70 LT-1 visuals

[Michael W.]

Re: 70 LT-1 visuals

Ken,

I thought the intake manifold part # was different than what you posted. Were there two different intake's in the 1970 M/Y?

A 3959594 intake is the correct number for a '71 or '72 LT-1. The 1970 number is 3972110 I think.

[Dennis D.]

Re: 70 LT-1 visuals

Great Terry. Thanks another very helpful piece to the puzzle.

[Dennis D.]

Re: 70 LT-1 visuals

Thanks mike. Assume intake is the same with or without NA9

[Timothy B.]

Re: 70 LT-1 visuals

A 3959594 intake is the correct number for a '71 or '72 LT-1. The 1970 number is 3972110 I think.

That's what I always thought Mike but I don't think there is much difference between the two.

[Terry M.]

Re: 70 LT-1 visuals

Perfect Ken. Thats a great bunch of info. Car is supposed to have NA9. Is the carb different in that case? Also not an original California car, but I seem to remember that all NA 9 cars didn't necessarily originate the order from there

Yes the NA9 carburetor is different. Different numbers and different primary float bowl. I am sure there are internal differences as well. Numbers are called out in the 1970-72 TIM&JG, I don't trust my memory for such things. There is also an aluminum heat shield under the carburetor and the carbon evaporative emissions canister that later (beginning in 1971) became standard.

NA9 was required on 1970 Corvettes sold in California, but we have seen a number of NA9 cars that were originally sold in other states. So we should say NA9 was manditory on 1970 Corvettes sold new in California, but optional in other locations.

[Kenneth B.]

Re: 70 LT-1 visuals

That's what I always thought Mike but I don't think there is much difference between the two.

Yes there is. The 71/72 594 intake has the firing order#'S cast on the runners & the 70 3972110 dose not. It's a easy way to tell.

[Dennis D.]

Re: 70 LT-1 visuals

Great stuff guys. Lots of info for my trip next week. Will post pics for opinions.

[Kenneth H.]

Re: 70 LT-1 visuals

Yes, guys, the correct intake manifold is part number 3972110. Below is the corrected list:


1. No 1970 LT-1 had A/C.

2. All LT-1's are 4 speeds (M21 was standard, M20 was optional, automatic not available).

3. Tach has 6,500 RPM red line and the console tag will show 370hp.

4. All 70 LT-1's came with the A.I.R. system. If A.I.R was removed manifolds should still have holes for the tubes.

5. LT-1's had a copper radiator without an overflow canister on the passenger side fender well. There should also be no holes where one had been mounted.

6. All 70 LT-1's had Transistor Ignition. It may have been removed, but if it was removed look for the 3 holes on the front face of the driver side inner fender well where the Amplifier box was mounted.

7. The aluminum intake manifold should have a Winters snowflake with casting #3972110.

8. LT-1's had a Holley carb so there is only 1 fuel line, and no return line like a Quadra-jet carb. Also the fuel tank is different. There should be no nipple on the passenger side, side wall for a return line.

9. LT-1's had solid lifters/flat tappets and make a distinct sound when the engine is running.

10. LT-1's use 2.5" exhaust pipes like the big block cars. But the manifolds were still 2" set up. So the pipes flair from 2 to 2.5" about 6 inches from the manifold. The exhaust hangar at the transmission is also different.

11. LT-1's have the same heavy duty half shaft retainers as big block cars. Look at the rear end side yokes, there should be caps with bolts. Base cars used Ubolts with nuts.

12. Early 70 LT1s couldn’t be ordered with power steering due to the 6 quart oil pan. Some time during the production year the 5 quart pan was introduced and the smaller size allowed for accommodation of power steering. It’s possible that the engine code was changed from CTU to CTK to reflect this change.

[Lynn H.]

Re: 70 LT-1 visuals

Just a thought on #2 on your list, that applies kind of across the board with C3 cars (particularly high performance variety).

2. All LT-1's are 4 speeds (M21 was standard, M20 was optional, automatic not available).

There is a difference in an "automatic" body versus the "manual" body at quick glance. This would be something to look for in any possible counterfeit. All 70 LT1 's wouydl be manual so any "automatic body would be suspicious.

