1972 LT-1 numbers questions

[Michael W.]

Re: 1972 LT-1 numbers questions

Thank you for these pictures !
Do you think that was possible the surface of the stamping was milled down to clear the original markings and restamped ?
We can see on my stamp pictures an offset between Deck block surface and cylinder head : the surface of the pad is much lower than the level of the head gasket surface...

I've looked at the pictures several times and do not see the offset you refer to.

[Christian R.]

Re: 1972 LT-1 numbers questions

Maybe I'm wrong...
This is the offset :

[Patrick H.]

Re: 1972 LT-1 numbers questions

Maybe I'm wrong...
This is the offset :

That's just a lip on the head. Look at the left side of your photo where they come against each other.

[Joe L.]

Re: 1972 LT-1 numbers questions

Maybe I'm wrong...
This is the offset :

Christian-------


That is the "recess" on the cylinder head that I mentioned in my post above. It has absolutely nothing to do with the block surface.

[Christian R.]

Re: 1972 LT-1 numbers questions

Hello,

Thank you for this information and all your suport !
I'm going to buy the car Friday. I have asked the buyer to check if the engine has 4-bolt mains, but he didn't check this. However, he's ok the write on contract that if the engine will be only a 2-bolts engine, I can return the car and he refund me, of course ;-)

I'll keep you in touch.

Regards.

[Michael W.]

Re: 1972 LT-1 numbers questions

Not sure I understand the focus on four bolt mains. Their presence would not confirm the originality of the engine or that the car is or was an LT-1.

[Joe L.]

Re: 1972 LT-1 numbers questions

Not sure I understand the focus on four bolt mains. Their presence would not confirm the originality of the engine or that the car is or was an LT-1.

Mike------


There's something about 4 bolt mains that has a certain "cachet"; it transcends rationale thinking.

[Christian R.]

Re: 1972 LT-1 numbers questions

Hello,
Last Friday, I bought the LT-1 ! Yes, to me it is a real LT-1 Corvette with A/C at 95 %.

In absence - for the moment- of any documentation (I'll looking for tank sticker and sticker between tach and speedo.), all could be fake.
But with a certain sense of logical, it is almost impossible to modify a car such mine. The engine is a four-bolt mains, I've controled this by removing the oil pan.
True, this could be added on a 2-bolt block, but the work worth not the gain to me because if this was made, it was made in the 80ies in the US. and in this time, the LT-1 had not a big value as today, I guess.
Other facts are : one fuel line 3/8" and correct fuel pump. Correct rear axles. correct exhaust line 2.5". and it is a genuine A/C car or a really well transformed one....
Again, I thank you all and - it is sure - I'll be back with a lot of practical questions regarding my 'Vette :-)
Christian

[Joe L.]

Re: 1972 LT-1 numbers questions

Hello,
Last Friday, I bought the LT-1 ! Yes, to me it is a real LT-1 Corvette with A/C at 95 %.

In absence - for the moment- of any documentation (I'll looking for tank sticker and sticker between tach and speedo.), all could be fake.
But with a certain sense of logical, it is almost impossible to modify a car such mine. The engine is a four-bolt mains, I've controled this by removing the oil pan.
True, this could be added on a 2-bolt block, but the work worth not the gain to me because if this was made, it was made in the 80ies in the US. and in this time, the LT-1 had not a big value as today, I guess.
Other facts are : one fuel line 3/8" and correct fuel pump. Correct rear axles. correct exhaust line 2.5". and it is a genuine A/C car or a really well transformed one....
Again, I thank you all and - it is sure - I'll be back with a lot of practical questions regarding my 'Vette :-)
Christian

Christian------

Actually, I have very little doubt that this is an original LT-1. However, it has many removed or replaced parts on it, including the cylinder heads.

[Christian R.]

