I am currently in the process of revising the engine of my Merc, the following questions have arisen. On the pistons it says 0.30, but when I measure there are 8.096 cm ~ or 3.187 in, but std is 3.187, I was at least so far opinion.In the case of the Ross pistons, a size of 3.248 was given at 0.30.Can anyone help me, I don't understand this information anymore Greets Marcus
Yes, that seems strange for sure. Every Merc flathead block came from the factory with a 3.187 bore as STD, so who knows what is going on. I'd mic the bores as you're probably going to be putting new pistons in it anyway.
You need to measure just below the lower ring groove - on the thrust sides of the piston (90 degrees from the pin bores), then also lower down on the skirt. You'll probably find that the pistons are .030 over. Again, you need to use a dial bore gauge and measure the bores - for size, taper, etc..
Ross Pistons: Ford Flathead Ford/Mercury Dome Top Forge Racing Pistons But the distance from STD to the next size is greater than 0.30.. or how is that calculated?
ROSS is only one piston manufacturer - they decide what sizes to produce and sell. The pistons at 3.248 are considered .060 over. If you check with different piston suppliers, you'll find a variety of sizes and compression heights (based on crankshaft stroke). A bunch of different folks make flathead pistons -- in all sorts of sizes, different ring configurations, different materials, different skirt styles, etc.. As a suggestion, if you're new to these topics/details, you might get with a competent machine shop.
Not quite new to the topic, I read a book... Joking aside.. I used to be a car mechanic and a little bit of what else do I know.The Summit employee confused me a bit, he gave me an order number for 0.30 supposedly but they had a different measure, but he assured me it would be the right ones... That's when I started to doubt a bit and so far I've only had to deal with metric measurements. you would have a recommendation for pistons.
Just curious, you have .030 oversized pistons now, is there a reason you want to replace them with the same sized piston?
I don't see where Ross has .030 pistons - though if you call them and talk to their Application Engineers, they'll probably make them (if they don't stock them). They have a reasonable up-charge for custom sizes. Try to get metric rings if you can - they're much better than the older 'Grant' type rings we all ran. Most importantly, figure out what the block needs - before you order pistons. My guess is that it will need to be bored to a larger size (especially if you're buying new pistons - might as well do it right). If you're going to bore it, you might think about a 3.3125" more . . . gives you more cubic inches.
I would do an 1/8" over bore to 3 5/16" if I needed new pistons. The cost is the same and "there ain't no replacement for displacement". I've done it three times now and never came close to water.
I know its more difficult to work with a system you don't normally deal with. Just for clarity when you talk to an American technical person, .30 is the same as .300 and means 300 one thousandths of an inch and is commonly spoken as threehundred/thousandths. Thirty thousandths would be written as .030 instead of .30 . Just don't want you to maybe order something you can't use. Since you were unsure about where to measure the piston, you might want to look on Amazon and order a book on building flathead motors before spending any money. The book should help you not make any major mistakes in building your engine and save you more than it costs. No book in particular but here is one example.
yes, that's exactly the book what I've already bought. As a German with school English, it sometimes takes a little longer to get through. Since I don't know much about the past of the current engine, I wanted to play it safe and install new pistons. Since it was noticed when disassembling that there was no oil but jelly in it... But the cylinder treads do not have grooves or indentations. And without cross-grinding.
I’d imagine the goop that formed was from just sitting for a long time not run like that. Is the cost of machine work the issue, or finding someone that’s competent with the type of engine ? I don’t see the need to replace pistons with the same sized pistons, unless they have damage.
I already plan to give the block to an engine builder, unfortunately they are not so firm here with such units. That's why I want to have some background, because there aren't many of us and they like to talk something up.
So as mentioned before, find out as much information on machining a FH V8 as you can. Ask here and on the FordBarn for clarification of what you read/etc if needed. Then inspect and measure everything yourself. Then go to machinist and explain what you want done. This includes the entire block, parts, etc. Once they have that information, they can tell you if it’s possible or what they can do. Just my suggestion since I feel you need to help them help you.
If you are going to get new pistons, then you surely want to have the block's cylinders bored out to a larger size, then honed (that is where you get the cross-hatch from), then put the new pistons and new rings in the engine. I would not buy new pistons to put in worn cylinders - kind of a waste of money. I would buy 3 5/16" pistons (3.3125) and bring those to the machine shop - and they will bore the block to fit the pistons. You always want to have the pistons in hand when you go to the machine shop. Also, they will need to balance the complete rotating assembly --> crank, rods, pistons, bearings, flywheel, clutch. Feel free to DM me for any help you need - be happy to help. What crankshaft do you have? A Ford crankshaft at 3 3/4" stroke or a 49-53 Mercury crankshaft at 4.00" stroke?
Before you do anything, you need to have the block cleaned --> hot-tanked (or baked, tumbled) and magnafluxed. If at all possible, it is good to have the block pressure tested and sonic tested. You can buy a pressure testing kit from Speedway. You don't want to invest a lot of parts and money in the engine until you know the condition of the block.
Looking at the next to the last picture it looks like cracks in the cylinder. Maybe just the picture, but check it out carefully.
Years of seeing pics and the real thing hint these 'cracks' are merely 'fissures'. BUT, absolutely have block examined as @Bored&Stroked recommends! This is compulsory. (a 'must') @tubman suggested a bore of 3-5/16". I have built 4 different flatties for my own cars thru the years, and have bored them all to 3-5/16", but used the Merc 4" crank. (this was called a "five sixteenths by quarter", as the '49-'53 Merc crank had 1/4" more stroke than the Ford's 3-3/4".) BTW, the last 2 flatheads I have now had the "jelly" in the valley. (Just old oil that is dirty, engine never properly warmed up and oil never changed!)
A Merc crank is an excellent upgrade, but an 1/8" overbore with a Ford crank is still 258ci, bigger than the vaunted stock Mercury. Cheaper, easier to find, and with lower piston speed; a worthwhile upgrade.
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