548 CI BBC Advice

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69top502
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Re: 548 CI BBC Advice

Post by 69top502 » Tue Mar 21, 2017 11:42 am

I hear you on the money thing TBart, I really do. However, in my mind it would be money well spent to get a cam done just for your engine from Camking. I got one from him and it did exactly what he said it would do in terms of horsepower, torque and peak rpm. I mean he hit exactly, and I know I have have a cam matched to my engine. IMHO, you can get some big numbers out of yours at the compression you are at right now. Just need a cam to bring it all in. And I would not hesitate to put a nice mild solid roller in it.

Bill
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Re: 548 CI BBC Advice

Post by Newold1 » Tue Mar 21, 2017 1:21 pm

TBART1970

As others have posted here, leave the domes on the pistons alone. They are not tall enough to impede good combustion and flame front in the chamber and you need the decreased volume for the most compression you can squeeze from your build.

As for camshaft I think its really important for you an some others to realize that the well designed camshaft profile and spec. will be "The Keys To The Kingdom of Power" on a true performance build !
Not spending a little bit more to use the best possible camshaft for this build is selling yourself short and now is the time to get the right camshaft in the engine and really gain the available torque and power your engine is easily capable of. Mike at CamKing has forgotten more about correct camshaft design and building than the best of the rest of us will ever probably know! I know a great cam will bring your project home and you won't have to go back into the engine and change that part again. Hell, that's a lot of work to change a camshaft in an engine especially in the car and its a reasonably expensive change when you consider the cost of another camshaft then and the time and parts needed. If you get to a point where you want to or have to change things like throttle body, distributor gears, etc. those are much easier and less costly changes on the engine and a lot less work and expense.

Get that camshaft ,distributor and oil pump drive interface issue truly identified and fixed so that you do not do metal injection harm to your new rebuild!

As for final power and I had a chance to read up on Musi's 555 Edelbrock engine with your intake, throttle body and EFI system as well as look at a simple dyno power and torque graph. apparently he achied about 723HP and torque over 650 lb/ft. and under 6000 rpms on the power. That should allow you to stay with a good hydraulic roller camshaft coupled with a nice set of hydraulic roller lifters and be fine with your valve spring pressures on your heads. The only thing I saw that was in my mind a flaw was that the torque took a serious 50lb/ft.+ drop around the 3200-3600rpm area on the testing and in my mind that's not a great thing on this type engine and I suspect it could possibly be a tune and timing problem but it could also be from the camshaft in this combination as that is possible and preventable. It could be that your intake and throttle body in this case can get you close to these numbers with a great camshaft and also understand they apparently were using a fully CNC'd set of Edlebrock heads and I am not sure how those would flow compared to the heads you are using.

Do it all right now and achieve the great results now, you'll stay happy longer later!

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Re: 548 CI BBC Advice

Post by CamKing » Wed Mar 22, 2017 12:28 pm

TBART1970 wrote: what would the duration need to be raised to in your opinion to make up for going to solids?
When going from a hydr to a mechanical, you need to add 4-6 degrees at .050".
If you want a mechanical roller to run like the Edelbrock cam, you need to be at least 252/260 @.050"
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Re: 548 CI BBC Advice

Post by WBR33 » Sat Mar 25, 2017 9:20 am

I didn't see it posted anywhere, so I'll ask?

What heads are these? Edelbrock? Which model, what valve size? Looks like they may have had some chamber porting/polishing? Any other work to them?

What model spark plug are you running in them?

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Re: 548 CI BBC Advice

Post by gvx » Sat Mar 25, 2017 1:27 pm

TBART1970 wrote:Stupidity of intake being thicker than most intakes. Oil pump shaft too long and trying to get it figured out in the car. On the dyno, different intake and distributor, standard pressure pump originally, then switched to Titan which caused other issues. Will be fixed on rebuild now that I know what needs to be done, on the engine stand before it goes in the car again.
May or may not be related but just this week I had a customers SBF with an import distributor. On initial startup the distributor had rotational torque wanting to rotate the the distributor with the clamp just snug I got the timing close shut the engine off and clamped the distributor tight. Started the engine the distributor quickly rotated and broke the ignition module, twisted the plug wires immediately and died. Replaced with a brand name distributor and all was fine. Blamed it on the import related quality of the aluminum casting? Another Import part issue goes into the skeptical column for me. (the driveshaft locator sleeve showed galling on the matching surface area of aluminum housing).
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Re: 548 CI BBC Advice

Post by David Vizard » Sat Mar 25, 2017 2:28 pm

I have been reading this post with both interest and great frustration.

A lot of things have been stated about getting the cam right which is exactly a spot on assumption. Only problem is that no two recommendations seem to be anything like close especially on the most important aspect of cam specing ie the LCA.

Remember the ‘128 number’ post I did that stated quite emphatically that this was the most important thing (128 that is) you could know about specing a cam for a SBC or Ford. I also followed that up with the 133.5 # for a big block Chevy’s. This caused one of the great ST uproars and I am sure that at best only a couple out of ever hundred ST posters actually took it seriously. Meanwhile others were determined to take a stand based on an opinion rather than tons of dyno tests that substantiated these unfairly described ‘rule of thumb’ calculations.

