1978 Z28 Engine Code

[TheFastForester]

Everything seems to be matching up numbers-wise on my '78 Z28, however I am confused a bit on the engine code suffix:

V0223CHS
18N572537

The engine build date (0223-Feb. 23) is a month prior to the cowl tag production date of 03C (third week of March). That's the way it should be according to my research. I've got the PZ off the rear axle, which would indicate 3:73 posi that the Z28 had in 1978.

The thing confusing me is I have a Borg Warner 4 speed manual transmission in the car. All the sites I looked at says the engine suffix of CHS should go with an automatic transmission. Stegmiller's site says for the suffix:

Z28 CHS th

Which means to me it's the numbers matching engine for the Z28, but what does th stand for on that site? I assumed the m/t would be for manual tranny.

Could this car have been switched from an auto to manual tranny? I am the 3rd owner so I don't know the complete history of the car, but that never came up in the discussion of its history. Thanks for any help on this.

 

[Gary S]

You have a puzzle there. My Son and I wrote Stegmiller's site many years ago, and the information we had back then said that CHS was the code for a 78 with automatic tranny. I just checked the information here on NastyZ28
http://www.nastyz28.com/camaro/camaro78.php#engine
and it agrees.
Bottom line here is that I can't shed any light on your car. From everything we know, the CHS coded engines belong in a car with an automatic tranny.
If you can, get under the car and see if the floor pan looks like it might have been modified to take the manual tranny shifter. That might be a clue as to the possibility that the car might have been converted from auto to manual.
If the engine VIN matches the VIN of the car, you know that this is the original engine. If there is no evidence of a tranny change, then there is also the possiblity that the wrong coded engine might have been put in the car.
Don't tell EPA or NHTSA if you find that out.

 

[TheFastForester]

VIN's match, so does the rearend gear code (PZ 3:73 posi) for the Borg Warner set up that year. Sure wouldn't think the original owner swapped out the whole drive train from engine on back?! I'll get underneath and look around a bit, maybe put up a pic or two from under there as well.

Anybody else w/ '78 Z28's out there, that have the manual tranny and original engine care to share their engine suffixes? Thanks!

 

[WS6]

what does th stand for on that site?

Tubro-Hydramatic ??

 

[TheFastForester]

Thanks WS6, I think you are correct. After I did some more research last night figured it stands for Turbo-Hydramatic.

 

[gin man]

I'm not familiar with 78s but would the dash give you a clue? If it has a PRNDL setup, even one that has been covered up, that would seem to point to it originally having an automatic.

 

[TheFastForester]

Gin Man, asked that same question on here before when I first got the car. Thought it was unusual to have the dash opening for the PRNDL setup, without anything showing in it. Asked around, and have looked at many manual tranny cars since, and they all seem to have that built into the dash the same way.

Anybody know of anything else I can try? I tried pulling a VIN off the Borg Warner I have on the car, looks like 13 066-903 behind the side plate. On the passenger side of the tranny case have 1304065 903, below that W.G. Div. and FpC1 below that. Tag above these casting numbers looks like ?.10.78.

And now for some pics that Gary S. suggested I take underneath, showing the connecting rods to the stickshifter from below looking up at the floor pans. How does this look Gary?

 

[Gary S]

I don't see anything that indicates the tranny has been changed. If you thoroughly search the rest of the tranny, you should find a partial VIN stamped on it. If it matches the VIN of your car, you can be sure that the tranny is original, and the car was originally a 4 speed.
Usually this VIN will be stamped along the flange where the main case and the tailshaft bolt together in a vertical position, but GM used different locations with different cars and transmissions.

 

[TheFastForester]

Thanks for the tips Gary. After reading your post, talking with Mike Smallwood at YearOne, and doing some research I found on-line on the Borg Warner T10 I have determined this is the original tranny that came with the car. Numbers match the VIN on both the engine block code and transmission case. All dates I've found on the car (VIN, engine, tranny, trim tag, and rear-end housing point to a birthdate on this car in Feb/Mar of 1978!

Also Gary you might note an edit should occur on the websites (Nasty Z28, Stegmillers, others that seem to copy your info) that the CHS engine code is for a manual tranny in the Z28. Mike at YearOne looked in his Chevy Engine Code "Bible" and found the CHS suffix in 1978 was for the Z28 Camaro, 350cid, 175HP, man transmission, LM-1 with the single 4BBL carb. I think most people look on line for this type of info these days and won't by the $30 book that lists the codes.

On another note, while I was on the phone with Mike at YearOne, he looked in what he called the "white book". Is that the assembly manual he's referring to? But he found the "error" there as well, CHS listed as an auto tranny code. Maybe that's where you guys got the info for your web sites?

Anyway I am pleased as punch after all this research that my numbers match! And thanks for all the help.

 

[MadMike]

I'm going to look at the master code book tonight and see what chevy has to say. Either there's a typo on the net, or this car doesn't follow what we'd call "normative practice".

Either way, the original poster has his original, numbers matching drivetrain present.