My '88 K1500 Sportside has the 305cid TBI and currently has 258,000 mi. on it and runs really well. There is a puff of smoke at initial startup after sitting overnight, I figured it is probably valve guides. Not a real issue at this point in time.
What I am debating about is whether to keep the 305 and have it rebuilt when the need arises, or to scrap the 305cid and go 350cid or 383cid. The 305 with 258,000mi is all stock and has never been cracked open for major work. So a bore and rebuild would be fairly cost effective, but on the other hand.... a bit more get up and go would be nice.
Does anyone have any opinions on the advantages vs. disadvantages would be...... for example... cost, mpg, complications during swap etc....
I currently get about 15 to 17 mpg. What could I expect with a 350cid or
383cid?
I definately want to keep the truck for a while, it has never been wrecked, never bumped....(with the exception of 3 door dings about the size of a dime) and has absolutely no rust in it anywhere. Everything in it works with the exception of the oil pressure gauge, which I believe to be a bad sending unit. I am only the second owner with all paperwork.
Wrong, wrong, wrong and wrong. He will get better MPG fugures with the 350 as it'll take less pedal to get it up to speed. Cooling systems between 305 and 350 are identical. Transmissions are identical. Springs are identical (engines weigh the same). Steering is identical. Ignition system is identical. Will need bigger fuel injectors and a new PROM for the ECM, that's it.
Doesn't need a bigger rad and/or bigger AT cooler.
Wrong and wrong. See above for explanation.
Stick to what you know, bitching about drum brakes on a truck you don't even own.
I would definately trash the 305 and go with a Goodwrench 350 crate motor. The only mods needed are replacing the computer chip and injectors with ones designed for a 350 (just buy a hypertech chip... it will give you even a little more power).
I would stay away from the 383 conversion... TBI units are almost impossible to do non-stock mods on.
As far as gas mileage goes, you won't see too much of a difference with the 350. It'll drop a little, but not more than 1 MPG unless you hot-rod it (which you will be tempted to do since you are used to the dog-305 that's in it now).
305 and 350 weigh the same, use the same radiators (for the most part, unless it's a 2500 or 3500, then they usually have 4 core radiators) and there is NO difference in the fuel, steering and ignition system between trucks with 305's and 350's. Like I said in another post, the only things that need to be changed are the injectors and the computer chip.
305 to 350 swaps usually yeild less than 1 MPG decrease, at least in the 5 or 6 that I have done on various vehicles.
I swapped a 305 out of my old '89 C1500 and replaced it with a used
350 of the same vintage. MPG with the 305 was around 17-18 on the highway and 15-16 in town. with the 350 my MPG was 16-17 highway and
14-15 in town. The extra power was DEFINATELY worth the cost of 1 MPG.
I only said that a larger motor _might not_ be compatible with the current setup. The original poster also asked about putting in a "383cid" motor, which would probably necessitate some major changes. I don't think that motor was available in 1988 Chevrolet trucks.
Are you sure that the transmissions are identical? The original poster didn't mention what transmission his '88 K-1500 Sportside truck has. Is it a 5-SPD OD (MM5), a 3-SPD (MX1) or a 4-SPD (MX0)? I don't think that the 3-SPD (MX1) was available with the 350 in any configuration. But it was available on 117.5-in wheelbase C/K-1500 trucks with the 5.0L (305) motor. Would it be possible to mate a 350 motor to a 3-SPD (MX1) if there is no PROM for it?
Here are the 1990 EPA figures for the various motor/transmissions combinations. I believe that the figures were the same for 1988:
EPA's mileage figures are useless and never accurate... they don't even measure MPG on the tests... just tailpipe emissions. I wouldn't use them for anything other that comparison between cars. (you'll notice they don't even take into account what rear end or GVW package the truck has... BIG factor in REAL fuel mileage)
383 is simply a 350 block bored and stroked to 383 cubes. Weighs the same, looks the same, bolts up the same. All that would be needed would be bigger injectors and a custom PROM. Depending on how the engine is balanced (internal vs. external) he might need a new flexplate/flywheel and harmonic balancer.
If a transmission will bolt up to a 305, it'll bolt up to a 350, simple as that. Flywheel might have to be changed, but the bellhousing bolt pattern is the same, which is the important part. If it's a standard transmission the PROM doesn't care what transmission it is, simply relying on the VSS signal to determine vehicle speed, so yes, he could retain use of the ECM so long as the PROM is calibrated for a 350 CID motor.
You poor bugger, when are you going to realize that you shouldn't believe everything you read. EPA "estimates" are based on tailpipe emissions, not a real-life road test.
I was unaware of the tailpipe measurements. According to the EPA site, this is how the tests are done:
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How are fuel economy estimates obtained?
The fuel economy estimates are based on results of tests required by the U.S. Environmental Protection Agency (EPA). These tests are used to certify that vehicles meet the Federal emissions and fuel economy standards. Manufacturers test pre-production prototypes of the new vehicle models and submit the test results to EPA. EPA re-tests about
10% of vehicle models to confirm manufacturer's results. The vehicles are driven by a professional driver under controlled laboratory conditions, on an instrument similar to a treadmill. These procedures ensure that each vehicle is tested under identical conditions; therefore, the results can be compared with confidence.
There are two different fuel economy estimates for each vehicle in the Fuel Economy Guide, one for city driving and one for highway driving. To generate these two estimates, separate tests are used to represent typical everyday driving in a city and in a rural setting. Two kinds of engine starts are used: the cold start, which is similar to starting a car in the morning after it has been parked all night; and the hot start, similar to restarting a vehicle after it has been warmed up, driven, and stopped for a short time.
The test used to determine the city fuel economy estimate simulates an
11-mile, stop-and-go trip with an average speed of 20 miles per hour (mph). The trip takes 31 minutes and has 23 stops. About 18 percent of the time is spent idling, as in waiting at traffic lights or in rush hour traffic. The maximum speed is 56 mph. The engine is initially started after being parked overnight. Vehicles are tested at 68 F to 86 F ambient temperature.
The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test).
NOTE: To make the numbers in the Fuel Economy Guide more useful for consumers, EPA adjusts these laboratory test results to account for the difference between controlled laboratory conditions and actual driving on the road. The laboratory fuel economy results are adjusted downward to arrive at the estimates in the Fuel Economy Guide and on the labels seen on new cars, light trucks, and vans. The city estimate is lowered by 10% and the highway estimate by 22% from the laboratory test results. Experience has proven that these adjustments make the mileage estimates in the Fuel Economy Guide correspond more closely to the actual fuel economy realized by the average driver.
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