1970-71 Nos Lt1

[Paul Y.]

I picked up an NOS December 10, 1970 dated short block in the original crate last week and I thought I would post some pictures of the markings on it and paint inspection marks. I can find a lightly stamped CE on the pad that is very faint.

[Paul Y.]

Re: 1970-71 Nos Lt1

Here is a couple more. Can anyone tell me what these inspection marks mean on the block?

[Timothy B.]

Re: 1970-71 Nos Lt1

Paul,

I can't help with the markings but that is a very nice piece.. Where did you find the motor..

[Duke W.]

Re: 1970-71 Nos Lt1

The crayon marks on the block may be from inspectors, and/or ID this job to receive the LT-1 crankshaft, however, the block is othewise identifiable because I think it was the only '70 SB machined for four bolt main caps.

The "H" on the piston is probably the size group and there should be some codes underneath to indicate the piston size for each cylinder. The pistons were installed with the block upside down. There were about four piston size groups, and one was selected based on bore measurement for each cylinder.

John Hinckley can probably provide more info.

Is the cam sprocket nylon-tooth or steel-tooth?

Duke

[Joe L.]

Re: 1970-71 Nos Lt1

I picked up an NOS December 10, 1970 dated short block in the original crate last week and I thought I would post some pictures of the markings on it and paint inspection marks. I can find a lightly stamped CE on the pad that is very faint.

Paul------


This is a 1971-72 LT-1 short block, not also applicable to 1970. Note the piston crowns. This style crown is the 9.0:1 CR used for 1971-72 but not 1970.

[Joe L.]

Re: 1970-71 Nos Lt1

The crayon marks on the block may be from inspectors, and/or ID this job to receive the LT-1 crankshaft, however, the block is othewise identifiable because I think it was the only '70 SB machined for four bolt main caps.

The "H" on the piston is probably the size group and there should be some codes underneath to indicate the piston size for each cylinder. The pistons were installed with the block upside down. There were about four piston size groups, and one was selected based on bore measurement for each cylinder.

John Hinckley can probably provide more info.

Is the cam sprocket nylon-tooth or steel-tooth?

Duke

Duke-----


All 1970-72 LT-1 were equipped with 4 bolt main caps.

If the installed camshaft sprocket is anything other than nylon-toothed aluminum I'll be amazed.

[Stephen B.]

Re: 1970-71 Nos Lt1

I had a genuine NOS 1970 LT-1 short block a couple of years ago. It did not have any marking on it.

[Steven G.]

Re: 1970-71 Nos Lt1

Duke-----


All 1970-72 LT-1 were equipped with 4 bolt main caps.

If the installed camshaft sprocket is anything other than nylon-toothed aluminum I'll be amazed.

I believe other small blocks used 4 bolt main caps as well, not just LT-1's, I'd expect to see the same on my L-46. Steve

[Terry M.]

Re: 1970-71 Nos Lt1

The "H" on the piston is probably the size group and there should be some codes underneath to indicate the piston size for each cylinder. The pistons were installed with the block upside down. There were about four piston size groups, and one was selected based on bore measurement for each cylinder.

John Hinckley can probably provide more info.

Duke

The cylinder bore size codes were stamped on the oil pan rail while the case was upside down. I don't know what those codes were -- numbers or letters -- but they air-gauged the bore and lights on the machine told the operator what character to stamp on the rail near that bore. I would expect ALL small blocks from Flint to have these bore size stamps, and I would not be surprised that Tonawanda used a similar process.

Duke, I believe truck small blocks of this period also used four-bolt main bearing caps.

[Joe L.]

Re: 1970-71 Nos Lt1

I believe other small blocks used 4 bolt main caps as well, not just LT-1's, I'd expect to see the same on my L-46. Steve

Steve-----


I did not say that other small blocks of the period did not use 4 bolt mains; I simply stated that all 1970-72 LT-1's were equipped with 4 bolt mains.

For 1969-70, all Corvette small blocks, base engine to LT-1, were equipped with 4 bolt mains. For the 71-72 period, some base engines may have been originally built with 4 bolt mains and some not.

[Paul Y.]

Re: 1970-71 Nos Lt1

Joe, I figured that because of the December cast date. So would the 186 head of the 1970 engine up the compression? If so how much?

[Paul Y.]

Re: 1970-71 Nos Lt1

Tim, Thank you. I found it in a sub division of Denver on the local craigslist. It had been in the seller garage since the 70's sometime. It came from Burt Chevrolet, known as a high performance parts dealership.

[Paul Y.]

Re: 1970-71 Nos Lt1

Duke, the cam sprocket is nylon toothed.

[Joe L.]

Re: 1970-71 Nos Lt1

Joe, I figured that because of the December cast date. So would the 186 head of the 1970 engine up the compression? If so how much?

Paul-----


Sort blocks for SERVICE were produced for 1970 LT-1 applications as late as 1975. So, the cast date of the short block does not imply whether it's for a 1970 or later LT-1. It's the short block assembly PART NUMBER that identifies it as well as features like piston configuration.

The 186 head would up the compression ratio of this short block to ABOUT 10:1.

[Ronald L.]

Re: 1970-71 Nos Lt1

What is important is what the casting date is...?

On those marks, as inspectors did their thing, it got a mark.

Terry, yes, I have seen them on the BB's from Tonawanda.