 Dropped valve seat, What are the symptoms? |
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| 914rat |
 May 25 2009, 03:33 PM
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#1
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Member  Group: Members Posts: 279 Joined: 3-July 06 From: Maryland Member No.: 6,362  |
So I changed out my carbs from Webber 44's to Dellorto 40's draind my tank added a fuel pressure regulator and guage and the car starts right up.I go to take her for a ride and get a ticking noise on the pass side and popping and backfiring and bucking like it's got a bad plug dist cap or timing issue.Everything passed on inspection.The engine is a 2056,009 dist with petronics and Jacobs energy box.I'm going under today to check for an exhaust leak(that sounds like what the ticking noise is).Would an exhaust leak cause the backfiring and popping and bucking?
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| Dave_Darling |
May 25 2009, 05:56 PM
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#2
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914 Idiot Group: Members Posts: 14,984 Joined: 9-January 03 From: Silicon Valley / Kailua-Kona Member No.: 121 Region Association: Northern California 
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Symptoms can include:
No compression on one cylinder. Noticeable particularly when you crank the starter, due to the noise. "RR-RR-RR-..-RR-RR-RR-.." A very rich mixture due to the charge on one cylinder being pushed back into the intake, raising manifold pressure. A gaddawful racket caused by roughly 1/8" of clearance on one valve. Occasional very soft-sounding backfires in the intake. ...These were not all on the same dropped seat... It does vary from case to case. --DD |
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| type2man |
May 25 2009, 07:40 PM
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#3
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Member Group: Members Posts: 353 Joined: 3-March 09 From: Miami, Fl Member No.: 10,127 Region Association: South East States |
Did you have this issue before you switched the carbs out? If you didnt, then your carbs need tweaking...
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| DBCooper |
May 26 2009, 06:24 AM
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#4
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14's in the 13's with ATTITUDE Group: Members Posts: 3,079 Joined: 25-August 04 From: Dazed and Confused Member No.: 2,618 Region Association: Northern California |
QUOTE(914rat @ May 25 2009, 02:33 PM)  Would an exhaust leak cause the backfiring and popping and bucking? Backfiring on deceleration, yes. Not the popping and bucking though, which sounds more like a clogged low speed jet. Easy enough to check, and much better news than a dropped valve. Did you know these Dellorto's before? I've bought used carburetors with different sized jets. Hell to tune and acts just like a clogged jet until you realize you haven't actually measured every one of them to make sure they're correctly marked and somebody hasn't reamed some of them at some point in a past life. |
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| SGB |
May 26 2009, 08:37 AM
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#5
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just visiting Group: Members Posts: 4,086 Joined: 8-March 03 From: Huntsville, AL Member No.: 404 Region Association: South East States |
I put my money on a loose (or pulled) exhaust stud...
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| 914rat |
May 26 2009, 04:21 PM
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#6
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Member Group: Members Posts: 279 Joined: 3-July 06 From: Maryland Member No.: 6,362 |
QUOTE(SGB @ May 26 2009, 06:37 AM) I put my money on a loose (or pulled) exhaust stud... Went under the car last night ,exhaust seems fine.I bet it's a fun ride down Montesano Mtn in a 914. |
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