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Vizard/Jones BBC Cam Specs for the Shootout

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Vizard/Jones BBC Cam Specs for the Shootout

Postby Lockwire » Tue Oct 18, 2011 3:42 pm

Recently David Vizard sent a note asking on behalf himself and Mike Jones if I would act as referee for the BBC cam shootout for Davids book. To David and Mike thank you regarding my integrity. Now here are the Specs as they mailed them to me.
Stuart Smith


David Vizard Specs

Stuart,

Cam shootout specs - here they are -

These are from a list of profiles from Mikes library or lobes based on such.
Mike did say he would design additional profiles as required here.
Here is what my Cam Master program calls for with the spec of engine being built.

In. Lobe
330 @ 0.012 tappet lift
310 @ 0.020 "
282 @ 0.050 "
0.525 lobe lift
0.922 lift after lash with 1.8/1 R/Ratio

Ex. Lobe
346 @ 0.012 tappet lift
324 @ 0.020 "
294 @ 0.050 "
0.500 lobe lift
0.830 valve lift after lash with 1.7/1 R/Ratio
LCA 110.5 Required.
Note:- If Mike only grinds LCA's to whole numbers as is the case for most cam grinders then I will opt for 111 LCA.

Mike Jones Specs

Stuart,

David Vizard asked me to send my cam shootout spec to you for posting. Here it is:

Intake: 332 @.012"(Seat), 312 @.020", 284 @.050", .525" lobe lift, .925" net valve lift w/1.8 RR
Exhaust: 344 @.012"(Seat), 326 @.020", 295 @.050", .497" lobe lift, .825" net valve lift w/1.7 RR
Hot Lash .020"/.020"
LSA 111

Mike Jones
Jones Cam Designs
JRC Technologies Group
7859 Commerce Dr.
Denver, NC 28037
(704)489-2449
Stuart Smith
smithmotorsportspg@windstream.net
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby F1Fever » Tue Oct 18, 2011 4:37 pm

Why are the exhaust lobes so much bigger? is this what the port is calling for or is this to help the engine hold on longer up top

I also find it funny how close the averages from the other thread are...

285/296 - .897/.855 - 111.6 st
282/294 - .922/.830 - 110.5 dv
284/295 - .925/.825 - 111.0 mj
Last edited by F1Fever on Tue Oct 18, 2011 5:04 pm, edited 1 time in total.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby dbusch » Tue Oct 18, 2011 4:47 pm

i just wonder how the piston to valve clearance and the base circle will turn out. my calcs show a .890 base circle.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby rookie » Tue Oct 18, 2011 4:53 pm

If you’re just tuning in this is the build in reference here viewtopic.php?f=14&t=28424
Has Anything You've Done Made Your Life Better?
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby mbrooks » Tue Oct 18, 2011 8:48 pm

when a cam is ground what is the +/- manufacturing tolerance for the degrees?
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby Nick Campagna » Tue Oct 18, 2011 9:26 pm

What is the tappet diam / roller diam ? flat or roller
Is the defect in what I see, or what I'm seeing with ?
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby Old School » Tue Oct 18, 2011 9:36 pm

dbusch wrote:i just wonder how the piston to valve clearance and the base circle will turn out. my calcs show a .890 base circle.


These would be my concerns also. With a .480 lobe on a std bbc core it is getting way too small. There is going to be a lot of deflection with the core.

What are the valve spring specs that will be used? What is be the pushrod diameter and thickness?

Its hard to tell without working it out on the dyno but with 15:1 compression I would think that the intake cam centerline will be no more than 109, maybe straight up. The tappet lift at TDC should be close to .165 for the 282 and .170 for the 284 installed on 110 intake centerline. That's not terrible for p/v clearance.

Some very good cam pickers. Going to be interesting. The two cams are so similar the performance should likewise be similar. Odds are the engine will make nearly identical power/torque all the way through the range.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby gmrocket » Tue Oct 18, 2011 10:08 pm

Old School wrote:
dbusch wrote:i just wonder how the piston to valve clearance and the base circle will turn out. my calcs show a .890 base circle.


These would be my concerns also. With a .480 lobe on a std bbc core it is getting way too small. There is going to be a lot of deflection with the core.

What are the valve spring specs that will be used? What is be the pushrod diameter and thickness?

