548 CI BBC Advice

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zwede
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Re: 548 CI BBC Advice

Post by zwede » Sun Mar 26, 2017 8:49 pm

Kevin Johnson wrote:
zwede wrote:So I just did some googling to make sure I was right, and it turns out I wasn't really right after all. Typically multiplication and division are considered the same priority and you do them left-to-right. So as you had the formula is technically correct.

That said, may I suggest adding the extra parenthesis anyway as it makes it clearer?
I think you are remembering more than you realize:
https://en.wikipedia.org/wiki/Order_of_operations wrote: ... However, in some of the academic literature, multiplication denoted by juxtaposition (also known as implied multiplication) is interpreted as having higher precedence than division, so that 1/2x equals 1/(2x), not (1/2)x. For example, the manuscript submission instructions for the Physical Review journals state that multiplication is of higher precedence than division with a slash,[9] and this is also the convention observed in prominent physics textbooks such as the Course of Theoretical Physics by Landau and Lifshitz and the Feynman Lectures on Physics.[nb 1]
The more you learn about mathematics and logic the more confusing it can become.
Possibly. I graduated in 1990 so it's been a while. But I won't claim to have read much theoretical physics though! :)

TBART1970
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Re: 548 CI BBC Advice

Post by TBART1970 » Sun Mar 26, 2017 9:16 pm

David Vizard wrote:TBART1970

I am getting the inference here that the 'new cam' is on a 110 lca. If so I would not even bother to take the engine to the dyno unless I wanted to find out how much less the engine will make compared to a 107. But that said the use of a 2.25 intake on a 540 is not the way to go and it's use would revise my recommendation here to a 106 LCA. This build is bordering on lca limit depending on the profile you may use.

Now you have posted the flow figures and assuming they are right I can tell you within very close limits (about +/- 3%) what it will make given the right cam.

Would you want this info??
DV
I would like to know what you think it would make with my cam, and what it would make with a proper cam compared to my Dyno numbers.

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Re: 548 CI BBC Advice

Post by David Vizard » Sun Mar 26, 2017 9:26 pm

TBART1970 wrote:
David Vizard wrote:TBART1970

I am getting the inference here that the 'new cam' is on a 110 lca. If so I would not even bother to take the engine to the dyno unless I wanted to find out how much less the engine will make compared to a 107. But that said the use of a 2.25 intake on a 540 is not the way to go and it's use would revise my recommendation here to a 106 LCA. This build is bordering on lca limit depending on the profile you may use.

Now you have posted the flow figures and assuming they are right I can tell you within very close limits (about +/- 3%) what it will make given the right cam.

Would you want this info??
DV
I would like to know what you think it would make with my cam, and what it would make with a proper cam compared to my Dyno numbers.
TBART

I can tell you what it will make assuming the bottom end is a typical quality street performance build that replicates my cam programs friction model. However i will have to guess what the motor will make with an incorrect cam as my cam program does not address the situation in the same manner as most simulation programs.

If you take the time to look through the 525 tests posted a couple of pages back you should get a good idea of what an incorrect LCA will cost. Took a lot of dough to do those tests so might as well make use of them.

I will see if I can do this tomorrow (Monday27th)
DV

PS let me make a guess here - you don't have my BBC performance book!
David Vizard Small Group Performance Seminars - held about every 4 weeks. My shop or your shop. Contact seminar organizer at marvingvx@gmail.com for details.

Roadknee
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Re: 548 CI BBC Advice

Post by Roadknee » Sun Mar 26, 2017 11:21 pm

David Vizard wrote: Applying my BBC LCA formula:- LCA = 133.5 –(cylinder displacement in CI/intake diameter *.91) Works out for this engine to be ---- 107.45. How does that stack up against guesses based on even really experienced ST posters?
DV
From David's other Thread started August 2016 (about the middle of page 4) viewtopic.php?f=1&t=47278&hilit=133.5&start=60
David Vizard wrote:
RevTheory wrote:David,

I just noticed there's no "x .91" in this equation like there was in the 128 deal. Was that a typo or omitted by design? Also, any adjustments for rocker ratios above 1.7?


Rev
Mr. Rev sir,
Not a typo it's just a plain 133.5.
No there is not a correction in this simplified formula for rockers over 1.7 on the intake. But for each 0.1 of a ratio above spread the LCA by about 0.4 of a degree.

Of note here is that anyone who has read my books on BBC will know that the advertised ratio of rockers varies hugely from the advertised ratio. The real ratio's are in the book and as can be seen some rockers are as much as 0.4 under ratio and some are as much as 0.2 ratio higher. Knowing which is a power bonus.

