HarleyTechTalk

Technical Forums => Twin Cam => Topic started by: Y2KRKNG on July 09, 2019, 06:49:30 AM

Title: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 06:49:30 AM
Alright fellas, I've got one that's stumping me. It's a exhaust leak noise in the front cylinder along with the tell-tale sharp crackling on decal. It all points to exhaust gasket leak or even HG leak, But I just cant find it. I've R&Rd the Thunderheader and then smoke tested the gasket seal, No leak. I've also did a good visual and a soap test on the HG and cant find anything. I've CCPd it and it's still right on 200psi. I've also replaced the lifters.  Any suggestions?
Title: Re: "Blown Head Gasket" sound
Post by: les on July 09, 2019, 06:56:46 AM
Do you have manual compression releases?
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 07:08:07 AM
Do you have manual compression releases?


yes, I've activated them while riding but haven't done more testing. I WILL! TY

What's the best way to take them out of the equation? Possibly remove and plug with a bolt?
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 08:09:53 AM
It's not the compression releases. The sound is right at the exhaust post and present (but slight less noticeable) at the rear cylinder. It follows the exhaust "cadence".   Am I just hearing the ext valve slam shut???  I'm going to R&R the pipe(again) and put new tapered gaskets and new split rings in.  I just cant ignore that the sound is right at the pipe and that the decel crack is telling me air in getting in.
Title: Re: "Blown Head Gasket" sound
Post by: dirty jim on July 09, 2019, 08:13:36 AM
A long neck BBQ lighter found my leak, after I took the heat shields off. Pipe was cracked due to a lowside crash. Looked like a hair line scratch, until you torqued down the header flanges. Happy Hunting.
Title: Re: "Blown Head Gasket" sound
Post by: Hossamania on July 09, 2019, 08:16:43 AM
My thought was also to check for a cracked pipe.
Title: Re: "Blown Head Gasket" sound
Post by: chaos901 on July 09, 2019, 09:20:19 AM
Note to self:  Remember the BBQ lighter suggestion for finding exhaust leaks.
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 09:43:40 AM
Quote from: chaos901 on July 09, 2019, 09:20:19 AM
Note to self:  Remember the BBQ lighter suggestion for finding exhaust leaks.

So I'm guessing that you're looking for a change in the flame pattern
Title: Re: "Blown Head Gasket" sound
Post by: Boe Cole on July 09, 2019, 09:45:44 AM
back in the day, used to find them by introducing atf fluid into the intake.  The smoke really pinpoints the problem and does not hurt anything internally.
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 10:10:24 AM
Well by golly it's the ext gaskets!
Title: Re: "Blown Head Gasket" sound
Post by: chaos901 on July 09, 2019, 10:45:13 AM
QuoteSo I'm guessing that you're looking for a change in the flame pattern


Certainly.  I don't smoke so I can't use that, strips of thin paper don't work so good, trying to feel for it burns my hands, need to be more careful.  Seafoam sprayed into the intake smokes too, that may wok.  Just wanting options.
Title: Re: "Blown Head Gasket" sound
Post by: 86fxwg on July 09, 2019, 11:37:20 AM
Quote from: chaos901 on July 09, 2019, 10:45:13 AM
QuoteSo I'm guessing that you're looking for a change in the flame pattern


Certainly.  I don't smoke so I can't use that, strips of thin paper don't work so good, trying to feel for it burns my hands, need to be more careful.  Seafoam sprayed into the intake smokes too, that may wok.  Just wanting options.
Stethoscope,but remove the solid pointer & install 5/16 steel brake line in its place works for another option.
Also find vacum leaks too.

86
Title: Re: "Blown Head Gasket" sound
Post by: dirty jim on July 09, 2019, 12:23:41 PM
Yes flame pattern changes. Looks like someone is trying to blow it out.
Title: Re: "Blown Head Gasket" sound
Post by: Hossamania on July 09, 2019, 12:46:58 PM
Quote from: Y2KRKNG on July 09, 2019, 10:10:24 AM
Well by golly it's the ext gaskets!

We like cheap fixes!
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 09, 2019, 01:51:19 PM
She's fixed. Rock solid! No more SE style gaskets! Ever! I figured I could double stack them and they'd suck less, but nope.
Title: Re: "Blown Head Gasket" sound
Post by: BVHOG on July 10, 2019, 08:10:09 AM
If you want an SE style gasket that actually works, seals up and doesn't squish into the port then the Cometic C9247  Drag no 0934-6318 work extremely well.
Title: Re: "Blown Head Gasket" sound
Post by: jamminhd2000 on July 10, 2019, 08:48:34 AM
 :agree:
Title: Re: "Blown Head Gasket" sound
Post by: Y2KRKNG on July 10, 2019, 12:20:28 PM
Quote from: BVHOG on July 10, 2019, 08:10:09 AM
If you want an SE style gasket that actually works, seals up and doesn't squish into the port then the Cometic C9247  Drag no 0934-6318 work extremely well.

I was using the one that came in my Cyco top end gasket kit with the MLS style HG paired up with my Thunderheader.