Tech / Tech Articles

Time to Rebuild (Part 1)? 7 Ways to Tell if Your Engine Needs a Rebuild Without Doing a Complete Teardown

Engine rebuilds come in many different varieties.

Take a look at the vast array of engine rebuild kits available through Summit Racing, and you’ll see the contents vary from kit to kit. Some include things like gaskets, bearings, and piston rings. Others are more comprehensive and also come with pistons, timing set, and a camshaft. The bottom line is, the extent of the rebuild — and the rebuild kit required —depends on the condition of the engine internals and your plans for the engine. For example, if you’re plucking a used engine from the junkyard and plan to use it for a performance build-up, you might consider a complete rebuild with machine work. On the other hand, if your existing engine is encountering problems, you may only need a few pieces to get it running right again.

The key is understanding the problem areas and how to fix them.

Some obvious signs of a rebuild candidate are power loss, poor fuel mileage, and excessive oil consumption. Fortunately, there are a few ways to narrow down where your problem(s) lies without doing a complete teardown of your engine. You may need a massive rebuild. You may need to replace one set of components. Here are some ways to find out:

Check Your Oil — and Oil Pressure

Excessive oil consumption and low oil pressure are not only a signs of trouble, they’re also hints as to where the problem is located. These problems are typically linked to the clearances between the parts within your engine. As the parts wear, the clearances increase, allowing oil to escape into your engine where it is burned off. This typically shows up as a bluish smoke emanating from your exhaust.

The usual suspects for excessive oil consumption and low oil pressure include broken piston rings, worn valve guides, and worn bearings.

Listen to Your Engine

Those odd sounds coming from your engine can foretell problems.

More importantly for you, they can provide clues as to where the problems exist. For example, a broken piston ring will make a rattling noise. Excessive clearance between the piston and cylinder bore will sound more like a knock. A chatter at half engine speed is the telltale sign of valvetrain-related issues.

Grab an automotive stethoscope and get in tune with the health of your engine.

See our original post on engine noise for more information.

 

Look at Your Spark Plugs

Your spark plugs say a lot about your engine’s performance.

Reading your spark plugs is a good way to tune your engine, adjust the air/fuel mixture, and check for detonation. And if the plugs have wet black deposits on the threaded portion and plug insulator, they may be telling you it’s time to replace worn out piston rings or intake valve guides. In this instance, the wet deposits are caused by oil entering the combustion chamber.

 

Check the Compression

Along with oil consumption, loss of compression is a top indicator of internal engine problems. This could include a blown head gasket, worn pistons rings, worn cylinder bore, cracked cylinder head, or burnt exhaust valves.

So how do you narrow it down further?

There are a couple of ways:

Leakdown-Tester-05-1600x1200Compression Testing: Using a compression gauge, you can do comparative testing of an engine’s cylinders. The pressures between the cylinders shouldn’t vary greatly. For example, in HP Books’ How to Rebuild Small Block Ford Engines, author Tom Monroe suggests the lowest pressure shouldn’t vary from the highest pressure among the cylinders by more than 75 percent. If pressure in one or more of the cylinders differs by more, try adding a tablespoon of oil to the bad cylinders. If this causes the pressure to increase, the rings and bore are at fault, and you’ll need to rebuild.

Leakdown Testing: A leakdown tester is a more comprehensive way to test your engine’s condition. Typically, if a leakdown tester finds an engine leaks 20 percent of the test pressure (applied by leakdown tester), the problem is a broken piston ring, burnt valve, blown head gasket, or cracked cylinder head or cylinder wall.

Examine Your Coolant

If you suspect a blown head gasket, examine your coolant.

If there is an unusual amount of coolant loss from your radiator, it’s a sign that cylinder pressure is leaking into your cooling system. Carefully remove the radiator cap and look at the coolant surface with the radiator warmed up. If you see bubbles, that means cylinder pressure is leaking into your cooling system. If you detect a gasoline or exhaust smell within the coolant, you probably have a blown head gasket on your hands. There are also Combustion Leak Detection kits available to aid in realizing that hard-to-find blown head gasket!

 

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Look at Your Valves

If you’ve found compression loss and eliminated your head gaskets and pistons rings as the cause, turn your attention to your valves. Burnt exhaust valves or sticky valves (won’t close) will prevent a combustion chamber from fully sealing, causing a loss in compression. Remove your valve covers and check to see if the valves are fully closed using calipers or dial indicator. If a fully closed valve leaks, it’s probably burned.

