Maximum amount can be bored on block ?

[ramair]

I need help . Here is what happened years ago I wanted to rebuild my 1936 Oldsmobile 213 flathead that is original to my 1936 GMC truck. The machine shop that I worked with said that it had been rebuilt twice and that 60 over pistons would not make it, they recommended a replacement block that would possibly have less wear. I found one on the opposite side of the country , bought it and had the machine shop check it out and start the rebuild. Now comes the fun part, that happened 30 years ago , the machine shop never finished it before they retired, they said come get it. Good news all machine work done including new parts to put together at 40 over, bad news we found that they did not magnifluxed block and all kinds of internal cracks are around the oil galley area . I did not want to try welding as if it leaked coolant I would not see it until I would pull the dipstick..  I went and found my old original engine and it was cracked in same area.  So I just bought another engine from Indiana. We cleaned it up , it is crack free but it has 40 over pistons and worn to a taper finally down to my question, so far I can not tell if I were to make up 80 over pistons would I make cylinder walls to thin, same question about sleeving engine?

[JACK M]

A good machine shop should be able to test the wall thickness. Some blocks can be bored way over, some not so much.

I have heard of .120 over Hemis, I have one that is .060.

If it were me I would consider sleeving to original.

[CarlLaFong]

Flathead Fords were, routinely bored 1/8 over by hot rodders. My gut feeling is that Olds engine would survive an .080 over bore. Do you need to take it from .040, all the way to .080, to remove the taper?

[ramair]

My machinist feels that the 60 overbore would not clean up the bore, however compared to all the time and money to get to this point I feel that it would be worth the time to set boring bar up on engine and try it.  Another thought was to take one of the boat anchor engines that I have and try boring it to 80 or 250 and see if I push through water jacket 

[edinmass]

Why not just hone it out to the minimum necessary and have a set of custom made pistons at say. .067 much less expensive than sleeving or risking over bore. 

[joe_padavano]

Sand cores shift.  The fact that one particular casting is able to be bored 1/8" over does not mean that another casting for the same motor has the same capability.  Have the cylinder walls sonic tested. This is the ONLY way to know for sure on that particular block.

[Frank DuVal]

Sleeve it.

 

I once rebuilt a Nova 4 cylinder for a friend. It was so worn it would quit running at the toll booth on the way to work. Dropped block off at machine shop, they called and asked how did it even run to wear this much, .060 pistons fell through the holes. 4 sleeves later she had a “new” standard bore block! Same engine as Mercruiser 4 banger. Wall between cylinder 1 and water pump is thin. The sleeve was clearly seen through the water pump opening when I got it back.

 

Back then I did ask about larger than .060 pistons, but he said block too thin. He did add that the old 215 235 sixes could be bored .125 with pistons available to match.

 

Ask the machine shop how about sleeving. A good block should sleeve fine.

Edited October 22, 2018 by Frank DuVal (see edit history)

[wayne sheldon]

As others have said. It varies from engine to engine. Not only the make/year/model. Also the individual casting (core shifts), and that specific blocks history. How badly are the water jackets rusted inside? (I have seen a few rusted clear through!)

Model A Ford blocks used to be routinely sleeved to .125, many other engines tend to max out around .080. I have no experience with '30s Oldsmobile blocks.

Sleeves are often the best way to go. However there are some risks involved with sleeving cylinders.

I goofed many years ago.  Bought a model T block, was told it was .020 over, bought new high dome pistons for it. When I began to rework (a term I use when I do less than a true rebuild) the engine, I discovered the .020 pistons would barely start into the top of each cylinder, and not go down more than a half inch. Then I carefully measured. Turned out, it was .015 over with about .003 taper. Solution? A ridged hone. A ridged hone is a wonderful thing, seldom used these days. People freshen engines with a flexible hone, and if the taper or out-of-round is beyond a minor .002 or .003, they immediately toss a boring jig on top of it. It took a couple hours with a slow speed right angle drill, and careful measuring. But that ridged hone cleaned and straightened that bore to a perfectly fitting .020.

You begin at the small bottom of each cylinder, and as the hone rounds and enlarges the small part of the cylinder keep working higher and higher while expanding the size adjustment on the hone until it all lines up straight and round (and of course, proper fit).

