line boring

Thanks for all your help. I want to make this old car as dependable as possible since I plan to drive the crap out of it.
Later,
Dick

 

I would skip the harden seats if it was mine. You can not drive it hard enough to kill a stock seat in a car. If this was a truck pulling a heavy load all day, then yes, add the seats, but not your car. A replacement seat is just something to worry about falling back out if not done right. Ask your local shop to show you some examples of bad heads due to seat failures.

Joe

 

"How they fail" is simple.They are retained by an interference fit and will come out if it is insufficient or crack and then come loose if too much. Issues almost always come back to precision measuring capabilities or lack of it. I've inspected several heads and have yet to see one where the seats were beat down and agree with those who believe the risk outweighs any benefit.

 

Your right to question "how could you align hone a Jimmy block", simply, it cannot be done because of the different size housing bores as you mentioned, they can only be line bored, and is the only method available still today to correct the out-of-round or out of alignment housing bores of these engine and the Stovebolts as well. Also, a competent machinist can easily perform this task without affecting the cam to crank centerline enough to matter. It was also common practice back in the day for people who wished to eliminate the use of shims under the main caps to line boring their blocks and make them like the later Stovebolts that didn't use shims as a method of controlling bearing clearances.

So don't think of line boring as being an unorthodox method to repair some of these old vintage engines, its really quite natural to do this. All the engines like the Model A even had to be line bored when they were re-babbitted.

 

Curt,I'll disagree with you from my experience.In the last 15 years I have put together a GMC 302,four 235-261's and a SBC. Everyone of these engines had the valve seats replaced. Every one of these heads had the exhaust valves recessed,the seats pounded in.Some so bad the original seat was starting to peen over into the bowl. You can recut the seats of course but the valves are too far into the valve seat for best performance .I can say there was never a problem,in fact the GMC has about 70,000 miles on it now and sold to a HAMB guy.I'm just a hillbilly hobbist engine assembler,use a local shop to do the machine work.The shop gets a little sloppy at times but does immaculate valve work.

 

If the crank is tight after installing it with lube and caps are torqued to spec, line bore it. Otherwise leave it alone.

 

I realize this is an old thread, but wondering about something. When line boring, does the crankshaft actually move up a few thou.? What happens to the pilot bearing on a manual trans.?

 

Maybe one or two thou if done right. Pilot bearing has enough clearance.

 

What do the bearings look like now? Can you easily turn the crank now? If the bearings look good just worn and you can turn the crank in the block without stops and starts leave it alone. Don't fix things that aren't broken. g

 

I see my old post came up. I thank all of you for the advice. I am still running the original 235 6 in my 54. I did not rebuild another engine. I did change the intake and exhaust to Fenton's. This old motor carries 50 psi of oil pressure going down the highway and runs like a top. I'll run her as is until she needs help.
Later,
Dick

 

I believe you made the correct decision for the time being. Tim