4-7 Cylinder Swap
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I now know that a 4-7 firing order swap on a 8 cyl motor can increase horse power by almost 10% on most motors.
Is there a simial swap on 6 cyl motor? Have you done one? If so, who made your new crank?
Is there a simial swap on 6 cyl motor? Have you done one? If so, who made your new crank?
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Comments
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What? changing the firing order can increase power in the 8 cyl? Is this true, has anyone tried it? What is the theory that would make this work? Would that firing order change cause any additional pressure on the crank and increase wear?
This is something I have never hear of on any engine.
BST RGDS
GARY ( happychris )0 -
If it ain't broke, fix it until it is!0
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I recall reading about this. I I recall correctly, this applies to V-8 engines, and then only with certain ones, and it has to do with balancing out power-robbing crankshaft harmonics at very high RPMs, such as with race car engines.0
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junkcarfann wrote:If I recall correctly, this applies to V-8 engines, and then only with certain ones, and it has to do with balancing out power-robbing crankshaft harmonics at very high RPMs, such as with race car engines.
Yes, the documentation I was reading was V-8 data. SBC, BBC and some of the Fords engines were listed.
I am sorry if my post was not specific enough.
But with all the engineering experts on th is forum, I thought I woudl ask.
Can this be done with a straight six or straight 8? You guys with computerized engine simulators should be able to tell us rather quickly.0 -
Chevy has done this on the Corvette LS series engines the past few years.
From what I hear there are several cam manufacturers that are offering these cams now. I've heard everyrthing from a 10 hp increase to 10% increase.
Terry0 -
A good friend of mine who I have built several SBCs for and I were just discussing this the other day. This option is available for SBC engines, with 1-8-4-3-6-5-7-2 firing order, and the way you do it is run a swap-firing-order cam and re-index the distributor to 1-8-7-3-6-5-4-2. Cylinders 4 and 7 are on TDC at the same time, but in a stock engine, 7 is on TDC of Compression stroke, ready to fire, and 4 is on TDC of exhaust stroke-- the swap firing order cams flip this. The idea, in theory, is to eliminate the harmonics caused by two adjacent cylinders firing in series: On a stock engine, 5 and then 7 fire, next to each other. The probem here is, all it does is move this: Now 4 and 2 fire, next to each other. This doesn't eliminate the harmonics, but it does change them. Also, cylinders 2 and 4 have shorter intake runner lengths to the plenum than 5 and 7 do, which could account for something. The bottom line is, the power difference is not great, and is seen ONLY at very high RPMs-- this is why the 4/7 swap cams most manufacturers sell are circle track cams. No need to consider this for a street engine, and it does not apply to an inline configuration.
Also, just to clarify, the late LS-series engines do not use this 4/7 swap configuration-- their firing order was changed to 1-8-7-2-6-5-4-3. #2 and #6 still fire on the same bank, but two cylinders apart.0 -
James: Thank for the post. It matches what I was reading this weekend. I just could not find any thing on straight 6 and 8 blocks. It was an interesting bit of info and made wonder enough to ask.0
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I think that's what Chrysler's Crossfire was about wasn't it?
Cousin Jim's Hotrod 302 Fraud had 2 different firing orders and somebody swapped distrubutors and it wouldn't run so wound up cheap in the junk yard. He figgered it out and now has a nice running hot rod.
Interestingly, while most 4s had 1342, my buddy got a mid 20s Durant which was 1243.
I'm glad Hudsons were straightforward.0 -
Don't you guys watch TV? This was no Horsepower on Spike this last weekend. If I remember right they did it on a chevy and got an additional 10% or more on the dino. They said they thought it had something to do with the way the engine breathed. Good thing this was on early before I went to play with the Hudson.
Jay0 -
Breathed: See above about intake runner length.
Firing Order: All my 4 cylinder tractors are 1234.
Durant: In 1930, due to the national economy and the money he had lost in investments, William C. Durant was managing a bowling alley in Flint, Michigan. The thing is, Durant cars were being made at the time. Can you imagine, being manager of a bowling alley, and a car bearing YOUR name pulls up in the parking lot!0 -
On the Ford small block they offered two different firing orders orginally based on engine size. The 221-260-289-302 has one where the front two
cylinders fire one right after the other, the 1-5 order. When Ford came out
with the 351 windsor they altered this order to fire 1-3 but this was done
to reduce front main bearing stress with the 1/2" longer stroke on the 351.
Ford has mixed this firing order into the 302 in several years starting in 1982
in the Mustang GT and was used in just about all 5.0 HO engines used until
the mid 90's.
I have used both in my racing 302's and found that when using a dual plane
intake manifold either firing order works well but on single plane engines the
1-3 firing order cam makes the engine more responsive. Has to due with the
air-fuel mixture being drawn into cylinder #1 and not enough to properly fill
#5 in the 1-5 firing order cam due to plenum volumn and design in single
plane intakes. I never did dyno this to confirm my suspessions but on my last
302 with identicle cam profiles other than the firing order it reduced the et
in the quarter mile by .200+ and picked up 3mph with no other changes at
all.
I really doubt it would help out our Hudson engines at all due to the present
firing order does not fire any two cylinders side by side.
More useless facts from:
PaceRacer500 -
jamcoats wrote:Breathed: See above about intake runner length.
Firing Order: All my 4 cylinder tractors are 1234.
Durant: In 1930, due to the national economy and the money he had lost in investments, William C. Durant was managing a bowling alley in Flint, Michigan. The thing is, Durant cars were being made at the time. Can you imagine, being manager of a bowling alley, and a car bearing YOUR name pulls up in the parking lot!
Wasn't Durant one of the founders of GM also?0 -
That is correct, the primary one at that. If I recall correctly, he had sold Durant off therefore it was never a part of GM.0
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about 5-6 years ago car collector mag. ran an article on billy durant. he was the main force behind GM. he sold durant to fund this set of acquisitions. i think it was out of spite! he started his automotive career helping henry leland start cadillac, after they were leaveraged out of the company(leland went on to start lincon) billy went to help david dunbar buick get his struggling company in the black then got fired after they were competitive, then he met luis chevrolet and they started their own company only to be forced off the board of directors a couple years later, distrusting of partners by now he started durant. these three were his first targets later bought oldsmobile and then in the late 20's acquired oakland and in 32 changed the name to pontiac. oakland started as the pontiac(mi) buggy co. i'm sure this is more info than anybody here wanted to know about GM(my previous religion, i now worship at the house of HUDSON) hudsonly, walt0
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