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stevedak
Dodge Dakota
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6/02/2006
15:53:25
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 Subject: cam lift measurement
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Message:
My hayes manual says to measure the cam lift at the valve to determine cam wear. I measured and got just under 0.200 (exhaust) and 0.213 on an intake. These numbers were way lower than spec (.347/.400). I measured using my dial gauge in-line with the push rod. I measured a second time at the edge of the rocker arm (over the valve) with roughly the same results. I have hydraulic roller lifters. Is this the correct and accurate way to measure cam wear?? is my cam that bad??
92 Dakota 3.9 V6
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N56629
Dodge Dakota
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6/02/2006
18:02:57
| RE: cam lift measurement
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Message:
You are doing something very wrong. The difference between the pushrod and valve should be about 1.6 to 1 with the valve moving .0016 fore every .001 movement of the pushrod.
.213 at the push rod should equal .340 at the other end of the rocker.
If your cam only had .200 lift on either the intake or exhaust it would barely run if at all. I've seen some very squished cam lobes but that is usually only on a couple of cylinders at the most.
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stevedak
Dodge Dakota
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6/04/2006
11:51:13
| RE: cam lift measurement
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Message:
N56629
Thanks for your comments. I repeated my measurements several times and it never came out right. I finally put my dial indicator directly on top of the push rod and got .253-.255. This should be about .408 with the 1.6 ratio, which is in spec. I don't know why I couldn't get the same measurement at the rocker arm, directly over the valve stem, but it sounds like I'm ok.
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N56629
Dodge Dakota
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6/04/2006
20:54:44
| RE: cam lift measurement
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Message:
For one thing your rocker is making a rotational move while your pushrods and valves are making linear moves. It's difficult to mearsure the arc about which the rocker moves. Try putting your indicator on the spring retainer rather than the rocker.
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J and J Auto
GenII
6/10/2006
02:02:35
| RE: cam lift measurement
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Message:
The cam off base circule is .270 with the 1.6
ratio .432 lift
Your lifter may be calasping while your checking
it put your dial indicater on the push rod rocker
removed find the base 0 and check should be .270
Larry
J&J Auto
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stevedak
Dodge Dakota
JOIN HERE
6/11/2006
19:29:21
| RE: cam lift measurement
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Message:
Thanks Larry. The heads are apart right now. I check the measurement when its back together. My book doesn't give a measurement for the cam lobe. Can't I measure the cam itself??
Thanks again
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J and J Auto
GenII
6/11/2006
21:36:39
| RE: cam lift measurement
IP: Logged
Message:
sure can just put your mag base right on the cyl
deck if you have enough length on your idicater
rod if not drop a lifter in and go right off that
the cam from base is .270 int and exh the same
.270
in other words the lifter will come up .270
270 thousanths multiply that x 1.6 and you have
your lift .432
Larry
J&J Auto
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