And, I will tell a little trick of the trade. Flip the stones over (end for end) often to offset the tendency for the stones to wear tapered.

 

Just another option to be considered.

[Restorer32]

We would have the engine sleeved back to standard or whatever piston size is available. Not that expensive to have done.

[Terry Wiegand]

There must be something that I am missing here.  I have always been of the understanding that GMC used the 6-Cylinder Buick engine.  According to Dunham and Gustin's book, BUICK - THE COMPLETE HISTORY, when Buick introduced the Straight Eight in 1931, all of the tooling for the 6-Cylinder engine went to GMC.  I know that Oldsmobile used flathead engines in their cars for quite some time.  I just did not know that GMC used a flathead engine.

 

Terry Wiegand

South Hutchinson, Kansas

[Guest]

GMC also used the split head Pontiac and other L-head engines in their trucks.  

Pontiac/GMC

1926-1927 Pontiac Split-Head straight-6 (also modified for GMC Truck models)

This engine displaced 186.7 cu in (3.1 L) (3.25x3.75) and was rated at 40 hp (30 kW; 41 PS) @ 2400 rpm 

In 1929, the "split head" Pontiac six was increased in displacement to 200 cu in (3.3 L). The horsepower rating increased to 60 hp (45 kW; 61 PS) @ 3000 rpm

1928–1954 Pontiac GMR straight-6 (also modified for GMC Truck models)

The 223 was a side-valve engine, and used a timing chain. The 223 cu in (3.7 L) straight-6 was used in Pontiac automobiles (1937–40) and GMC trucks (1938 only).

Oldsmobile

The 215 cu in (3.52 L) 215 was used by Oldsmobile and Chevrolet. The 215 in the Chevrolet 1⁄2-ton pickup trucks featured babbitt connecting rods.

The 230 cu in (3.8 L) 230 was shared between Oldsmobile and GMC trucks.

GMC engines

GMC as a marque really only produced a few engine designs, the straight six, a V8, and a V6 which was also available as a V12 for a brief period. GMC used many engines from other GM divisions, as noted below.

228

GMC replaced the Pontiac 223 with their own 228-cubic-inch (3.7 L) 228 in 1939. This OHV (overhead-valve) engine was produced through 1953. This is the smallest low-deck engine, all three of which have 3.8125" stroke and 3.5625" bore, with 7" connecting rods.

236

GMC also developed an OHV/pushrod engine in 1939. The 236-cubic-inch (3.9 L) 236 was produced through 1955. This is a low-deck engine. The bore was 3.625".

248

Those same years (1939–1955), GMC produced a 248-cubic-inch (4.1 L) engine, the 248, which was similar to the 236. This is the largest low-deck engine. The bore was 3.71875".

256

The 256-cubic-inch (4.2 L) 256 was different from the 236 and 248. It was also an OHV/pushrod engine, and was built for just two years, 1940 and 1941. This is the smallest raised-deck engine, all three of which have 4" stroke and 7" connecting rods. The bore was 3.6875".

270[edit]

The last GMC-only straight six was the 270-cubic-inch (4.4 L) 270. It was produced from 1941 through 1963, and was an OHV/pushrod engine. This is a raised-deck engine. The bore was 3.78125"

 

 

Edited October 22, 2018 by Guest (see edit history)

[ramair]

Terry, you know me as a Buick Big six guy, so you know I would not be trying to fool anyone. The 1936 GMC T-14 1/2 ton truck was the first year of this light duty class, they borrowed a lot from Chevrolet except the engine, Gmc had pressure lube in their larger trucks. I believe they chose the Oldsmobile 213 because it was a similar length of the stovebolt six. Even so each 36 gmc that I have looked at has a “factory sledgehammer “ dent on the firewall.  Ask me what happens if you pound out and fill that dent with engine removed? The 1937 gmc stayed with olds in 37 it was now a 230 ci, 1938 was pontiacs and finally 39 was the start of the famous overhead valve 6 cylinder

[Ben Bruce aka First Born]

Man, seems like Dunham made some mistakes.  I have noticed other mistakes in his book.  Maybe just un intentionally misinformed.