Its hard to tell without working it out on the dyno but with 15:1 compression I would think that the intake cam centerline will be no more than 109, maybe straight up. The tappet lift at TDC should be close to .165 for the 282 and .170 for the 284 installed on 110 intake centerline. That's not terrible for p/v clearance.

Some very good cam pickers. Going to be interesting. The two cams are so similar the performance should likewise be similar. Odds are the engine will make nearly identical power/torque all the way through the range.


i wonder if it will be A, B, A, B, test method and if the engine be run in first with a milder cam to seat everything?
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby dbusch » Wed Oct 19, 2011 8:08 am

yup, the core will be very flimsy lol. A SBF std core is about the same as a BBC, and i wont go over .490 lobe lift on those.

the cam is not a bad choice since the heads are a limitation for a 565 trying to make peak power past 7K. but, i would have gone with at least 112 or 113 lobe sep with intake at 110.

the two cams are too close together to bother with. they should grind one on 113 to make it a more meaningful test.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby 900HP » Wed Oct 19, 2011 8:51 am

dbusch wrote:yup, the core will be very flimsy lol. A SBF std core is about the same as a BBC, and i wont go over .490 lobe lift on those.

the cam is not a bad choice since the heads are a limitation for a 565 trying to make peak power past 7K. but, i would have gone with at least 112 or 113 lobe sep with intake at 110.

the two cams are too close together to bother with. they should grind one on 113 to make it a more meaningful test.


I don't think they are testing camshafts. I think they both want to make more power than the other one, and neither wants to lose. Vizard's program came up with one cam, Mike's program came up with another. Yes, they are very similar but neither one knew what the other was doing and that's how it worked out.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby CamKing » Wed Oct 19, 2011 9:00 am

dbusch wrote:i just wonder how the piston to valve clearance and the base circle will turn out. my calcs show a .890 base circle.

The Base Circle will be .900" +.000"/-.001"
.900" is the barrel diameter on the cores we use for cams with more then .480" lobe lift, so the cam won't flex any more then it would with a .480" lobe.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby CamKing » Wed Oct 19, 2011 9:06 am

Lockwire wrote:David Vizard Specs
LCA 110.5 Required.

I figured David would have gone narrower on the LSA, because that's where we normally disagree. :-k
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby dbusch » Wed Oct 19, 2011 9:46 am

CamKing wrote:
dbusch wrote:i just wonder how the piston to valve clearance and the base circle will turn out. my calcs show a .890 base circle.

The Base Circle will be .900" +.000"/-.001"
.900" is the barrel diameter on the cores we use for cams with more then .480" lobe lift, so the cam won't flex any more then it would with a .480" lobe.


so you are comfortable with .525" lobe lift on that core? maybe the cam wont flex any more, but the pressure angle is going to be severe. I think you guys should stop at .495 lobe lift with the std core, and go .525 when you go with the 55mm core. that makes more sense to me, and people reading the magazine wont be shaking their head in disbelief.
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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby Rick360 » Wed Oct 19, 2011 9:55 am

Using the DV LCA chart from his book, he should have picked a LCA at 104-105º for this engine. The 565ci engine with only a 2.35" intake valve puts the CID/ValveDiam (30.05) off the chart on the left at 98-99ºLCA with an adjustment of +2º for the valve arrangement and +3.5º for the 15:1 compression ratio.

Hmmm .... wonder why he didn't spec the cam the way his book proclaims is the way to do it based on the results of thousands of dyno tests?

I can't imagine an engine like that wanting a 104-105LCA, but that's what his book would lead you to believe.

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Re: Vizard/Jones BBC Cam Specs for the Shootout

Postby 900HP » Wed Oct 19, 2011 10:14 am

you also need to add for the 1.8 rocker ratio (vs. 1.5 the chart was written around) not to mention the high compression allows for much longer exhaust duration and earlier exhuast valve opening which is also explained in the book. Earlier exhaust valve opening = wider LSA. As David explained it to me, once the compression crosses the 14.5-15:1 range, they become much more sensitive to having too narrow of an LSA (which is the inverse of a 10.5:1 motor). Also with this engine being under-valved and under-flowed in every aspect they need the exhaust duration to get it to "hang on" at upper rpm as well as possible. I believe that is why the compression ratio is so important to the overall combination.
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