To rebuild or not...

[vssman]

Here's a bit of history: I have a 68 200 in my 63 falcon 'vert that has an exhaust manifold leak. I tried to pull the manifold but ended up breaking a couple of bolts. I then pulled the engine to try to remove all of the rest of the bolts without breaking any more and to drill out those that did break. The top end was surprisingly clean when I removed the valve cover to attach the lifing chains to the head bolts. After pulling the engine, I noticed the rear freezeout plugs looked new. I also noticed the head gagket was fiber and beasured .050" where it was sticking out between the block and head. When I got the exhaust manifold off, I was surprised to see a port divider already installed.

Now for the questions: Seeing the gasket was already replaced, I pulled the head. The cylinder walls are clean without scratches but the cross hatching is gone. I'd guess the engine has probably 15 to 30k miles on it looking at the amount of "crud" on the valve train and wear in the cylinders - even that might be high. Back in the day when I worked at a garage, I recall seeing a lot of sludge on the sixes when replaing valve covers. I can slide a .015" shim between a straight edge and the edge of the piston top. So what to do? I don't have a bore gage to measure taper and I don't know (yet) what the CC's are for the head. My goal is to have a reliable weekend driver with a bit of punch. I have a HW 32/36 to put on it and will be upgrading the dist to a DUI. I figure I should at least get a 78 or later head although a CI or OZ would also be do-able. It's apart, so now would be the time to put in a cam. Would you guys at least re-ring it if the cylinders are straight or leave it alone? I don't want to spend if it doesn't have to be spent but want to do a reasonably good job. FWIW, I also have a 3.03 to put in it as soon as I find a yoke and driveshaft that can be modified to fit. Thoughts???

 

[shmoozo]

My first thought is that it sounds like the bottom end is in good shape so unless you have reason to believe that the bearings or rings are worn I wouldn't even mess with it other than perhaps to install a mild performance cam (perhaps a 264/274 cam with about 112 degrees of lobe separation like the Clay Smith model 264D-112 that Mike sells) with new lifters and appropriate valve train components while you have it out of the car. If you do decide to upgrade the cam you might want to consider one of the dual roller timing sets Mike sells while you are at it. A mild performance cam like that would probably liven up the car's performance a bit without really screwing anything up too much. You'd still have a smooth idle and decent fuel economy, for example.

Then again, if you want to install new rings, I say go ahead. Remember to hone the cylinders if you do, and frankly, since you are going to need to remove the pistons and crank to do that I would say replace all of the lower end bearings while you are at it -- unless the bearings look brand new, I mean. They're not colossally expensive and you might as well replace them while you have the engine apart. Seals and gaskets should generally be replaced whenever you have the engine apart, of course.

Another thing to consider while you have the head off is to considering doing a 3 angle valve job and some port work on it if you decide to stick with one of the stock log style heads. That's clearly not as important with the CI head, but I'd absolutely go with a larger carb than the HW 32/36 if I went with the CI head. Frankly, I'd look at a small 4 barrel if I was installing the CI head. I gather that the Autolite 4100 as tweaked by Pony Carbs can be a really good match for these engines.

Of course all these mods add up to a pretty hefty price tag, but you could always do the lower end stuff now and the head work and such later.

 

[rbohm]

8) i would say it depends on the condition of the cylinders at this point. if they look good and you can still see the honing marks from the previous build(check the tops of the pistons and see if they are std or over sized). if the hone marks are still visible then leave the cylinders alone. i would also remove the oil pan and pull a main cap and a rod cap and see what the bearings look like. again if they look good then leave well enough alone. these little sixes are tougher than marines.

 

[vssman]

Thanks for the replies. I'm going to borrow a Starrett bore gage from work and measure the cylinders. I'll post what I find. I tried with a telescoping gage and micrometer but couldn't get an repeatable read - Danm Chinese tools... If they measure within range, I'll probably be looking at a re-ring/bearing, cam and (at a minimum) later model head with as much port work as possible done to it and direct mount the carb (if possible). I do have a spare Holset HX35 turbo laying around in the garage just itching to be put under a hood...

If I replace the head with another log unit, should I get another port divider?

 

[vssman]

Here's what I measured:

Bore: 3.6820" to 3.6825" all cylinders both lengthwise and across the engine near the top and on top of the piston at the bottom of the stroke. Piston to deck clearance after cleaning the top of #1: 0.023" not 0.015" I measured earlier. Stroke: 3.145" with a vernier from the top of the block to the top of the piston at the bottom. Head: 53cc. I'm thinking that neither the head nor block were machined to compensate for the thicker head gasket. Now for a few more questions. I don't have a manual that covers the 68 200 specs. Can anyone list them? Do these measurements support a hone & re-ring without a re-bore? The pan will come off this weekend and I'll look at/measure at the crank. How close does the block normally get decked? Should I leave 0.005", go right to the top of the piston or leave more? Like I said earlier, I want to do it right but don't want to waste money if I don't need to. Thanks in advance for suggestions and advice...

 

[rbohm]

8) i might put a fresh set of rings and bearings in, but i would not hone the cylinders, unless you do a thorough cleaning of the block afterwards.

 

[Lazy JW]

You're pretty deep into it already, and reading between the lines I feel that you won't be satisfied without putting a set of rings in there. I wouldn't bore it though. And bearings are cheap.

The biggest thing I see that you will likely regret later is the fact that the deck height is bad and the compression will be fairly low due this plus the head not being milled (get the pistons right even with the block or even a few thou above). This will come back to haunt you in your quest for performance UNLESS YOU INSTALL THAT TURBO. If you turbocharge, then best to leave both the deck and the head CC's alone.
Have fun,
Joe