The Stovebolt Site Forums The Shop Area Engine Shop 216 STD piston size

Hi,

I've been using my 41 Chevy for a few years now but it's been using a bit more oil than is was at the start and the plugs are a bit oily unless really warmed up so thought I'd look at new rings.

I've taken the head off today and was hoping to see a size marking on the piston - but only a piston number appears to be there.

The pistons are 3.495" in diameter and I wondered if these were STD, or if not what size they are?

Thanks

216 or 235?

216

On further searching looks like they are 3 1/2 at standard so think that must be what I have if I add on .005 for the accuracy of my gauge.

Seems pretty amazing to me that after 70 years (the numbers show it as a 43 engine) it's still at STD bore, or maybe that's what my issue it?

I would measure the clearance between the skirt and the cylinder to get more information.

Sounds like your measuring the piston not the bore. The bore is
where the wear takes place not the piston.

Denny Graham
Sandwich, IL

I've pushed the piston to the side and slipped a feeler gauge down the sides of the bore to see what the gap is. I can get a 0.010 feeler down the side as a tight fit which doesn't sound like the bores a worn much.

Maybe I'll just get a new set of rings and try it out...

Are you measuring at the side of the skirt near the bottom of the piston and near the bottom of the bore? I think it would produce quite a clatter with that kind of clearance.

if you can get .010 feeler gage in there anywhere, that is a considerably excessive amount of clearance. how did you measure the piston that accurately while it is in engine? (3.495)

Thanks for the feedback so far.

Just to clear up what I've done. I've removed the head and sump and removed number 1 piston and measured it at 3.495 with my digital calliper at its widest.

The rings were pretty loose and easy to remove so I've taken these off and then placed the piston back in the bore (no rings) and at this stage I can fit a .010 feeler which holds the piston on place approx half way down the bore.

Other than a bit of black smoke on start up, the oiling of the plugs which meant making sure it was full warm before stopping and the slightly excessive oil consumption the truck was running pretty well with no noises Other than the usual noise a 216 makes :-)

What are the tolerances for piston clearance? Am I looking at a re-bore?

Cheers

It is hard to imagine an engine running with that kind of clearance. I would have thought it would self destruct. Anyway, with original cast iron pistons, a feeler gauge of .002" would give some drag and a .003" feeler would lock it up.

I am going out on a limb however most OEM engine or ring manufactures recommend at.019 cyl wear and or taper, to bore to next size. Which could be .040 oversize if the wear/taper is one direction. Mic. the cyl for wear and make a decision on how you want to proceed. Less than .015 and I would install a set of rings. Remanufacturing the engine is always best however a ton of these engines were inframe overhauled by guys without any special tools to measure the cyls.

Thanks.

Decided to get the manual out and have a good read - probably the first thing you should do but being a man I never like to read manuals - and on reading it says that the pistons are 'out of round'.

Looking further on in the manual it states in capitals - so people like me can see it - "THE FEELER GAUGE MUST BE PLACED BETWEEN THE PISTON AND THE CYLINDER WALL ONE QUARTER OF THE WAY ROUND FROM THE PISTON PIN ENDS"

On doing this a feeler gauge of .005 holds the piston in place, so this is closer to the .003 recommendation.

Given the cost of new pistons and a rebore I think I'll try new rings first (I only do about 2500 miles a year and with the current set-up it runs OK) and save a full rebuild for a future date.

Hi,

A follow up question - hope someone can help.

With the head off I decided to strip it and I need valve guides and a full new set of valves!

As I live is Scotland I'm going to try and get everything in the same place to ease the postage costs. I usually get my stuff from Jim Carter but wondered if anyone had any recommendations for suppliers of rings, valves, guides, sump gasket and manifold gasket.

Thanks

your engine may be different, (I have a 51 manual) but says if taper is over .005 to rebore. .005" clearance may be closer to the specs, however it is still nearly twice the specified clearance. You are still going to spend a considerable amount of money replacing rings, which probably won't seat properly due to the fact that 80,000 miles is a considerable amount for one of these engines and will most likely show an appreciable amount of wear. I won't even pretend to tell you what to do with your engine, this is just some food for thought.