 

 

Perform a Cam Exam

Some rebuild kits also include a performance camshaft. This is because camshaft lobes wear over time, necessitating the need for a new camshaft. While you’re inspecting your engine, you may also want to check for camshaft lobe wear by double checking the lifts of each individual lobe. Camshafts usually experience wear on one lobe at a time, but you should replace the camshaft and lifters even if the wear is confined to a single lobe.

If you find cam lobe wear but haven’t noticed excessive oil consumption or compression loss, you can probably just replace your camshaft. However, if your engine is burning oil and compression is low on some cylinders, you’ll likely need a complete rebuild.

Using this guide, you may replace one or two components (ring and valve job) or do a complete rebuild with one of the many engine rebuild kits available. In our next installment, we’ll look at some tips for rebuilding your engine and provide some options for your project.

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10 Comments

  1. Randy Oehlert says:

    Sorry but I don’t agree with a couple of diagnosis and repairs.
    Low oil pressure, that should be explained more in detail, I’ve had a lot of guys worried about there oil pressure being to low after the engine has come up to normal operation temperature, ie. 20psi. at 650rpm idling jumps 40 to 50psi.with engine rpm.over 1500. There’s nothing there to worry about, also could be the oil,type & weight conditions and ambient temperatures, lot of people think they should be running 60 to 80 psi oil pressure, I have seen the lifters blown out of there port on SB Chevy engines because the person put in a high pressure /volume oil pump. I ask why did you need that type of oil pump? They have no idea,there buddy said they should.
    .ok why?
    Ok, enough on that subject only I’ve seen about as much damage to the engine from to much oil pressure as from low oil pressure.
    And you should never install a new camshaft without installing new lifters with the new camshaft, if it’s a pushrod engine i replace push rod’s and rockers, yes maybe that’s overkill ,maybe because I’ve been building only high performance.
    My engine builds may cost more than someone else’s, but if you don’t have time to do it right,when will you have time to do it over.
    That was put in my head by one of my professors in mechanical engineering and for some reason it’s stuck with me, hopefully I learned more than that.
    Well my 2 cents has turned into a dollar.
    I’ll shut up now. BTW I do enjoy reading pretty much everything on all cylinders puts out, I’ve shared your articles with several other people that now read on all cylinders.

  2. 80 PSI exiting from a small orifice can cut a “hole” or “groove” into the typical beer can materials used in today’s modern engine. OK………… “disagreement discussion” to begin in 4 – 3 -2- 1. Be gentle!

  3. Pingback: Time to Rebuild (Part 2): The Hows and Whys of Choosing an Engine Rebuild Kit - OnAllCylinders

  4. I appreciate you tip to listen to your engine when deciding whether or not your engine needs a rebuild or to be replaced. I didn’t realize there were specific noises that engines will make when a rebuild is better than a replacement. I also like what you said about looking at your engine’s spark plugs.

  5. My son has my husband’s old car from college and lately it has been having some problems and I wanted to look up if it needed specific repairs. It has been eating up oil faster than normal, and there has been some smoke when he turns it on sometimes as well. We should probably take it in and see if everything is ok with the piston rings and everything else. Thanks for the information!

  6. Ali Malgami says:

    Thanks for the information!
    I am interested in engine maintenance and looking forward more.

  7. Ken Burdick says:

    My oil pressure is 40-50 hot but I use 1 quart oil every 500 miles. I have blue smoke at idel and great oil pressure. Now what is my problem?

  8. Ray blocker says:

    My question when you rebuild 5.7 350 in a 97 Suburban is it all right just to rebuild the upper half only does that hurt anything or do you have to rebuild the whole if someone to give me an answer to this it would be great

    • If you havent had an oil change in a while drain your oil I use a little water bottle to catch some and check for flakes in every one of my engines if there’s flakes you need a bottom end rebuild if not you can just rebuild the top but dont go high performance top end and make a whole lot of horsepower and blame us for it eating a piston

  9. It all really depends on your maintenance routine for the engine. You can keep on replacing if you are not putting up quality. I always opt for ATL Diesel Inc. They are an online business which provides with quality engine kits and parts. I am attaching their website in case any of you wants. https://www.atldiesel.com/

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