548 CI BBC Advice

General engine tech -- Drag Racing to Circle Track

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David Vizard
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Re: 548 CI BBC Advice

Post by David Vizard »

TBART1970 wrote:
David Vizard wrote:OK Let's get back to those Edelbrock heads on this 565 incher. Take a look at the intake flow of the heads I ported for the GM 572 project posted else where.

The Performer heads are the thick blue line and the DV ported AFR's the thin line. At first sight it looks like the AFR's flow curve just disappears of the top of the chart into space but the reality is I drew these charts on a .700 lift scale before I realized I needed at least 0.800 to show where the AFR topped out. At about 800 the curve leveled out here - the flow was 404 cfm. Max flow was 409 at 900 lift.

As you can seefrom the gragh the Edelbrock Performer, almost tracked the AFR's over much of the lift. But in many respects the true difference as seen by the engine can be much more than we are perceiving here. Sure those big high lift flow numbers are an obvious asset to the breathing capability of the cylinder but that, contrary to what may seem logic, has minimal to do with affecting the poptimal LCA. To see how the cylinder is far more affected by the low lift flow the valves have we need to look at a graph of the flow per sq inch of the CD.
That is what we will do tomorrow.
DV
548 cu inch
4.600 bore 4.125 stroke
finally the right #'s!
DV
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TBART1970
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Re: 548 CI BBC Advice

Post by TBART1970 »

All stated in first post and in line one.
.
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Re: 548 CI BBC Advice

Post by Newold1 »

I agree, this engine had some mechanical issues that probably affected time for adjustments and fine tuning but it achieved a result that was maybe just a little short of the OP's original expectation. The OP came on here asking for a little advise on camming, not asking for a pick a part of the entire build. Obviously per Mr. Vizard's concise and proven methods somethings could have been improved with ideal parts and rework but this OP is not looking for that at this point and he is just trying to get back to the dyno with some cam change and optimize what he has. Let's not over critique or analyse this situation here. I think all of us should just convey the idea to all new members here on Speedtalk that they should use and listen to good knowlgeable peers here and that the time to collect information and discuss choices and expectations is before they start choosing and buying parts and building their engines!!

I'll say it again " plan your work and then work your plan!"
The Older I Get, The Dumber I Get :wink:
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Re: 548 CI BBC Advice

Post by TBART1970 »

Thanks.
raynorshine
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Re: 548 CI BBC Advice

Post by raynorshine »

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
David, does this formula work for SBC's? or is there another formula?
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Re: 548 CI BBC Advice

Post by wyrmrider »

there is another formula and a couple of very long threads to go with it
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Re: 548 CI BBC Advice

Post by statsystems »

raynorshine wrote:
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
David, does this formula work for SBC's? or is there another formula?

The 133.5 is for canted valve heads. 128 is for inline valve heads. The equation stays the same other than that. IIRC there is also some corrections made for CR and maybe some other stuff but that doesn't change the formula.

I'm sure DV will correct this if I'm wrong.
digger
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Re: 548 CI BBC Advice

Post by digger »

What about hemi ?
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Re: 548 CI BBC Advice

Post by statsystems »

digger wrote:What about hemi ?
IDK...guess DV will need to chime in.
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Re: 548 CI BBC Advice

Post by MadBill »

When I threw a dart at the board, it hit '135' as the magic number...
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Re: 548 CI BBC Advice

Post by CamKing »

cstraub wrote:With the oiling issues this thing has the dyno sheet is a mute point.
Especially with hydraulic lifters.
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Re: 548 CI BBC Advice

Post by TBART1970 »

Different intake on the dyno, dyno distributor, standard volume Moroso pump and standard shaft. Other than the valve adjustment, nothing was really wrong on the dyno. Oil filter from dyno runs was cut open and there was not much in there, not until I put it in the car did the problems start.
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Re: 548 CI BBC Advice

Post by FC-Pilot »

TBART1970 wrote:Different intake on the dyno, dyno distributor, standard volume Moroso pump and standard shaft. Other than the valve adjustment, nothing was really wrong on the dyno. Oil filter from dyno runs was cut open and there was not much in there, not until I put it in the car did the problems start.
Had the same issue with a customers engine. After talking it over for an hour or so, I asked what filter he put on. He said Fram. I told him to go and get a K&N and call me back before he fired it again. 20 minutes later I got a call from him and I told him to fire it. Immediately had full pressure and never so much as bobbled from that day on.

I am just asking as a sanity check.

Paul
"It's a fine line between clever and stupid." David St. Hubbins
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Re: 548 CI BBC Advice

Post by S10LS2 »

cstraub wrote:This things does not need cams thrown at it ......it needs the issues that it has fixed. The oil contamination being the number 1. It seems that the distributor gear issue has been addressed.
Thank you.
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Re: 548 CI BBC Advice

Post by S10LS2 »

Newold1 wrote:I agree, this engine had some mechanical issues that probably affected time for adjustments and fine tuning but it achieved a result that was maybe just a little short of the OP's original expectation. The OP came on here asking for a little advise on camming, not asking for a pick a part of the entire build. Obviously per Mr. Vizard's concise and proven methods somethings could have been improved with ideal parts and rework but this OP is not looking for that at this point and he is just trying to get back to the dyno with some cam change and optimize what he has. Let's not over critique or analyse this situation here. I think all of us should just convey the idea to all new members here on Speedtalk that they should use and listen to good knowlgeable peers here and that the time to collect information and discuss choices and expectations is before they start choosing and buying parts and building their engines!!

I'll say it again " plan your work and then work your plan!"
:roll: Says the guy with 4or 5 posts at least 5 paragraphs long. Didnt know the manifold, throttlebody, head flows, and most of the major info needed. Yet made many posts on how wrong everything was. All while calling the op a newbie to the speedtalk ways.. I can call you a newbie as well, because when you post as much as you do without asking the correct questions before you post an answer, that is long and drawn out, yet says not much. But he should change cams again. No head info till page 4 no induction info till page 4 or 5. Dont even know what the exhaust is. Sit back newold1 and let the non newbie engine guys help this fella sort his engine out. It did not seem to me that op was looking for as much cam and other advice as you gave him in his first post. Seems like he had more important issues than if another camshaft is going to get him what he needs.. Sort out the basics first and the engine will make him more than happy for a while instead of suggesting more cam swaps.
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