Well I did it!

I couldn't be happier!
I now have a 1970 454 LS5. 390HP TurboJet
It is numbers matching, and the one thing that made me go for it is when I pulled the VIN and ran it through GM's Vintage Vehicle Service with George Z.
It came back with the data. An original Canadian car sold here, with the list of options it came with.
It shows.
Power windows
Tilt Steering, PW Brakes
4 Speed code M21
3.08 rear Positraction

and when I drove it home I was impressed with the torque and feel of it. Power all over in any gear.. You could start off in third with no problems!! LOL
*Also I noticed that first gear is Long, and could probably go to 60MPH before shifting into second

What tranny's came with this car? Is it possible they came with M21's and 3.08 rear's ? I can't remember the letter after the serial number on the tranny to distinguish if it was an M20 or M21
But then again if the Vehicle document said M21 then It would be the 2.20 first gear, I believe an M20 has a 2.52
Would they have come with the M20 Also?
Would they have thrown in an M20 tranny and put code M21 for simplicity on the Vintage Vehicle document.. They are both Muncies.

*With this 10.25 Compression would I need octane booster or something. It runs fine. I hear no pinging or anything.



I will post some pics here for all to see.

 

 

LS5 could be ordered with M20 or M21. The rear ends used for the LS5 were 3.08 and 3.70. Everyone seems to claim they have a 3.08 rear and an M21, but that doesn't really make much sense as it would be smarter with the higher gear in the rear to order the lower gear in first. Other than not making sense, I lack the experience to have an intelligent view of how many LS5s were ordered with 3.08 rear and M21 trans.

 

You're lucky it's a Canada car and you can get that documentation. Can't get it for a U.S. car.

This is what's on my 70.
If you have a 3.08 rear the code would be something like this:
CAW 013 E1
CON T (side mount carrier)
I have a M-20, but it's a small block.
Here's a few links for more info and you should register your 70.
http://www.1970corvetteregistry.org/codes.html
http://www.corvetteactioncenter.com/...1970/70id.html
http://www.motorera.com/corvette/1970/vet70.htm
Hope this helps and good luck with your 70!
Glenn

 

M21 with the 3.08s seems odd but quite a few cars had this combo. Also a few 71 LS6s ordered this way,
guess they wanted the top end and with the torque of the big block, it was manageable.
No way to know how many M21s had 3.08s though.


1970-72 LS5

Available 4-speeds and axles

With Air Conditioning
M20........3.08 all

Without Air Conditioning
M20........3.08 std, 3.36 opt
M21........3.36 std, 3.08, 3.55 or 3.70 opt

 

M20 is an A
M21 B
M22 stone crusher C

 

My car has No AC..
When I go under the car I'll try to see what letter code it is.

It would be wise to have the M20 with the 3.08 combo. It would pull harder in first.
LOL .. I know Top speed runs for sure.. At 60MPH it's loofing at very Low RPM.s Which is good..
But with the M21 or M20 the Top Speeds would be the same I think as fourth is 1:1 ratio.

Who has any road articles on the 70 LS5 model? Like quickness and Top Speed. Etc
and hopefully an article that uses an example with a decent gear like a 3.70 or something.

 

congradulations!.. get us some pics when you can...

I have a 70 LS5 and it is wonderful... rare, and fun to work on... and a torque monster...

yes standard on the car would be the m-20, but about a 4th of the cars were orderd with the m-21 close ratio

look on the side of the transmission.. up by the front, for the stamping, if it says P____A, it is a m20, if it says P____B, it is a M21.

unless it has been restored you will get to learn the underside of that car real well in the future!!

good luck and holler if questions!

- Joe

 

Don't think I've ever seen a road test article on the 70 model. Car and Driver did a big test in 71 where they tested 4 Corvettes equipped with all engines offered. Usually the LS5 would be fully optioned and this one was no exception so it was slower than normal, plus it also had an automatic. It ran the 1/4 mile in 14.2 @ 100 mph. This was still quicker than the LT1 which ran 14.5 @ 100 mph. The LS6 was M22/3.36 and it was only slightly quicker at 13.8 @ 104 MPH. As far as top end, your car will redline at 140 mph and it should pull to it. In the C & D test, they went to Nevada for top speed testing and the LS5 automatic ran 141 mph. The LS6 with it's higher redline and power went 152 mph. These are the lower compression engines so I guess for 70 you could reduce 1/4 mile times by a couple of tenths, Top speed wouldn't really change unless you over rev it or swap to 2.73s.