If you are looking for max output from your BBC this is stuff you need to know as you could be throwing 30 hp out of the window.
DV

DV
David, could you please clarify whether the 0.91 multiplier is applicable in the 133.5 formula?

Thanks

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Re: 548 CI BBC Advice

Post by David Vizard » Mon Mar 27, 2017 8:50 am

BBC LCA formula:- LCA = 133.5 –((cylinder displacement in CI/intake valve diameter) x 0.91)

Cylinder displacement is of course for one cylinder.

Guys - notice I took the advice to put in the extra brackets into the formula to make clearer the order in which to do the calcs.
Should have done that first time around!!

DV
David Vizard Small Group Performance Seminars - held about every 4 weeks. My shop or your shop. Contact seminar organizer at marvingvx@gmail.com for details.

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Re: 548 CI BBC Advice

Post by ijames » Mon Mar 27, 2017 10:32 am

David Vizard wrote: BBC LCA formula:- LCA = 133.5 –((cylinder displacement in CI/intake valve diameter) x 0.91)

Cylinder displacement is of course for one cylinder.

Guys - notice I took the advice to put in the extra brackets into the formula to make clearer the order in which to do the calcs.
Should have done that first time around!!

DV
Or you could just write it as: LCA = 133.5 - 0.91 * cylinder displacement in CI / intake valve diameter or LCA = 133.5 - (0.91 * cylinder displacement in CI / intake valve diameter)

Put the multiplications before the division and it's less confusing to read :mrgreen:

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Re: 548 CI BBC Advice

Post by David Vizard » Mon Mar 27, 2017 1:06 pm

First - Carl you are right that formula layout would have been the simplest - BUT I have become a bracketeer as poor eyes make it easier to pick out sections of the formula when each op is in brackets. Often what I am working with can go right across an Excel sheet and then some. But thanks for the input anyway.

Now on to TBART1970'S dilema.

I ran your intake flow numbers through my flow program and the cam selection program.

I hate to add to your problems with this build but those heads are about as much of a total mis-match for a 540 as you can get (though truthfully we could make it worse with a little more effort).

The LCA for the best torque from what you have is 103.5 in at 5 advance. Best of luck trying to get a cam like this for less than about a grand. If you were to use a cam like this the airflow would limit the HP to 766 HP. Now that number may look a little on the high side and I would have to say in this case it could well be over the mark by as much as 20 hp. Why? Mostly because in the program I had not catered for such low flow heads and such big inches. I would never have built an engine like this but obviously some folk do so I will need to increase the range here. Anyway I am thinking that 736 lbs-ft is on, along with 740 odd HP but only with the right cam!

If you use a 110 LCA cam the torque will be down by at least 50 lbs-ft. A 108 would be significantly better but still down some 30 lbs-ft.

Check out the data from my flow program below.

there is more to come on this but the Serdi has just become vacant and I need to jump on it before someone else does.
Look for more data on the heads showing why they are not what you need - maybe tomorrow.
DV
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Re: 548 CI BBC Advice

Post by wyrmrider » Mon Mar 27, 2017 2:15 pm

just use reverse polish notation (RPN) and avoid all this ambiguity

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Re: 548 CI BBC Advice

Post by sjre » Mon Mar 27, 2017 2:39 pm

David just a few questions. First i read where this was a 4.6 bore .A 103-104 lsa with fuel inj? He said this dynoed at 750 tq already .Also approx 60 hp from a lsa change with no change in duration ?
Thanks joe

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Re: 548 CI BBC Advice

Post by cstraub » Mon Mar 27, 2017 5:19 pm

TBART1970 wrote:Anyone like to take a guess at what the new dyno numbers would be with new cam compared to old cam? I was told by Chris Straub, the dyno numbers i.e. the torque was that high because of the the 1/8 turn down lifter adjustment. I was never told the Morel hydraulics needed to be adjusted 1 to 1.25 turns down. Also don't forget about the small intake and carb on the dyno, hopefully bigger intake and carb next time, will be upping compression to about 10.2 to 10.5.
Tom,
Couple things on this sir. First, if the distributor gear was in failure mode all this time sir and creating debris then that stuff will end up in the lifters. When you swap the L and F in lifter you get FiLter. So that could have been part of the noise.

On the 1/8"f of turn. I did not say the created the high torque, I said lack of correct adjustment on the lifters can lead to loss of rpm. We tell everyone that with an iron block and aluminum cylinder heads the lifters need 1 full turn of pre-load. We put an instruction sheet in the lifters and I have posted this on the net since 2003 when Morel first came out with hydraulic roller lifters.

The design of that intake is for torque. I think the dyno numbers well reflect your goals on power being met with one observation......this thing is making that kind of power with oil contamination in the cylinders. The build has a serious oil control issue and with the cylinders being contaminated this can result in the engine being down on power.

