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Old 06-26-2013, 02:56 AM
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Advance my camshaft 4 degrees?

My first post!
So I am putting together a engine from parts that have been sitting around.
Came across this article after degreeing my camshaft.

Chevy Small Block Cam - Super Chevy Magazine

Articles main findings;

The Power Of Separation
How much effect a wide vs. narrow lobe-separation angle has on power is precisely what we wanted to test, so Comp Cams ground five identical-duration solid roller camshafts with a different lobe-separation angle on each for us to try. The test was simple: Install all five cams straight up in the same engine with no changes in between. Since we wanted to cover the broadest separation spectrum for street cams, we asked Comp to grind 106-, 108-, 110-, 112-, and 114-degree lobe separations to see how that alone would affect power.
Our rather mild small-block was a 0.030-over 350 using a few good-breathing parts to make power. Basically, our tests showed that most of today's cam manufacturers have it correct when they grind their cams with a 108-110-lobe-separation angle, because it was within this range that our test motor worked the best. The difference in peak power, made between the best and worst cams, was more than 20 hp with the 108-lobe cam making the most at 475 hp and the 112-lobe cam making the least at 452 hp.

Read more: Chevy Small Block Cam - Super Chevy Magazine



My engine details are;
350cid-.030 dished pistons .025 in the hole
Vortec heads untouched with 7733sh1 .015 gaskets
Summit 1784 cam, identical to Crane 284 h012 (228/228,284/284,480/480 Lobe separation 112, lobe centers 107/117
Car is a 3350 lb Chevy Nova with th350,3000 stall and 3:73 gears.
Anyone have any thoughts on the article, specifically where they show the horse power gains from advancing cams to 108?

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Old 06-26-2013, 04:28 AM
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you'll need to look at the came card it might be ground with 4* advance already.
then check with a degree wheel.
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Old 06-26-2013, 05:24 AM
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Quote:
Originally Posted by fueler View Post
My first post!
Welcome aboard!


Quote:
Lobe separation 112, lobe centers 107
It already has 5 degrees of advance ground into it.

I would install it as-is w/the factory advance (in other words, straight up w/no added advance) after degreeing it in.
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Old 06-26-2013, 05:26 AM
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Well your cam is already advanced and on a 107deg in C/L.

So you would have to in fact retard it by 1 deg to get it to a 108 deg installed in a C/L

Look at the LSA (112)...Most cams are made so that they go in with 4 to 6deg of advance already.

Never move the cam without degreeing it first to determine its true installed event timing.
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Old 06-26-2013, 06:03 AM
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Are you mixing up the values of LSA and lobe CL? From what I'm reading it appears you're thinking that LSA can be changed by advancing or retarding the cam. If this is your thought you are dead wrong.
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Old 06-26-2013, 06:44 AM
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It's true. LSA cannot be changed once a cam is ground.

It's "popular" among the old-school crowd to "move" the LSA from 110 to 112 (example is Comp XE grinds), believing it makes the engine more "drivable", spreading the power out over a broader range. Following "convention" this would be true. However, most modern cams are not ground in the same manner as older designs. With the assymetric lobes, the "tighter" LSA provides a very good power band and makes more "peak" power than a similar grind on a "wider" LSA.

There's an ongoing dispute over this among Pontiac hobbyists vs. engine builders, with the "tractor motor" crowd arguing the old-school ways. It's a moot point, as the modern versions make sgnificantly more power and deliver better efficiency. The "cool" thing about the Pontiac is the inability to "lose" the low-end, even when using cams aimed at "high end". Makes for a real nice street performance engine. Small blocks are a bit more "sensitive" to this due to the lack of BIG torque.

FWIW

Jim
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Old 06-26-2013, 10:51 AM
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ditto to what GregT posted. You can alter ICL later if you think its required.You dont need to fine tune until you have other variables in order.
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Old 06-26-2013, 11:27 AM
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Wow, thanks to everyone for all the responses!
The cam was degreed and all measurements verified. Correct 5 degrees advanced ground into cam. So I am gonna leave it straight up.
I am glad I asked the great engine minds here!
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Old 06-26-2013, 04:58 PM
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Quote:
Originally Posted by fueler View Post
The cam was degreed and all measurements verified. Correct 5 degrees advanced ground into cam. So I am gonna leave it straight up.
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