Tweet
A question was recently posed to me off-board regarding connecting rods used for the above applications. As it happens, there is some "incorrect" information contained in GM parts publications on this subject. Here's the deal:
1969 L-88 and ZL-1 originally used connecting rod GM #3959187. This was a heavy duty, floating pin-type connecting rod. It used rod bolts GM #3959186 which were a HD, 7/16" rod bolt.
In July, 1970, the GM #3959187 connecting rod was replaced, for SERVICE, by the GM #3969804 connecting rod. The latter rod was designed for and destined for the still-born 1970 LS-7. It is, basically, the same forging with improved finishing and, most importantly, an improved rod bolt. The rod bolt used for these rods was a special, ground shank, boron steel rod bolt of GM #3969864. It is possible that some very late 1969 L-88/ZL-1 engines, PRODUCTION or SERVICE also originally used the GM #3969804 rods. I don't think so, but it's possible.
In any event, it is unlikely that the GM #3969804 rod was ever used in a PRODUCTION engine. However, it is an improved version of the GM #3959187 rod which was used in PRODUCTION for 1969 L-88/ZL-1. Regardless, the last use in PRODUCTION for either the 3959187 or 3969804 rod was the 1969 model year.
For the 1971 model year, the next and last use of a SHP big block in the form of the LS-6, a different rod was used. This rod was of originally of GM #3963552. It was a very stout rod, but not quite as stout as the 3959187/3969804 rod. Also, it was machined for PRESS FIT piston pins and it used knurled shank rod bolts of lesser strength than the boron steel bolts used for the earlier L-88/ZL-1 rods. However, the 3963552 was actually the first "high tech" big block rod. It was designed to reduce mass in non-critical areas and maintain strength in critical areas. While its beam cross section is smaller than the '187'/'804', it's nearly as strong overall. Its rod bolts are of adequate strength for most street or, even, racing applications, but they can be easily improved on.
The GM #3963552 rod was discontinued in August, 1986 and replaced by GM #14096151. That rod was, in turn, discontinued in April, 1992 and replaced by GM #10198922 which continues to be available to this very day. All of these rods are very similar. I don't know how they differ but the forging appears to be the same for all, the 4340 material is the same, and the rod bolts are, basically, the same.
All of the above rods can be used interchangeably in any big block engine, be it Mark IV, Mark V, Mark VI, or Mark VII. The small end may need to be converted/bushed to accomodate the style piston pins being used (i.e. pressed or floating). This can be easily done by a competent machine shop. All PRODUCTION big block engines and most SERVICE engines use a 6.135" center-to-center connecting rod.
The GM #3969804 rod was discontinued a few years ago. While it was the strongest of any big block rod ever offered by GM, it was very expensive. When discontinued, it carried a GM list price of over $200/each.
The GM #10198922, the evolution of the LS-6 rod, is still available and carries a GM list price of about $125/each. This rod can be improved by the addition of ARP-2000, Wave-Lok connecting rod bolts. However, considering the cost of the rod, the ARP bolts and the resizing work necessary to install the bolts, one would be up to nearly $200/each by the time all is said-and-done.
Until recently, there was a great deal available on the GM #10198922 rods. They were available as a set of 8 under GM #12496661 for about $400, GM list. This was one of the best deals on connecting rods EVER. Alas, it's a "goner"; the 10198922 rods are now only available individually. I wish I had bought 10 sets of these rods when they were available. At the set price, they were a GREAT rod at a GREAT price.
At the present time, considering the price of the 10198922 rods, even at discount prices, or the cost of NOS sets of the 3969804 rods, it's just not prudent to go this way. That's because one can purchase a set of aftermarket, cap screw type rods of FAR better quality and strength for less. If one wants maximum strength in a rod, the aftermarket STEEL rods are the ONLY way to go. If someone wants to go with a GM rod, then I recommend the 10198922 refitted with ARP Wave-Lok bolts. This rod is PLENTY strong enough for any street application, lighter than the earlier L-88/ZL-1 rods, and available from GM.