Re: 1972 LT-1 numbers questions

Hello Joe,

Yes, you're right : the cylinder heads are numbers 3881482 and of course, the mechanical lifters are also gone. What is wrong is also the carb.
These are sadly very expensive components to replace....
I'm however not a purist of authenticity. Maybe one of the previous owner was tired to adjust periodicaly the lifters and to have a too big carb only here to make big horsepower at high rpm, like people loved in the 70's.
I want to drive my car through week-end trips with my lovely wife Cathy, not to make drag races or something like this...
But beware, I love horsepower as well :-)
I've thought today to stock original engine and trans and buying a 383 cid crate engine and 5-speed gearbox. The engine would be painted and equiped (intake and exhaust manifolds, water pump,valve covers, air cleaner,...) like a LT-1, but with more modern technology. As long as it looks almost original from outside, it doesn't hurt me.
What do you think about that ?

[Joe L.]

Re: 1972 LT-1 numbers questions

Hello Joe,

Yes, you're right : the cylinder heads are numbers 3881482 and of course, the mechanical lifters are also gone. What is wrong is also the carb.
These are sadly very expensive components to replace....
I'm however not a purist of authenticity. Maybe one of the previous owner was tired to adjust periodicaly the lifters and to have a too big carb only here to make big horsepower at high rpm, like people loved in the 70's.
I want to drive my car through week-end trips with my lovely wife Cathy, not to make drag races or something like this...
But beware, I love horsepower as well :-)
I've thought today to stock original engine and trans and buying a 383 cid crate engine and 5-speed gearbox. The engine would be painted and equiped (intake and exhaust manifolds, water pump,valve covers, air cleaner,...) like a LT-1, but with more modern technology. As long as it looks almost original from outside, it doesn't hurt me.
What do you think about that ?

Christian-------


In your case, I would not recommend doing what you suggest. You have what is almost certainly the original LT-1 block. So, I'd say your best bet is to restore it to its original configuration, externally and internally. That really shouldn't be all that difficult.

No cylinder heads of GM casting number 3881482 ever existed. You must be reading the number incorrectly

[Christian R.]

Re: 1972 LT-1 numbers questions

Hello,

Here is pictures of cylinder heads. I think you're right : casting number is 3991492. This seems to be a replacement head from '71 (on casting if I've good read...).
What still unclear to me is the presence of mechanical lifters...

Regards
Christian

[Joe L.]

Re: 1972 LT-1 numbers questions

Christian------


Casting numbers are often quite difficult to read correctly. The numbers here are 3991492 and that is consistent with the "double hump" casting symbol I observed on the end of one of the heads. This is a 1970 style cylinder head, very similar to the heads used for 1970 LT-1. I don't know that this head was ever actually used in PRODUCTION but was sold widely in SERVICE for many years. The date on these heads could indicate 1971, 1981, or, even, 1991. These are 64 cc combustion chamber size as compared to the 76 cc size of the original 1972 LT-1 heads. They were probably installed to raise the compression ratio. Valve size is 2.02/1.60, the same as the original 1972 LT-1 heads.

There's no way to tell if the engine has hydraulic lifters or mechanical lifters by the photos you've posted. You MIGHT be able to tell by trying to force down on the push rod end of the rocker arms. If you can get any sort of depression, then the engine has hydraulic lifters. If not, they're mechanical type. You might need to try this on several of the rocker arms. If you get depression on ANY, that means hydraulic lifters.

[Christian R.]

Re: 1972 LT-1 numbers questions

Hi,

I've Yesterday tried to check the lifters via rockers arms. I wasn't able to push one a bit ! I've seen the 2 nuts rockers fixing art, but unable to see on the web an original LT1 engine picture of valvetrain... Plenty with aftermarket rockers, but no one with original ones :-( If someone could have such a picture ?



Another poitn is my AC compressor : during return trip with the COrvette, it seems it had failed (red hot, burn smell...).
Someone knows a rebuilt service in the US ?

Merry Christmas :-)
Christian

[Joe L.]

Re: 1972 LT-1 numbers questions

Christian------


These look like they could be original rocker arms. I can see an "O" on one of them (the others are obscured by oil puddles). The double nutting is definitely NOT original. These originally used stover-type lock nuts or, in some cases, toplock lock nuts.

The valve spring caps (retainers) do not appear original to me. They appear to have a black finish. Original GM valve caps did not have a black finish. However, this is no big deal as they are most certainly 100% functional.