VCCA Home Forums TECHNICAL - GENERAL Mechanical - Engine, Trans, etc what is allowable cylinder taper

On a 216 how much taper is OK before oversize pistons are required? 41 shop manual says check bore with dial indicator to determine condion but no tolerance is given.
Thanks, Jay

Any above 0.002" is generally considered too much for race engines. Get around engines can tolerate up to 0.005" or more. Oil consumption will increase as taper does. I ran a '31 Chevy engine with 0.008"-0.010" for a few thousand miles. Despite the piston slap noise it did just fine.

The later manual says up to .005". More or less depends on the type of rings used (should be expander type) and what type of use the engine will be subject to. Years ago when we overhauled engies the guys would not bother to check the wear unless the ring ridge was really big. Also if installing aluminum pistons I would have the block bored for a tighter piston fit.

I re-built my 37 with .006 taper. Never used a drop of oil and runs like a top.

I would not go over .005".

Chevrolet offered pistons that were as little as .001" oversize.

The .001" over were for new cars that had piston slap because the bore was a little too large. We used to install them when the car was under warranty.



was considered a standard high-limit size. Would be difficult to find a set now.

Also, according to the parts book there were not any .010" pistons available for the 1941-52 passenger cars with a 216 engine. The next available size was .020".

I still rebore an engine with more than more than .004 taper or out of round as the rings will fatigue and break beyond that.
Tony

Thanks guys, the machine shop says I have .010 taper and out of round .008-.010...He recomends a complete rebuild, I guess he's right.
Jay

I'd say go with the recommendation of the machine shop. Unless it's Mike's, of course.

(Sorry, that there was right insensitive. But, still, I couldn't help myself)

Charlie

Go with the complete rebuild.

Most definitely go with the full rebuild at a machine shop with a good reputation, not all local shops can do the job properly and sorry I dont know any US machine shops.
Tony

Man, that's the truth! With a vintage engine is usually a good idea to stay away from your local machine shop unless you want a lot of headaches and grief.

Local machine shops should be able to clean blocks & heads, refurbish heads, bore & hone blocks etc. Some can even grind camshafts, crankshafts. It is the babbitt bearings that will be beyond their expertise.

Wouldn't one prefer insert rod bearings to babbit?

I would go with the inserts. Five years ago I would have said stay with the babbitt.
If the crankshaft is turned to an undersuze they just make the babbitt thicker for the babbitted rod. With the insert the insert is thicker and the babbitt on the insert stays thin + an insert will have thinner babbitt to begin with.
The thick babbitt tends to compress and the rod loosen.

Yep, definitely go with inserts if you can.