Miss At Idle / Exhaust Suck

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Jul 12, 2018 | 10:40 PM

#11

racefan41

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From: Shawnee, KS

You said you tested for for spark, did you spray/mist some water on the wires and boots to see if you had any arching going on?

Jul 13, 2018 | 10:10 AM

#12

99DR

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From: Missouri (LOZ Region)

Quote:

Originally Posted by racefan41

You said you tested for for spark, did you spray/mist some water on the wires and boots to see if you had any arching going on?

no need. As I stated, the compression in cylinder #6 is 50 psi. No need to check anything else. That is the issue. I’ll do a leakdown test tonight and see exactly where the pressure is leaking...but I suspect a bad exhaust valve.

Jul 13, 2018 | 04:53 PM

#13

racefan41

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Joined: Jan 2016

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From: Shawnee, KS

Quote:

Originally Posted by 99DR

I noticed after I posted that, that your issue was found. I should have read through a little better.

Jul 14, 2018 | 04:37 PM

#14

99DR

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From: Missouri (LOZ Region)

Quote:

Originally Posted by HeyYou

Have the heads checked for cracks. Either that, or just replace them with some NEW, aftermarket, better castings.

OK, so I got the diagnosis completed.

Compression (wet)
1: 150
2: 160
3: 155
4: 150
5: 160
6: 60
7: 150
8: 160

I did the leak down test and it became apparent very quickly what the issue is. A fairly loud whoosh was coming from the tailpipe. I have to wonder if they could have made it a little more difficult to remove that rear inner stud on the valve cover! It appears to have been made for a Hobbit with 5 micro universal joints! Anyway, time to order a new head. The plenum looks clean, but I might as well add the Hughes fix while I have it torn down.