 

M20 and M21 would have the same top speed as they are both 1:1 in 4th gear. The rear would make the difference. Redline at 5600 rpm means input shaft to the differential at 5600, with 3.08 gears, that means 5600/3.08 = 1818 rpm of the tires. My 235/60R15 tires are 26.9 inches in diameter, so:

1818 rev/min x (26.9 x Pi inches per rev) =153,652 inches/min

153,652 inches/min / 12 inches/foot = 12,804 feet/min

12,804 ft/min x 60 min/hr / 5280 ft/mile = 145.5 mph

So the top speed of my car is around 146 mph, unless I have the cajones to push the engine past redline (I don't). You can calculate for your own car by inputting the appropriate rear gear and tire size and chugging through the same calculation. I can also short-cut if I decided to replace my 3.08 with a 3.70 by saying 146 * 3.08 / 3.7 = 122, so a car with the same tires I have and the high performance rear would reach redline at 122 mph. There is no way I am giving up those 24 miles of top speed!!!!

Edited to add: I think I remember reading that the top speed on a 1970 LS5 manual car was 151 mph. I believe the difference is caused by the bias ply tires of the day being somewhat narrower, but somewhat bigger in diameter than the tires I am presently using.

 

Yeah PK you're right, theoretical top speed at redline should be about 146 mph. Guess the converter slip on the automatic car slowed it down a little. The original F70s were supposed to be 26.92 inches in diameter but not sure if they would grow more or less than a modern radial. Yeah, I'll bet the 70 could pull a 3.08 to redline and a little beyond.

 

Congrats on the 70 454...

 

Mine is also a Canadian car with the GM Canada documentation, It's a 71 LS5 with a M21 and 3:36 rear end.

:CHEERS:
Rick

 

I am impressed with it's Tremendous power all over the place. Down Low and Mid range. Atleast I can be assured this thing will rocket all the way to 140MPH or more if needed. LOL.
I won't be testing Top Speeds.. But I do have an M22 Rockcrusher I might just put in for fun.(That High pitched Whine like a Blower).. I'll still keep the original M20/M21 as it's gotta stay with the car.

Here are some pics
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Nice car man - I just bought one myself (1970 454 4-speed) 3 weeks ago - same color and real similar options (PS/PW/PB/tilt-tele) too. But...your air cleaner looks like it's from a 71 or 2, no? Or was that different for Canada?

I sympathise with the torque - damn thing pulls like a mac diesel from 1600rpm upwards. Can't get enough of it.

There's a lot of mixed comment on this forum about additive - personally, for me I'll keep it at 91RON with additive to be safe - heck, at $2.50 a bottle it's cheap insurance.

you have fun now and get it pimp for the Summer...

Simon.

 

**** - forgot to add I still have not wiped the smile off my face. My wife thinks I'm crazy...

 

Thanks Spinadog! Your car looks great!! & very similar to mine.
I think you have the correct chrome valve covers and air cleaner. Mine might not be correct. The engine tranny and rear end are all correct for the car.
Chassis is mint. The car had a frame off 10 yrs ago. and is all sandblasted and looks great underneath.

With additive.. That's a good question. We have Sunoco 94 Octane here in Canada, and that's what I always use even on my Pontiac TA which has 10.5 compression.
But with this motor.. I wonder if I should look into any additive or if it's even neccessary.

But the way it drives.. Actually it does sound a little like a "TurboJet" LOL

 

Ref. the octane question- and this applies for any car, any year.

If your engine is not knocking/pinging, you do no need and will not benefit from adding 'octane booster'.

If it is pinging, you have the option of backing off the timing a little, or buying gasoline that is 1)not legal for street use 2) very expensive.

Most octane boosters in a can are snake oil, be careful what you buy.

 

Very early 1970 cars had the open element air cleaners, the non-early ones look like that, and have a chrome top. It looks like yours might have a chrome top, but it is hard to tell in the picture.

Also, 1970 454s all came with an aluminum intake manifold, of that I am darn sure. What I am not sure about is that I believe the intake was not painted GM engine orange when it left the factory. However, mine is the right part number and date code, but is painted GM engine orange, I presume by whomever detailed the engine compartment before I purchased the car. I see yours is painted too, but I have seen many of them as bare aluminum. Does anyone know which is correct?

 

Oh and on fuel additives, I 100% agree with Mike on this one. Most of the stuff you buy in a bottle or can at the auto parts store is worthless. If you carefully read the bottle, somewhere in the fine print it will tell you that a whole bottle will increase the octane of one tank of gas by 0.1, that is one tenth of a point. Here in NJ, the premium gas is 93 octane by the R+M/2 methodology, I don't know how that compares to Canadian gas, but I stomp all over the pedal on mine and I have never heard it ping.