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572/720R cam in blown 496?

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Old 06-09-2009, 10:58 PM   #1
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Default 572/720R cam in blown 496?

I have a Howards solid roller, .642 intake lift, .628 exhaust lift 243/246@50. It is an older cam, I wasn't thinking clearly when I ordered it, for a few bucks more I could have gotten it with a iron gear, but instead I ended up with a billet steel gear on the cam.

It ate a stock GM HEI gear in about 250 miles. The brass gear I tried next also only lasted about 500 miles. I blew $100 on the "indestructible" composite gear from comp cams, it only lasted about 2000 miles...the face of all of the teeth are ground down.

Time for a new cam, this time something more reliable.

Anyone have a comment on running the ZZ572/720R cam in a blown 496?
Camshaft type (P/N 88962216): Mechanical roller
Camshaft lift (in): .714 intake/.714 exhaust
Camshaft duration (@ .050 in): 266 intake/274 exhaust

My engine is a tall deck, canfield 350cc intake port heads, 7.95:1 cr, 8-71 Bowers 23% overdriven, pair of 750 AFB's, 4L80E 3500 stall
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Old 06-10-2009, 12:17 AM   #2
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It sounds to me like you don't have enough endplay in the camshaft. That will wipe out the distributor gear regardless of what it's made out of. Ideally we want .005"-.010" of endplay in the cam. I assume you are using some type of thrust button on your roller cam (as required), but did you double check the endplay when you installed it? The roller buttons are adjustable with shims and are the easiest to set, while the nylon ones generally come a bit long (reducing endplay) and need to be sanded or ground down to the proper length to achieve proper endplay. Also, Cloyes offers a two piece cast aluminum timing cover that has an adjustable button built in that's real easy to set. If you're not using this particular set-up, stay away from the stamped steel covers or even the thin cast aluminum ones for that matter, unless you have an adjustable stop on the back of the water pump to reduce deflection of the cover. These covers will flex too much while the engine is running and allow for excessive endplay. Not good either!

Oh yeah, what's the LSA on those cams? I would imagine they would be a little tight for a forced induction application. Not that they won't work, but they'd be less than optimum.
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Old 06-10-2009, 11:25 AM   #3
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The Howards is 114 installed 4 advanced

The 572 cam is 112

The motor has been assembled a while, I don't recall the end play on the cam. More than zero, less than ??? I can't remember.

The 2 piece cover is cool, but I have a short water pump to clear the blower belt, so I don't think it will fit.
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Old 06-10-2009, 04:40 PM   #4
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Quote:
Originally Posted by twinturbo496 View Post
The Howards is 114 installed 4 advanced

The 572 cam is 112

The motor has been assembled a while, I don't recall the end play on the cam. More than zero, less than ??? I can't remember.

The 2 piece cover is cool, but I have a short water pump to clear the blower belt, so I don't think it will fit.
There MUST be .005"-.010" endplay in the cam or you will wipe out the distributor gear and you must use some type of thrust button on a roller cam. If you're using a stamped cover, you need to set up some type of stop off the back of the pump to contact the timing cover to prevent deflection of the cover allowing excessive camshaft endplay. Oh, and the Howard's cam should work better for your application....in theory!
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Old 06-10-2009, 04:40 PM
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