Re: SMALL BLOCK FIRING ORDER SWAP
[Re: sgcuda]
#2665405
06/13/19 07:21 AM
06/13/19 07:21 AM
|
Joined: Jan 2003
Posts: 8,033 Tulsa OK
Bad340fish
master
|
master
Joined: Jan 2003
Posts: 8,033
Tulsa OK
|
The Comp cam in my 416 small block is a 4/7 swap. If I remember right Comp said it helps relieve some stress on the last crank journal. Something that was also interesting is they said it moves the hot spot created by 5-7 firing close to each up closer to the front where the coolant is removed faster due to being so close to the outlet.
Last edited by Bad340fish; 06/13/19 07:25 AM.
68 Barracuda Formula S 340
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: moparmacka]
#2665436
06/13/19 09:45 AM
06/13/19 09:45 AM
|
Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 14,514
So. Burlington, Vt.
|
Might want to try some different lobes while you’re at it.
Is what’s wrong with the current cam top secret?
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: moparmacka]
#2665451
06/13/19 10:40 AM
06/13/19 10:40 AM
|
Joined: Oct 2007
Posts: 4,210 New York
polyspheric
master
|
master
Joined: Oct 2007
Posts: 4,210
New York
|
it won't hurt It's going to affect mixture distribution: where is the next vacuum pulse in the manifold? Not where it was, everything back to factory assumes 5-7 overlap. Is it important? YRMV.
Boffin Emeritus
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: AndyF]
#2665478
06/13/19 11:52 AM
06/13/19 11:52 AM
|
Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
|
master
Joined: Sep 2014
Posts: 4,457
Washington
|
Do it. There is no reason not to, except when you can't get the cam core.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: moparmacka]
#2665564
06/13/19 04:08 PM
06/13/19 04:08 PM
|
Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 14,514
So. Burlington, Vt.
|
Yeh, those older Crane race 420 lobes are pretty good.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: madscientist]
#2665625
06/13/19 08:24 PM
06/13/19 08:24 PM
|
Joined: Dec 2003
Posts: 22,717 Bitopia
jcc
If you can't dazzle em with diamonds..
|
If you can't dazzle em with diamonds..
Joined: Dec 2003
Posts: 22,717
Bitopia
|
Do it. There is no reason not to, except when you can't get the cam core. So cam cores are pre shaped? I would have thought they all start out as full circle lobes?
Reality check, that half the population is smarter then 50% of the people and it's a constantly contested fact.
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: jcc]
#2665632
06/13/19 08:35 PM
06/13/19 08:35 PM
|
Joined: Sep 2014
Posts: 4,457 Washington
madscientist
master
|
master
Joined: Sep 2014
Posts: 4,457
Washington
|
Do it. There is no reason not to, except when you can't get the cam core. So cam cores are pre shaped? I would have thought they all start out as full circle lobes? There are some roller cores that are full round. They are called UGL for Un Ground Lobe. All the cast cams are made with the lobes in shape. That's one reason why Comp made 110 the de facto LSA. It's easier to move the LSA a couple of degrees either way and still get the lobes on the core. I've been begging people for years to start changing up the firing order on all the cores to the 4/7/5/2 swap. No reason not to do it, other than they don't want to do it.
Just because you think it won't make it true. Horsepower is KING. To dispute this is stupid. C. Alston
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: LA360]
#2665666
06/13/19 10:03 PM
06/13/19 10:03 PM
|
Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 14,514
So. Burlington, Vt.
|
Actually, it’s not just grinder time but also the delivery time.
“Most” billet roller cams start as semi-finished cores. They have a lobe lift, lsa, and duration in that configuration.
The bearing journals are done, along with the dist gear being cut........ and, the heat treat is already done. The heat treat on a billet core doesn’t go all that deep(deeper on some material than others), so the finished product can’t be way off than what the semi finished core starts out as.
To do a cam from an UGL core, which is not heat treated, you burn up 2 roughing wheels(about $100/ea) getting the profile semi roughed in on the core.
Then it needs to be sent out for heat treating....... which is where the big time delay occurs. After getting it back from heat treating it gets the cam lobes finished.
It’s a much more efficient process to get a cam done from the semi-finished core.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: moparmacka]
#2665668
06/13/19 10:19 PM
06/13/19 10:19 PM
|
Joined: Jan 2003
Posts: 14,514 So. Burlington, Vt.
fast68plymouth
I Live Here
|
I Live Here
Joined: Jan 2003
Posts: 14,514
So. Burlington, Vt.
|
Oh, and took your advice on the pushrods. Going to a straight 3/8 0.080 or 0.135 wall.
While it’s true, had I put it together I would have used 3/8 x .080 pushrods for that type of combo...... that sentiment is not shared by many(any?) top builders, who would absolutely feel that what you have in the motor now would be unquestionably superior.
Last edited by fast68plymouth; 06/13/19 10:26 PM.
68 Satellite, 383 with stock 906’s, 3550lbs, 11.18@123 Dealer for Comp Cams/Indy Heads
|
|
|
Re: SMALL BLOCK FIRING ORDER SWAP
[Re: moparmacka]
#2665698
06/14/19 02:01 AM
06/14/19 02:01 AM
|
Joined: Aug 2003
Posts: 43,285 Bend,OR USA
Cab_Burge
I Win
|
I Win
Joined: Aug 2003
Posts: 43,285
Bend,OR USA
|
I've spent hours writing down different firing orders based on which two pistons are at TDC at the same time, when you do the 4/7 swap all you have accomplished is to move the problem from the driver side rear block to the front passenger side of the block, correct 1843 6572 Standard Mopar V8 and early Chevy V8 firing order. The 7-4 swap =1873 6542 if you change it to: 1543 6872 you then change the two cylinders firing in line from each other to the passenger side two rear cylinders, correct I'm done for tonight on this but a custom built crankshaft could remedy the issues, correct
Last edited by Cab_Burge; 06/14/19 02:06 AM.
Mr.Cab Racing and winning with Mopars since 1964. (Old F--t, Huh)
|
|
|
|
|