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I have located problems with the engine and have began repairs. The major problem was a bad temperature sending unit for the engine computer. The computer was sensing a cold condition and enriching the fuel delivery to compensate. The thermostat was also changed to the original design of 195 degree. The engine is performing better than when new and fuel economy is going up!
Next week I will be checking the operation of the O2 sensor. If it is measuring high O2 the computer could be enriching the fuel delivery to compensate.
The SBC Truck heads shown are originally from the "GM Truck engine Early 90's" project. I used the Truck to pull my 68 Camaro to the races last night. The engine is now very powerful and pulls the heavy enclosed trailer effortlessly. At 10:1 compression with no detonation, very impressive.
 Using a 1/16" ball end mill I cut the initial grooves with a die grinder mounted to a hand made fixture that is designed to cut a straight line. I cut them 0.040" deep because the deck is very thin, when deck thickness allows, I cut deeper (0.060" to 0.080"). I cut the initial grooves parallel with the deck surface. The groove finishing is done with a hand held hacksaw blade and a thin triangle file. I contour the bottom of the floor into the combustion chamber cavity and widen to groove to 0.125" at the cavity. The heads are casting number 14101083. Here are the specs I found for the heads: Cylinder head assembly used on 285 hp 350 engine (P/N 12353641). This cylinder head assembly includes 1.94" intake valves, 1.50" exhaust valves, valve springs (P/N 3901068) and valve spring caps (P/N 14003978). This cylinder head has 64cc chambers. The cast number for this head is P/N 14101083 or 14096217. This cylinder head has 1987 and later intake manifold bolt pattern. The center two bolts are at a 72º angle.
 The information I found on the pistons show a 10cc dish.  With this information I calculated the compression ratio, the results follow... Production engine estimate: Cylinder Head Volume (cc) 64 Piston Head Volume (cc) 10 Gasket Thickness (in.) 0.040 Gasket Bore (in.) 4.166 Cylinder Bore Diameter (in.) 4.0 Deck Clearance (in.) 0.030 Stroke (in.) 3.48 STATIC COMPRESSION RATIO 9.0:1 **************************************************************** After the valves and springs were removed, the heads were delivered to the machine shop for milling. A cut of 0.050" was made to raise the compression. If the heads were installed with compression raised with out the grooves it's likely the engine would suffer from detonation. The grooves will provide needed turbulence to allow the modified engine to run on regular pump gas with raised compression. Both the grooves and the higher compression combine to improve combustion and thermal efficiency.  The gasket was used as a reference to determine where to end the groove, cut too far and you could interfere with gasket seal. 
With the grooves completed I cc'ed the heads to get information to recalculate the compression ratio. Because the dished pistions provide limited squish area the decision was made to subsutite a thinner head gasket to achive the desired compression ratio. This will reduce the squish clearance to 0.056".
Modified engine estimate:
Cylinder Head Volume (cc) 58
Piston Head Volume (cc) 10
Gasket Thickness (in.) 0.026
Gasket Bore (in.) 4.166
Cylinder Bore Diameter (in.) 4.0
Deck Clearance (in.) 0.030
Stroke (in.) 3.48
STATIC COMPRESSION RATIO 9.96
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Written by suburbanman on 2007-09-12 09:42:42
found heads casting #14102193) i will be grouving my 1994 suburban heads .Questionhow wide did you made your initial grouve in your project ( not mention ) | Written by TomSimon on 2007-03-13 14:48:28
The picture of the suburban looks like it was taken at Sacramento Racway, Was it? |
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