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Old 01-09-2013, 02:42 AM
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firing order issue

Ok this might be a dumb question but, I just want to verify this with you guys.

ok the standard firing order of a sbc is 1, 8, 4, 3, 6, 5, 7 , 2.
The ones that are 180 degrees apart are 1-6, 8-5, 4-7, and 3-2.

in a 4-7 swap and or a 3-2 swap, do the cylinders that are 180 degrees apart still the same as the standard firing order? it looks like it to me.

I am getting a set of headers and this is kind of a big deal seeing that I am spending 1300 on the set... stahl btw.

Help would be great.
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Old 01-09-2013, 05:35 AM
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You have to have the right Cam To do a 7/4 swap.. The new firing order would be 1, 8, 7, 3, 6, 5, 4 , 2 ,As far as I know about it..
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Old 01-09-2013, 07:05 AM
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The firing order is determined by the camshaft. Obviously, you set ignition timing on #1, on the compression stroke, just before TDC.
The second cylinder in the firing order has the camshaft lobes 45 CAMSHAFT degrees "retarded" from the lobes for #1, because the second cylinder fires 90 CRANKSHAFT degrees after #1.
The third cylinder in the firing order has the camshaft lobes 90 CAMSHAFT degrees "retarded" from the lobes for #1, because the second cylinder fires 180 CRANKSHAFT degrees after #1.
The fourth cylinder in the firing order has the camshaft lobes 135 CAMSHAFT degrees "retarded" from the lobes for #1, because the fourth cylinder fires 270 CRANKSHAFT degrees after #1.
The fifth cylinder in the firing order has the camshaft lobes 180 CAMSHAFT degrees "retarded" from the lobes for #1, because the fifth cylinder fires 360 CRANKSHAFT degrees after #1.
For the rest of the cylinders, add 45 degrees to the rotation of the camshaft, and 90 degrees for the rotation of the crankshaft
I hope you can see the pattern for the rest of the cylinders.
These numbers work on a 90 degree V-8
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Old 01-09-2013, 09:00 AM
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these firing orders are used by some v-8 race cars
1-5-4-8-6-3-7-2 4-------------8 3-------------7 2-------------6 1---

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Old 01-09-2013, 09:03 AM
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Blight,I hope you told Jere the true horse power of your engine to get the correct tube size
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Old 01-09-2013, 11:51 AM
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Yes we got the tube size correct. and the length etc. and i know how the swaps work. I just need to make sure that those are still 180 degrees apart. The tubes are going to be connected. I'm doing a 360 degree header.
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Old 01-09-2013, 11:52 AM
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Quote:
Originally Posted by vinniekq2 View Post
these firing orders are used by some v-8 race cars
1-5-4-8-6-3-7-2 4-------------8 3-------------7 2-------------6 1---

BMW 134 Judd V8 - Georg Plasa - 40. Trierer Bergrennen 2011 - YouTube
Their crank is different I don't think that would work for me. i am going with the ls firing order. The only reason I am doing it is for stress on the crank. I understand the huge cost difference. Reliability finishes the race.

I just verified that is a 180 degree crankshaft they use in the KV675. The firing order patterns for 180 crank dont work with cross plane.

Last edited by blight; 01-09-2013 at 12:02 PM.
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Old 01-10-2013, 03:49 AM
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Quote:
Originally Posted by blight View Post
Ok this might be a dumb question but, I just want to verify this with you guys.

ok the standard firing order of a sbc is 1, 8, 4, 3, 6, 5, 7 , 2.
The ones that are 180 degrees apart are 1-6, 8-5, 4-7, and 3-2.

in a 4-7 swap and or a 3-2 swap, do the cylinders that are 180 degrees apart still the same as the standard firing order? it looks like it to me.

I am getting a set of headers and this is kind of a big deal seeing that I am spending 1300 on the set... stahl btw.

Help would be great.
AFAIK as long as you don't use standard order tri-Y/4 Into 2 Into 1 headers w/the 4-7 swap cam you'll be OK.
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Old 01-10-2013, 09:05 AM
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Jere shahl 360 header,probably 1 3/4 pipe for a low/medium horse power 327
not using a tri y from what I understand
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Old 01-10-2013, 11:15 AM
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Quote:
Originally Posted by vinniekq2 View Post
Jere shahl 360 header,probably 1 3/4 pipe for a low/medium horse power 327
not using a tri y from what I understand
Him and edd headerman and travis knowlton all agree 1 and 5/8s is what I need. We should be any where from 480-560ish hp. the design was for hp over all. its a 7500ish rpm engine. we will see what it actually does on the dyno.
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Old 01-10-2013, 11:53 AM
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Quote:
Originally Posted by blight View Post
Him and edd headerman and travis knowlton all agree 1 and 5/8s is what I need. We should be any where from 480-560ish hp. the design was for hp over all. its a 7500ish rpm engine. we will see what it actually does on the dyno.
I'm a little surprised that for a 560 hp 327 the primaries aren't at least stepped or 1-3/4 but then I'm no fluid dynamicist.

What are the power peak rpm for 480 and 560 hp?
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Old 01-10-2013, 12:02 PM
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Originally Posted by cobalt327 View Post
but then I'm no fluid dynamicist.
Pretty fancy stuff there Mark.
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Old 01-10-2013, 12:09 PM
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Quote:
Originally Posted by cobalt327 View Post
I'm a little surprised that for a 560 hp 327 the primaries aren't at least stepped or 1-3/4 but then I'm no fluid dynamicist.

What are the power peak rpm for 480 and 560 hp?
The problem with that is we really wont know for sure until its on the dyno. They can quote 7200rpm or 7500rpm or 7800rpm but its going to be (around) there if you follow me. there are too many other factors that can make a difference. like the degree of the cam. I just trust that the guys who have been doing this for so many years no their shiz-

They were saying too big is about as bad as going too small. I don't really want a lot of tq because my car weighs less than my civic- but you have to have some tq to get hp.
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Old 01-10-2013, 12:14 PM
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Originally Posted by techinspector1 View Post
Pretty fancy stuff there Mark.
That's why they pay me the big... ah hell, you know better!

Richard, what do you make of the size of the primaries on this deal? I remember you used your software to show the output using bigger long tube headers was close to the 1-5/8 headers, and this was on a milder build than a 500-plus hp/ 7500 rpm engine.
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Old 01-10-2013, 12:17 PM
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Quote:
Originally Posted by blight View Post
The problem with that is we really wont know for sure until its on the dyno. They can quote 7200rpm or 7500rpm or 7800rpm but its going to be (around) there if you follow me. there are too many other factors that can make a difference. like the degree of the cam. I just trust that the guys who have been doing this for so many years no their shiz-

They were saying too big is about as bad as going too small. I don't really want a lot of tq because my car weighs less than my civic- but you have to have some tq to get hp.
The thing is, smaller primaries will help torque more than hp. This is almost an oversimplification, but I'm sure you get the gist. This isn't a dig at you- I'm just trying to understand the expert's advice is all.
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