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Not trying to be disagreeable but you guys need to use your head for something besides a hat rack.The sb chevy fires a cylinder every 90 degrees.It doesn't matter which firing order you use its still firing every 90 degrees.Changing the profile of a cam when you change the firing order will confuse the whole deal.You ever see anything any smoother than a stock engine that will idle at 800rpm.
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4/7
It would appear that firing 2, right after 4, would stop detonation because cold water is coming in at the front of the block, and to a point, thats true. When you fire 7 right after 5, it's being cooled by water that has already gone by 3 other cylinders. For drag guys that run an electric water pump, which BARELY moves enough water through the block to keep up (and keep water pressure up at the restricter holes in the head gasket, which makes the distribution equal), the 4/7 swap isn't a bad idea. Circle track guys run higher water pump speeds, lines of the back of the intake, ect.; so there are better things to spend your hard earned money on.
On a lot of our engines (budget allowing), we restrict the water pump hole, and feed the middle of the block. If you can get all 8 cylinders to run the same temp, I believe it's worth a few hp. My 2 cents.TBComment
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Read my post on rocker choices.Same thing applies here.If you will find a good engine builder and listen to him you will be dollars ahead.Old wives tales are as abundant in racing as any where else.Comment
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Im not an engine builder nor a cam guy i dont know a thing even now im going to have to ask when i change heads what cam i need and i been told 5 times already... But to my knowledge what kills engines and breaks parts besides the obvious too much HP and RPM? Harmonics more then one post here has said that "it seems to run smoother" thus reducing the jitters in these HP giants wouldnt it be worth it to you if none other then maybe your motor doesnt wear the parts out so fast to try it... Dave said it in his LS1 cam that his SB2.2 runs smoother lol»»*†HÀ†§ HÓ††™««Comment
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He also said it came that way.If it came that way then he has never tried the regular firing order in it.If you are going to buy a cam its your money.Buy what you want even if you are needlessly spending money.Comment
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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..Comment
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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...»»*†HÀ†§ HÓ††™««Comment
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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.Comment
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or it was built to meet strict epa emissions guidelines....Originally posted by perfconn View Post
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...Comment
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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 itComment
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Yep, Exactly!Originally posted by perfconn View PostOld enuf to know better, still too young to givadamm.Comment
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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...Comment
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On the 18726543 firing order,a cylinder is fired alternately from left bank to right bank every 90*.Originally posted by sj valley dave View Post
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 AdamsLast edited by 500BOMBER; 03-12-2012, 09:39 AM.Old enuf to know better, still too young to givadamm.Comment
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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.Comment
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Yep, yer right about that. My bad.Originally posted by perfconn View PostOld enuf to know better, still too young to givadamm.Comment
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