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Head Gasket Replacement with valve job: $500 up
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Most all engines have two major components: the engine block and the cylinder head. The block contains the crankshaft and the pistons. The pistons go up and down in the cylinders, which are a part of the block. The top of the cylinders is covered by the CYLINDER HEAD. This is ths other "major part" of an engine.

Although there are exceptions, (mostly in older engines), most engines have the valves in the cylinder head. These are called "overhead valve engines." The intake valves open to admit the fuel air mixture into the cylinder. The exhaust valves open to let the exhaust gasses out. All four cycle engines have at least two valves per cylinder. Some engines have more valves per cylinder to increase power and efficiency. Many newer engines have 3 or 4 valves per cylinder.

Most engines have a gasket sealing the head to the block, called the HEAD GASKET. It must seal in the extreme high pressure in the cylinder as the engine runs. On a water cooled engine it must also seal the coolant passages between the block and the head. There is also usually one or more oil passages sealed by the head gasket. These passages supply oil to the valves and valve mechanism in the head.

Heads give trouble in two basic ways: valves can stop sealing (burned or sticking) and head gaskets can fail.

In the case of a burned valve, the cylinder will no longer fire. If it's a burned intake valve, the engine will backfire through the intake manifold. A burned exhaust valve is less noticeable. The exhaust sometimes will have a "putt-putt" sound to it. An old trick is to hold a dollar bill so it flaps over the exhaust pipe: if the bill gets "sucked in" every so often it can be a burned exhaust valve. A compression test or leakdown test will tell you if you have a bad valve.

Normally head gasket failure is from overheating. Often a engine will blow a hose or water pump and overheat. Several months later the head gasket will fail. Of course if you get an engine hot enough the head gasket will fail immediately.

Head gaskets commonly fail in two ways: a combustion leak between two cylinders or a combustion leak into the water jacket (cooling system). If a compression test shows two cylinders with low but equal compression, and the two cylinders are next to each other, the gasket is probably blown between those cylinders. If you have bubbles blowing out of your radiator or coolant recovery tank (the plastic tank usually on the fender that has a cap saying "engine coolant" on it) the head gasket has probably failed between a cylinder and a passage in the water jacket.

To repair any of these problems requires removing the cylinder head. To do it right, I send the head to an auto machine shop. If the gasket is blown, I have them pressure test the head to make sure it is not cracked. If it tests good I will have them do a valve job on it while it is off. This involves resurfacing the valves and the valve seats and brings the head back to a "like new" condition. They will also resurface the head, providing a smooth surface for the new head gasket.

If a valve is burned but the head gasket was still good the pressure test is unnecessary: the head just needs the valve job.

The pictures below show a 350 Chevrolet V-8 head and gaskets. This head gasket failed between two cylinders. The customer complained of lack of power along with pinging (spark knock) . When I checked the compression I found two adjacent cylinders with 60 pounds of compression. The other cylinders had 150 pounds of compression. Incidently, I had put a water pump on that vehicle about 3 months before I did this work!

DON'T LET YOUR ENGINE GET HOT: WATCH YOUR GAGES AND STOP... OR ELSE!!!




Here are some more images of Auto and Truck cylinder heads


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Thank you for visiting the ECONOMECHANIX WEB SITE. Please feel free to comment. We also serve the surrounding communities of Alachua, High Springs, Hawthorne, and Newberry! Gainesville has been my home since 1974, and I've loved Gvl and the Gators since I came here in the fall of 1974 to attend the University of Florida. I loved it so much I stayed and opened my car repair business. Originally it was out of the back of a 1963 Chevrolet wagon, but in 1977 a fellow mechanic and I opened an auto repair shop with actual walls, etc. I stayed in the same location for 26 years, and recently moved my operation to property I bought 15 miles east of Gainesville. I am doing most all the repairs myself now, having reduced my overhead from $1500 per month to practically nothing. I do work by appointment only. I mostly work only on my established customers cars, but I will occasionally take on new clients. E-mail me and I will either make arrangements to look at your car, or I will recommend you to someone who will.

George G. Scott, Jr.


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Auto, Car, and Truck Article List

A
ABS: Anti-Lock Brake Systems
ADVANCE: Car ignition timing
ALTERNATORS and Car Battery
AUTOMATIC TRANSMISSIONS
B
BAD CAR DESIGNS
BATTERIES: Auto, Car or Truck
BELTS AND HOSES
BEARINGS
BODY AND BUMPER REPAIRS
BRAKE REPAIRS: Car or Truck
C
Car Washing and Care
CARBURETORS:Car & Truck
CHECK ENGINE LIGHT
CLEANING: Engine Cleaning
CLUTCH REPAIRS: Car & Truck
COMPRESSION: Car Engine
COMPUTER CAR CONTROLS
CV JOINT OR CV AXLES
D
DISTRIBUTORS (IGNITION)
E
ELECTRIC WIRING REPAIR
ENGINES: Car & Truck
ENGINE CLEANING
EXPANSION PLUGS
F
FREEZE PLUGS
FUEL AIR MIXTURE
FUEL INJECTION: Car & Truck
FUEL PUMPS: Car & Truck
G
GAGES AND "IDIOT LIGHTS"
GASKETS AND SEALS
GLASS: WINDOWS AND WINDSHIELDS
H
HEADS & HEAD GASKET
HOSES AND BELTS
I
"IDIOT LIGHTS" AND GAGES
IGNITION TIMING: Car & Truck
J
AUTO JACKS: lifting cars safely
K
L
LEAN "Car runs lean"
LIGHTS: WARNING OR "IDIOT LIGHTS"
Limp Home Mode
M
MIL Light
MANUAL TRANSMISSIONS
N
NO START: Car Won't Start
O
OIL CHANGES
OIL: What's right for your car?
OIL LIGHT ON OR GAGE LOW
P
PCV Valve
Q
R
RADIATORS: Car and Truck
RICH: Car runs rich
S
SEALS AND GASKETS
SERVICE ENGINE SOON LIGHT
SPARK PLUGS
STARTERS: Auto, Truck
T
THERMOSTATS
TIMING: IGNITION TIMING
TIMING BELT & TIMING CHAIN
TIRE REPAIR
TRANSMISSIONS: AUTOMATIC
TRANSMISSIONS: MANUAL
U
V
VACUUM ADVANCE
WARNING LIGHTS OR "IDIOT LIGHTS"
Car Washing and Care
W
WATER PUMP REPAIR
WINDOWS AND WINDSHIELDS
WIRING REPAIR
X
Y
Z

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