1969 L-88 and ZL-1 originally used connecting rod GM #3959187. This was a heavy duty, floating pin-type connecting rod. It used rod bolts GM #3959186 which were a HD, 7/16" rod bolt.
In July, 1970, the GM #3959187 connecting rod was replaced, for SERVICE, by the GM #3969804 connecting rod. The latter rod was designed for and destined for the still-born 1970 LS-7. It is, basically, the same forging with improved finishing and, most importantly, an improved rod bolt. The rod bolt used for these rods was a special, ground shank, boron steel rod bolt of GM #3969864. It is possible that some very late 1969 L-88/ZL-1 engines, PRODUCTION or SERVICE also originally used the GM #3969804 rods. I don't think so, but it's possible.
In any event, it is unlikely that the GM #3969804 rod was ever used in a PRODUCTION engine. However, it is an improved version of the GM #3959187 rod which was used in PRODUCTION for 1969 L-88/ZL-1. Regardless, the last use in PRODUCTION for either the 3959187 or 3969804 rod was the 1969 model year.
For the 1971 model year, the next and last use of a SHP big block in the form of the LS-6, a different rod was used. This rod was of originally of GM #3963552. It was a very stout rod, but not quite as stout as the 3959187/3969804 rod. Also, it was machined for PRESS FIT piston pins and it used knurled shank rod bolts of lesser strength than the boron steel bolts used for the earlier L-88/ZL-1 rods. However, the 3963552 was actually the first "high tech" big block rod. It was designed to reduce mass in non-critical areas and maintain strength in critical areas. While its beam cross section is smaller than the '187'/'804', it's nearly as strong overall. Its rod bolts are of adequate strength for most street or, even, racing applications, but they can be easily improved on.
The GM #3963552 rod was discontinued in August, 1986 and replaced by GM #14096151. That rod was, in turn, discontinued in April, 1992 and replaced by GM #10198922 which continues to be available to this very day. All of these rods are very similar. I don't know how they differ but the forging appears to be the same for all, the 4340 material is the same, and the rod bolts are, basically, the same.
All of the above rods can be used interchangeably in any big block engine, be it Mark IV, Mark V, Mark VI, or Mark VII. The small end may need to be converted/bushed to accomodate the style piston pins being used (i.e. pressed or floating). This can be easily done by a competent machine shop. All PRODUCTION big block engines and most SERVICE engines use a 6.135" center-to-center connecting rod.
The GM #3969804 rod was discontinued a few years ago. While it was the strongest of any big block rod ever offered by GM, it was very expensive. When discontinued, it carried a GM list price of over $200/each.
The GM #10198922, the evolution of the LS-6 rod, is still available and carries a GM list price of about $125/each. This rod can be improved by the addition of ARP-2000, Wave-Lok connecting rod bolts. However, considering the cost of the rod, the ARP bolts and the resizing work necessary to install the bolts, one would be up to nearly $200/each by the time all is said-and-done.
Until recently, there was a great deal available on the GM #10198922 rods. They were available as a set of 8 under GM #12496661 for about $400, GM list. This was one of the best deals on connecting rods EVER. Alas, it's a "goner"; the 10198922 rods are now only available individually. I wish I had bought 10 sets of these rods when they were available. At the set price, they were a GREAT rod at a GREAT price.
At the present time, considering the price of the 10198922 rods, even at discount prices, or the cost of NOS sets of the 3969804 rods, it's just not prudent to go this way. That's because one can purchase a set of aftermarket, cap screw type rods of FAR better quality and strength for less. If one wants maximum strength in a rod, the aftermarket STEEL rods are the ONLY way to go. If someone wants to go with a GM rod, then I recommend the 10198922 refitted with ARP Wave-Lok bolts. This rod is PLENTY strong enough for any street application, lighter than the earlier L-88/ZL-1 rods, and available from GM.
Comment