I have one more question about my 1991 Chevrolet.

PILOTBILL

MEMBER
1991 CHEVROLET LUMINA
280,000 MILES

I have one more question about my 1991 Chevrolet Lumina 3.1 Liter V6 Engine. If I am correct, the big valve is the exhaust and the small valve is the intake. Is this correct? I also wish to thank HMAC300 for his helpful information on the STEP-BY-STEP valve adjustments (which I haven't done yet). Before I do the adjustments, I must be sure which valves are the exhaust and which valves are the intake. Thank you all again.

Sunday, October 28th, 2012 AT 8:14 PM

2 Replies

CARADIODOC

MECHANIC
34,364 POSTS

Intake valves are larger because barometric pressure, (engine vacuum), is all that makes the air go in. Exhaust valves don't have to be so large because pressure from the piston pushes the exhaust out. Intake valves are cooled by the air and fuel coming in. Exhaust valves have hot exhaust gases passing over them so they have to cool while they are seated by transferring the heat across the seat. With a smaller diameter, that heat has less distance to travel. That prevents the valve from melting and burning away.

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Sunday, October 28th, 2012 AT 8:28 PM