SCCA Enterprises TB 006-2015 GEN3 Muffler

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Former Specracer National Champion
Former Specracer National Champion
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PostPosted: Fri Dec 04, 2015 6:02 pm
SCCA Enterprises Technical Bulletin 006-2015
GEN3 Muffler Kit G1190523

We have received concerns centered around Muffler to Tail pipe fitment.
After testing a batch of Prototype mufflers (10), fitment and the security of the slip joint seemed to be acceptable.
Our header vendor is producing the “Spec Muffler” for us. It’s just what we need, no more, no less. The Muffler reduces the sound level 2 to 3 db, is re-packable all without consuming engine output.

However customers installing Mufflers from batch 1 or 2 have voiced a concern with the slip joint being too tight or to loose.

In either case, here are some suggestions to help with installation of the mandatory “Spec Muffler” update.

First of all, Follow the instructions. When cutting the tail pipe to install the muffler, the total length of the tail pipe should not be changed. Keep with-in +/- .375” This is a GCR rule. Instructions are posted and available on our web site under
“Spec Racer Ford Tech Doc’s” ... -addendum/

too tight or too loose…

On the tight side, you could use a sand paper drum to smooth the ID surface of the slip joint area of the muffler. If the tail pipe was coated previously, be sure and carefully remove all of the coating from the slip area of the 2 tail pipe pieces. Some of the fitment problems seem to come from the normal variance of the muffler tubing OD, usually around +/- .020”. We and our vendor have no control over that variance.

On the looser side,

We changed the number of slits cut into the slip joint area of the muffler. It is acceptable to have up to “4 slit’s” cut in the slip area. That will ease a tight fit and let it clamp more securely on a looser fitting combination of parts. This can be done with a1/16” thick cut off wheel and a die grinder.

We chose to use a band type clamp, they offer the most service flexibility. They do not dent the slip area of the muffler or tail pipe pieces. I think some people are being a little too cautious tightening the clamp.…I tested some clamps to failure from our current batch of a couple hundred.

SAE Torque for a .250” steel grade 5 to 6 fastener dry is around 8 to 10 Ft Lbs. I placed a clamp on a 30 MM deep socket. Held the socket in a vise, torqued the T bolt in steps and noted the results. Each sample clamp failed in the same way.

Short summary:
8 to 10 Ft lb all is well
12 to 14 Ft lb all is well
16 to 18 Ft lb starting to deform or bend the “T Bracket” where the band wraps around it and
starting to bend the .250” X 28 T bolt
20 to 29 Ft lb continues to deform or bend the “T Bracket” and bend .250” X 28 T bolt
30 to 31 Ft lb the Band fails where it raps around the “T Bracket” part of the clamp.

Be sure and get the clamp tight on first install and retighten after the
first couple of track sessions. If you are unsure how tight to tighten the nut on the T
bolt…aim for 11 to 12 ft lbs …use a torque wrench to get a feel for it.

If you still have an issue with the slip joints, you can use any style commercially
available 1.750” exhaust tube clamp. “Caution” the thinner the clamp, the more it dents the muffler and tail pipe slip area and make it very difficult to service.

As an option, you could use an approved clamp and orientate the muffler body in the
vertical position, use 2 small tack welds on the inlet end of the muffler. (non-serviceable
end closest to the header collector) I would never tack weld the outlet tail pipe piece to
the serviceable end of the muffler.

Repacking serviceability

The serviceability or removing the aluminum end cap from the Muffler has been difficult for some. A revision has been made to how the muffler is assembled . The revised Muffler end cap Part # G390525 availability TBD. Can be installed on the earlier mufflers. No change in performance between the end cap designs, strictly for ease of serviceability.

I have also heard reports of the screws that hold the end cap to the body loosing up. It’s a good idea to check those during the first couple of track sessions as well. After everything has been heat cycled several times and they are tight, they should be fine.

Last, if you continue to have problems with the muffler update. Please document with pictures and send all data to
Mike Davies
SCCA Enterprises

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PostPosted: Sat Dec 05, 2015 11:59 am
Thanks Mike

I will be Gen 3 2016 season- with mixed emotions, hate to have had to give up the GEN2 motor. Sold and gone.

will the new spec muffler version be available soon, like prior to the start of 2016 season?

Does "mandatory" mean it is required for all races now?


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Location: Texas
PostPosted: Sat Dec 05, 2015 12:10 pm
they are available but out of stock right now, i think for a week or two. I ordered one last week. At TWS most of the G3s had them installed.
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Former Specracer National Champion
Former Specracer National Champion
Posts: 92
Joined: Fri Jun 08, 2012 5:42 pm
Location: Denver, Co.
PostPosted: Sat Dec 05, 2015 12:35 pm
Yes a "Spec muffler" is mandatory for all SCCA events starting 2016 competition season going forward, there are 2 versions 98/99db version the TB is written about the 88/89 db version for Laguna.
Mike Davies
SCCA Enterprises

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PostPosted: Sat Sep 03, 2016 4:22 pm
The link isn't bringing up the document; can someone provide the correct link or send me the document?
Scott Cypher
SRF3 #577 G3

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