Harold Brookshire lobes and intake centerline.

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Harold Brookshire lobes and intake centerline.

Post by AMXstocker1 »

So we recently put together a 427 inch amc 4.205 x 3.85 engine has indy heads with 2.08 and 1.65 valves they flow 320@.700 314@ .600 the cam is a lunati grind with Harold's lobes grind#68034-68036-106 cam is 263 and 271 @ .050 and .707 lift with a 1.7 rocker on a 106 lobe seperation This is were it becomes interesting we had this engine put together and the builder didn't spec the cam the cam was speced by a friend who I respect who said this cam should be installed at 101 and lashed .016 hot or .011 cold on an iron block with aluminum heads. This information is relayed and discussed between the person who speced the cam and our builder and we get the engine back it sounds good seems fine, and it's a dog first time out runs 10.52 at 125 with like a 1.45ft car feels lazy. This is in a proven working car with a known working carburetor. Car is an amx wieghs 3150lbs 904 torqueflight with a 8inch ati converter 28 inch tires and a 4.30 gear. So we take it home and I run valves and find .018 to .020 cold I tighten them up to .011 take the car back out a week later its better 10.30 at 128 with 1.36 60 ft footbraking which I thought was good but still not were it should be so talked to our friend who speced the cam and he asked of I had checked were the cam was installed and I said I was told 101 and he said you should double check.it so we did just using #s on balancer at first and found 106 so then we pulled it apart and verified with a degree wheel and found 106 at this point we decided to move it 4 degrees advanced to see if we could get closer to what it should be and it appears to be 102 ran it three times checked it 3 times and got 102 each time so put it back together and the weather's changed and haven't made it back to the track. The question is well this make a positive difference and if so how much.
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Re: Harold Brookshire lobes and intake centerline.

Post by abc »

Not knowing all the details, typically, closing the valves sooner will lower the rpm at which the engine makes peak torque. If that is what you need to do, then yes, it will go faster/quicker in the 1/4.
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Re: Harold Brookshire lobes and intake centerline.

Post by midnightbluS10 »

I broke the original post into actual paragraphs and complete sentences so it's a little easier to read for anyone who wanted to read this post. Walls of texts are hard to read and stay interested in.



"So we recently put together a 427 inch amc 4.205 x 3.85 engine that has indy heads with 2.08 and 1.65 valves. They flow 320@.700 314@ .600 and the cam is a lunati grind with Harold's lobes grind#68034-68036-106. Cam is 263 and 271 @ .050 and .707 lift with a 1.7 rocker on a 106 lobe separation.

This is were it becomes interesting. We had this engine put together and the builder didn't spec the cam. The cam was speced by a friend who I respect who said this cam should be installed at 101 and lashed .016 hot or .011 cold on an iron block with aluminum heads.

This information is relayed and discussed between the person who speced the cam and our builder. We get the engine back it sounds good seems fine, and it's a dog first time out runs 10.52 at 125 with like a 1.45ft. Car feels lazy. This is in a proven working car with a known working carburetor. Car is an AMX. It wieghs 3150lbs with a 904 torqueflight and an 8inch ati converter, 28 inch tires and a 4.30 gear.

So we take it home and I run valves and find .018 to .020 cold. I tighten them up to .011 and take the car back out a week later. Its better 10.30 at 128 with 1.36 60 ft footbraking which I thought was good but still not were it should be. So I talked to our friend who speced the cam and he asked if I had checked where the cam was installed and I said I was told 101. He said you should double check.it so we did just using #s on balancer at first and found 106. So then we pulled it apart and verified with a degree wheel and found 106.

At this point we decided to move it 4 degrees advanced to see if we could get closer to what it should be and it appears to be 102. Ran it three times checked it 3 times and got 102 each time so put it back together and the weather's changed and haven't made it back to the track. The question is will this make a positive difference and if so how much?"
JC -

bigjoe1 wrote:By the way, I had a long talk with Harold(Brookshire) last year at the PRI show. We met at the airport and he told me everything he knew about everything.It was a nice visit. JOE SHERMAN RACING
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Re: Harold Brookshire lobes and intake centerline.

Post by ou812 »

Ultradyne was known for wanting 6° of advance in most of their grinds...so that may be why your friend told you that?

His lobes can have quite a large amount of asymmetry so it's best to check them using the lobe center line method and check .020 before and after max lift to find true center line.
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Re: Harold Brookshire lobes and intake centerline.

Post by In-Tech »

Shoot Brian, you are forgiving. I check my TDC lobe centerline @ .005" up/down max lobe lift, probably overkill :wink:
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Re: Harold Brookshire lobes and intake centerline.

Post by Stan Weiss »

Note this is just for illustration purposes.

This is a couple of lobes I generated almost 9 years ago when talking with someone about their cam. Since they could not share their actual data with me. Both lobes have almost the same duration and almost the same area at each data point. One is symmetrical and one is full asymmetrical. Below they are setup so the lifter raise starts and ends at almost the same data points. Notice the difference in ICL at each data point for the full asymmetrical lobe.