 

  Ben

[Guest]

I think it was true when the Buick tooling was given to GMC.  However it took them years to turn the engine into what they wanted for their truck. The block had GMC cast into it, the timing gears were changed, distributor advance curve,  plus many other small things.and advance was different.

It seems as if the newer books have only re-compiled pictures and data from earlier publications.  No one seems to do basic research any more.  The last few books I have looked at seemed to have no newer information that books that I had bought decades ago.

 

[Terry Wiegand]

Thanks guys.  I did not know that there was such an extensive connection with Pontiac back at that time.  Back in the early 1950's, one of my great uncles was in the ornamental iron and sheet metal business.  I remember that he had a 1950 GMC, 1-Ton Panel Delivery truck (talk about a huge truck!) and this truck had the Dual Range Hydra-Matic transmission in it.  I always thought that that was sorta odd that a truck like that would have an automatic transmission.  Now, looking back, I'm sure that this was some sort of specially ordered option for this vehicle.  I am pretty sure that my Dad said that the truck was a 1950 model.  My Dad worked part time for him for a little while and he drove the truck some on deliveries.  I do remember him saying that the thing  drove and rode like a log truck.  I was about 6 or 7 years old at that time.

 

Terry Wiegand

South Hutchinson, Kansas

[Rusty_OToole]

Engines back then were expected to be rebuilt 2 or 3 times during their working life. Practically all of them would take a 1/8" overbore, some larger. If you could find a factory repair manual it should tell you. Or you could have the block sonic tested. A few years ago a local Dodge specialist rebuilt the engine for a 1941 Dodge, he said it had the thickest cylinders he ever saw. This guy is used to rebuilding Chrysler hemis and 440 for hot rods.

[ramair]

Thank you all for input,  I will have it tested for wall thickness and then I will try to see if it cleans up at .060.  I called around and Egge has a record of selling one set of custom made .080 pistons, but that does not mean anything

[edinmass]

Check the wall thickness, then hone to the minimum you need, and have the pistons made, as it costs the same for a standard oversize or special as long as they are an made to order item. Why take the risk? I am told Egge no longer makes pistons. There are several great companies that do, but recently some have changed hands. There is also a new company in Colorado that does fantastic work, and just made two sets for us, but their name escapes me. I'm down south for the winter, so I can't check the box.

[901 Packard]

I don't know guys, if it is worth fixing, then it is worth fixing right. Bore and sleeve is the way to go. I just did my 901 Packard and it only cost $ 1,000 to soak the cylinder block, bore and sleeve back to standard dia. Egge had the pistons on the shelf, and I was back in business in 2 weeks. Fooling around with a hone is OK, but having perfect bores is more important to me.

[edinmass]

A ridged hone will give you a perfect bore. You did eight sleeves and hone for 1K!!!! Wow that is cheap........in New England almost 95 percent of the machine shops are gone, and the few left are clueless to the pre war stuff. We just did a 904 last year and it was quite a bit more than that. If you live in an agricultural area I understand that it is often much less expensive to do these type of repairs. I secured an extra 904 block before we did the work just in case we had a problem..........Pressing in the liners can cause a problem, not too often but it is a risk, as is going into the water gallery and then having sealing issues. As usual there are a half a dozen correct ways to do things......... often its time more than cost that dictate how the repair is done. 

Edited October 25, 2018 by edinmass (see edit history)

[901 Packard]

Yea, this is definitely an old school kind of place in Conway SC. Everyone there should have retired 10 yrs ago.  They had maybe 150 blocks on the floor, and 50 crank shafts hanging from the ceiling. They do a lot of local race track kind of stuff, along with big diesel farm tractors. He said he has done several Packard Straight 8 blocks over the years, but most were cracked from freezing up north. Fortunately mine is a CA. car, then to Fla, then to Minn. but must have had antifreeze, because no sign of abuse. He charged me $ 30 to install a new ring gear, I could not get the money out of my pocket fast enough. This car was in West Petersons family, so pretty well cared for prior to my ownership. 

[trini]

Puegot industrial engines use replaceable cylinders . Do some research on line or check with scrap yards. You may be able to get liners that will probably work with a little machining.