76 GMC Camper Special 350 4 barrel

[truckdriver]

I found a 76 Camper Special with 58,000. Completely stock, the glove box sheet says it has the m40 turbo. I thought it would be a 400 but have been told it would be a 350 turbo. Was considering a crate 383 or 502 high torque. Would the 350 turbo be enough for the 383? Cruising at highway speeds, would the 383 get just a couple of miles per gallon more or would there be a huge difference? Haven't been able to determine my differential ratio yet. How does everyone like the 502HT?

[russgt]

M40 is the turbo 400. Yes, a th350 can be built to handle good power, put if you plan on doing heavy towing with a lot of power, then I would use the 400 with a good tranny cooler.

[geezer#99]

Easy to tell what you have!
Vacuum modulator points to the rear on a T350 and to the side on a T400.

[Firebirdjones]

I really like my 502HT. I had considered rebuilding the original 454 to a 496 and doing it the way I want, but lack of a decent machine shop nearby had me lean towards the crate engine for the same price.

I primarily use my truck for towing hence the reason for a cubic inch increase. The 502HT performs better than I thought it would.

[truckdriver]

Brought the truck home and it has the turbo 350. Surprised an 8200lb gvw has a 350 but maybe that was a common match with the 350 motor.

[hatzie]

SPID tells what it left the factory with. The M40 TH400 was replaced in the last 36 years. The TH350 was cheaper to buy used so it's not surprising.

[truckdriver]

Just found several posts in chevytalk saying m40 up to 1976 in 3/4 and lighter meant HD trans and they were TH350.

http://www.chevytalk.org/fusionbb/sh...4/pid/1761165/

[truckdriver]

Guess I can't link like that. Several people commented that their 3/4 m40 was a TH350.

[Firebirdjones]

Originally Posted by truckdriver

Brought the truck home and it has the turbo 350. Surprised an 8200lb gvw has a 350 but maybe that was a common match with the 350 motor.

Correct. You will find the 400 turbo's behind the big block trucks regardless of the GVW. Even 1/2 ton 454's will have the 400 turbos.

350 engines got the lesser trans.

[hatzie]

http://gmpartswiki.com/getpage?pageid=55577

M38 = THREE SPEED AUTOMATIC 11.75" TORQUE CONVERTOR Chevrolet built
M40 = TH400


Your SPID lists M40 so it had a TH400. Look next to the gas pedal for the TH400 kickdown switch.

[truckdriver]

http://www.chevytalk.org/fusionbb/sh...4/pid/1761165/

No kickdown switch. I know the original owner. 58,000 miles. No work done on transmission.

Thanks for the great link.

The link to chevy talk is now good. What do you make of their conversation?

[57NAPCO]

I have a 76 GMC camper special (10000 GVW) with a 467 ci BB and a turbo 475 out of a motorhome. I dig it.
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[Firebirdjones]

Originally Posted by truckdriver

http://www.chevytalk.org/fusionbb/sh...4/pid/1761165/

No kickdown switch. I know the original owner. 58,000 miles. No work done on transmission.

Thanks for the great link.

The link to chevy talk is now good. What do you make of their conversation?

Sounds like an original 350 turbo truck, as I would have suspected with the small block.

[hatzie]

Originally Posted by truckdriver

http://www.chevytalk.org/fusionbb/sh...4/pid/1761165/

No kickdown switch. I know the original owner. 58,000 miles. No work done on transmission.

Thanks for the great link.

The link to chevy talk is now good. What do you make of their conversation?

My link is to the appropriate RPO page in the 1973-1979 GM Light Truck parts book. If the TH400 & TH350 were both Production Option M40 I would expect a notation in the parts manual about this caveat.

It's possible that GM used the M40 RPO for TH350 auto till 1976. It's also possible that the SPID was screwed up or the line was short the TH400, so, the TH350 was subbed in for some trucks. 100% speculation without talking to someone who was there. It would be interesting to compare broadcast sheets to the SPID label.

My 76 K20 Camper Special originally had the TH350/NP203 with a 350. The SPID was missing but the broadcast sheet jammed in the seat springs called out M38.