The Stovebolt Site Forums The Shop Area Engine Shop Curious about 228 GMC Differences through the years

Im wondering if there were any differences between early 228s and later 228s.

Also, is there a date code stamped on the heads or block somewhere? I know the casting number is 6107326 but inliners say thats 1939-1952

Some GMC engines, including 228s, I think, had domed pistons and a different combustion chamber shape to the head. Others were flat tops and a different head. 228 and 248 have the same stroke crankshaft, but different bore sizes. Ditto for 270 and 302- - - -both 4" stroke.
Jerry

There are date codes on my '52 GMC 228.

My head is casting number 2136477. That head is designed to be used with domed pistons. If you use flat pistons, you would have very low compression ratio, probably so low the engine wouldn't run. The casting number is shown on the first attached picture. It is on the top surface of the head, above where the #4/#5 exhaust port exits the head.

The casting date of my head is F 16 2 as shown in the second attachment below. The F decodes as June (A = January, B = February, etc.) with the last character being the year, a 2 in my case. The one or two digits between the first and last are the day of the month. No 228 engines were made before 1939 and none after 1953. Also, none made during the WW II years, so no 1942. So my head was cast on June 16, 1952. Casting date for the head is on the top surface of the head, above where the #2/#3 exhaust port exits the head.

As Jerry said above, using a block with domed pistons and a head designed for flat pistons will result in pistons and valves trying to occupy the same space and really ugly noises.

My engine casting number is 6107326 as shown in the 3rd attached picture. It is on the driver's side of the engine block, about an inch above the oil pan and partially hiding behind the exhaust pipe. I couldn't find my block casting date without getting dirty right before supper time.

Another interesting number is the engine serial number. It is stamped on a machined pad just to the rear of where the distributor plugs into the block. Mine is shown in the 4th attachment. A leading alphabetic character may or may not be there. The next 3 digits are the engine size, 228, 236, 248, 256, 270 or 302. The final digits are the sequential serial number.

The alphabetic character (the book calls it a suffix, but I've only ever seen it as a prefix) signifies slight machining differences on this particular engine during manufacturing. The fifth attachment below is the magic decoder ring. The "B" prefix on my engine signifies that it left the factory with a 0.005" overbore (and pistons) and standard main and rod journals.

Block casting date is down below the pin that holds the throttle return spring.

Thanks for the details fellas. I have an old 228 that I was trying to id. Turns out the data plate is missing the the flat spot behind the distributor has been ground down or never marked. The cylinder head casting number is 6107412 date code L198. Block casting number is 6107326 and date is j256. Im wanting to buy a maintenence manual as a rebuilding guide and was wondering if I should buy an earlier or later manual since there might be mechanical differences.

Looks to me like someone took a grinder to the engine serial number. I can almost read the last digit as a 2. Mine is a lot smoother than yours.

So L198 would be December 19, 1948 and J256 would be October 25, 1946. Check the frame on the passenger's side near the front axle. It may be stamped with the truck's serial number. More stuff about parts and truck ID can be found here.

My GMC Master Parts Book X-154001 covers 1939 thru 1954 GMC truck models 100 thru 470 (all but the biggest trucks). It shows pistons with a compression ratio of 6.75:1 prior to 1953. My '52 has domed pistons with a casting number 2136477 head. There were other pre-1953 head casting numbers used on 228 engines.

In '53 GMC switched to flat pistons with a compression ratio of 8:1.

If you would settle for a .PDF file of a 1953 GMC Master Parts Book, fellow 'Bolter SlimSix (aka Andy) used to sell copies that he had made. Try contacting him via a "Private Message".

Bill, what about a casting number that ends in a 0?

My documentation shows no heads with a casting number ending with a zero.

My documentation does show one block with a casting number ending with a zero. 2193980 is a 302 block manufactured in 1952-4.

Apologies, date code ending in 0. In my mind, I'm considering 1940 and 1950. It is a 228 head casting number 2136477 and block number 6107326 both date codes are 1 day apart A270 and A280. Serial number A228281749

Is there a general preference for the style of piston and head? Domed vs flat? I have domed pistons and head on my 228 that needs a rebuild and with my inexperience and before I sink a bunch of money into it, I just want to make sure I'm not making a mistake.

