74 L82, 4 speed, EGR valve information

[Eric D.]

Hello,
I'm looking for a reference manual giving me the part number for a 74 ,L82, 4 speed EGR valve. As well is there a date code stamped into these valves?
Regards,
Eric

[George H.]

Re: 74 L82, 4 speed, EGR valve information

Yes there is. Page 196 3rd Edition of the 1973-1974 NCRS tech manual. The 1974 EGR Valve for a L82 4-speed is Part Number 7040299, broadcast code MT. Date code is stamped into the valve and it is five digits.

George HUnt
Team Member 1973-1974 Tech Manual, 3rd Edition

[Eric D.]

Re: 74 L82, 4 speed, EGR valve information

George,
Thanks for the information. How do i decode the 5 digit date code #

[Dan H.]

Re: 74 L82, 4 speed, EGR valve information

Hi Eric, back in 1974, a fellow shipmate on my Mine Sweeper had a new 74 4 sp and I remember it would start to pop, about every 3 or 4 months, it was the EGR valve he said, put in a new one and all was good. They were cheap back then, couple bucks? Buy a bunch, you,ll probably need them if you drive it much.
Dan

[Tom R.]

Re: 74 L82, 4 speed, EGR valve information

How do i decode the 5 digit date code?

Per the 73/74 manual:

EGR Date Codes
Through April 1973, cars equipped with EGR valves use a four-digit date code.For example, 180 2 translates as the 180^th day (Julian date) of 1972. The last digit (2 in this case) represents the shift or assembly line. A five-digit date appears on EGR valves mid-year and into 1974. A five-digit code includes a digit (fourth) for the year. An EGR valve with MT code on a 1974 (Trim tag date code D10) has 15631 (156^th day of 1973).

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[James G.]

Re: 74 L82, 4 speed, EGR valve information

Mr Holstein,
You were on a minesweeper in 74?
My father was on an experimental minesweeper out of Charleston SC from 67-71... MSS1, they used huge gen sets to generate and pulse massive electric fields to generate magnetic signatures of other ships as large as aircraft carriers. IT was supposedly unsinkable, filled with blown in eps foam and then filled with water (to keep the hull from buckling under shock waves) , they used FIVE- 12-71 2 stroke diesels with superchargers and turbochargers - 4 - 20 feet above the waterline with pinion driven thrusters which could pivot 360 degrees and hold the ship stable in place in a heavy current.

Photo of them doing shock tests in the Gulf circa 1969. (whole crew in the pilot house which was set on shock absorbers)
Tail end of the 500 foot long ship is visible in the right side of the photo.

https://www.navsource.org/archives/11/11170106.jpg

I have a 74 L82 4 spd egr I will post a photo of the date on it.
I do recall, that my brother's early 73 L82 has a different dating method.
100_1209.jpg

[Leonard M.]

Re: 74 L82, 4 speed, EGR valve information

I do not have the 73-74 Judging Guide, but question when the 5 digit date code started. Does your description mean to say a 5 digit code appears in mid-year 1972?
Here is an EGR I removed from a low mileage 1973 Camaro engine. I decifered the stamp to mean the 16th day 1973; last digit unknown. How did you determine the last digit was a shift?
I'll add that A.I.R. pumps were stamped similar but with a 6 character stamp; first 3 digits day of the year, 4th digit the year, 5th digit maybe the shift(?) and last was a letter usually a S for which I have not seen a good answer as what it stood for.
EGR Date Codes
Through April 1973, cars equipped with EGR valves use a four-digit date code.For example, 180 2 translates as the 180^th day (Julian date) of 1972. The last digit (2 in this case) represents the shift or assembly line. A five-digit date appears on EGR valves mid-year and into 1974. A five-digit code includes a digit (fourth) for the year. An EGR valve with MT code on a 1974 (Trim tag date code D10) has 15631 (156^th day of 1973).
DSCN9389.jpg

[Tom R.]

Re: 74 L82, 4 speed, EGR valve information

I do not have the 73-74 Judging Guide, but question when the 5 digit date code started. Does your description mean to say a 5 digit code appears in mid-year 1972?

We don't make this stuff up...there are technical manuals that assist...like the 1968-82 NCRS Corvette Spec Guide. We had a team of 24 who looked at a lot of EGR valves, both four digit and five digit. At some point we drew the conclusion published in the manual.

[James G.]

Re: 74 L82, 4 speed, EGR valve information

Leonard,
The 5 digit date came into use during the 1973 model year.
My brother's survivor 1973 L82 which was built October 1972 has a 4 digit date code

MT7040299 181 1
_MG_3912.JPG

[Leonard M.]

Re: 74 L82, 4 speed, EGR valve information

James, I know and agree with what you say, that in 1972, factory supplied EGR valves made in 1972 had a 4 digit date stamp. and that 1973 factory supplied EGR valves made in 1973 had a 5 digit date stamp.
The question I asked Tom was regarding what he wrote. Saying that the 5 digit date code appeared in mid year doesn't make any sense to me especially after I posted a 1973 EGR valve dated Jan 16th, 1973.
Telling me that "We don't make this stuff up", 24 guys looked at a lot of EGR valves and they used the 1968-82 NCRS Corvette Spec Guide (I have that guide and cannot find any information on EGR valves) didn't answer the question.

[George H.]

Re: 74 L82, 4 speed, EGR valve information

The GM EGR Valve on my 1973 LS4 4-speed is stamped NR 7047066 and is date coded 02231. The Engine build is T0619CWM (June 19th, 1973) and the Trim Tag is L06, July 6, 1973. Clearly, the EGR valve on my '73 has a 5 digit date code, not 4. The first three digets are the Julian day of the year, the next diget the year, and the fifth is the shift or line it was made on. It certainly appears that not all 1973 model year Corvettes had a 4 digit EGR date code up until April of '73. I''m not sure of the month a 5-digit date code for EGR's was introduced and it may be different months depending on the engine; L48, L82, LS4.

[James G.]

Re: 74 L82, 4 speed, EGR valve information

Leonard,
Do you know the date that the Camaro was assembled?

The lag time from EGR dates to car build seems to be approx 4-6 month, which would coincide with the JG.
1973 L82 EGR date 181- car date C11 4 months
1973 LS4 EGR date 022- car date L06 - 6 months
1974 EGR date 156- car date D10 - 5+ months


FWIW I consider Jan -Feb to be mid prodution year.

[Tom R.]

Re: 74 L82, 4 speed, EGR valve information

Leonard
My apology if that came across as arrogant. Understand the perspective of Corvette engineers in the early 70s...they were overwhelmed with safety regs, emission controls and fuel economy standards. Its speculative, but there may have been an assumption that one part number would be all that was needed for Corvette engines, But then studies showed that the different engine horsepower configurations required a unique EGR valve calculation. Or, it could be a simple as the vendor, believe it was Stant, left off the year code and GM/Corvette caught it mid-production. We don't know. Also, I'm not sure when GM began to standardize EGRs across the GM Fleet...as you note, the Camaro had a five digit code. What about Chevelle? Pontiac? Buick?

[Leonard M.]

Re: 74 L82, 4 speed, EGR valve information

Tom, Thank you for the additional information. Attached is a picture of the engine stamp the Jan 13th EGR came off. The CHH engine was used for Camaro and Nova. The W in the vin portion is for the Willow Run plant so this engine was installed in a Nova. Unlike Corvettes, I could not find find monthly production information for the Nova, but based on the total units produced, this vin and the months of production, I'm guessing the car this engine came out of was assembled in April, so even though not a Corvette, it would be similar to the information in the Corvette Judging Guide.
DSCN8831.jpg