VCCA Home Forums TECHNICAL - 1945 AND NEWER 1946-1948 42 and 48 chev truck engines

Hi,
I have a 42 chev ex army truck with a seized motor.I also have a 48 chev truck motor in very good condition.Will it fit into the 42 with out any problems?
The 42 has engine number BFR 488281 with a block cast number of 839910 and 9/42.The 48 motor is R 320341 with a block cast number 3835327 along with GM 48.
They appear similar even with the engine mounts .The 48 rear mounts should unbolt to fit the 42.
I am just asking if anyone knows ,It may save me a lot of wasted time.
Are the cylinder heads the same ?
Cheers from a hot Australian (105 deg faren here today)

The 839910 block is a 1942 235 truck engine. This engine was used in the army trucks.
I can not find a record of the 3835327 block casting number. I have both the US and Canadian casting numbers. The R320341 does not match up with any US engine numbers.
The 48 on the side of the block indicates it either a 1948 or 1949 engine. Its possible that it a 216 engine also, such as from a car or smaller truck.
If it has a 1948 head it will have the small 8MM thread spark plugs. If from a 1949 will have the usual 14MM spark plugs. I can think of no way to determine a 216 engine froma 235 in 1948 and 1949 other than measuring the bore or stroke.
The 1942 and 1948 heads will inter change between the years and the 216 and 235 heads were the same. There were some small improvements made in 1948 such as the valve stems had two groves, one for the keepers and one for the O ring seal. The spring top retaining caps were different, In the later years the newer heads were sold as replacments for the 1941-42 egines.
If you remove the head the 216 will have a 3 1/2" bore and the 235 will be 3 9/16. Bore 3 3/4" VS 3 15/16".
The 216 will work OK but will have less low sped power. All the bolt on parts will fits also.
We are having a January heat wave also today. The present temp. is 29 Deg. F....also couldbe -20 Deg this time of the year.

I have pulled the head off the 42 and both engines are 216.
Both heads have the same cast number but as you said,the 48 has the smaller plugs.The 42 has the caps on top of the valves where the 48 has the provision for the valve stem seal.
Which head is the better to use?I will have to fix either one.
Thanks
Rusted

The 1942 head should have the small plugs also. At one time the "holes" may have been drilled out and 14MM plugs installed.
The 1942 engine would have had the "caps" on top of the intake and exhaust valves..Most were thrown away years ago due to the fact that they made the valve train noiser as they wore.
Which is the best head to use, I would say the one in the best condition. That would be no cracks and the valve seats that have not been ground down too far. I would use the 1948 valves, retiner caps, etc. and O ring seals on either head. New valves are easier to find and better quality exhaust valves are available. The exhaust valve seats can also be ground to 45 degrees and the 1950- and up to the 1970's valves can be installed. That valve was also used in 283-327 V8 engines.