4A-GE Big Port Specs


Final Torquing of 5S-FE Head Bolts



Cylinder compression
@ 250 rpm		 STD
Limit
Difference between cylinders		 179 psi
>142 psi
< 14 psi
Cylinder compression Stock Big Port with TVIS 9.6:1
Cylinder head warpage Cylinder block side Limit
Intake manifold side Limit
Exhaust manifold side Limit 		0.002"
0.002"
0.0039"
Valve seats Refacing angle
Contacting angle
Contacting width 		30°, 45°, 60°
45°
0.039-0.055"
Valves Overall length STD intake
exhaust
Limit intake
exhaust
Valve face angle
Stem diameter intake
exhaust
Stem oil clearance STD intake
exhaust
Limit intake
exhaust
Margin thickness STD
Limit 		3.9213"
3.9272"
3.9016"
3.9075"
44.5°
0.2350-0.2356"
0.2348-0.2354"
0.0010-0.0024"
0.0012-0.0026"
0.0031"
0.0039"
0.031-0.047"
0.020"
Valve guide bushings Inside diameter
Outside diameter STD
Outside diameter O/S 0.05 		0.2366-0.2374"
0.4344-0.4347"
0.4363-0.4368"
Valve springs Free length
Installed tension @ 1.366" STD
Limit
Squareness limit 		1.6177"
35.9 lbs
32.2 lbs
0.071"
Valve lifters Lifter diameter
Cylinder head lifter bore diameter
Oil clearance STD
Limit 		1.1014-1.1018"
1.1024-1.1032"
0.0005-0.0018"
0.0039"
Manifolds Warpage intake manifold limit
Exhaust manifold limit 		0.0020"
0.0118"
Camshafts Thrust clearance STD
Limit
Journal oil clearance STD
Limit
Journal diameter
Circle runout limit
Cam lobe height STD
Limit
Stock duration
Stock lift 		0.0031-0.0075"
0.0118"
0.0014-0.0028"
0.0039"
1.0610-1.0616"
0.0016"
1.3823-1.3980"
1.3862"
204° @ 0.050"
7.52mm
Cylinder block Cylinder head surface warpage limit
Cylinder bore diameter STD
Limit STD
O/S 0.020 		0.0020"
3.1890-3.1902"
3.1980"
3.2177"
Piston and rings Piston diameter STD
O/S 0.50
Piston oil clearance
Piston ring groove clearance #1
#2
Piston ring end gap STD #1
#2
Oil
Limit #1
#2
Oil		 3.1846-3.1858"
3.2043-3.2055"
0.0039-0.0047"
0.0016-0.0031"
0.0012-0.0028"
0.0098-0.0185"
0.0079-0.0165"
0.0059-0.0205"
0.0421"
0.0402"
0.0441"
Connecting rods Thrust clearance STD
Limit
Rod oil clearance STD
U/S 0.25
Limit
Bearing center wall thickness STD #1
#2
#3
U/S 0.25
Bent limit per 3.94"
Twist limit per 3.94"
Bushing inside diameter
Piston pin diameter
Piston pin oil clearance STD
Limit 		0.0059-0.0098"
0.0118"
0.0008-0.0020"
0.0007-0.0029"
0.0031"
0.0585-0.0587"
0.0587-0.0588"
0.0588-0.0590"
0.0633-0.0635"
0.0012"
0.0020"
0.7879-0.7883"
0.7876-0.7880
0.0002-0.0003"
0.0020"
Crankshaft Thrust clearance STD
Limit
Thrust washer thickness STD
Main journal oil clearance STD
U/S 0.25
Limit
Main journal diameter STD
U/S 0.25
Bearing center wall thickness STD #1
#2
#3
#4
#5
U/S 0.25
Crank pin diameter STD
U/S 0.25
Circle runout limit
Main journal taper & out-of-round limit
Crank pin taper & out-of-round limit 		0.0008-0.0087"
0.0118"
0.0961-0.0980"
0.0006-0.0013"
0.0005-0.0021"
0.0039"
1.8891-1.8898"
1.8797-1.8801"
0.0788-0.0789"
0.0789-0.0791
0.0791-0.0792"
0.0792-0.0793"
0.0793-0.0794"
0.0835-0.0837"
1.6529-1.6535"
1.6435-1.6439"
0.0024"
0.0008"
0.0008"


    Some tips...:
  1. When using aftermarket, high quality piston rings, ALWAYS follow the included instructions to the letter. Most manufacturers will specify the grit and pattern to be used when honing your cylinder walls. Also, most manufacturers will tell you to follow your service manual's piston ring arrangement for OEM-type rings--listen to 'em! Otherwise, you'll just throw away your big-buck rings because they won't seat properly.
  2. On a freshly rebuilt motor, use high quality 20W-50 mineral-based oil to break in the rings. Crank the motor ( with the ignition/spark plugs and fuel injectors disconnected) until you see the oil pressure gauge rise. Connect the ignition and fuel systems, then start her up. Run the engine at a varying 2000-3000 rpm for at least 30 minutes. You may see nasty grey-blue exhaust smoke for the first minute, but don't worry--this may be normal. If you assembled the motor correctly (and depending on what kind of piston rings you're running), the rings should seat after 10-15 minutes and sometimes as quickly as a few minutes. Shut down the motor after the alotted time, change the oil and oil filter (careful, it's hot!), refill with new mineral-based 20W-50 oil and you're ready to rack up the miles gently!
  3. After the rings have seated and the engine has cooled down all the way, retorque the head bolts (or nuts, if you're using studs). I like letting the motor cool down overnight. A blown head gasket would suck after all of your hard work, wouldn't it?
  4. I like to change the oil after a fresh rebuild when no more than 500 miles have gone by. If you're really anal about how your engine's progressing through its break in, you can always send a small sample of your oil to some specialist laboratories for analysis.
  5. Let the engine warm up a little bit before you drive off in the morning. I usually start driving when the engine's cold idle goes down to about 1500 rpm or so. Drive gently and your engine will thank you for it.
  6. Don't zing the engine to redline right away. With every 500 miles or so that passes, increase your "theoretical" redline little by little. That way, the new engine components develop a nice, smooth-going relationship, rather than forcing them to get along like a pitbull and rottweiler who are fighting for some territory.
  7. Keep an eye out for the litte leaks that'll inevitably pop up.

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