Intake valve discolored

[plyroadking]

I have been having a rough idle for awhile and finally bought another compression gauge, #2 came in at 60 while the rest were running around 130lbs, I pulled the head and the intake valve on #2 has a rainbow discoloration on top. I left my spring compressor in Iowa so can't pull the valve till it arrives here. I took a piece of paper and stuck it between the valve and the seat then turned the engine over till the valve closed and tried to pull the paper out. On one side it pulled out without tearing, so im assuming I have a warped valve?

[randroid]

plyroadking,

The rainbow coloring comes from excessive heat, which explains the warped valve, but what befuddles me is how that particular valve got warped while the others did not. I will let sharper minds than mine delve into that mystery because #2 is not particularly susceptible to overheating on its own.

-Randy

[TodFitch]

plyroadking,

The rainbow coloring comes from excessive heat, which explains the warped valve, but what befuddles me is how that particular valve got warped while the others did not. I will let sharper minds than mine delve into that mystery because #2 is not particularly susceptible to overheating on its own.

-Randy

Maybe it was adjusted too tight...

[Niel Hoback]

The hole in the water tube at that location was plugged? I'm going with too tight.

[Don Coatney]

Did you do a "wet" and dry compression test per the book?

[plyroadking]

Thanks for the replies! I read the page in the book but didn't notice any "wet or dry" procedure, I just pulled all the plugs and spun it over with the gauge connected. I doubt its a water delivery issue as the block was boiled out 2 months ago, and I've been running it in the car for 4 years with no problems. I took a closer look and #4 intake has a light discoloration also, I have a wolf whistle but I refrain from using it when it's cold outside, also my heat riser flap is froze in the open position. When you say adjusted "too tight" do you mean the clearance between the lifter and valve base?

[greg g]

read the "precaution with oil test section in the middle column.

If your heat riser will rotate, turn it as far as it will go clockwise and fasten it there. Usually an old vise grip will have enough weight to hold it open or you can use some mechanics wire to keep it in that position. That position will Close the intake manifold to exhaust flow.

[54Illinois]

Is it better for the heat riser to be closed all the time, or open all the time? Mine does not work correctly.

[Jerry Roberts]

Is it better for the heat riser to be closed all the time, or open all the time? Mine does not work correctly.

When describing the action of the heat riser , the terms open and closed mean different things to different people . Put it exactly as Greg described it in the above post .

Edited June 27, 2012 by Jerry Roberts