is that the torsional twist on a piece of steel, ie: crank can be altered by what the firing order is due to harmonics and twisting put on the steel at different point along the axis...Not saying he is wrong or right, but that is what he was trying to impart to me about the 4 cylinder firing order on the LS-1...he said otherwise there was no reason for GM to change it...

[500BOMBER]

..... it just seems to idle smoother and doesn't have that characteristic hard rump/rump...LOL No idea why, just figured that maybe the 18726543 firing order had something to do with it...Any other ideas TB or Perfconn? I was never sold on the 4/7 swap, Thanks for any replies..

On the 18726543 firing order,a cylinder is fired alternately from left bank to right bank every 90*.
The 18436572 order has 2 cyl's firing 90* from each other on both banks. So does the 18736542 order. Hense the smoother sounding idle on 18726543.
That is also why I feel the 4/7 deal is nothing more than hype.
Steve Adams

[perfconn]

The LS firing order also has 2 cylinders on each side firing 90 degrees from each other.The 2-6 on one side and the 3-1 on the other side.You are also not doing away with 2 cylinders firing next to each other(1-3) so every thing considered,I think its all sales hype.I've never seen any benefit on back to back cam changes on a dyno or on paper either.

[500BOMBER]

The LS firing order also has 2 cylinders on each side firing 90 degrees from each other.The 2-6 on one side and the 3-1 on the other side.You are also not doing away with 2 cylinders firing next to each other(1-3) ....

Yep, yer right about that. My bad.

[runyou-2]

Bottom line it is worthless.

Read the previous post.All your doing is having 4/2 cylinders firing next to each other.

I agree.There's NO question at all here!
I have a comp 4/7 swap that comp designed* along with JE using a dished piston (12.8@50cc,235 runners) and step headers in my 14* IRON head 434.This engine IS the baddest bull i have EVER stomped on...BUT,i feel it IS on the Lazy side and THAT is exactly why they wanted to go with the swap to aid not blowin the tires off.I have tried both ways and....MAYBE,Maybe, i notice the swap being a little lazy,Maybe.As far as power....there is NO way a person could stomp the pedal and honestly tell you there's a big difference.No way,just another marketing joke.

With respect; I have to hand it to Jimmy Naylor!!!! He computed and came up with his own cam design and gave me his #,s to compare what comp would come up with.The man all but nailed it perfect.I'm not so sure,I probly should have went with his numbers.When he speaks,i listen.