: How to turn engine to TDC w/ plugs out



larryntripp
06-26-05, 01:10 AM
I've got my plugs out and am ready to air test my cylinders for a headgasket leak. I built a tool from bbobynski's instructions, but not sure how to turn the engine to get each cylinder to TDC. Suggestion was to use accessory belt, which I presume is the serpentine belt, but I couldn't budge it. Do I need to get a wrench on the bottom pully somehow to turn it? Its not very easy to get to. I got the impression from his response the engine should turn easily. What am I missing?

eldorado1
06-26-05, 01:56 AM
I've got my plugs out and am ready to air test my cylinders for a headgasket leak. I built a tool from bbobynski's instructions, but not sure how to turn the engine to get each cylinder to TDC. Suggestion was to use accessory belt, which I presume is the serpentine belt, but I couldn't budge it. Do I need to get a wrench on the bottom pully somehow to turn it? Its not very easy to get to. I got the impression from his response the engine should turn easily. What am I missing?

You're going to want a big wrench on there anyways to keep the engine from turning.... Yes, you need to get a wrench on the 'pulley' bolt. Don't worry about it backing out, it's in there tight, but don't put too much 'loosening' torque on it.

It would also help to remove the serpentine belt to make it easier to turn, although it should be pretty easy to turn already. It won't just 'flop over', it'll take a bit of effort, but less than your lugnuts take. ;)

Ranger
06-26-05, 02:58 AM
While someone is turning the engine with the wrench, drop a 12" long (or longer) 1/4" diameter dowl rod down the spark plug hole. It will rest on the piston and you then can see when it reaches TDC. If the cylinder does not pressurize, then you are TDC on exhaust stroke and you'll have to turn it again to TDC on compression stroke.

larryntripp
06-26-05, 10:09 AM
OK, great. Thanks. Now, how will I know if I have it on TDC exhaust as opposed to compression? I won't have a pressure gauge on the cylinder nor my compressor that will tell me. It sounds like I have only a 50/50 chance of getting the piston in the correct spot. Will I hear air out the exhaust? Not sure my little compressor generates enough air volume for that. Also, wouldn't there be a systematic sequence of which piston reaches TDC compression after the previoous? That way you could move from one to another in some sort of logical sequence, knowing the next TDC is compression after confirming the first one.

JimD
06-26-05, 11:24 AM
OK, great. Thanks. Now, how will I know if I have it on TDC exhaust as opposed to compression? I won't have a pressure gauge on the cylinder nor my compressor that will tell me. It sounds like I have only a 50/50 chance of getting the piston in the correct spot. Will I hear air out the exhaust? Not sure my little compressor generates enough air volume for that. Also, wouldn't there be a systematic sequence of which piston reaches TDC compression after the previoous? That way you could move from one to another in some sort of logical sequence, knowing the next TDC is compression after confirming the first one.

When you are at TDC with exhaust valves closed, you will know it because the combustion chamber will pressurize very quickly (small volume).

The logical sequence to follow is the firing order. Cast into the front of the right head.