Engine Spec Info

[mach0415]

Some of you have been very helpful in my original diagnosis of an intermittent miss found in http://www430.pair.com/p15d24/mopar_forum/showthread.php?t=29601 I thought it would be more appropriate to start a thread just for the mechanical part of the miss, as it is no longer a simple driveability adjustment. I am now interested in expertise with engine specs.

I pulled all 6 pistons and found only one to be the original style, with the hole below the lower oil control ring, a cut, and another hole in the skirt area. (the others have a split skirt the whole length) The difference in distance from the top of the upper compression ring land between the two styles is approx. double the thickness ...whatever.

I measured the bore with my trusty bore gauge and found only .007-.010 difference from stock. I measured the pistons and despite the "10" stamped on all but the mismatched one, all were stock, at 3.25". My taper is less than .005"

So, I decided to check the old rings' end gap and stopped when .067" worth of feeler gauge still slipped easily in the ring gap at the lower point of the stroke, while in the cylinder bore Its amazing this thing even ran! But, it does explain the ridiculously low compression readings I was getting. The valves appear to be okay, but I will re-guide and lap them. Lots of slop in the guides.

The question is, Can I get away with putting a stock set of pistons in this and go to a .010" oversize ring set and file as needed, given the lower compression ratio? or do I absolutely need to go up a size on my pistons too?

Thanks,

Mark

[Rusty O'Toole]

Is the bore straight or tapered? If you are talking about .007 to .010 of wear, .007 is considered the limit for reringing.

If the cylinders have been trued, you might have to knurl the pistons to prevent piston slap. Then install the .010 over rings.

The .010 over rings will work in a tapered cylinder just not for as long. 20000 to 30000 miles vs. 50000 to 80000 if the cylinders are true.

[mach0415]

So I got a lead on an engine and trans from a 1951 Dodge car as a transplant for my ailing 1939 Dodge 218 (also an evident transplant). At first I was cutting back flips thinking it was a 230 with fluid drive. That is until I asked for the serial number and was told the number is D1311804-5. Great, another 1939 Dodge 218 with a 3 speed...

I will be doing some serious contemplating as to what I want to do to get 'er running again.

[41/53dodges]

So, I decided to check the old rings' end gap and stopped when .067" worth of feeler gauge still slipped easily in the ring gap

these engines seem to not care about much as far as compression, I just tore mine down to find not .067", but .246" ring end gap! the thing ran like a champ before, but its getting new rings now!

[mach0415]

Is the bore straight or tapered? If you are talking about .007 to .010 of wear' date=' .007 is considered the limit for reringing.

If the cylinders have been trued, you might have to knurl the pistons to prevent piston slap. Then install the .010 over rings.

The .010 over rings will work in a tapered cylinder just not for as long. 20000 to 30000 miles vs. 50000 to 80000 if the cylinders are true.[/quote']

it has about a .005" difference top to bottom

[Rusty O'Toole]

it has about a .005" difference top to bottom

Stock size pistons should be fine. And they are a lot cheaper than oversize pistons.

Vintage Power Wagons has NOS pistons cheap, last time I looked I think they were $75 for a set of six.

http://www.vintagepowerwagons.com/pdf/parts/01engine.pdf