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CAM_______Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area____ICL
_________0.00600____58.53_|__98.53_|_337.06_|__49.93_|_110.00
_________0.01000____55.25_|__95.25_|_330.50_|__49.90_|_110.00
_________0.02000____49.10_|__89.10_|_318.19_|__49.81_|_110.00
_________0.04000____40.10_|__80.10_|_300.20_|__49.54_|_110.00
_________0.05000____36.37_|__76.37_|_292.74_|__49.36_|_110.00
_________0.10000____21.04_|__61.04_|_262.09_|__48.24_|_110.00
_________0.15000_____8.36_|__48.36_|_236.73_|__46.61_|_110.00
_________0.20000____-3.14_|__36.86_|_213.73_|__44.69_|_110.00
_________0.25000___-14.08_|__25.92_|_191.84_|__42.22_|_110.00
_________0.30000___-24.84_|__15.16_|_170.31_|__39.19_|_110.00
_________0.35000___-35.75_|___4.25_|_148.50_|__35.60_|_110.00
_________0.40000___-47.18_|__-7.18_|_125.65_|__31.47_|_110.00
_________0.45000___-59.69_|_-19.69_|_100.61_|__25.94_|_110.00
_________0.50000___-74.62_|_-34.62_|__70.75_|__18.78_|_110.00
_________0.55000___-99.50_|_-59.50_|__20.99_|___5.54_|_110.00

CAM_______Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area____ICL
_________0.00600____58.55_|__98.51_|_337.06_|__49.93_|_109.98
_________0.01000____55.54_|__94.96_|_330.50_|__49.90_|_109.71
_________0.02000____49.91_|__88.28_|_318.19_|__49.81_|_109.19
_________0.04000____41.66_|__78.54_|_300.20_|__49.56_|_108.44
_________0.05000____38.25_|__74.49_|_292.74_|__49.38_|_108.12
_________0.10000____24.20_|__57.88_|_262.09_|__48.24_|_106.84
_________0.15000____12.59_|__44.14_|_236.73_|__46.61_|_105.78
_________0.20000_____2.05_|__31.68_|_213.73_|__44.69_|_104.81
_________0.25000____-7.97_|__19.82_|_191.84_|__42.22_|_103.90
_________0.30000___-17.84_|___8.15_|_170.31_|__39.19_|_102.99
_________0.35000___-27.83_|__-3.67_|_148.50_|__35.60_|_102.08
_________0.40000___-38.30_|_-16.05_|_125.65_|__31.47_|_101.12
_________0.45000___-49.77_|_-29.62_|_100.61_|__25.94_|_100.07
_________0.50000___-63.45_|_-45.80_|__70.75_|__18.78_|__98.82
_________0.55000___-86.25_|_-72.77_|__20.98_|___5.81_|__96.74
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Re: Harold Brookshire lobes and intake centerline.

Post by Walter R. Malik »

In-Tech wrote: Mon Nov 28, 2022 1:16 am Shoot Brian, you are forgiving. I check my TDC lobe centerline @ .005" up/down max lobe lift, probably overkill :wink:
Max lobe lift is not the real centerline, a lot of times.
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Re: Harold Brookshire lobes and intake centerline.

Post by tuffxf »

To answer your question,
Yes and noticeable!
Just make sure you have adequate intake p-v clearance
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Re: Harold Brookshire lobes and intake centerline.

Post by Bigchief632 »

ou812 is correct, a lot of ultradyne cams they said to install 5+ degrees advanced. Your friend who told you 101 installed, is probably right from ultradyne/Lunati. Most times when the cam company has said to install at whatever intake centerline, and we've played with it on the dyno via a jesel belt drive, in almost every case, where they said to put it made the most power. This wasn't once or twice, but dozens of times. It was never earth shattering, but it was something. In this case, not sure, as fbird88 said, the on track performance will tell the tale. No way to know for sure unless you dyno it back to back and or run it at the track. The dyno would be the best indicator, as the weather and track prep could easily nullify any gain or loss.
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Re: Harold Brookshire lobes and intake centerline.

Post by In-Tech »

Walter R. Malik wrote: Mon Nov 28, 2022 10:30 am
In-Tech wrote: Mon Nov 28, 2022 1:16 am Shoot Brian, you are forgiving. I check my TDC lobe centerline @ .005" up/down max lobe lift, probably overkill :wink:
Max lobe lift is not the real centerline, a lot of times.
Yes Walter, we are talking about asymmetrical lobes. But you need to start with one known good point and adjust from there. If you don't know the lobes you are usually guessing anyway. 99% of all the cam cards are written from simple math, NOT the design of the lobe. Jones excluded.
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Re: Harold Brookshire lobes and intake centerline.

