Question about rebuilding engine

setherek · 09-20-2002, 01:15 AM

I was just wondering how much it would take for a rebuilt engine to regain all it's power when rebuilt. Because I had my engine rebuilt and they told me to take it back after 500 miles so they can make some adjustments so it could regain all it's power. The thing I noticed was that it has less power right now than it had before I rebuilt it, is this normal? Thanks in advance.

jim_howard_pdx · 09-21-2002, 01:04 PM

Having built alot of engines, this is what I suppose your shop meant.

First, after 500 miles you need to drain the oil and replace the oil filter. I usually do the first 200 miles with NON DETERGENT OIL and then change the oil at 500, and 1,200 miles. I will often use the best possible filters during this time to catch the bad stuff that can damage the bearings and I ALWAYS USE A MAGNET TYPE OIL PAN BOLT. You will not believe how much metal you pick up on the first 6 oil changes. I don't care how carefully you clean the block and heads. The amount of metal is frightening.

Second, they will probably kick up the engine's ignition timing. Many shops will run a new engine at 2-4 degrees advanced, and then bump it up to 6-10 degrees after initial break in.

Third, they might have disengaged the vacume advance on the distributor, or limited it. This will give you more power when returned to optimum settings.

Fourth, if you have a 4 barrel carb, they may have disengaged or limited the amount of secondary throttle opening. Returning this to optimum will give you maximum power.

Fourth, they will adjust the carburetor for maximum performance.

Some thoughts....

When we rebuild engines, we typically bore the cylinders and fine hone each bore to exactly match the replacement pistons. On a race engine, we will measure each piston individually, index it, and use a torque plate to simulate the distortion caused by the head bolt torque. When we bore and hone this way we make the best optimum cylinder possible. This is not expensive, and I recommend it on ALL REBUILDS.

The final hone will be looser for a forged aluminum piston than a siliconized hypereutectic cast piston since the forged piston expands to a larger size under wide open throttle combustion temperature.

I will use a .006 hone on a forged piston and a .0025 to .004 hone on a silicate cast piston. I prefer to rebuild any engine of over 300 horse power with a quality forged piston. That way you can change cams and add a supercharger without breaking stuff.

The new rings require time to wear in order to seal properly to each bore. We make a hatch grid on the final hone to promote fast wearing during the first 500 miles. Standard iron rings require 200-1,000 miles to wear down to proper seal. A chrome moly ring will require 5,000 miles to wear down to proper seal. For this reason, we use a double or cross hatch on the final hone in order to make it wear as fast as possible.

When I rebuild engines I try to clean up the intake and exhaust ports of casting flash. I typically blend the port to the gaskets I am using on the intake and exhaust. I like to use 3 angle valve jobs and stainless steel valves. These are not expensive and really wake up the engine. I always use a modern camshaft from a manufacturer I trust. I experiment alot with cams. Basically I like to use BIG VALVES and POCKET PORTING with a mild street/strip cam. This will get you acceptable mileage and a big boost in overall performance. I do not like to use BIG CAMS on street engines since they require strict attention to proper head and intake work, a properly designed exhaust system, and proper rear end gear ratios and special stall converters if using an automatic transmission. This means alot of changes everywhere.

I hope this helps. Let me know how your rebuild works out. My Mustang is running 13.7 quarter miles at 105 miles per hour with 3.25 gears and an automatic with basically a factory stall converter. The car gets about 15 miles per gallon, and runs at nearly 400 horsepower. It is faster than most stock 428 CJ Mustangs and is a gas to drive. This is the type of balance between power and performance for a street and highway driven car.

Email me at jim_howard_pdx@yahoo.com if you have additional questions.

thunderbolt · 09-22-2002, 10:32 PM

I just wanted to say thanks Jim for a great reply. You really put some time into that and it was very good.

Rev · 09-22-2002, 10:41 PM

That was a good explanation of a "break in".

Rev

09-20-2002, 01:15 AM	#1
setherek Registered Member Join Date: Sep 2002 Posts: 3	Question about rebuilding engine I was just wondering how much it would take for a rebuilt engine to regain all it's power when rebuilt. Because I had my engine rebuilt and they told me to take it back after 500 miles so they can make some adjustments so it could regain all it's power. The thing I noticed was that it has less power right now than it had before I rebuilt it, is this normal? Thanks in advance.

