"Pink" Connecting Rods

[Joe L.]

The above referenced subject came up in a recent thread and I thought I'd start a new thread to provide some additional information.

The "pink-dyed" connecting rods were the best small block connecting rods used in PRODUCTION for many years. These rods were standard large journal, forged steel rods that were further subjected to special heat treating, magnaflux inspection and shot peening. After all these processes, they were dyed with pink dye to differentiate them from standard rods.

The only applications they were used in PRODUCTION for were 1968-69 302 Camaro, 1969-70 Corvette L-46, 1970-72 Corvette and Camaro LT-1, 1973-74 Z-28 (essentially an L-82) and 1973-81 Corvette L-82. However, there were several different part numbers for the "pink" rods over the years. These were as follows:

GM #3923282-----Early 1968 302, 1969 L-46; discontinued from SERVICE December, 1971 and replaced by:

GM #3973386-----1970-72 LT-1, 1970 L-46, 1971-81 L-82, 1973-74 Z-28; discontinued from SERVICE January, 1982 and replaced by:

GM #14095071-----SERVICE only; discontinued May, 1992 and replaced by:

GM #14096846-----SERVICE only; discontinued and replaced by:

GM #10108688---- which remains available from GM. This is NOT a "pink" rod.

There was one other "pink" rod.This was GM #3946481. This rod was used for L1968-69 302. It was scheduled to be used for the still-born 1969 LT-1. No other applications. It was the same as the GM #3923282 except that it was designed for use with floating piston pins with "Spirolok" retainers. All other "pink" rods were designed for use with pressed piston pins and without retainers. The 3946841 was discontinued from SERVICE without supersession in May, 1998.

I have never been able to discern any physical difference between the 3923282, 3973386, 14095071, and 14096846. There must be some difference but I do not know what it is. All are functionally interchangeable.

Now for the current replacement, the GM #10108688. This rod was first used for 1993 LT1 and thereafter rapidly replaced virtually all other, large journal small block rods including, of course, the "pink" rods. It's manufactured of forged powder metal. It's so weight-precise and consistent that no balance pad is necessary on the rod cap. At the time that it co-existed with the last "pink" rod, it had a GM MSRP of less than 2/3 of the "pink" rod. Oh, and by the way, it's more than 2 times stronger than the "pink" rods. So, why would anyone pay BIG $$$ for an NOS or, even, used set of "pink" rods???? Beats me.

[Patrick B.]

Re: "Pink" Connecting Rods

Thanks for the information. I always associated the pink rods with the solid lifter LT-1's and Z-28's.

[Lawrence M.]

Re: "Pink" Connecting Rods

Joe,
Thanks for the great history lesson on the pink rods.

[Mike E.]

Re: "Pink" Connecting Rods

Good information! Thanks, Joe.

[Don H.]

Re: "Pink" Connecting Rods

Years ago I purchased an over the counter complete short block ("CE") still in the GM shipping crate. It was a high horse 283 with a 097 Duntov cam and it had pink rods. Don H.

[Joe L.]

Re: "Pink" Connecting Rods

Years ago I purchased an over the counter complete short block ("CE") still in the GM shipping crate. It was a high horse 283 with a 097 Duntov cam and it had pink rods. Don H.

Don------


Now, that really surprises me. All of the "pink" connecting rods I described above were large journal type rods. All 283's used small journal rods and I know of no small journal "pink" rods. So, I am 100% confident that there were no "pink" rods ever used on a PRODUCTION 283, special high performance variant or not. Could there have been a SERVICE 283 short block that used the large journal "pink" rods? It's remotely possible. Here's how it MIGHT have been done.

The 1957-60 SHP 283 partial engine (short block) was GM #3758458. The 1961 SHP partial engine was GM #3775413. Both of these engines used block GM casting #3756519. Any engine built using this block could not have also used the large journal "pink" rods since that would have also required the use of a large journal crankshaft which did not exist at the time that either of above-referenced partial engines were released.