The irony is that had I given a super complex formula many more people would have accepted it (probably because it would have been, for most, too difficult to understand and apply). Anyway I guess that’s life.

While sorting through some numbers for an article I came across some tests I had intended to use in my first BBC book but ran out of the allotted page count. The tests were done on my first 525 about a decade ago and run on the dyno of a cup car engine builder friend of mine since retired.

This engine , in the form it was for the power chart shown below, was equipped with a set of TFS 280 cc ports that I modified. Final intake port volume was 295 average the good & bad ports. With the 382 CFM average at 0.700 lift (used about 0.760 on intake for full lift here) These TFS heads (which seem greatly unappreciated) were an easy deal to modify and had a good port velocity (mean 303 ft/sec at 0.700) to flow which means the port energy was high(and for what its worth that is critical toward making good output over a wide range without using a monster cam and 12/1 plus CR)
The CR on this build was 10.7/1 The hydraulic roller cams were ground by Comp and used, as I remember, an intake profile of 290 seat and 240 @ 0.050. Lobe lift was right around 0.400. With a rocker that measured out at 1.9/1 (1.8 was stamped on it) at full lift intake lift was close to 0.760. Exhaust lobe was 297/244 with a 0.397 lobe lift. A measure ratio 1.79/1 rocker yielded an ex. valve lift of 0.710. Ex. port flow at that lift was 292 cfm with a mean port velocity of some 310 ft sec.

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?

I am not going to give my opinion here as I have a dyno and, for the most part, don’t have time for opinions, so check out the chart below.

For what it’s worth a 548 would need to have a degree or so tighter LCA. But here comes the crunch.

Getting that tight on a typical core is not practical. This means a special blank and that costs big money. When I am confronted with this situation I do have a $10 fix to bring the engines required LCA back into the realms of practicality without impairing output.

So -- for the engine in question on this post the LCA should be ??? ----- well I am sure whoever needs to know can work it out for themselves.

Now before I sign off here let me think if there is anything else I want to rant about on this thread.

Oh yes here’s one. Some pages back someone put in a link to a Harley tuners shop that had a calculator to work out what the Mach # was for your engine. Using it will give you a wrong answer. This calculator is, as near as I can tell, based on Taylor’s formula in his book ‘The Internal Combustion Engine in Theory & Practice’. That formula may work on a 6/1 CR, 2800 rpm 14 cylinder 1320 CID radial aero engine but it certainly won’t work on a high rpm long duration cammed high compression engine such as we generally are dealing with here. I have run a few record setting ProStock engines through this and the answers are not close enough to be any practical use. In my cylinder head program I have used a much revised version of this which falls in line with what we actually see in practice.

The subject of hyd. lifters for a BBC has also come up. I have said it before and it looks like I will need to reinforce my statement here. You had better use functional short travel lifters if you want to see top results. Don’t think that the margin from good to bad is trivial. On a build like this a set of average lifters can drop over 100 lbs- ft and a like amount of hp from your build.


And there is that Pat Mussi build a way back that seems to be held out as a yard stick for output. Before you jump to a conclusion here just work out the TQ and HP per cube it makes to get a realistic idea of its capability.

By the way here are a couple of points to note:- If your 10.5/1 BBC does not make close to 1.4 lbs-ft per cube then, assuming a typical friction model, it is because it has a cam on too wide a LCA. This is based on several hundred LCA tests in BBC’s with a view to writing an accurately informative book base on results not OPINIONS.

The dyno numbers below also support the statement I make in my seminars where I point out that if the induction stroke events are not optimized in the FIRST HALF of the induction stroke THERE IS NOTHING THAT CAN BE DONE TO REDEEM IT IN THE SECOND HALF!!! (BASED ON DYNO TESTS AND IN-CYLINDER PRESSURE TESTS) This statement also totally contradicts the popular main stream belief that the intake closing point is the most critical. That (again this is not an opinion) is total BS. I have extensive (like hundreds of dyno tests) that totally contradict this. Just for the record the number of tests I have done on this subject far exceed those done by the originators of the intake closure claim.

One last point to some of my critics here. One of the reasons I post in advance of giving out data is so I gather as many interested readers as possible. This way I hope not to be repeating the same thing time after time. Also what is the point in keeping what I am going to post a secret?? If it only gets read by a few folks I may as well not post at all and just sell what I know through my books and seminars. So for my detractors here, since I don’t criticize your way of posting can I get the say consideration in return – please?

One last thing here – a 4.5 stroke in a early 454 block for 525 inches works surprisingly well. Those extra inches provide torque on a pro-rata basis – if you use the right LCA cam that is.