09-21-2002, 01:04 PM	#2
jim_howard_pdx Registered Member Join Date: Apr 2002 Location: Portland Oregon Posts: 247	Rebuilt Engine Power Having built alot of engines, this is what I suppose your shop meant. First, after 500 miles you need to drain the oil and replace the oil filter. I usually do the first 200 miles with NON DETERGENT OIL and then change the oil at 500, and 1,200 miles. I will often use the best possible filters during this time to catch the bad stuff that can damage the bearings and I ALWAYS USE A MAGNET TYPE OIL PAN BOLT. You will not believe how much metal you pick up on the first 6 oil changes. I don't care how carefully you clean the block and heads. The amount of metal is frightening. Second, they will probably kick up the engine's ignition timing. Many shops will run a new engine at 2-4 degrees advanced, and then bump it up to 6-10 degrees after initial break in. Third, they might have disengaged the vacume advance on the distributor, or limited it. This will give you more power when returned to optimum settings. Fourth, if you have a 4 barrel carb, they may have disengaged or limited the amount of secondary throttle opening. Returning this to optimum will give you maximum power. Fourth, they will adjust the carburetor for maximum performance. Some thoughts.... When we rebuild engines, we typically bore the cylinders and fine hone each bore to exactly match the replacement pistons. On a race engine, we will measure each piston individually, index it, and use a torque plate to simulate the distortion caused by the head bolt torque. When we bore and hone this way we make the best optimum cylinder possible. This is not expensive, and I recommend it on ALL REBUILDS. The final hone will be looser for a forged aluminum piston than a siliconized hypereutectic cast piston since the forged piston expands to a larger size under wide open throttle combustion temperature. I will use a .006 hone on a forged piston and a .0025 to .004 hone on a silicate cast piston. I prefer to rebuild any engine of over 300 horse power with a quality forged piston. That way you can change cams and add a supercharger without breaking stuff. The new rings require time to wear in order to seal properly to each bore. We make a hatch grid on the final hone to promote fast wearing during the first 500 miles. Standard iron rings require 200-1,000 miles to wear down to proper seal. A chrome moly ring will require 5,000 miles to wear down to proper seal. For this reason, we use a double or cross hatch on the final hone in order to make it wear as fast as possible. When I rebuild engines I try to clean up the intake and exhaust ports of casting flash. I typically blend the port to the gaskets I am using on the intake and exhaust. I like to use 3 angle valve jobs and stainless steel valves. These are not expensive and really wake up the engine. I always use a modern camshaft from a manufacturer I trust. I experiment alot with cams. Basically I like to use BIG VALVES and POCKET PORTING with a mild street/strip cam. This will get you acceptable mileage and a big boost in overall performance. I do not like to use BIG CAMS on street engines since they require strict attention to proper head and intake work, a properly designed exhaust system, and proper rear end gear ratios and special stall converters if using an automatic transmission. This means alot of changes everywhere. I hope this helps. Let me know how your rebuild works out. My Mustang is running 13.7 quarter miles at 105 miles per hour with 3.25 gears and an automatic with basically a factory stall converter. The car gets about 15 miles per gallon, and runs at nearly 400 horsepower. It is faster than most stock 428 CJ Mustangs and is a gas to drive. This is the type of balance between power and performance for a street and highway driven car. Email me at jim_howard_pdx@yahoo.com if you have additional questions. __________________ 1966 Customized for daily street and highway domination. 358 Windsor running 425 HP C-4 Auto and 3.25 Posi

09-22-2002, 10:41 PM	#4
Rev Registered Member Join Date: Nov 1998 Location: Houston, Tx. Posts: 3,887	I agree That was a good explanation of a "break in". Rev __________________ '66 Coupe, 306, 350-375 HP, C-4, 13.07 e.t., 104.8 mph, 1/4 mi. O.B.C. #2 '66 coupe

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09-22-2002, 10:32 PM	#3
thunderbolt Registered Member Join Date: Oct 1998 Location: Houston, TX, USA Posts: 380	I just wanted to say thanks Jim for a great reply. You really put some time into that and it was very good.