However, in July, 1970 the GM #3758458 was discontinued and replaced by GM #3970176 and in October, 1970 the GM #3775413 was discontinued and replaced by GM #3970178. It's possible that these engines used a large journal block. However, the only 3" stroke forged crankshaft that could have been used would have been the 1968-69 302 (Z-28) crankshaft. That's a "rare bird" indeed. If all this was actually done and in order to use the large journal "pink" connecting rods, the partial engine assembly would have been, essentially, a 302 with a 283 bore and pistons and '097' camshaft. The only 283 bore block I know of with large journals was the 307 block. As I say, I would consider it REMOTELY possible.

The GM #3970176 and 3970178 partial engines lived a very short SERVICE life. Released in July and October, 1970, respectively, they were discontinued without supersession in, respectively, September and July, 1972. So, if you had one of these SERVICE engine assemblies you would have had to obtain it pretty much within that time frame.

By the way, the highest performance small journal connecting rod ever available from GM was the GM #3864881 used for 1965-67 327 and 1967 302. I have many NOS examples of this rod. None are pink-dyed.

[Duke W.]

Re: "Pink" Connecting Rods

Don------



By the way, the highest performance small journal connecting rod ever available from GM was the GM #3864881 used for 1965-67 327 and 1967 302. I have many NOS examples of this rod. None are pink-dyed.

Joe, I didn't think the ...881 rod went into production until the '66 MY and maybe not even at the beginning. Do you know the release date?

For reference these are what I call the "second design" 327 rods. The little "hump" of additional material adjacent to the bolt seats considerably improves their durability. This was a weak point on the first design 327 rods. I rebuilt my SWC's 340 HP engine at about 115K. I ran great, but I was worried about the rods that I knew were weak, and sure enough, Magnaflux inspection revealed a crack clear across one of the the bolt seats on #7. I dodged a bullet.

Duke

[Richard F.]

Re: "Pink" Connecting Rods

Don------


Now, that really surprises me. All of the "pink" connecting rods I described above were large journal type rods. All 283's used small journal rods and I know of no small journal "pink" rods. So, I am 100% confident that there were no "pink" rods ever used on a PRODUCTION 283, special high performance variant or not. Could there have been a SERVICE 283 short block that used the large journal "pink" rods? It's remotely possible. Here's how it MIGHT have been done.

The 1957-60 SHP 283 partial engine (short block) was GM #3758458. The 1961 SHP partial engine was GM #3775413. Both of these engines used block GM casting #3756519. Any engine built using this block could not have also used the large journal "pink" rods since that would have also required the use of a large journal crankshaft which did not exist at the time that either of above-referenced partial engines were released.

However, in July, 1970 the GM #3758458 was discontinued and replaced by GM #3970176 and in October, 1970 the GM #3775413 was discontinued and replaced by GM #3970178. It's possible that these engines used a large journal block. However, the only 3" stroke forged crankshaft that could have been used would have been the 1968-69 302 (Z-28) crankshaft. That's a "rare bird" indeed. If all this was actually done and in order to use the large journal "pink" connecting rods, the partial engine assembly would have been, essentially, a 302 with a 283 bore and pistons and '097' camshaft. The only 283 bore block I know of with large journals was the 307 block. As I say, I would consider it REMOTELY possible.

The GM #3970176 and 3970178 partial engines lived a very short SERVICE life. Released in July and October, 1970, respectively, they were discontinued without supersession in, respectively, September and July, 1972. So, if you had one of these SERVICE engine assemblies you would have had to obtain it pretty much within that time frame.

By the way, the highest performance small journal connecting rod ever available from GM was the GM #3864881 used for 1965-67 327 and 1967 302. I have many NOS examples of this rod. None are pink-dyed.

Hi Joe
I have a 3970166 CE (1962-65 327) SP/HP short block I purchased in 1971. This short block should have the GM#3864881 connecting rods correct? Thanks in advance for sharing your expertise.

