Highway & Heavy Parts Answers Your Diesel Engine Questions: Rebuild Kits


customer q and a month | Highway & Heavy Parts


Everyday we receive questions from you, the customer, through email, social media, and from calls into our sales department.

It's difficult to answer everyone's questions that come in, so this month, we're answering a number of those questions about fuel injectors, turbochargers, and fuel systems. 

But today, we're focusing in on rebuild kits! We've got a list of five questions we here a lot about rebuild kits, and in this post we'll take you through the answers to them. 

You can also check out our video for more information on rebuild kits:



Do you have questions about your diesel engine? We have ASE Certified Technicians on-staff who can help you out!

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Diesel Engine Rebuild Kit Customer Questions

We get questions about rebuild kits all the time. What is the right one for my engine? How do I know if it's the right time to rebuild? Here are answers to a few of the questions we see a lot:


What is the profitability of rebuilding a diesel engine versus buying a new remanned diesel engine? 

In the end, you're going to be surprised at the cost that you'll run into when you purchase a complete reman engine, as well as the amount of work that's going to come along with that. Swapping a lot of your parts over from your current engine to a long block—bell housing, all your brackets, sometimes fuel system components.

Even worst case scenario, if you have to take your engine out of the truck and machine your block and put a crank in it, I think you're going to be further ahead rebuilding your own engine. One, it's going to be significantly less money. Good quality parts are out there available to rebuild that engine.

It's also going to be something that you know exactly what you're getting. When you buy a reman engine from the OEM, a lot of times you don't necessarily know what you're getting in that engine. Are you getting a crank that's been turned a couple of times? You better believe that everything in it is going to be a remanufactured product. 

So, it's likely going to be cheaper to do your engine yourself, and you're going to know exactly what you got with it when you're done.


Do the piston rings in your rebuild kits come with "pre-set" end-gaps?

Yes, the rings are pre-sized.

Now, of course, you want to check the ring end gaps, and if you have special needs with your particular engine, certainly, check and make sure they're within specification. But, yes, the rings should come pre-gapped. 


When do I know it's time to rebuild my diesel engine? 

You know, typically, with Class 8 diesel engines, you're looking for somewhere between 700,000 and  one million miles. Unless, of course, you get into a situation where maybe you had coolant in your oil, or oil contamination of some sort.

Indicators that you may need to go into your engine include dust, dirt, and debris coming through your air cleaner, low power, smoke, blow-by, and knocking sounds. And if it's anything over 500,000-600,000 miles, and you have to go into it for one of those symptoms, it would be best to explore the opportunities of an overhaul kit. Then you can just take care of it while you're in there working on that engine. 

Think your engine may need a rebuild? Take a look at these common signs that it might be time to rebuild your diesel engine.


What's the difference between inframe and overhaul kits? How do I know which one I need?


inframe out of frame rebuild kits | Highway & Heavy Parts


The difference between an inframe and an overhaul is essentially just gaskets. Both kits are going to come with pistons and rings and liners and bearings. The inframe kit is going to come with a head gasket set and a pan gasket. The overhaul kit is going to come with a complete engine gasket set. The things that don't come in the in-frame are going to be front cover gaskets, bell housing gaskets, front crank seal, rear crank seal, and oil cooler gaskets.

So, a complete engine gasket set comes in an out-of-frame or over haul, and a head gasket and pan gasket come in an inframe.

Want to know more? Check out our article on how to choose a rebuild kit for your engine.


What's the difference between the C15 and C15 ACERT engine rebuild kits? Can you rebuild a C15 engine with a C15 ACERT rebuild kit? 

So, the C15 and C15 ACERT are going to be different engines altogether, as far as the rebuild kit goes. The only thing they really share is the name.

The pistons on an ACERT are a one piece forged steel piston. The pistons on a C15, 6NZ or MBN are going to be a two-piece piston,  with a steel crown and an aluminum skirt. They have different connecting rods and different crank shafts. So, it isn't really feasible to rebuild your C15, 6NZ or MBN with an ACERT kit. You'll have to change a lot of components, so that's not a really good swap that way. The C15 ACERT definitely has more durable pistons, heavier connecting rods, and larger rod bearing journals, so it's just altogether a stronger bottom end than the standard C15.

Are you having problems with your C15 ACERT? Check out our post to learn when it's time for a rebuild kit for your C15 ACERT diesel engine. 


If you have any further questions about rebuild kits from any major OEM, be sure to give us a call, or reach out to us through social media or our website. 


Still have questions about rebuild kits? Our ASE Certified Technicians can help you solve your diesel engine problems. Give us a call at 844-304-7688, or request a quote online