Ticking, compression, funny idle

Nixon1 · 05-18-2003, 08:04 AM

A few questions.. First, I've got this ticking noise...sounds like it's coming from the right bank...I'd guess cylinder #8. Why? Cylinder #8, last I checked, was down to 125 on compression...all others are 155-160. It's a click/tick noise... Comes and goes. I'm thinking I've got valve problems....but what else could it be/what's it sound like to you guys? Also..my idle is a little on the strange side. Sometimes it's completely normal, other than a slight backfire every couple seconds.... But sometimes it gets 'lopey'....the rpms dont really bounce, maybe a maximum of 50 rpms...which I'd attribute to electrical things with the gauge...as in, amp gauge bounces up and down a little and when I use something like power windows, the tach moves like 50 rpms even though the engine isn't actually doing that. So what could cause it to sound like I've got a mild cam sometimes, and then other times sound completely normal? I'm thinking that's related to the #8 cylinder issue too. Thanks guys.

84LX89GT · 05-18-2003, 02:52 PM

My "guess" would be that you have a possible sticking valve. If the stem of the valve gets varnish/gunk on it, it doesn't want to move freely. It can come and go with temperature, be intermittent, and this would also cause lower compression because the valve would not close all the way .It would also cause funny idle from pulses coming back in the intake or if on exhaust side causing engine to slow down trying to compress exhaust again, backfiring if it's the intake valve letting the piston push air back into intake (or exhaust). It the valve is sticking it will also cause a ticking from excessive clearances from the valve not seating fully and the rocker having to "tap" the valve.
Chances are if you figure out what's going on with cylinder 8, it will solve the problem, just a guess though

Nixon1 · 05-18-2003, 03:26 PM

Thanks..I've been thinking the exact same thing. I'd buy a new set of heads...I have enough money...but my transmission is going out..

05-18-2003, 08:04 AM	#1
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Ticking, compression, funny idle A few questions.. First, I've got this ticking noise...sounds like it's coming from the right bank...I'd guess cylinder #8. Why? Cylinder #8, last I checked, was down to 125 on compression...all others are 155-160. It's a click/tick noise... Comes and goes. I'm thinking I've got valve problems....but what else could it be/what's it sound like to you guys? Also..my idle is a little on the strange side. Sometimes it's completely normal, other than a slight backfire every couple seconds.... But sometimes it gets 'lopey'....the rpms dont really bounce, maybe a maximum of 50 rpms...which I'd attribute to electrical things with the gauge...as in, amp gauge bounces up and down a little and when I use something like power windows, the tach moves like 50 rpms even though the engine isn't actually doing that. So what could cause it to sound like I've got a mild cam sometimes, and then other times sound completely normal? I'm thinking that's related to the #8 cylinder issue too. Thanks guys. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

05-18-2003, 02:52 PM	#2
84LX89GT Mustangs Join Date: Jul 2000 Posts: 1,938	My "guess" would be that you have a possible sticking valve. If the stem of the valve gets varnish/gunk on it, it doesn't want to move freely. It can come and go with temperature, be intermittent, and this would also cause lower compression because the valve would not close all the way .It would also cause funny idle from pulses coming back in the intake or if on exhaust side causing engine to slow down trying to compress exhaust again, backfiring if it's the intake valve letting the piston push air back into intake (or exhaust). It the valve is sticking it will also cause a ticking from excessive clearances from the valve not seating fully and the rocker having to "tap" the valve. Chances are if you figure out what's going on with cylinder 8, it will solve the problem, just a guess though __________________ 2005 Suzuki Hayabusa GSX1300-R 1980 Ford Thunderbird - 255 V8 ported heads, 5.0L ported stock headers, O.R. H-pipe and Flowmaster 2-chambers, dual roller timing chain hi-po Mack Truck hood emblem 1985 Mustang GT 5.0L T5, F-303, GT40p, headers, off-road h, flowmasters, MSD stuff, etc. Sold 02/06/04 1989 Mustang GT ET: 13.304@102.29 mph (5-24-03) Sold - 1998 Mustang Cobra coupe, 1/4 mile - street tires: 13.843@103.41 (bone stock)

05-18-2003, 03:26 PM	#3
Nixon1 Registered Member Join Date: Jan 2003 Location: Palm Bay, FL Posts: 432	Thanks..I've been thinking the exact same thing. I'd buy a new set of heads...I have enough money...but my transmission is going out.. __________________ '91 Mustang GT 5.0 AOD Daily Driver Current stats: NEW 302 short block, E-303 cam (@.050, 220/220, .498/.498, 110 degrees), 1.6 roller rockers, Performer RPM heads (aluminum, 1.9/1.6, 60cc chambers), Cobra intake, Granatelli 75mm MAF, Billet AFPR, Equal-Length Shorty Headers, Off-Road X Pipe, Flowmasters, 4.10 POSI 13.73 at 103.8, ~2.2 60'

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