jmX

For those doing spring swaps without an air compressor, what method did you use to figure out when a piston was TDC.

Did you stick a feeler in the spark plug hole? Did you set the crank so #1 was TDC and then rotate 90 degrees and do 2 more, then another 90 and 2 more, etc?

Just curious what everybodies tricks were. The info is going into my cam/spring writeup and I'm always looking for a new trick or idea

(BTW, I've usually used the air compressor method so I havent had to do this much)

Doug Tschantz

When we would do a CLT test in school we always took the spark plug out and layed a srewdriver or something that wouldn't damage the top of the piston just inside the head and cranked the motor over till we felt the piston reach TDC; kind of barbaric but it worked. I mean you know you have gone to far when you feel the piston start to fall again. Finding TDC on #1 and rotating 90* thereafter might be a little more civilized though!


Doug
00 Pontiac

jaywoo

Screwdriver trick for me.

felton316

Used my pinky finger and pulled it out before it gets squashed.

SmaknaSS

iTrader: (1)

I used the plastic staw from the WD-40 can. Dont drop the straw in the cylinder!

-Joseph-

iTrader: (12)

I sometimes don't pull the plugs if I'm not using air, or not replacing the plugs. The are 2 pistons at TDC every 90 degrees, so you can do 2 different (4 springs) cylinders valvesprings at the same time. So if I'm doing a camshaft at the same time, I would have the timing marks lined up together right after reinstalling the chain. With the timing gear marks together your at TDC firing position for #6 cylinder, not #1. It is the #1 beginning position for the 4 stroke engine cycle though (TDC right before intake stroke). Its amazing how many people do not know that!

When there you can do #1 and #6 cylinder valvesprings. Turn crankshaft 1/4 turn or 90 degrees and do #8 and #5. Turn crankshaft 1/4 turn do #7 and #4. Turn crankshaft 1/4 turn and do the remaining #3 and #2 cylinders.

If you do one more final 1/4 turn the engine will be at TDC #1 firing position and you can check your lifter preload in that exact spot for intake and exhaust.

Buckshot

I marked TDC on #1 piston while doing my h/c swap. I marked the pulley as pictured below with the heads still off and #1 piston at TDC. This way I can leave the intake manifold and front end motor components on. The other marks on the pulley indicate the 140 degrees I torqued the bolt to. Now, it's possible that the pulley may slip someday but the matching marks on the pulley and bolt would probably rotate relative to each other if that happened since the pulley is not keyed. I also can rotate the crank easily with a wrench without having to move the rack by using this modified socket I made.

robertbartsch

JMX:
I just forwarded you an e-mail that gives detailed instructions on how to do a spring change without using air to keep the springs up.

...basically you align the cam to TDC for #1, change the springs on it and then turn the crank a set number of degrees to the next pistion on the firing order....

As you know, if the piton is at the top, the valves can't fall down (much)....and you can change the springs

Cal

iTrader: (1)

I didn't use any air to change my springs last weekend. Here's how I did it:

1) Identify which is the exhaust and intake valve on a particular cylinder. (I looked down the intake port since I had the intake manifold off)

2) Turn the crank until the exhaust valve opens and then closes. Immediatly after the exhaust closes, the intake will start to open and you have TDC.

This valve train event is very distinctive and easy to identify because you can rock the crank back and forth and see the intake and exhaust bumping up and down like they were on a teeter-tooter. If you want the other TDC (combustion,) you can just rotate the crank exactly one turn from this point.

I did all 8 cylinders this way without a single mistake and saved myself the trouble of taking out the plugs or messing with air fittings.

BTW, I printed out your very fine write-ups on the heads & cam, YT rocker, and LS6 PCV installs and used them in the garage to check off each step along the way. I just crossed out the heads part since I didn't install heads. I'll try to email you with a list of small items you could add to what you have; one that comes to mind now is to have some black impact wrench style high-strength 8 mm sockets on hand for the rocker bolts.

Visceral

iTrader: (1)

I did it the same way that Doug notes on the LT1s. Every LS1 Ive done has had air around, so we've used the pressurized cyl method.

Buuut... I like Joseph's way with the timing marks alot. If you are doing a cam, the timing marks are in front of your nose.

In the future, I'll probably try that way, if it holds the valve high enough to easily get the keepers on with a well compressed spring. Trouble with the piston method on low CR cars is that sometimes the piston isnt high enough to hold the valve high enough to get the keepers in with the spring well compressed.

chris

jmX

Good tips everybody...sometimes I agree that since the valve does go down some to touch the piston, it can be hard to compress the spring enough and still get the locks out, but it seems to work for most of you guys so maybe it's not that bad.

This info will help the non-air compressor guys out a lot.

DaleMX

iTrader: (4)

Used a long 3/16's wood dowel to get close then used a flashlight and a mirror to spot the piston in the bore. Dirty piston top is hard to see, but the rings (grooves) on the top of the piston are easy enough to spot. I could have brought the piston up until it hit the dowel, then kept track of how many degrees of rotation it took to get to the top, but didn't think of it until I was done.

Using stock heads and had plenty of room for compression to get the keepers on.

Cal

iTrader: (1)

The valve does not have to drop very much to hit the piston if you really have it at TDC. It looked like about 1/8 inch to me. I had no problems compressing the springs enough, and I was using the cheap Napa tool!

Scalpel

iTrader: (4)

jMx, ya' need to do a write-up on this one, too

eallanboggs

iTrader: (1)

Next time you go to a Chinese resturant put the wooden chopsticks in you pocket when you finish eating. They work great for finding TDC. Just turn the crank over slowly.