5.7 tks vacuum readings

[the man]

I have searched but could not find this particular case. Engine is a 2006 5.7L TKS with TB V ignition. Timing is set at 10 BTDC. Vacuum gauge on the intake jumps rapidly from 6-14 at idle. At about 2000 rpm it reads a steady 17, on deceleration it goes to a steady 23.

and- it runs rough at idle, vibrates, and has significant lack of power under load. Any diagnosis from this info? I have read the info in the sticky but did not see these symptoms listed.

thanks!

 

[alldodge]

Re: 5.7 tks vacuum readings

A rapid vacuum gauge bounce at idle usually means worn valve guides. What is the history of the engine?

 

[the man]

Re: 5.7 tks vacuum readings

A rapid vacuum gauge bounce at idle usually means worn valve guides. What is the history of the engine?

engine has 176 hours on it. it did spend several long stretches sitting outside without starting, beyond that it has had oil changes and winterizations as needed.

also, just checked all wires with inline tester- they are all firing and I have re-checked that wires are led to correct cylinders

 

[alldodge]

Re: 5.7 tks vacuum readings

With that kind of bounce I would still do a compression test

 

[the man]

where to check vacuum on 5.7l TKS

where to check vacuum on 5.7l TKS

Where is the correct place to check vacuum on a late model (2006 in this case) 5.7L Mercruiser TKS? I see a port (3/8"?) with a plug in it just behind the carburetor, in front of the distributor. It looks like it is the intake for #8. Is this the place to check vacuum, or am I doing this wrong?

Thanks in advance.

 

[tfret]

Re: where to check vacuum on 5.7l TKS

Re: where to check vacuum on 5.7l TKS

Yes. That is where I check vacuum on my 1984 5.7L. I unscrew that plug and screw in a barb fitting (usually comes with the vacuum gauge kit). When your done just put the plug back in.

 

[the man]

Re: where to check vacuum on 5.7l TKS

Re: where to check vacuum on 5.7l TKS

Yes. That is where I check vacuum on my 1984 5.7L. I unscrew that plug and screw in a barb fitting (usually comes with the vacuum gauge kit). When your done just put the plug back in.

thank you. i am getting very erratic readings so i wanted to make sure i was not just reading one cylinder or something

 

[the man]

Re: 5.7 tks vacuum readings

Results: 'normal' compression except #4=40 and #5=25. Removed and inspected push rods, they looked straight but seemed really tight when loosening them. Adjusted all push rods and now she purrs. I am no master mechanic, but I have never heard of these coming out of adjustment to be too tight? Is this a common occurrence?

 

[alldodge]

Re: 5.7 tks vacuum readings

Glad you found the problem, and like you I've never heared of them tightening.