.060 bore OK for 258 6cyl?

[Bryan]

I pulled the intake/exhaust off my 258 today because I'm gonna replace the 1bbl with a 2bbl mainifold. Anyways I noticed a tag on the motor beneath the manifolds that, as it turns out, shows that I have a remanufactured motor that was turned .060 over. I guess this is a good thing but I know .060 is quite a bit. Any thoughts on this? FWIW the motor ran OK (other than carb) and never really overheated (although it would get pretty hot in the summer).

[BIG WILLIE]

Do u have any overheating issues. From what i understand it isnt recomended to go more then .040 over on amc blocks. Also because it is .060 over u cant have more taken off so that is the last rebuild on that motor.

[tgreese]

I think the 258 is different and should be ok at 0.060 - especially with a "middle" vintage block instead of '81-on lightweight block. I think that's the last rebuild cycle for that block though. My sources are at home, and I'll double check then.

BTW the stock radiator on my 258 was 2-row, and the only replacement I could find was a 2-row. You can have the radiator recored with 3 rows, which is what I did. Has a 195 thermostat, and runs right in the middle of the gauge all the time now. No opportunity to check it out in hot weather yet, but it seems fine.

[Bryan]

Big Willie & tgreese, using the stock 1974 gauge it never really seemed to get too hot. In winter it rarely gets to more than a quarter of the guage, and in summer rarely more than 3/4 of the guage. I have a 180 thermostat in there and put in a new water pump last summer. Over all I'm not concerned about the temp, and I'm an anal retentive freak so I watch temp like a hawk!!!

On a different note: tgreese you seem to be an expert on the 258/6.. there is a (metal) tube that comes out of the exhaust manifold and screws to the choke on the carb, I assume it has to do with the choke function some how (mine never did work). It was broken off inside the exhaust manifold, is this something that can be replaced? or is there another (similar) function on later model manifolds that accomplish the same thing? When I look for a later model 2bbl manifold will it have a similar tube/connection for the choke?

[tgreese]

Bryan, the TSM doesn't say anything (that I can find easily) about overbore size. Another source says that a 0.125 overbore is possible for a 258, but that seems way excessive to me. I personally wouldn't go more than 60 over without sonic testing the block for thin spots.

You're refering to the choke stove. The manifold heats up and supplies warm air from the choke stove to help unwind the bimetal coil in the choke cover, opening the choke. The carb applies a vacuum to flow the hot air, so if the stove is missing you should cap the connection. These chokes are thermoelectric, combining electric (from a push-on connector) and hot air from the choke stove.

The newer manifolds ('81 and later) don't have a choke stove. I don't have an example to look at, but I believe these chokes are all-electric. The electricity comes from the ignition through an oil pressure switch, so that the choke element heats up only when the engine is running.

If you're going to use a Motorcraft, there's an all-electric element available. You can get an oil pressure switch from Holley (used with electric fuel pumps) and set up an electric choke, or convert to a manual choke using a kit.

[Cecil14]

258 blocks are extremely heavy and most can handle .125" over pretty well. I wouldn't do it or recommend it but it can be done. .060" over is nothing, should be plenty good to go. Just keep an eye on temp and you'll be good.

Anthony

[Bryan]

Thanks for the help all.......