7mgte knocking

[87jt2ma70]

My 7mgte sounds like it is knocking. The noise is coming from behind the camshafts...i usef a stethoscope and located the sound. I also checked the bottom end for noise and it was quiet as well as the pulleys. The noise seems loudest on the camshaft backing plate. My guess is that it is the valve shims. I have included a link of the video. What do you guys think? Thanks in advance for the help

http://youtu.be/advLYPSssUA

 

[585Soup]

Best way to figure it out, pull the valve covers and look. Doesn't take long to do. If the valve shims look fine, you might want to pull the cam and inspect the valve springs and retainers. If that all looks fine, it might be more internal than you though(wrist pin on the piston), that's if it is all top end noise.

 

[GC89]

Check that both of the cam pulleys are 100% tight. I have heard of that making a lot of noise and not being completely obvious they were loose with the belt tension on them.

 

[87jt2ma70]

K thank you guys, right now i will check belt tension, then i will pull the valve covers and check shims if all looks good i will check springs and valves

 

[585Soup]

yeah, i'd even go through and check your cam bearing caps. make sure they are torqued down. i think they only need to be torqued to 13ft lbs if im correct.

 

[suprarx7nut]

I'm voting valve lash there.

 

[7mboze]

K thank you guys, right now i will check belt tension, then i will pull the valve covers and check shims if all looks good i will check springs and valves

just wanna add two things, 1. while the valve covers are off, get a feeler guage and check clearances of shims to camshaft because its hard to tell from looking. 2. it is possible it could be piston slap if the wrist pins are loose. this may only be the case for(some) forged pistons and tends go away after engine warms up.

 

[87jt2ma70]

I made sure the cam gears were tight as well as the cam journals torqued. Then i checked the clearences on all the valve shims and the clearences were the following.

Exhaust Intake
6- .305mm .178mm
.330mm .178mm

5- .305mm .279mm
.381mm .330mm

4- .381mm .356mm
.406mm .432mm

3- .457mm .406mm
.508mm .406mm

2- .432mm .381mm
.406mm .406mm

1- .279mm .254mm
.229mm .229mm

 

[Backlash2032]

Some of those seem rather excessive... Such as your .508 (.020").. IIRC exhaust should be .013"?

 

[87jt2ma70]

Yea they have wayy too much clearence in them. That is probably why the cams sound like they are knocking. I just checked tsrm and exhaust should be .20mm-.30mm (.008-.012in)
Intake should be .15mm-.25mm (.006-.010in)

 

[3p141592654]

... and they have too much clearance because the cam bearings are worn, like every high-mileage 7M. You can plastigauge to confirm.

 

[87jt2ma70]

Yea i will plasti gauge. I work at autozone so i can get 1 easy. I did some research and it seems like the cams can be lapped to tighten up the clearences and line bore the cam tunnel, then after that fix the shim clearance?

 

[3p141592654]

Yup. its no big deal, just needs to be taken care of.

 

[87jt2ma70]

Just recently it started making a new noise. Sounds like a small rod bearing knock but only when warmed up it wont make any noise when cold or after letting off the gas or giving it enough gas or on idle. It only does it when i give it a small amount of gas, 10-25%. Im hoping its not rod knock but if it is i have an old 7mgte laying around that i can do a full build on

 

[Ca104]

I'm not trying to thread jack at all but mine does the same thing, it sounded like detonation or a valve rattle but it only does it when warmed up and under load. I will definitely be checking the cam clearances tho and the cam gears and timing belt tension. It runs like total crap and has less power than a geo metro btw