Main bearing cap bolt location

[cruiser54]

I'm getting ready to drop the crank into my HO stroker block. Since I am used to Renix where all the main bearing cap bolts are the same, I need to now know where the two bolts go that have threads above the bolt heads. TIA. Pete

[5-90]

Only two?

I know that the 1996-up 6-242 block came with a main cap reinforcement bracket (I forget what they called it,) but that would require studs on at least the middle five main cap screws to attach (the part that goes into the block is threaded 1/2"-13, the part for the brace is threaded 3/8"-16.)

If you don't have this brace, then it shouldn't really matter where the "stud tops" go. Did you tear the engine down yourself? Was there something extra under the sump {apart from the crank & assoc. parts, and the oil pump and pickup?) If not, put them wherever you like.

Sounds like you may have gotten something "donated" when you weren't looking...

[cruiser54]

I took it apart and didn't take note over a year ago. No main bearing brace on the motor. I'm used to Renix where all the bolts are the same.

You're right. It probably doesn't matter.

[cruiser54]

I'm thinking that 2 of my main cap bolts are for the later motors with the "girdle". This engine was built by someone else and I'm freshening it up.

That said, what about using a girdle on the stroker? Is it a pain to get enough clearance for the oil pan after shimming the girdle away from the stroker crank? Is it worth it?

[amcinstaller]

someone here documented adding a girdle and i think he just stacked on like 2 washers or something. and sorry, i really have no idea anymore who it was.....

they did have pictures and the whole lot

[5-90]

I'm thinking that 2 of my main cap bolts are for the later motors with the "girdle". This engine was built by someone else and I'm freshening it up.

That said, what about using a girdle on the stroker? Is it a pain to get enough clearance for the oil pan after shimming the girdle away from the stroker crank? Is it worth it?

I was thinking about fabbing something up, when I finally get the RENIX block I want (gotta live with a 4.000" bore) and crank I want (early 12-cw 6-258 crank.) I'll probably have to relieve the oil sump rails as well - but I've got plenty of other stuff to do first.

The crank will probably end up welded & ground = 4.000" bore x 4.000" stroke x 6 cylinders = 301.59 ci, and I haven't decided how I want to do the cam yet, need to run more iterative testing. But, I'm aiming for a torque MONSTER - as a sleeper.

[cruiser54]

I've got a 12CW as a spare. I went with the lighter crank in this build.

Here's a photo/listing for the girdle. I think it's priced rather high.

http://www.ebay.com/itm/RA027-GIRDLE-20 ... es&vxp=mtr

[SilverXJ]

Besides the girdle you will need the bolts with the stud on the end and the nuts. That will get costly.

I used two hardened washers to space the girdle out form the crank throws.

I don't know why your engine just had two of the studded bolts. Maybe someone lost two, maybe someone broke two. Maybe they ran out of the usual bolts during factory assembly. I would also be checking the main bore in case someone also lost one of the main caps.

[I6FAN]

That said, what about using a girdle on the stroker? Is it a pain to get enough clearance for the oil pan after shimming the girdle away from the stroker crank? Is it worth it?

I'm not shure of the benefits of the "girdle" either(?). It's called a girdle, but to me, it's really a sort of "dampener" (two or more independent, moving/vibrating objects that's touching a third tends to dampen vibrations). When I hear "girdle", I'm thinking heavy, beefy bottom end bracing that bolts around pan rails and over main caps. People who race these engines throughout the harmonic (~5375rpm), would be the best opinion as to weather there worth it. SIXPAK, who posts here, used the 12 weight crank for years with no problems, and then switched to the 4 weight and girdle, and suffered several broken main caps in one season. I think that was more of a four-weight crank thing myself.

I was thinking about fabbing something up, when I finally get the RENIX block I want (gotta live with a 4.000" bore) and crank I want (early 12-cw 6-258 crank.)

Rumor was that the RENIX block had the thicker bores, but Lee (HESCO) says the later blocks are more suitable for safely attaining a 4" bore. I believe 2000'+, or something(?). The thrust side is actually thicker as well. I think it was PLECTANSKY ,who posts here, that did this with his land speed comanche. To me, if you want a 4" bore, sleeving would be a viable alternative. Although sleeving deteriorates some strength, some good quality sleeves should actually be pretty darn strong. I'm coming to the conclusion that this is <5300rpm engine anyway, and if you sleeve it with that in mind it would be okay.

[cruiser54]

Besides the girdle you will need the bolts with the stud on the end and the nuts. That will get costly.

I used two hardened washers to space the girdle out form the crank throws.

I don't know why your engine just had two of the studded bolts. Maybe someone lost two, maybe someone broke two. Maybe they ran out of the usual bolts during factory assembly. I would also be checking the main bore in case someone also lost one of the main caps.

The engine was a stroker built by Golen. Everything else is fine. Went back together today with plasti-gauge.

[5-90]

That said, what about using a girdle on the stroker? Is it a pain to get enough clearance for the oil pan after shimming the girdle away from the stroker crank? Is it worth it?

I'm not shure of the benefits of the "girdle" either(?). It's called a girdle, but to me, it's really a sort of "dampener" (two or more independent, moving/vibrating objects that's touching a third tends to dampen vibrations). When I hear "girdle", I'm thinking heavy, beefy bottom end bracing that bolts around pan rails and over main caps. People who race these engines throughout the harmonic (~5375rpm), would be the best opinion as to weather there worth it. SIXPAK, who posts here, used the 12 weight crank for years with no problems, and then switched to the 4 weight and girdle, and suffered several broken main caps in one season. I think that was more of a four-weight crank thing myself.

I was thinking about fabbing something up, when I finally get the RENIX block I want (gotta live with a 4.000" bore) and crank I want (early 12-cw 6-258 crank.)

Rumor was that the RENIX block had the thicker bores, but Lee (HESCO) says the later blocks are more suitable for safely attaining a 4" bore. I believe 2000'+, or something(?). The thrust side is actually thicker as well. I think it was PLECTANSKY ,who posts here, that did this with his land speed comanche. To me, if you want a 4" bore, sleeving would be a viable alternative. Although sleeving deteriorates some strength, some good quality sleeves should actually be pretty darn strong. I'm coming to the conclusion that this is <5300rpm engine anyway, and if you sleeve it with that in mind it would be okay.

Perhaps, but I think AMC used an iron alloy with a higher nickel content - kinda like Dodge used for the Gen-II Hemi and old RB V8 engines. It costs more, which is why it's not in common use.

But, I had to peel the head off of my 87XJ after the oil pump hand failed -
- Broke the #6 con rod
- Collapsed all twelve lifters
- Scored 11/13 crankpins
- And the top cylinder ridge was 0.0005" high - I broke that out with 120-grit stones.

This was post-lube failure, drove it halfway home anyhow, and after 280Kmiles of normal (for me - "rough," for anyone else) service.

I haven't been able to confirm the assay on the alloys, but that would be in keeping with AMC's design philosophy. They were usually just behind the curve on new stuff, so they went with what worked instead. That's why, for instance, the AMC Gen-II and Gen-III V8 engines all came from the factory with forged cranks & rods.