[DZAUTO]

Has anyone here actually done their own clearance notches at the bottom of the cylinders of a 350 block when building a 383? Did you get into the water jacket? How much clearance did you have between the notch and the rod, .010, .020, .030, more?
I'm not having a problem, I'm just curious if anyone has EVER gone into the water jacket and just how much clearance others have had. I honestly don't know just how much thickness is there for grinding the notches. Everytime I do one, I just make the notch as small as possible.

 

[Tom Mobley]

I've done plenty, never hit water or any other misadventures. This is one place a block that's machined off-center in the casting can create a lot of extra work.

I've got a really hi-tech gauge I use while grinding the bottom of the block, it's called "a piece of wire that's about .030." I don't really know why it has to be that much, I have a hard time envisioning the crank or rods moving around that much unless something alse is really bad wrong.

I have an old foot-long .030" feeler gauge I use for checking the clearance at the cam lobes. I really like to see some room there since small changes in cam timing can affect it lot.

>> "....I just make the notch as small as possible." I think that's really the key, remove as little as possible and get by.

How's your Corvette?

 

[BillK]

Tom,
There is plenty of room. I shoot for .050" and have never struck water. Somebody makes a neat tool that is basically a plastic crankshaft that is only long enough for two cylinders at a time. Looks like it would make it real easy for checking your progress as you gorind.

 

[Tom Mobley]

the way I do this kind of mock-up is this: many years ago I had a fake wrist pin made, it's a slip fit in a stock pressed pin rod. Over the years I've developed a drawer of pistons of various sizes and I always save back some used bearings in the popular standard and undersizes. I just install the crank on old bearings, only two are needed. I check the crank for clearance, sometimes problems arise in the back corner near the oil filter if it's an aftermarket crank with big counterweights. Then I just number the rods if they're not already, install the spare piston with rhe slip-fit pin on each in turn, and also in turn install the rod-piston assembly in each cylinder and check, grinding as I go along. If the cam is in place I can also check that clearance on each in turn as I go along. every few rods I toss the old bearing and start another, they can get messy if there's a lot of grinding.

Often there is as much or more grinding on the bottom of the cylinders as there is on the pan rails.

I actually use solid carbide burrs and clean up with a stone. I've had good luck lately with this polishing deal I get at a hardware store, it's like a flap wheel with scotchbrite between the sandpaper flaps. works like a charm on a high-speed grinder but wear out fast and not cheap item to begin with, six bucks per last I recall and I'll use two or three on a block if there a lot of grinding and I want it to look nice.

 

[CNC BLOCKS N/E]

We have a program in our CNC machine that is adjustable for different strokes and rod combinations and only tales about 2 minutes to do and so far never hit water yet.

 

[DZAUTO]

OK, thanks. That's exactly what I wanted to know. I don't build many 383s (because I build more SB400s). I have never had a problem grinding the notches, but this time I just though I'd see what, if anything, others may have encountered. I'll just keep on keepin' on.

Tom,
I still light a fire in the little red rocket when I get a chance. But since I've been working on my Masters, I haven't had many chances to do anything! The 70 conv is still sitting up on the lift since we got it home from CB05, waiting for me to pull the oil pan and beat it out (It slipped off of the jack in the motel parking lot and the jack went up into the pan sump, bad!). And I'm not actually building the 383, I'm helping one of my sons. I supervise, he wrenches!

 

[forcd ind]

i did my own, used a hi speed grinder that cuts it like butter-i had the motor bored first, then brought it home, trial fitted it for each cyl, then cut each one ind.-a couple didnt need cutting-a lot of guys use a mill, makes it look nicer, but then you still have to mock each one up anyway-
then everything gets a real good bath