L88 crank shaft

[Keith B.]

What is the diffrance in a L88 crank vs the standard 427/396 crank.

[Patrick B.]

Re: L88 crank shaft

L88 cranks as well as L-71 and L-72 cranks are tufftrided (a nitride surface harding treatment), but lower HP 427 (and 396) cranks are not. If the crank has been turned the tufftrided metal on the bearing surfaces is gone. Other than that there would be a slight difference in balancing because the piston weight would be different between L88s and L-71/72s.

[Michael H.]

Re: L88 crank shaft

What is the diffrance in a L88 crank vs the standard 427/396 crank.

If I remember correctly, only the L88 crankshaft has cross drilled main journals. ? (360* oiling)

All small and big block forged crankshafts of that era go through a surface hardening process, either tufftride or nitride.

Most cast iron crankshafts do not require either process as the surface "work hardens" as soon as it goes into service.

[Bill W.]

Re: L88 crank shaft

The 65 Corvette L78 / 396 crank is also tufftride and cross drilled . I believe it is the same crank as the L 88 . Maybe Joe L will have the answer .

[Michael H.]

Re: L88 crank shaft

The 65 Corvette L78 / 396 crank is also tufftride and cross drilled . I believe it is the same crank as the L 88 . Maybe Joe L will have the answer .

Bill, I don't think the L78/396 shaft is cross drilled.

Tuftried and nitride treated are not the same.

The crankshafts for the 65 396, 66 and 67 425-435 HP and 67 L88 are all different part numbers. The crankshaft for 68 L88 is yet another part number.

[Joe L.]

Re: L88 crank shaft

The 65 Corvette L78 / 396 crank is also tufftride and cross drilled . I believe it is the same crank as the L 88 . Maybe Joe L will have the answer .

Bill------


The 1965 L-78 crankshaft was not the same as 1967 L-88. It was not the same as 1966 L-72, either.

L-78 crankshaft-----------------GM #3882841---forged, tuftrided, cross-drilled, 1053 steel

L-72, L-71, L-89 crankshaft----GM #3882842---forged, tuftrided, cross drilled, 1053 steel

The L-88 crankshafts were as follows:

1967-------------------GM #3879621----forged, tuftrided, cross drilled, 1053 steel, for use with 3/8" rod bolts

1968-E69--------------GM #3942411----forged, tuftrided, cross drilled, 1053 steel, for use with 3/8" rod bolts

L1969 (also ZL-1)----GM #3967811----forged, tuftrided, cross drilled, 5140 steel, for use with 7/16" rod bolts

SHP 454 crankshafts:

1970-71 LS-6 (SHP)------------------GM #3963523----forged, nitrided, cross drilled, 1053 steel, for use with 7/16" rod bolts

1970 LS-7 (HD) (SERVICE only) ----GM #3963524----forged, nitrided, cross drilled, 5140 steel, for use with 7/16" rod bolts


I believe that the primary difference between all of the L-88 cranks had to do with balance. As a matter of fact, in 1971, all of the L-88 cranks, including the late 1969 made from 5140 steel, carried the exact same GM list price-----$110.80. The L-78 and L-72 cranks were only slightly less at $107.15 and $102.20, respectively. This implies there was not a whole lot of difference between them. As a matter of fact, in 1971 both of the SHP and HD 454 crankshafts were also the same price as the L-88 crankshafts (that's why I used 1971 as the comparison year).

[Joe L.]

Re: L88 crank shaft

Bill, I don't think the L78/396 shaft is cross drilled.

Tuftried and nitride treated are not the same.

The crankshafts for the 65 396, 66 and 67 425-435 HP and 67 L88 are all different part numbers. The crankshaft for 68 L88 is yet another part number.

Michael------

As far as I can tell, the L-78 crankshaft was cross drilled. However, I cannot be 100% sure.

The L-72, L-71, and L-89 used the same crankshaft----GM #3882842.

As you mention, Tuftriding and nitriding are not the same. However, they produce essentially equivalent effect on the crankshaft journals. Tuftriding is considered an "environmentally dirty" process and water pollution control laws have effectively rendered it "dead". Nitriding is more "environmentally friendly" and is still in use.

[Michael H.]

Re: L88 crank shaft

Michael------

As far as I can tell, the L-78 crankshaft was cross drilled. However, I cannot be 100% sure.

Joe,

Now I'm wondering too. I do remember cross drilling a lot of customers big block crankshafts in the late 60's but I suppose many were shafts from non high perf engines?

I think I remember that the tuftriding process was done with some pretty nasty acid or acid powder. I don't remember the name though.

[Bill M.]

Re: L88 crank shaft

I see that the 1970 cranks were nitrided. That triggered a memory from the summer of '69. I remember the resident engineer (he reported to Chevrolet Engineering in Warren, not to the Tonawanda plant manager) at Tonawanda bringing a nitrided crank into the dyno lab. for us worker bees to see. It may have been the first nitrided crank. I am (vaguely) remembering that it had a darker color than the tufftrided cranks. It was going to be installed in a boat.

[Michael H.]

Re: L88 crank shaft

I see that the 1970 cranks were nitrided. That triggered a memory from the summer of '69. I remember the resident engineer (he reported to Chevrolet Engineering in Warren, not to the Tonawanda plant manager) at Tonawanda bringing a nitrided crank into the dyno lab. for us worker bees to see. It may have been the first nitrided crank. I am (vaguely) remembering that it had a darker color than the tufftrided cranks. It was going to be installed in a boat.

Bill,

Do you remember if the machining on the counter weights was shiny or was it dull?

[Bill M.]

Re: L88 crank shaft

Bill,

Do remember if the machining on the counter weights was shiny or was it dull?

Nope. Sorry Michael. I just remember nitriding and that it was going in a boat.

edit: On second thought, back then I assumed it was a special part for marine use. Joe's post re. nitriding triggered the nitriding memory.

Bill

[Michael H.]

Re: L88 crank shaft

Nope. Sorry Michael. I just remember nitriding and that it was going in a boat.

edit: On second thought, back then I assumed it was a special part for marine use. Joe's post re. nitriding triggered the nitriding memory.

Bill

Thanks Bill. I'm pretty sure the machining would have been dull, almost grey but I don't remember for sure either.

I think the new nitride process began somewhere around the end of the 60's or 1970. The crankshafts for Z28/302 Camaro's was tuftride.

[Michael H.]

Re: L88 crank shaft

I just talked to Clem. He said all high perf solid lifter big blocks had a cross drilled c/shaft.

If that's the case, then the only difference between a 67 435 C/S and a 67 L88 C/S would be the balance due to different piston weight.