Cam Break-In Question

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Aug 31, 2006 | 12:55 PM

90Indy

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Pro

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From: Forney Texas

Cam Break-In Question

If you install a new cam and do not properly break it in and some of the lobes go flat, what would the symtom(s) be?

Thanks,

90Indy

Aug 31, 2006 | 01:07 PM

STL94LT1

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From: O'Fallon Missouri

Is it a roller camshaft? If so, there is no break-in period.

Aug 31, 2006 | 01:08 PM

90Indy

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From: Forney Texas

Quote:

Originally Posted by STL94LT1

Is it a roller camshaft? If so, there is no break-in period.

No, flat tappet.

90Indy

Aug 31, 2006 | 01:31 PM

CFI-EFI

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From: The Top of Utah

If a lobe goes totally flat, that valve won't open. Any loss of the lobe, reduces the valve lift by the loss of the lobe, times the rocker (1.50?)ratio.

RACE ON!!!

Aug 31, 2006 | 02:00 PM

byebyeL98

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From: Orange County NY

St. Jude Donor '10-'11-'12-'13

Depending on the wear to the lobe(s), the engine would run very rough, like it was only on 4 or 5 cylinders.

Aug 31, 2006 | 02:05 PM

redrose

Melting Slicks

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From: backwoods upstate ny

backfires, runs rough, low power

Aug 31, 2006 | 02:40 PM

GeosFun

Burning Brakes

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From: Redding Ca

Backfires sound like the ignition is firing a cylinder when the exhaust valve is still open. Cam going flat should not cause that

Aug 31, 2006 | 02:48 PM

kalister1

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From: Pasadena Maryland

Would that cause a tap?

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Aug 31, 2006 | 03:19 PM

90Indy

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From: Forney Texas

I was thinking the valve on the bad lobe would begin to make noise due to the decreased preload.

90Indy

Aug 31, 2006 | 04:41 PM

#10

fredk

Burning Brakes

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From: Muskoka Ontario

I lost a lobe in a Camaro and it went rat tap tat or a tap tat tap.

Fred

Aug 31, 2006 | 05:00 PM

#11

hippy

Le Mans Master

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Loss of power, backfiring thru the intake. Pull the valve covers and watch to see if the valves are moving, pretty simple.

Aug 31, 2006 | 07:45 PM

#12

CFI-EFI

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From: The Top of Utah

The only way an engine will back fire though the intake is if an intake valve is OPEN when the cylinder fires. A worn cam causes the valves to not open enough, not too much, or at the wrong time.

Quote:

Originally Posted by 90Indy

I was thinking the valve on the bad lobe would begin to make noise due to the decreased preload.

90Indy

More or less preload doesn't make any difference in the noise under normal conditions. But when a lobe goes away, not only does the preload disappear, clearance is introduced to the valve train for that (those) cylinder(s), which DOES make noise.

RACE ON!!!

Aug 31, 2006 | 08:45 PM

#13

cv67

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From: altered state

St. Jude Donor '05

Quote:

Originally Posted by kalister1

Would that cause a tap?

Yes, especially after adjusting it and it comes back. When it gets really bad it can pop back thorught the intake tract as you accelerate, cant miss it.

Aug 31, 2006 | 08:57 PM

#14

CFI-EFI

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From: The Top of Utah

I guess it could pop back through the intake, if it is an exhaust valve that doesn't open.

RACE ON!!!

Aug 31, 2006 | 09:03 PM

#15

cv67

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From: altered state

St. Jude Donor '05

Quote:

Originally Posted by CFI-EFI

I guess it could pop back through the intake, if it is an exhaust valve that doesn't open.

RACE ON!!!

Had that happen on both a 401 SST Javelin and a 67 Caprice. Sounded like some chickens clucking under the hood.

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