Hi all. I have a 1987 Chevy Silverado half ton that I'm thinking about doing a diesel swap in. Apparently the cummins swap is a fairly popular engine swap when it comes to these old trucks, because of the fuel economy that you get with them. However, I still have a few questions so its probably best if I just number them.


1. Is the cummins diesel engine really my best bet? If there is one out there somewhere, that will grant even greater fuel economy than the Cummins, then I'd prefer to go with that one instead. Provided of course, that its obtainable to the average citizen. Obviously something like the rare TS4 isn't going to be an option. But if there is some kind of other diesel that would garner better fuel economy than the Cummins, I'm all ears.

2. If it turns out that the Cummins is indeed my best option, which Cummins should I go with? I know a lot of people will say to use the old 12 vavle, but it occurs to me that with modern technology, things tend to get better and better. The GM LS motors, for example. They far outdo the engines they replaced. Would I be better of going with a Cummins out of say... a wrecked 2010 truck? You'd get all the benefits of much newer technology that way, right? Or wrong? I mean it stands to reason that the much newer engine should be more efficient.

3. If it turns out that the 12v is actually the best one to go with, I'm fine with that. I'm just looking to find the very best one obtainable. However, there is one complaint that many of the 12v guys have, and that's with the noise. Apparently, they are pretty noisy motors. So is there a way to make them run a little more quiet? I was thinking of a flowmaster hushpower muffler, with sound deadening material under the hood, and in the cab. Thoughts? Opinions?


4. What are some good power mods for the old 12 valve? My knowledge of engines lies more in the gasoline side of things. Do they sell a better, aftermarket head for the 12 valve Cummins? Or do people just port and polish the factory one? Or do people even mess with the head at all? What about the exhaust manifold? Could a header help with flow? Most of the conversions I've seen don't really go into much performance. I'm really only interested in performance gains that won't negatively effect fuel economy. How about a bigger turbo? Or water-meth injection?

 

Nobody actually uses this forum, do they.

 

this forum doesn't seem to be as hot as it was a couple of years ago

the answer to your question if you are looking for the best mpg I have to lean to the cummins and the ve pump will get a bit better than the p pump but the ve pump makes a little less hp but is still a workhorse I have a 91 that has been attached to a trailer for years that's its job to pull and its bone stock no inter cooler

stay with the 12v this engine is a medium truck engine not a pickup engine like gm and ford have chosen to use

now remember one simple thing if you want more hp you will sacrifice fuel economy the newer ones have boosted hp up and that has made mpg suffer

 

it runs in cycles, diesel swap forums will be popular agian what fuel prices go up to the next "new normal" and when a new generation of dodges dash boards fall out and the truck are for sale cheap.

I agree with the 12v for a truck that size, thats what ive got in mine, main reason is its common in an automotive platform in dodges so you dont have to add all the extras like power steering and vaccum pump and ac etc, A 4bt would be great too but they cost more than the 6bt just because of supply and demand, but if you found one you could use all the 6bt stuff on it.

 

This statement is very untrue. On a gas motor yes but not a diesel. Upping the hp will make the truck move with less throttle, you will not be running high boost at fwy speed as compared to stock. Only time the extra fuel consumption comes into play is if you have your foot in it, drive normal and it will actually get better mileage than stock as the motor has more hp and does not need to work as hard.

 

This is going to start some arguments, no doubt, but newer/modern (especially electronics) hasn't been good to diesels IMO. Simple, long-lasting, reliable, economical, and powerful is what you get with a 12-valve cummins.

Your biggest challenge with your half-ton is making the suspension and drivetrain handle it. 3/4 or 1-ton stuff would be recommended. There is even an aftermarket cummins engine crossmember for Chevy 4x4s. There is something to be said for getting a whole cummins donor truck. I wouldn't worry about power mods till after because most are cheap/easy and can be done afterwards.

If this all sounds daunting, the 6.2/6.5 does very well in a light truck, and fits with very few mods.

 

I guess we disagree then maybe you should look at some specs first like fuel consumption it doesn't matter which company the more hp the engines make the less mpg they get

most likely because it is too easy to use the power what it boils down to is it takes fuel to make hp whether you use it or not is irrelevant

the best case is look at the mpg of the duramax as the hp increased the mpg went down when cummins started using more hp the mpgs went down also check your facts

 

I disagree also. On a turned up mechanical cummins you control the fuel rate with your right foot. Pure and simple. The reason is, with a diesel, you can put in a tiny bit of fuel, or a whole heckuva lot - because you are not managing a precise air/fuel ratio to ensure combustion.

Yes, the newer diesel make more power stock, but they are also under tighter emissions regulations. They actually burn more fuel at light-loads/no-load to keep temperatures up, thus reducing particulates and hydrocarbons. Power and emissions win over fuel economy