tips to finding tdc
Thread Starter
Junior Member
Joined: Jan 2009
Posts: 32
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From: Pinson, AL
tips to finding tdc
ok, i know there have been many posts about this left and right and i honestly have read everyone of them for advice and it seems like i cant ever get it right. so now i am looking to you guys for help again, but why wouldn't i y'all are some of the smartest third gen minds out there. the first 3 times I've tried it was spitting back through the carb and shooting fireballs, and the 2nd time i tried i put the piston just about level with the spark plug(just trying it out) and it was acting like it wanted to start. so i don't know anymore i need your help desperately, I'm loosing my mind here and i miss driving my car. the set up i have going i went from a 305 to a 350 gm crate. i just had to build the top end, many thanks for any advice.
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Joined: May 2002
Posts: 564
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From: loxahatchee fla
Re: tips to finding tdc
http://forum.grumpysperformance.com/...php?f=52&t=966
http://www.2quicknovas.com/2qntdc.html
http://forum.grumpysperformance.com/...ee+wheel#p1699
How does one go about finding top dead center on a Chevy V8? Follow along...
You can get close by pulling the #1 plug and placing your finger over the hole. Then crank the engine over and when the pressure builds up to its greatest, you know you are close to top dead center. This works well for determining if the motor is about to fire the #1 cylinder (vs. #6), but isn't accurate enough to find out if your balancer ring has slipped.
A much more accurate way is to use a piston stop and a degree wheel. Thread in a piston stop (can be made from an old spark plug and a bolt) into the #1 plug hole, fasten a degree wheel to the crank and make a rigid pointer to go with the degree wheel. Be sure the pointer is stiff and mounted solidly so that it won't move on you A wire coat hanger with a loop at the end bolted to the block or head works well.
Turn the motor until the piston lightly hits the stop (we don't want to damage the piston, so take it easy; if you make you own piston stop, make sure the end of the bolt is smooth with no sharp edges that could gouge the aluminum piston).
Write down the number the pointer is indicating on the degree wheel. Now rotate the engine back the other way until it lightly hits the stop again. Write this number down as well. TDC will be exactly halfway between the two numbers that you recorded. Remove the piston stop and rotate the motor to this "middle" number. Look at the timing mark and check to see if it's lined up with zero on the timing tab. If its off by a bunch, your balancer is toast. If its just off a degree or two, just make a new mark on the balancer that lines up with zero on the timing tab.
A good way to create your own mark is just to run a strip of masking tape across the wheel about 1/16" from TDC, then apply another strip 1/16" from TDC on the other side (so there's a 1/8" gap). Then just lightly spray or brush on a little white paint. When it dries, remove the tape, and you'll be left with a bright, durable timing mark at top dead center.
If the heads are off the engine, using a dial indicator is a very easy way of finding TDC (just rotate the assembly until the dial indicator, pointing at the #1 piston, reaches its highest reading), but not all of us have access to such equipment.
http://www.2quicknovas.com/2qntdc.html
http://forum.grumpysperformance.com/...ee+wheel#p1699
How does one go about finding top dead center on a Chevy V8? Follow along...
You can get close by pulling the #1 plug and placing your finger over the hole. Then crank the engine over and when the pressure builds up to its greatest, you know you are close to top dead center. This works well for determining if the motor is about to fire the #1 cylinder (vs. #6), but isn't accurate enough to find out if your balancer ring has slipped.
A much more accurate way is to use a piston stop and a degree wheel. Thread in a piston stop (can be made from an old spark plug and a bolt) into the #1 plug hole, fasten a degree wheel to the crank and make a rigid pointer to go with the degree wheel. Be sure the pointer is stiff and mounted solidly so that it won't move on you A wire coat hanger with a loop at the end bolted to the block or head works well.
Turn the motor until the piston lightly hits the stop (we don't want to damage the piston, so take it easy; if you make you own piston stop, make sure the end of the bolt is smooth with no sharp edges that could gouge the aluminum piston).
Write down the number the pointer is indicating on the degree wheel. Now rotate the engine back the other way until it lightly hits the stop again. Write this number down as well. TDC will be exactly halfway between the two numbers that you recorded. Remove the piston stop and rotate the motor to this "middle" number. Look at the timing mark and check to see if it's lined up with zero on the timing tab. If its off by a bunch, your balancer is toast. If its just off a degree or two, just make a new mark on the balancer that lines up with zero on the timing tab.
A good way to create your own mark is just to run a strip of masking tape across the wheel about 1/16" from TDC, then apply another strip 1/16" from TDC on the other side (so there's a 1/8" gap). Then just lightly spray or brush on a little white paint. When it dries, remove the tape, and you'll be left with a bright, durable timing mark at top dead center.
If the heads are off the engine, using a dial indicator is a very easy way of finding TDC (just rotate the assembly until the dial indicator, pointing at the #1 piston, reaches its highest reading), but not all of us have access to such equipment.
Joined: Feb 2002
Posts: 3,462
Likes: 4
From: N. Illinois
Car: 92 GTA/ 00 TA
Engine: 383/350
Transmission: 700R4/T-56
Re: tips to finding tdc
That is the most accurate way for determing the condition of the balancer.
For timing purposes I do the following:
Stick my finger over the hole to determine if i'm on compression.
Then remove my finger,
Put a pencil in the hole,
Turn crank until pencil stops moving.
That's TDC compression.
At this point you can also see if the balancer is at least in the ballpark.
For timing purposes I do the following:
Stick my finger over the hole to determine if i'm on compression.
Then remove my finger,
Put a pencil in the hole,
Turn crank until pencil stops moving.
That's TDC compression.
At this point you can also see if the balancer is at least in the ballpark.
Thread Starter
Junior Member
Joined: Jan 2009
Posts: 32
Likes: 0
From: Pinson, AL
Re: tips to finding tdc
thank you very much for the help i will try it and tell you what happens, and can i ask you a question is it easier to take out the distributor and find tdc or just leave it in? i ask because some body told me it is better to do it without so that you can point your rotor button pointing to #1
Last edited by zombiereaper205; Nov 4, 2009 at 09:49 AM.
Joined: Feb 2002
Posts: 3,462
Likes: 4
From: N. Illinois
Car: 92 GTA/ 00 TA
Engine: 383/350
Transmission: 700R4/T-56
Re: tips to finding tdc
Leave it in while you find TDC compression #1. This way you can see which post it's pointing at and if it was the actual problem.
Pull it out and move it around only if you have to. But remember, it can only go in 2 ways due to the slot in the oil pump drive shaft. You may end up having to spin that in order to get your distributor to point exactly where you want it to point.
Pull it out and move it around only if you have to. But remember, it can only go in 2 ways due to the slot in the oil pump drive shaft. You may end up having to spin that in order to get your distributor to point exactly where you want it to point.
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