Massive Engine Knock on All Startups

[JackBauer]

is the engine idling funny or otherwise running poorly?

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[racingmason]

The sound had gotten worse over the last week and I noticed a slight smell of exhaust while sitting at stop lights idling. I decided to use the smoke machine again as I was beginning to expect something with the header flange or head mounting was the issue, and I could hear the noise further back on the engine. This time I unbolted the slip ball after the collector, got the smoke rolling and plugged the collector with my soon to be ex-wifes favorite bath towel. I saw smoke coming out of the air intake again but I could faintly see a small amount of smoke coming out from around the #7 flange to header area. Great, I think I finally found it. I removed all the c clips and locking retainers from the Stage 8 bolts, and painfully removed the back two header bolts. I noticed the weld had failed between the flange and the #7 header exhaust tube. It wasn't a complete failure but it looks like there was a contaminated TIG weld. The normal roll of staged dimes had what probably stared as a small pin hole and slowly opened up as the vibrations and heat expanded it. I sent it off the Kooks after a phone conversation and email exchange and they replaced it for free under their limited warranty. I just got the new header installed and she is quiet as can be. It is actually quieter than from when I first installed it as I would always hear this tiny ping and hiss with the windows down but attributed that to wall thickness of the headers compared to the stock manifolds. I left the c clips and locking retainers off so I can heat cycle the header this week and then go back and re torque the Stage 8 bolts, as they are a huge pain in the ass to do.

 

[96gt4.6]

I'm very glad to hear it was not NEARLY as serious as original thought Mason. That's about the best possible outcome to this one for sure, and certainly goes to show that sometimes even though something seems so obvious, it may not be at all.

I'm sure the wife will understand that a dish towel is much easier to replace than a motor at this point ;).

 

[Tommy V]

Wait what,it was a header leak,damm well imagine that!!!!Not giving op a hard time,just some of the prior post.Glad u figured it out.

 

[Tommy V]

As some have alluded on this thread, its time to pull the motor out and perform diagnostic tear down. Its interesting to read advice on this thread and realize only half the folks on this board actually know what they are talking about. Once you've determined its the motor itself...DONT RUN IT ANY MORE. Its time to pull it and tear it downl

Love this advice.

 

[Jay-rod427]

Been saying for quite some time with a few others header leak crack/weld.... SMDH... Glad you got it fixed and didn't listen to the shortblock crowd.

 

[Tommy V]

Been saying for quite some time with a few others header leak crack/weld.... SMDH... Glad you got it fixed and didn't listen to the shortblock crowd.

Hey what do know Jay!!! LOL

 

[racingmason]

Wait what,it was a header leak,damm well imagine that!!!!Not giving op a hard time,just some of the prior post.Glad u figured it out.

When I hear header leak I dont think of a weld failure, I think of loose header bolts or a gasket failure. I checked the volts, replaced the gasket with a new OEM one and it was still there. I didnt pull the header out earliar as it's a pain and I never would have expected a $2k set of quality headers to have a failed weld. The noise was way more prevelant from the bottom end then even near the actual failed weld with a stethoscope. Goes to show you even good TIG welders mess stuff up. I'm glad Kooks honored the warranty and hooked me with with a replacement part the next day. To

Time to luckey down and go after the Panda cars MT82 record et.

 

[Blown86GT]

Love this advice.

Wow ate some crow with that nugget huh tom. I'll take my online beatings for offering bad advice given I wasn't there. But hey, smart guys like you get it right every time no doubt. Cheers!

 

[Tommy V]

Wow ate some crow with that nugget huh tom. I'll take my online beatings for offering bad advice given I wasn't there. But hey, smart guys like you get it right every

Actually i have a good record on here so far,just ask some of the guys on this form!!

 

[DavidHuff]

Buy a Mechanic Engine Stethoscope on eBay for $8.00 and check your headers for leaks.
If you have a header leak you will know it very quick.
I have used a Stethoscope on my 1987 Buick Grand National to find header leaks and this tool works.

I suggested using a Mechanic Engine Stethoscope and using this tool properly would have found your problem!Just Saying

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