jrheyerly

I found a 1970 LT1 for sale recently. The aluminum intake, air cleaner and holley carb. are all original. My concern is the block. I can't see any numbers on the engine pad , passenger side. It is painted over in Chevy orange and I have the owners permission to lacquer thinner the paint off this area. Is it possible that the numbers are hidden beneath the paint?
It's funny because if they changed out the block, the replacement block should have legible numbers.
The rest of the car looks to be unmolested, except for Hurst linkage on the 4 speed and white paint job. The trim tag indicates 982 D. green Trim 400 black. I will post some pictures, if any of you would be nice enough to help me with this ID project. The price is 24,000 or offer.
If the block is NOM, I'm not interested. If by some miracle the block code is CTR, CTU, or CTV, I think this is a find.

Thanks,

Jeff

Mike Ward

A blank pad, more often than not, is a victim of some engine rebuilding shop's habit of decking every block they see. Replacement blocks are also sometimes blank, but the surface will appear different than a rebuilder's mistake due to the tooling used.

Post a pic if you can.

BBCorv70

You may want to check the casting number and date. If they make sense for the car it may suggest the block could be original.
The finish of the metal where the stamp pad would go may tell you something, look for broach marks. In this case if the broach marks look good but no numbers it may actually be a NOM?

If there are no numbers, it's a guess as to whether it's the original.

mar

As above it could be decked during a rebuild...if so it has lost most of it's numbers. Sometimes faint vestiges of numbers can be seen.

joewill

there is really no way to prove otherwize. if the pad is painted ( they were not painted at the factory and should be unpainted), the engine could have been decked during rebuilding and painted and it therefor could still be the original but without any numbers. a blank pad does not mean it is not the original engine. nor does a correctly stamped pad mean it is original. there are many factors to consider.


a wrongly ( or even correctly) dated block may have been acquired after the original blew up and restamped and painted, or not restamped and painted. I could give you several other scenarios.

bottom line is true original LT1's and 24K are somewhat mutually incompatible, unless the condition is poor.

you will need to look at other factors such and head casting nuumbers and cast dates along with the block casting date codes. plus several other factors to check out the car.

jrheyerly

Thank you for the info. Where are the block and head casting numbers located? I am going to post some pictures soon for review. I guess another test of an LT1 is a test drive. It should perform slightly better, even in tired condition than a base engine 300 hp 350.
Do you think the car is worth an offer, assuming it really is an LT1, minus the original engine block?

BBCorv70

Depends on whether this car without proof it's the original engine is something you would feel comfortable buying. If having the original block is of high importance to you I'd think this car may not be for you. You will probably run into similar questions when you resell it.

If you are looking for an LT1 for a driver, original block not a high priority, then the car could be worth making an offer with a discount assuming it's a NOM. How much discount, I don't know...

Does this car have any documentation supporting the claim it's an original LT1? Tank sheet? POP? Invoice?

joewill

head casting numbers and dates are under the valve cover, the block casting number and date are on the bellhousing flange, behind the distributor

understand how these cars are misrepresented ( not usually by the current seller.. he may not know either) and how they are faked, how numbers and dates are supposed to match up. if you require originality, then do your homework to understand how to confirm a car is actually an original LT1. There are suspension, ignition, hood, tachometer, and a long list of other things to look for that a LT1 expert could enlighten you to.

your test drive will tell you nothing unless you have a baseline to compare to. A LT1 has near the same torque that a base engine has. it just has a wider power band.. It pulls the same as a base engine, but it pulls longer.

Barry's70LT1

???????????????

Easy Mike

That could be a rather poor test, especially if you're looking at an LT-1 asking price. What if the LT-1 is very tired and the 300 hp is tuned to perfection?

joewill

they both output 380 ft/lbs of torque, but the LT1 will pull higher in the RPM range and thru a broader rpm range.

given the same gearing, if you stomp on it at 3200 rpm with a base engine, you will get the same neck snap if you stomp on it at 4000 rpm with the lt1.

with the base engine, as you rev it, you will run out of power and have to shift, but the LT1 will continue to pull and you won't have to shift until later.

the higher the peak torque rpm, the higher the horsepower calculates to be.

the point is, both engines will push you against the seat equally, the LT1 will push you against the seat longer and at a higher RPM