elementary manifold vacuum question

[David A. Cooley]

Ted,
Might want to check the valve adjustment... You may have a tight (or burnt)
valve.


At 12:28 PM 11/8/98 -0800, you wrote:
>
>I have a question for the collective. I think I have forgotten vacuum 101. I
>am trying to make sure everything is hunky dory before I strap my gm
>throttle body onto my car.I have a 77 mgb 1800 cc.
>
>this has siamesed intake and exhaust ports unfortunately.
>
>when it is cold and I hook up a vacuum gage to the intake manifold, at about
>600 rpm the needle fluctuates between 15-19 inches. meaning that the needle
>itself is nearly invisible I can see the trend. if I pinch the hose to the
>gauge, I can dampen down the 'pulses' and get it to stay steady. at higher
>rpms this effect goes away completely.
>
>as it warms up ,at 1000 rpm, it will fluctuate between 16-18 and eventually
>just settle down to a buzz at about 17+.
>
>the engine runs fine and idles fine by all appearances, no shaking or
>anything.
>
>I have no idea if the cam is stock or not.
>
>I remember that one is supposed to actually restrict the vacuum line to
>resolve this issue, I am just wondering if this sounds like word valve
>guides or seals.
>
>I don't know if the gm 1800 cc I have this from had this type of issue and I
>am wondering how this would affect the sensors on the throttle body/ECU. I
>don't seem to remember this as an issue on other engines.
>
>
>thanks for all the great support btw.
>
>Ted Stowe
> 
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           David Cooley N5XMT           Internet: N5XMT at bellsouth.net
     Packet: N5XMT at KQ4LO.#INT.NC.USA.NA   T.A.P.R. Member #7068
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