GMC engine identification

farmer boy · May 6, 2009

1997 GMC K1500 Z71 4x4. On the muffler it has one in one out which is 305 style but on the fan shroud it says 5.7 litre(350). It also says it complies with 1999 emissions standards. It has Z71 logos on the box but is missing the skid plate for the transfer case. It has a skid plate below the transmission area as well as tow hooks but the tow hooks were available without the Z71. It"s a rebuild which may be why the fan shroud is wrong on the year and possibly the engine. It gets terrible mileage which also leads me to believe it"s a 350. Any help is apperciated. The engine is also a Vortec

Tim[GA] · May 6, 2009

To identify the year of the vehicle. look at the Vehicle Identification label in the front window on the drivers side. The vehicle id is made up of 17 charcters. The 8th is the engine with a 305 {M} and the 357 {R}. The 10th is the model year with 1997 being a [V] and 1998 being a [W].
The engine id is marked on rear left side of the block near the bellhousing. The id will be nine digits. The second identifies the model year and the 4th through the 9th should be the last 6 digits of the vehicle identification.

buickanddeere · May 6, 2009

If the engine been swapped to something different. And the computer is still programed for the original engine. The of course mileage and performance will suffer.
It's possible something was tinkered together during the swap and there are faulty/missing sensors. It wouldn't be the 1st time somebody removed the check engine light bulb before selling a vehicle.
Any chance this vehicle had been a wreck and was build from parts of 2-3 donor trucks?
Then again a 1990's vintage 4X4 will not match the mileage of a VW diesel Jetta.
What mpg is the truck getting?

farmer boy · May 6, 2009

It's funny that you mention the that the engine light could have been removed. This truck has been sketchy since we bought it. I'm not sure it has ever come on in the 5-6 years we've owned it. The truck gets terrible mileage. Tops out at 10 mpg. Not too sure if it has always gotten that kind of mileage. We've only been doing short trips lately once a week or less which may have something to do with it. It also has hard starting. Almost always required to crank it over about 8-10 times. I'm looking into replacing the fuel pressure regulator and replacing the o2 sensor for the mileage as well as a tune up (plugs and filters.) The chances of it being built from 2-3 trucks is high. It's a rebuild and was in a major accident at one time. Not completely sure if it was a reclaim or a rebuild though. It has a filter minder on it which is normally only on diesels. I wouldn't say the performance suffers though. It has balls and power is there when you want it. Maybe it should have more power though.

farmer boy · May 6, 2009

Thanks for the information. If the vin# and engine# don't match up for the last 6 numbers than something isn't right. I'll check and get back to you tomorrow.

Roy in Ga · May 6, 2009

not sure the thinking is correct on the one in and one out. Sounds to me like a typical single exhaust but I will check. the easiest way to tell is on the drivers side where the engine and trans meet. Take a flashlight and look on the block it should have a 5.7L or 5.0L. There might be some build up and it is kinda tough to lay on the fender while trying to find out where to look if you are not sure but it is there!

farmer boy · May 6, 2009

The parts diagram shows the 5.7 with one in two smaller out. The 5.0 is 3" in 3" out.

sd pete · May 6, 2009

I have a 97 GMC 2500 4x4 auto with 5.7 and if babied while driving empty it can get 16. The mileage will go down when its used as a truck (10-12 mpg. And a lot less with a heavier load. It has 63,000 miles so i hope it lasts me for a long time.

Brian Jasper co. Ia · May 6, 2009

I have a 98 with a 350. It gets 19mpg on the highway. I have a bed cover which makes a noticeable difference. Ran it with the cover rolled up and it dropped off to 15mpg. If the fuel pressure regulator is leaking that would make for hard starting/poor fuel economy. You would likely see fuel in the oil too. To replace the regulator you have to get the complete injector asy in the intake. If the Cam position sensor is not hooked up or bad, it will also cause extended cranking time. The check engine light should prove out each time you start it and be on steady whenever the ignition is on and the engine is not running.
The filter minder is regular equipment from about 96 through 06.

MMfan · May 7, 2009

The one in two out muffler stopped when they went to the vortec engines. The vortec's have SFI fuel injection and a plastic intake manifold. The exhaust then became two cats, and two pipes into one muffler with a single exhaust out. A 1997 should have a vortec engine. If you have throttle body fuel injection and an aluminum intake, that is a 1995 or earlier engine.

GMC engine identification

farmer boy

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Tim[GA]

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buickanddeere

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farmer boy

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farmer boy

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Roy in Ga

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farmer boy

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sd pete

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Brian Jasper co. Ia

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MMfan

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