Before jumping in with both feet, make sure you can put your hands on a matching head and pistons. If you plan to re-use both your head and set of pistons you should have no problem. But if you need to replace either the head and/or piston set be advised that 228 engines used pistons that were domed on one side of the top, domed across the middle of the top or (not shown) flat top.

The first picture is of my '52 228. The 2nd picture is of a 228 piston that I do not know the heritage of.

Im currently out of town but when I get back I want to check the cylinder taper to see if it needs to be bored. I ordered a bore gauge that got delivered this afternoon. I have the pistons that we're domed on one side and the head to match. Photo is my block. I found these pistons from edge machine that I THINK match what I have in case I needed cylinder boring Egge Machine 228 pistons

I didn't see where they sold flat top pistons but I would 235 pistons work in a 228 flat top piston application?

Not trying to get off in the weeds just curious what the general consensus was on preference. Thinking out loud here but since egge has only this style available, maybe this motor would be the way to go.

Even if this engine doesn't need bored, I planned to send it to the machine shop for a valve job and to be magnafluxed and decked.

The 228 and the 235 share the same bore size (3 9/16") but I'm pretty sure the compression height is different, and I know the wrist pin diameter is a LOT different. All the GMC sixes run a 7" long rod, which will make a difference in the wrist pin to deck length between GMCs and Chevy engines, and the GMC rod has a much heavier construction. The GMC rod is also gun-drilled to provide pressurized oil to the wrist pins.
Jerry

Thanks for clearing that up Jerry, I figured it had to be more complicated than I was thinking.

Speaking of compression height, with my wedge domed pistons, if the deck gets machined and the head also is machined, will the standard head gasket still be sufficient? its difficult to say without measurements of course. I havent found thicker head gaskets anywhere just the standard one.

If you look carefully at the piston tops (and if they are original pistons) you will find two numbers stamped. One is the cylinder number, 1 through 6, front to back of the engine. That is so you can put them back in the proper hole if you remove them.

The second number on the piston should have a matching number on the top surface of the block. I can't find the decode table for a 228 right now, but the attached table for 270/302 engines works the same way.

After the block was bored at the factory, the cylinder was measured and special factory-only pistons were fitted into each cylinder. The piston had a number already stamped on it signifying its "size". The piston was installed into the block and the corresponding number was stamped in the top surface of the block.

Pistons with the number 1 stamped would be fitted to 0.00075" to 0.00100" under sized cylinders.
Pistons with the number 2 stamped would be fitted to 0.00050" to 0.00075" under sized cylinders.
Pistons with the number 3 stamped would be fitted to 0.00025" to 0.00050" under sized cylinders.
Pistons with the number 4 stamped would be fitted to standard size to 0.00025" under sized cylinders.
Pistons with the number 5 stamped would be fitted to standard size to 0.00025" over sized cylinders.
Pistons with the number 6 stamped would be fitted to 0.00025" to 0.00050" over sized cylinders.
Pistons with the number 7 stamped would be fitted to 0.00050" to 0.00075" over sized cylinders.
Pistons with the number 8 stamped would be fitted to 0.00075" to 0.00100" over sized cylinders.

Interestingly, mine are stamped with 3 numbers. All are stamped with "4 9" and then the cylinder number. On the deck, the cylinders are stamped with 4s and 5s. A quick check with my dial bore gauge shows that most cylinders are 0.003-0.005 larger than 3.5625 so I would take it that these are original standard pistons?

Looks just like my 228 which only has two numbers stamped into the top of the pistons. And "9" just doesn't compute with any of the info I have.

1932 to 1952 were pretty similar. I think some where they raised the compression a little, but parts interchange. 1953 was a one year deal with a relatively flat piston and the much smaller combustion chamber. Octane numbers increased a lot during the 1950's and early 1960's. A lot of aftermarket pistons were offered with pistons to raise compression ratio. A lot of engines that are being disassembled these days have aftermarket high compression pistons that were aftermarket and manufactured by companies that no longer exist. A lot of them were sold under the Burd trademark by Washawsky Bros/JC Whitney.

Daniel - A little web snooping shows Rock Auto currently offering a few different standard sized 228 ring sets as in stock.

I did find a couple of supposed NORS (New Old Replacement Stock) sets offered on eBay, but haven't taken the time to double check/confirm they are actually compatible with your 228.

Hope this is helpful info.