DV
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Re: 548 CI BBC Advice

Post by Newold1 » Sat Mar 25, 2017 3:05 pm

I don't think his was a case of import part defects. From his description I think it was just possibly improper part size issue with the oil pump drive shaft. There are only two standard lengths of oil pump drive shafts for a BBC. The shorter standard deck size and a longer tall deck size. There can also be an issue develop if a slip collar distributor is used and the collar height is set wrong. I am pretty sure even Titan and all other main cap mounted oil pumps have the input shaft height the same, at least all the ones I have seen or used. So I think this was just a parts use assembly issue that caused his problems. Not sure what he was reffering to on the extra thick intake manifold but most intake manufacturers also have the distributor sealing pad height pretty standard to a point where it should not cause a distributor, oil pump shaft problem.

As for the defective import performance parts spreading around the after market, don't get me started on one of my stupid rants. It always seems to start out "if its too cheap to be true, it probably is !!"
Lets not muddy this thread with that voluminous post and conversations. Start another thread and there will be plenty of examples and bleeping replies !!

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Re: 548 CI BBC Advice

Post by David Vizard » Sat Mar 25, 2017 3:54 pm

Newold1
Ref:-As for final power and I had a chance to read up on Musi's 555 Edelbrock engine with your intake, throttle body and EFI system as well as look at a simple dyno power and torque graph. apparently he achied about 723HP and torque over 650 lb/ft. and under 6000 rpms on the power. That should allow you to stay with a good hydraulic roller camshaft coupled with a nice set of hydraulic roller lifters and be fine with your valve spring pressures on your heads. The only thing I saw that was in my mind a flaw was that the torque took a serious 50lb/ft.+ drop around the 3200-3600rpm area on the testing and in my mind that's not a great thing on this type engine and I suspect it could possibly be a tune and timing problem but it could also be from the camshaft in this combination as that is possible and preventable.

I did not get to read the editorial on the Musi engine. From the above I see that it only produced 1.3 hp per cube and a lowly 1.17 lbs-ft per cube. Could you give me your thoughts on why it did not produce more??
thanks
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Re: 548 CI BBC Advice

Post by prairiehotrodder » Sat Mar 25, 2017 5:22 pm

i'd like to know what the 10 dollar fix is on the cam LCA issue. DV i read your books and especially all your cam info. According to your formula my 540 should be 101.25 LCA ? That just sounds weird but not sure.

2.3 intake valve x .91 =2.093
540 /8 = 67.5
67.5/2.093 = 32.25035833
133.5 - 32.25035833 = 101.25

The chart in your book puts me at 104.5 i think.
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Re: 548 CI BBC Advice

Post by David Vizard » Sat Mar 25, 2017 5:38 pm

prairiehotrodder wrote:i'd like to know what the 10 dollar fix is on the cam LCA issue. DV i read your books and especially all your cam info. According to your formula my 540 should be 101.25 LCA ? That just sounds weird but not sure.

2.3 intake valve x .91 =2.093
540 /8 = 67.5
67.5/2.093 = 32.25035833
133.5 - 32.25035833 = 101.25

The chart in your book puts me at 104.5 i think.
Your math is wrong. The result is 106.8 assuming it is a 10.5/1 CR. this is how it goes:- first divide 67.5 by 2.3 that equals 29.348. Multiple 29.348 by 0.91 and that equals 26.707. Subtract that from 133.5 and the answer is 106.79.

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Re: 548 CI BBC Advice

Post by zwede » Sat Mar 25, 2017 5:42 pm

With all respect, David: Multiplication before division. He was right according to how you wrote the formula. There's a parenthesis missing and it should be:

LCA = 133.5 – ((cylinder displacement in CI/intake diameter) * .91)

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Re: 548 CI BBC Advice

Post by prairiehotrodder » Sat Mar 25, 2017 5:45 pm

Hey thanks David. My motor is actually 10.0 CR so that would slightly tighten the LCA correct?
Higher CR as well as better heads both want wider LCA right?
Brian
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Re: 548 CI BBC Advice

Post by David Vizard » Sat Mar 25, 2017 5:51 pm

prairiehotrodder wrote:Hey thanks David. My motor is actually 10.0 CR so that would slightly tighten the LCA correct?
Higher CR as well as better heads both want wider LCA right?
Brian
yes Brian that's right.
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Re: 548 CI BBC Advice

Post by David Vizard » Sat Mar 25, 2017 5:58 pm

zwede wrote:With all respect, David: Multiplication before division. He was right according to how you wrote the formula. There's a parenthesis missing and it should be:

LCA = 133.5 – ((cylinder displacement in CI/intake diameter) * .91)
As soon as I saw this I thought Jeez what a silly mistake. I have looked at that formula hundreds of times not looking for a mistake so I read what I expected to see not what was there.

Had a case like this with one of my editors. He passed a MS over to me and asked me to correct a sentence. I read it, re-read it, and then re-read it again. I passed it back and said there was nothing wrong with it. Reply" it's perfect other than the missing word" When you write as much as I do you tend to read what you thought you put not what is there. Also editing your own work is a boring job since you are reading stuff you may well have read half a dozen times before.
But all that said thanks for bringing it to my attention.
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Re: 548 CI BBC Advice

Post by zwede » Sat Mar 25, 2017 6:24 pm

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?

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