1969 L78 muffler date
 

Pic 1 is one of the mufflers off "OLE BLUE".
Pic 2 is cowl tag on "OLE BLUE".
Pics 3- 7 are from a 2002 thread here.

Am I correct assuming muffler dates are Jan 30 and Jan 31 1969?

"OLE BLUES" Mufflers were welded to double wall head pipes just like the Yenko.
Outlets were broken so they were removed.

Interesting that the Yenko is undercoated and "OLE BLUE" is not.

Reply on Team Chevelle pointed out the "A" is for the manufacturer- Arvin.

...the stampings I see are 2 31 9 and 2 30 9

2 is February usually...

Definitely the second month.
Finding out the "A" is for the manufacturer Arvin and not January clears up most questions.

What remains is the car was picked up 2/26/69 and that does not add up well. Estate car so no questions could be asked.
Got records with car but nothing about exhaust when new.

Quite sure this is silliness to many, but we like the ultra-minutia stuff and finding facts.

Henry offered the possibility it had chambered exhaust, and Gerald did not like the noise.
Pure speculation of course but he did know of one owner doing that in his area.

Another pair of Arvins
Pics 1- 3 were taken off a 1970.
Pic 4 is the Yenko from 2002 thread here.
Pic 5 is from her car.

Looks to me the replacement pair [note part number] off the 70 may be dated 123rd day of 1974.
Dates match just like hers.

If that is the case the 31st day of 1969 is a perfect fit on her car.
Many- Many parts on her car with Jan 1969 dates.

Would have thought this had been looked into with some sellers really bragging up "factory exhaust" on cars.

We simply want to know the real story on muffler dates.

Just scored this pair on epay.
Arvins in boxes.
Looks to me we have first shift, 144th day of 1971 mfg. by Arvin.

Starting to make a little sense????
What say you?

Scored switch in pics 3- 4 last night on epay. 68 Chevelle only and in good shape.

Same seller with a couple more NOS Arvins.
Small block this time.
One with just the "A"?

Looks like Arvin changed how they marked mufflers sometime between early 1965 and early 1969.

I thought there were only 28 or 29 days in February.

FYI the 65 mufflers are 2 1/2" inlet and 2" outlet.
Small block.

You are correct and there are only 31 days in January.

Not going to call it a proven fact but it is looking like

Prefix on the 69- later examples is a shift or whatever designation.

The next stuff is the date.

Suffix "A" is for the manufacturer "Arvin".

This is a work in progress.

The pair in post 7 are small block also.

Direct in hand comparison between one of hers and one of the NOS ones.
Same other than weep holes and nipple in the inlet end.

FWIW we have a repop exhaust for one of the converts
The pipes fit the repop muffler.
They do not fit this.

Sorry about the other mufflers the seller had.
Looks like this pair were the only BB ones.

Enjoy or ignore- your call but I am satisfied with this info.

Pics 1 and 2 show markings are same font
Pic 3 shows weep holes in replacement top and bottom Makes it a R or L.
Pic 4 shows same construction.
Pic 5 shows double wall head pipe.
Pic 6 and 7 show same construction with the service part having a nipple spot welded in where the head pipe would be welded in on a factory setup. Same muffler other than that.
Pic 8 shows comparison of marking placement.
Pic 9 shows the rippled seam is the same.