So IMO if you go after the oil issues that is has and get the depth correct on the distributor gear you can move forward.
Chris Straub
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http://www.straubtechnologies.com
www.distributorgears.com

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Re: 548 CI BBC Advice

Post by cstraub » Mon Mar 27, 2017 5:20 pm

David Vizard wrote:TBART1970

I am getting the inference here that the 'new cam' is on a 110 lca. If so I would not even bother to take the engine to the dyno unless I wanted to find out how much less the engine will make compared to a 107. But that said the use of a 2.25 intake on a 540 is not the way to go and it's use would revise my recommendation here to a 106 LCA. This build is bordering on lca limit depending on the profile you may use.

Now you have posted the flow figures and assuming they are right I can tell you within very close limits (about +/- 3%) what it will make given the right cam.

Would you want this info??
DV
David,
My cam the original is on a 108LSA with a ICL of 103.
Chris Straub
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http://www.straubtechnologies.com
www.distributorgears.com

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Re: 548 CI BBC Advice

Post by David Vizard » Mon Mar 27, 2017 6:40 pm

sjre wrote:David just a few questions. First i read where this was a 4.6 bore .A 103-104 lsa with fuel inj? He said this dynoed at 750 tq already .Also approx 60 hp from a lsa change with no change in duration ?
Thanks joe
Joe - I plugged in a 4.5 bore because I believed this was a 540. With a 4.6 bore things will be a little different (565 CID). The torque numbers will be up to 770 Lbs-ft.

For what it is worth with the heads properly prepped there is, even at 10.5/1, 790 lbs-ft in this build if all the other aspects of the parts combo is on the money.

Check the chart a few pages back and you will see what can be lost with the wrong LCA even with a sound engine spec in all other respects.

DV
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Re: 548 CI BBC Advice

Post by cstraub » Mon Mar 27, 2017 6:50 pm

David Vizard wrote:
sjre wrote:David just a few questions. First i read where this was a 4.6 bore .A 103-104 lsa with fuel inj? He said this dynoed at 750 tq already .Also approx 60 hp from a lsa change with no change in duration ?
Thanks joe
Joe - I plugged in a 4.5 bore because I believed this was a 540. With a 4.6 bore things will be a little different (565 CID). The torque numbers will be up to 770 Lbs-ft.

For what it is worth with the heads properly prepped there is, even at 10.5/1, 790 lbs-ft in this build if all the other aspects of the parts combo is on the money.

Check the chart a few pages back and you will see what can be lost with the wrong LCA even with a sound engine spec in all other respects.

DV
4.6 bore x 4.125 Stroke
Chris Straub
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http://www.straubtechnologies.com
www.distributorgears.com

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Re: 548 CI BBC Advice

Post by David Vizard » Mon Mar 27, 2017 7:19 pm

Joe,
Take a look at this test from the 572 thread. The 107 cam had slightly less duration than the 112 but look at the torque difference at 3300 rpm - it was almost 60 lbs-ft up.
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Re: 548 CI BBC Advice

Post by TBART1970 » Mon Mar 27, 2017 7:57 pm

David Vizard wrote:First - Carl you are right that formula layout would have been the simplest - BUT I have become a bracketeer as poor eyes make it easier to pick out sections of the formula when each op is in brackets. Often what I am working with can go right across an Excel sheet and then some. But thanks for the input anyway.

Now on to TBART1970'S dilema.

I ran your intake flow numbers through my flow program and the cam selection program.

I hate to add to your problems with this build but those heads are about as much of a total mis-match for a 540 as you can get (though truthfully we could make it worse with a little more effort).

The LCA for the best torque from what you have is 103.5 in at 5 advance. Best of luck trying to get a cam like this for less than about a grand. If you were to use a cam like this the airflow would limit the HP to 766 HP. Now that number may look a little on the high side and I would have to say in this case it could well be over the mark by as much as 20 hp. Why? Mostly because in the program I had not catered for such low flow heads and such big inches. I would never have built an engine like this but obviously some folk do so I will need to increase the range here. Anyway I am thinking that 736 lbs-ft is on, along with 740 odd HP but only with the right cam!

If you use a 110 LCA cam the torque will be down by at least 50 lbs-ft. A 108 would be significantly better but still down some 30 lbs-ft.

Check out the data from my flow program below.

there is more to come on this but the Serdi has just become vacant and I need to jump on it before someone else does.
Look for more data on the heads showing why they are not what you need - maybe tomorrow.
DV
4.600 bore 4.125 stroke.
See dyno Sheet on first page. First cam was on a 108.

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