Idle/Stall/Valve Lash issues
Thread Starter
Heel & Toe
Joined: Aug 2015
Posts: 19
Likes: 0
Idle/Stall/Valve Lash issues
Hey guys.
Bought my 85 Coupe last January for next to nothing- with a spun rod bearing. Rebuilt bottom end of the motor (turned crank, new bearings) but in the diagnoses of the bearing, I checked the top end too, looking for bent pushrods and such. Obviously I had to significantly alter my valve lash in order to do this and now, after resetting it (I thought) the valvtrain is excessively loud and the car is stalling at idle. It'll run for maybe 80 seconds before it dies.
I took the throttle body off, cleaned it and the IACV, and (because it was there) bypassed the throttle coolant. Once I reinstalled the TB, the issue seemed to be worse and I can't seem to find the issue. No vaccum leak as far as I can tell.
Could the issue be the valve lash? I know I'll need to correct that regardless. But I'm not sure if that's the cause of the problem or a separate issue. Thanks!
Bought my 85 Coupe last January for next to nothing- with a spun rod bearing. Rebuilt bottom end of the motor (turned crank, new bearings) but in the diagnoses of the bearing, I checked the top end too, looking for bent pushrods and such. Obviously I had to significantly alter my valve lash in order to do this and now, after resetting it (I thought) the valvtrain is excessively loud and the car is stalling at idle. It'll run for maybe 80 seconds before it dies.
I took the throttle body off, cleaned it and the IACV, and (because it was there) bypassed the throttle coolant. Once I reinstalled the TB, the issue seemed to be worse and I can't seem to find the issue. No vaccum leak as far as I can tell.
Could the issue be the valve lash? I know I'll need to correct that regardless. But I'm not sure if that's the cause of the problem or a separate issue. Thanks!
Melting Slicks
Joined: Jan 2014
Posts: 2,185
Likes: 381
From: Lunenburg MA
If the valve train is loud, it's either misadjusted or you have low oil pressure. I hope you also changed the cam bearings and thoroughly cleaned all the oil passages before you put it back together.
In any case, there are a million threads and videos around on how to adjust the valves on a SBC. I prefer the warmed up and running, but messy method. I'd fix that before I worried about anything else. Misadjusted valves can make it run badly for sure.
In any case, there are a million threads and videos around on how to adjust the valves on a SBC. I prefer the warmed up and running, but messy method. I'd fix that before I worried about anything else. Misadjusted valves can make it run badly for sure.
Thread Starter
Heel & Toe
Joined: Aug 2015
Posts: 19
Likes: 0
Yeah, I cleaned everything our pretty extensively and did 2 oil changes in a row just to flush it out.
I'm going to readjust the valve lash and see if that helps the car run more smoothly. Oil pressure is fine as only the drivers side cylender bank is noisy (the only one i messed with inthe first place) and I'm reading good pressure.
I'm going to readjust the valve lash and see if that helps the car run more smoothly. Oil pressure is fine as only the drivers side cylender bank is noisy (the only one i messed with inthe first place) and I'm reading good pressure.
Melting Slicks
Joined: Nov 2010
Posts: 2,216
Likes: 113
From: Michigan
I see no mention of a new cam, so I'll assume you kept all the lifters in the correct order when reinstalling them.
If it is a new flat tappet cam or even just new lifters did you follow break in procedure? Even if it's just new pushrods and rockers I break them in like a cam kinda.
If it is a new flat tappet cam or even just new lifters did you follow break in procedure? Even if it's just new pushrods and rockers I break them in like a cam kinda.
Thread Starter
Heel & Toe
Joined: Aug 2015
Posts: 19
Likes: 0
No new cam. No new lifters. The only new parts were the freshly turned crank and bearings. Budget fix, I know, but should be fun for awhile.
Initially I thought the issue with the motor was top end (sounded like a bent pushrod) so I pulled the valve cover on the drivers side cylender bank and checked all the pushrods for any kind of damage, cleaned them, and then returned them to their positions. I then attempted to reset valve lash but it doesn't look like I did it correctly and now I'm stalling out.
Initially I thought the issue with the motor was top end (sounded like a bent pushrod) so I pulled the valve cover on the drivers side cylender bank and checked all the pushrods for any kind of damage, cleaned them, and then returned them to their positions. I then attempted to reset valve lash but it doesn't look like I did it correctly and now I'm stalling out.
Race Director
Joined: Aug 2000
Posts: 11,470
Likes: 763
No new cam. No new lifters. The only new parts were the freshly turned crank and bearings. Budget fix, I know, but should be fun for awhile.
Initially I thought the issue with the motor was top end (sounded like a bent pushrod) so I pulled the valve cover on the drivers side cylender bank and checked all the pushrods for any kind of damage, cleaned them, and then returned them to their positions. I then attempted to reset valve lash but it doesn't look like I did it correctly and now I'm stalling out.
Initially I thought the issue with the motor was top end (sounded like a bent pushrod) so I pulled the valve cover on the drivers side cylender bank and checked all the pushrods for any kind of damage, cleaned them, and then returned them to their positions. I then attempted to reset valve lash but it doesn't look like I did it correctly and now I'm stalling out.
Thread Starter
Heel & Toe
Joined: Aug 2015
Posts: 19
Likes: 0
Turned the crank by hand to the top of the compression stroke for each cylender and then tightened to zero lash. Found zero lash by tightening to the point where I could still spin the pushrod by hand,but turning any further prevented it from moving. Then I gave each a half turn.
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Race Director
Joined: Aug 2000
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Turned the crank by hand to the top of the compression stroke for each cylinder and then tightened to zero lash. Found zero lash by tightening to the point where I could still spin the pushrod by hand, but turning any further prevented it from moving. Then I gave each a half turn.
try a re-adjustment across the board, turning the nut until you FIRST feel resistance, and adjust your 1/2 turn.
BTW, you don't need to get TDC for each cylinder, here's pretty much the factory method -
Get #1 to Top Dead Center - adjust
Exh.- 1 – 3 – 4 - 8
Int.- 1- 2 – 5 - 7
Get #6 to Top Dead Center - adjust
Exh.- 2 – 5 – 6 – 7
Int.- 3 – 4- 6 - 8
Adjust until you first feel resistance on the pushrod spin and then add either 1/2 or 3/4 turn.
BTW, I personally use a .0015 feeler gauge to find zero lash. with the feeler gauge between the rocker arm and the valve stem, adjust the nut until you first feel the gauge grab - and no further. at that point, you should be within .001 of zero lash. now adjust 3/4 turn.
hope this helps -