[Joe L.]

Re: "Pink" Connecting Rods

Hi Joe
I have a 3970166 CE (1962-65 327) SP/HP short block I purchased in 1971. This short block should have the GM#3864881 connecting rods correct? Thanks in advance for sharing your expertise.

Richard-------


Yes, assuming it's not something like the remote possibility I described above. What is the casting number on the block?

[Joe L.]

Re: "Pink" Connecting Rods

Joe, I didn't think the ...881 rod went into production until the '66 MY and maybe not even at the beginning. Do you know the release date?

For reference these are what I call the "second design" 327 rods. The little "hump" of additional material adjacent to the bolt seats considerably improves their durability. This was a weak point on the first design 327 rods. I rebuilt my SWC's 340 HP engine at about 115K. I ran great, but I was worried about the rods that I knew were weak, and sure enough, Magnaflux inspection revealed a crack clear across one of the the bolt seats on #7. I dodged a bullet.

Duke

Duke------


I do not have an actual release date. However, I believe the 3864881 was introduced into PRODUCTION sometime during the mid-1965 time frame. That would be consistent with the part number sequence. It was also included in later 1965 model year editions of the P&A catalogs as being applicable to 1965 Corvette. However, it was not shown in early editions of the 1965 catalogs. Within the late 1965 to early 1966 period it replaced for SERVICE all of the earlier 283 and 327 connecting rods. The phased replacement was probably due to the desire to exhaust SERVICE inventory of the previous part numbers. Of course, anyone "in the know" during that phase-in period would have specified the 3864881 for their earlier application.

[Gary R.]

Re: "Pink" Connecting Rods

I had those in my 75 L82. When I brought the block and piston to a local CT machine shop I brought new pistons to be fit to those rods. When wepicked up the parts the rods were installed only they were not my Pink rods. I had before and after pictures and was told they didn't use pink rods or forged pistons. When I measured the block it was uniformly overbored. He continued to deny any wrong right up to the day we were going to court. He suddenly decided to settle. I never did get the rods back but I suspect they were sold to someone else he took advantage of. The 030 ovebore was wrecked as well and 040 would be needed. Just a memory when I hear about pink rods. I think that shop is still in business but I wasn't the last one to bring him to court.

[Richard F.]

[Richard F.]

Re: "Pink" Connecting Rods

Joe I recorded the block number as #3959512.

[Joe L.]

Re: "Pink" Connecting Rods

Joe I recorded the block number as #3959512.

Richard------


That's what I suspected. The 3959512 was a SERVICE-only block released in 1969 and used for SERVICE engines for pre-1968 small block applications. As I recall, it has provisions for a road draft tube. I do not recall if it uses the pre-1968 crankshafts or the larger journal 1968+ crankshafts.

[Joe L.]

Re: "Pink" Connecting Rods

I had those in my 75 L82. When I brought the block and piston to a local CT machine shop I brought new pistons to be fit to those rods. When wepicked up the parts the rods were installed only they were not my Pink rods. I had before and after pictures and was told they didn't use pink rods or forged pistons. When I measured the block it was uniformly overbored. He continued to deny any wrong right up to the day we were going to court. He suddenly decided to settle. I never did get the rods back but I suspect they were sold to someone else he took advantage of. The 030 ovebore was wrecked as well and 040 would be needed. Just a memory when I hear about pink rods. I think that shop is still in business but I wasn't the last one to bring him to court.

Gary------


Not trying to be the devil's advocate, but if a machine shop were rebuilding engine components they would probably hot tank the rods before re-sizing the big end. The hot tanking would remove any trace of the pink dye. Without the dye, these rods are difficult, if not impossible, to distinguish from the standard 350 rods (that's why GM used the usually liberally applied dye in the first place). Did you have some other way of distinguishing the rods you brought to the shop?