305 Questions

[BPR Speed]

Something is wrong. Even if you put a 350 computer on your 350, I wouldn't drive it. 411 or nothing. My dually had a blackbox and Whippletronics on it for 80,000 known miles, likely more prior, and it worked its ass off and never blew up. Sorry for the threadjack OP, I like Schurkey's comment about the 305 being a placeholder myself.

The fuel pump appears to have went out. It was popping the ECM-B fuse and had extended crank issues, low fuel pressure at the rail ect. I picked the truck up in this state and had the intent to rebuild it anyways. They're was a lot of neglect this truck received in the past. It's being sorted out now.

 

[Mikes98]

I’m looking at buying a 95 extended cab short bed with a 305 and NV3500 for $1300 My main concern is power with the 305. I’m used to the 350 Vortec in my 97. What are your opinions?

'95 was the last year for the L03 ...from what I've read it put out about 170HP and 255ft/lb of torque. It's got the throttle body injection. The truck does have a unique setup with the extended cab and the 5-speed ...which, IMHO, makes it probably kind of rare ...with the 5.0L making it even rarer. I've got a spot in my heart for rare and oddball combinations and engines and this truck would defintely pique my interest. This was probably spec'd by the PO to save gas ...get that extra MPG over the 350 and automatic. I have to wonder what the final drive is. If it's too tall it can really kill any level of acceleration/fun factor for the sake of fuel mileage. I had a '95 S10 with the 4.3l and a 5-speed but it had some stupid ridiculous 2 point something final drive ratio that killed any pizzaz the V-6 could muster. If your expectations are appropriate, this truck could be just fine. And as you have a stable of other vehicles for things like towing, this truck could make a nice daily driver. Given its rarity status I would definitely consider buying it ...especially if it's in nice condition.

I have the Vortec 5000 in my '98 GMC short-bed, std cab, 4L60E; I've owned it since 2001. The 5.0 in my truck is the last generation of the engine, the L30; it puts out 230HP/285ft/lbs and it runs the truck just fine. No, it's not a speed demon but the 3.42 gearing on it allows for some level of brisk acceleration and towing capacity. It's definitely not the choice for heavy duty towing but I don't have a need for that; she'll pull my 8' utility trailer loaded for bear with mulch, logs, general cr@p or my DR650 no sweat. (What *is* rather sweaty are the $h1tty 10" rear drum brakes). I get a solid 16-17 mpg in mixed driving and last time I checked it'll eek 20 mpg on the interstate running 70-75 mph ...it's not the most aerodynamic thing on 4 wheels. The only mod to the engine was installing an under drive crank pulley to mitigate the AC compressor load; it did put a good whack on the engine and you could feel it engage running down the road; not any more. An overdrive pulley for the alternator was included (to make sure it stayed on line at idle).

IMHO trying to greatly improve on these engines is rather a waste of money ...especially in a truck. The 5.0L is a compromise engine in that they are more robust than the 4.3L but not as fuel hungry as the 350. They have narrow bores so they are limited in how well you can make them breath and for the money you'd spend on one trying to make it a 350, you could just get a 350. But me, myself and I would keep the truck original. The only thing I would consider doing to it, if needed, would be to put a lower final drive in it if it's got the "Mileage Champ" gearing.
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Biggest issues I've had with mine have been the big end rod bearings and a leaking intake gasket. I get piston slap on cold weather starts and I'm looking at my third water pump swap (apparently a regular issue).

From my understanding, GM started making engines in Mexico about the '98 time frame (don't know if the '95 MY engines were made in Mexico). The crankshaft journals on these engine were finished to some rather loose tolerances across the crank and the way they made up for the differences was using various under and over sized rod bearing shells to bring things into spec. Maybe this was standard production across the board, IDK, but they had issues with incorrect bearing shells being installed (on Mexican-made engines) such that you might end up with some loose tolerances; that's what happened to me. A rod knock in #7 at about 135K that wouldn't go away. It had started way much earlier but would go away as the engine warmed; worse in the cold, not so bad in the warm. I ended up replacing all the big end shells; not fun. But, you can do it without pulling the motor. The shells on #7 were toast (and some of the others were looking poorly as well). No more rod knock and a 10PSI increase in oil pressure.

My first water pump swap was under an extended warranty I bought when I got the truck. In the troubleshooting process for the pump, the dealership found the intake to cylinder head gasket leaking. This ended up being a $1000+ repair and paid for my warranty ($50 deductible for me). Since then I've installed a second pump and now, leaking, this one will need replacing.

The piston slap thing is a GM V-8 thing I've read ...so I guess it's "normal" for these engines and not really an issue. My engine sounds more like a diesel on a cold start in winter with the "clip-clopping" of a couple of pistons; worse in the cold, no factor in the warm. Goes away fairly quickly as the engine warms.

 

[97C1500TJ]

I also have a little piston slap in the cold on my 350. 225K on the motor. Hopefully it isn’t too bad because I’m not putting a motor in it yet.

Yes I believe the truck to be an oddity with the extended cab, 5 speed, and stepside bed.

 

[97C1500TJ]

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[1997]

nice score, keep it stock imo , definitely an odd combo.

 

[L31MaxExpress]

It's fine. A 305 will go just as many miles as a 350 or 4.3l v6.
From your posts above it looks like you already have a tow rig, A gmt400 with a 5.7, and an isuzu. From a utility standpoint I'm not sure you gain or lose anything by replacing the Isuzu with this 305 powered truck. I wouldn't expect it to be anymore powerful than the isuzu, but if it's a clean truck go for it. I like to tinker with automobiles, and a good clean rig at a good price is not easy to come by.
If it were me, and clearly it isn't, I would buy it and sell the isuzu. Then I'd drive one of the other two rigs while I cleaned up this one. Once it was sorted out, I'd drive it full time while I focused on making the other 5.7 gtm400 what I want it to be.

305 will run circles around the 3.5L V6 in an Isuzu.

The 305 with a little cam, headers, volant intake, underdrive crank pulley and e-fans was a great runner in my 99 Tahoe. 22-23 mpg cruising 75 mph.

 

[97C1500TJ]

305 will run circles around the 3.5L V6 in an Isuzu.

The 305 with a little cam, headers, volant intake, underdrive crank pulley and e-fans was a great runner in my 99 Tahoe. 22-23 mpg cruising 75 mph.

The Isuzu V6 is quite pitiful and burns oil to the point I say it’s a two stroke. I’ll miss the 4x4 capability. Guess I’ll have to get a third 400….

 

[RichLo]

Nice Score! truck look nice and clean.

I learned something in this thread too, I guess my truck is 'rare'? 1993 GMC SLX k1500 ECSB 305 5-speed, w/ 3.42s

 

[Dirty Jim]

The later 305s are ok. They made as much power as the TBI 350s. Don't hear many complaints about those old boat anchors haha!

 

[Mikes98]

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Wow!. You didn't mention the stepside. I would definitely keep the truck stock. There is a website called "Comp nine"; it is a very sophisticated VIN decoder. When it first came out (many years ago) it was free; now you have to pay for the service. But it will tell you *everything* about your vehicle (in my case my '98 GMC). The other thing it will do is show you how rare your vehicle is with respect to the options on it based on the model year. I never expected my humble 5.0L SL shortbed to be any kind of rare but ...the Comp nine search came up with *4* '98 C1500's that were ordered with the same options on my truck ...that's 0.004% of the total production run (100,504) of the same year ('98) and model . It would be interesting to find out how many trucks like yours were built in '95 ...I'm thinking yours is gonna be pretty rare.