Post by CamKing »

Stan Weiss wrote: Mon Nov 28, 2022 8:36 am
CAM_______Lift______Opens___Closes__Duration
_________________Deg_BTDC__Deg_ABDC_____________Area____ICL
_________0.00600____58.55_|__98.51_|_337.06_|__49.93_|_109.98
_________0.01000____55.54_|__94.96_|_330.50_|__49.90_|_109.71
_________0.02000____49.91_|__88.28_|_318.19_|__49.81_|_109.19
_________0.04000____41.66_|__78.54_|_300.20_|__49.56_|_108.44
_________0.05000____38.25_|__74.49_|_292.74_|__49.38_|_108.12
_________0.10000____24.20_|__57.88_|_262.09_|__48.24_|_106.84
_________0.15000____12.59_|__44.14_|_236.73_|__46.61_|_105.78
_________0.20000_____2.05_|__31.68_|_213.73_|__44.69_|_104.81
_________0.25000____-7.97_|__19.82_|_191.84_|__42.22_|_103.90
_________0.30000___-17.84_|___8.15_|_170.31_|__39.19_|_102.99
_________0.35000___-27.83_|__-3.67_|_148.50_|__35.60_|_102.08
_________0.40000___-38.30_|_-16.05_|_125.65_|__31.47_|_101.12
_________0.45000___-49.77_|_-29.62_|_100.61_|__25.94_|_100.07
_________0.50000___-63.45_|_-45.80_|__70.75_|__18.78_|__98.82
_________0.55000___-86.25_|_-72.77_|__20.98_|___5.81_|__96.74
Above is a true asymmetrical profile, and nothing like what Harold called an asymmetrical.
Harold's "Asymmetrical" profiles are completely symmetrical above .050" lift. The only difference, is he would put a slow lash ramp on the closing side, and no lash ramp on the opening side. They would just accelerate quickly, right off the base circle. This would make for a much later intake opening point, so you would need to advance them more to get the intake opening point closer to where it would be with a profile that had an opening lash ramp.
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Re: Harold Brookshire lobes and intake centerline.

Post by CamKing »

In-Tech wrote: Mon Nov 28, 2022 12:57 pm
Walter R. Malik wrote: Mon Nov 28, 2022 10:30 am
In-Tech wrote: Mon Nov 28, 2022 1:16 am Shoot Brian, you are forgiving. I check my TDC lobe centerline @ .005" up/down max lobe lift, probably overkill :wink:
Max lobe lift is not the real centerline, a lot of times.
Yes Walter, we are talking about asymmetrical lobes. But you need to start with one known good point and adjust from there. If you don't know the lobes you are usually guessing anyway. 99% of all the cam cards are written from simple math, NOT the design of the lobe. Jones excluded.
Since Harold's "Asymmetrical" profiles are symmetrical above .050", and the only difference is the lack of a lash ramp on the opening side, most of his profiles are about 4 degrees shorter from lash point to .050" on the opening side, compared to .050" to lash point on the closing side.
That means the center point between the opening and closing lash points is 2 degrees behind the center point at any lift above .050".
This means, if you set the intake centerline at 101, using any checking procedure that checks above .050" lift, the centerline at the lash point will be around a 103.
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Re: Harold Brookshire lobes and intake centerline.

Post by AMXstocker1 »

Thank you for all the info. Hopefully we can catch a decent day at the track before it gets really cold here in Oklahoma.

Some of you have cleared up what our friend was telling us. He said the cam needed to be in at 101 and it wasn't just for lower rpm. Now reading about the no lash ramps this makes since.
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Re: Harold Brookshire lobes and intake centerline.

Post by Walter R. Malik »

CamKing wrote: Mon Nov 28, 2022 1:27 pm
In-Tech wrote: Mon Nov 28, 2022 12:57 pm
Walter R. Malik wrote: Mon Nov 28, 2022 10:30 am

Max lobe lift is not the real centerline, a lot of times.
Yes Walter, we are talking about asymmetrical lobes. But you need to start with one known good point and adjust from there. If you don't know the lobes you are usually guessing anyway. 99% of all the cam cards are written from simple math, NOT the design of the lobe. Jones excluded.
Since Harold's "Asymmetrical" profiles are symmetrical above .050", and the only difference is the lack of a lash ramp on the opening side, most of his profiles are about 4 degrees shorter from lash point to .050" on the opening side, compared to .050" to lash point on the closing side.
That means the center point between the opening and closing lash points is 2 degrees behind the center point at any lift above .050".
This means, if you set the intake centerline at 101, using any checking procedure that checks above .050" lift, the centerline at the lash point will be around a 103.
Really, what matters is not the actual degree but, that you know where it is, if adjustments need to be made.
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Re: Harold Brookshire lobes and intake centerline.

Post by Geoff2 »

All of this really shows how futile it is finessing about a particular ICL, unless the combo is an exact copy of a known combo. Pick a number & try it. Adv/ret from there.
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