VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1912-1928 1926 engine parts interchangable with 1928 engine

I am stripping a 1926 engine with a 28 head. I want to keep parts that are interchangable with my 28 engine. Are the rods, pistons and crankshaft interchangable? The head is a late 28 dual-port head with eight bolts attaching the rocker arm assemblies. My 28 engine has a 28 dual-port head with only four bolts attaching the rocker arm assemblies. Is one of them a better head to use?

Thanks,
James.

Chem Eng what's the casting numbers on your head. 346886 or 348540.
1927 or 1928 respectively.

If the head uses 8 bolts to clamp the rocker arm shafts to the head,then it will be a head from late '27,back to '26 maybe even '25.
1928 heads used only 1 clamping bolt on the 4 rocker arm shaft clamping blocks.

O.K. I just checked and the head with eight bolts clamping down the rocker arm assemblies casting is 348540. It does have dual-port exhaust. The other letter and numbers on the head are j-1-8. I have read that this means it was cast on October 1, 1928. Am I correct?

Thanks,
James
VCCA member

Hi ChemEng,
Just had a look in my 1928 Master Parts price list book,and it lists both P/No.'s 346886 & 348540.
The cyl head with P/No. 346886 is the late 1927 Capitol AA single exhaust port head that uses the same valves(1 21/32" head dia)as does the 1928 National AB series cyl head.This head has the 4 rocker shaft clamps with the 2 bolts per clamp.
The cyl head P/No. 348540,is the correct cyl head for a 1928 National AB.It has 4 rocker shaft clamps,but the clamps have only 1 bolt per clamp.
The cyl head P/No. 346886 rocker shaft clamps are P/No. 326305
and are used on Capitol AA & LM series trucks,and have 2 hex head cap screws 5/16" X 1",with 18 threads per inch.
The cyl head P/No. 348540 rocker shaft clamps are P/No. 348568
and are used on National AB passenger cars,as well as 1928 Capitol LO & LP series trucks,and use 1 hex head cap screw,7/16" X 1",with 14 threads per inch.
The "J 1 8" casting code does mean that that particular was cast on the 1st of October 1928.

Thanks CP'S29 for additional information. I checked the rocker arm shaft clamps, they are P/N 326305 with two bolts per clamp attached to head P/N 348540. Is it possible Chevrolet woud have casted this combination for export engines or canadian cars and trucks?

Thanks,
James

Update on 28 Chev. head. An unusual combination that must have worked,but likely a poor choice(lower valve lift). The 1926 head probably cracked and was replaced with a 1928 head. 1928 head has been machined to accept the 1926 rocker arm shafts and rocker arm shaft clamps.

It's up on the shelf now ready to collect lots of dust and a home to spiders.

Still would like to know if the crankshaft and connecting rods are interchangable with a 28 engine?

Thanks for the help in solving this one.
James.

Chemeng the 1928 Chevy parts book shows Sup, U, C, & N use crankshaft # 344648. This replaces the older crank #344613.The connecting rods are P/N is 346877. It looks like 1925-1928 take the same parts.