In an automatic car the passenger floor pan is cut and modified for the vacuum modulator on the automatic transmission. They did not do this on the standard or manual cars,(such as the 70 LT1). Picked out a couple of bogus cars with this one.

Lynn Houk

[Kenneth H.]

Re: 70 LT-1 visuals

I have #14297 a Bridgehampton Blue 70 Lt-1 coupe. It and all other real 70 Lt-1s I have seen have the holes in the trailing arms for rear stabalizer bar brackets even though they do not have the bars.

Patrick, I know that you know your stuff, and if we could get confirmation on the trailing arm holes do you mind if I add it to the list?

Thanks.

[Terry L.]

Re: 70 LT-1 visuals

Patrick, I know that you know your stuff, and if we could get confirmation on the trailing arm holes do you mind if I add it to the list?

Thanks.

Ken,

Both of my Lt1's, 7802 March 25th build date and 7040 March 17th build date, Do not have the holes in the trailing arms. The trailing arms on 7802 still retained the riveted brake rotors, original shims, heavy duty half shafts and punch mark in the hubs. All the parts associated with the rear end appeared to have be unmolested before I started restoration.

Terry

[Michael W.]

Re: 70 LT-1 visuals

Patrick, I know that you know your stuff, and if we could get confirmation on the trailing arm holes do you mind if I add it to the list?

Thanks.

Trailing arms with holes have been seen on non LT-1s so this is not a determining factor.

[Dennis D.]

Re: 70 LT-1 visuals

FYI my 70 L-46 has the holes. I actually installed the bar back in '78 when I had the car repainted.

[Patrick B.]

Re: 70 LT-1 visuals

It has long been my theory that most if not all LT-1s got big block trailing arm assemblies and that big blocks had different spindles as mentioned in the 1970 dealer Sales Albums. Terry cites the example of 2 fairly early (3rd month of production) examples without big block sway bar holes.

The 1970 assembly manual also calls out "rear hubs and bearings" as a difference from the base vehicle for both the LS-5 option (page LS-5 sheet A2) and the LT-1 option (page LT-1 sheet A2) and cites the parts list or bill of materials as the source of part numbers for these differences. Unfortunately, the bill of materials is not part of the assembly manual. However, in the case of the LS-5 there is an illustration (page LS-5 sheet B1) that shows the part numbers of the rear trailing arm assemblies as 3936469-70 (as opposed to the part numbers 3936467-8 for the base car). The complete trailing arms apparently including the brake calipers were furnished to the St. Louis plant as an assembly, so the simplest way to equip LT-1s with big block "rear hubs and bearings" would be to use big block trailing arm assemblies despite the superfluous sway bar holes.

I think it is pretty clear that the rear hubs (spindles) for big blocks and LT-1s are different from the base vehicle. The pictures below show the spindles on a July 3 built LT-1 (14297). The trailing arms and spindles are original with the rotors still riveted on. I bought the car in 1972 with 8,000 miles on it and I have all the service receipts of the first owner none of which involve the trailing arms or spindles. I believe the indentations on the left projection of metal inside the wheel contact ring of the spindle are markers of the big block spindles.

I am curious if the LT-1s without sway bar holes have spindles marked like those in the pictures, and I would expect the L-46 with sway bar holes to have those markings as long as the trailing arms are original (all service trailing arms had the holes, adding to the confusion about LT-1s). My guess is that the L-46 is a later car and there was certainly no problem in using an interchangeable heavy duty part if necessary to keep the line moving. The LT-1s without sway bar holes are harder to understand. Assuming they are documented vehicles, there seem to be two possibilities. One -- early LT-1s used a third variation of trailing arm with heavy duty spindles and no extra holes (too bad we don't have the early bill of materials) or two--the factory was not rigorous about using heavy duty spindles on LT-1s if it was necessary to use small block parts on hand to keep the line going.

[Gerard R.]

Re: 70 LT-1 visuals

Great info as usual,how about some pics of your LT-1's.