What might cause this

Posted by Few_Description2155@reddit | projectcar | View on Reddit | 15 comments

Can’t get my 302 to idle so I tried the vacuum gauge and it does this. The vacuum gauge is in the correct hole on the carb. I haven’t tried the other carb but they are both edelbrock. It will idle with the choke but I don’t have the chokes fully set up yet so when it goes further out is when I had let the choke off a little. I’ve been trying to get this thing to hold an idle for months and sometimes I’ll do something and it will but when I drive it it gives up. The vacuum gauge makes me think something else is wrong with it and I’m just chasing my own tail readjusting the carbs over and over. Any wisdom or common sense things I might not have would be greatly appreciated as to what this means or other things I can try to make it idle.

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AwwFuckThis@reddit

I’m another vote for broken valve spring.

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yotehunter422@reddit

I believe this is from a pretty major valvetrain issue, like a broken spring or valve seat. I’d pull the valve covers or do a leak down/compression test.

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booty_fewbacca@reddit

Test it with another gauge to be sure

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SteaksauceB@reddit

broken valve spring does that, for sure.

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Joe_Ald@reddit

My gauge was like this when I had a broken Valve. The car wouldn’t use and I can could maintain it running rough with throttle.

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BigOlBahgeera@reddit

Check your timing, then smoke test for leaks or use starter fluid/carb cleaner around the carb gaskets and intake manifold to find a leak. If no there's no leaks, timing is good and carb is tuned ok then your probably looking at burnt valves/bent pushrods, low compression, misfire or collapsed lifter/wiped lobes on cam. Do a compression test then pull the valve covers and spin the motor by hand an see if all the rockers have full travel

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gankindustries@reddit

Leaky valve?

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Fred2p1u@reddit

Do a pressure test on cylinders.. may have leak between them

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fanofbacon12@reddit

Epilepsy?

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Fred2p1u@reddit

Earthquake?

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anivadd@reddit

Have you tought about more accurate electornic vacuum/pressure cauges? I have a relative who might still sell vp testers designed specially for carb engines, 2 and 4 ports. We are located in Finland tho :/

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Scorpi01234@reddit

Would u be able to get a compression tester and give that a go and see what the readings are? Its very erratic which may be the gauge but if the motor is unknown it wouldnt really be a bad idea to give a compression test a go. Could be the valves arent sealing well blowing compression into the intake manifold, maybe even a bad head gasket

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