Finding top dead center.

by BicknellWelding Sat Apr 27, 2013 6:19 pm

Ok, rookie question. I need to find top dead center in my brothers 87 monte. I pulled the stock distributor to install an Edelbrock intake and carb. What I didnt know was that the stock one is computer controlled, so I need to go with the older vacuum advance style. Correct me if I'm wrong....The #1 cylinder needs to be all the way up on a compression stroke? Also, when installing the new distributor, the rotor should face #1 ? I haven't had to do this in years, any help would be appreciated

by jerry46765 Sat Apr 27, 2013 7:01 pm

From another post:

Pull #1 spark plug out,
disconnect power from HEI,
hold your thumb over the #1 spark plug hole,
crank the engine until, you feel compression (piston coming up),
stop cranking,
pull distributor cap off and make sure rotor is right before #1 in the cap,
if not adjust it...

Install #1 plug, connect HEI power, start engine, enjoy...

by jerry46765 Sat Apr 27, 2013 7:05 pm

And no, at the end of the compression stroke is TDC.
You want to fire before TDC.

There are only so many teeth on the distributor gear.
You will know when you have it lined up.

by bracketchev1221 Mon Apr 29, 2013 12:02 pm

When you feel cylinder pressure, turning the engine by hand in the clockwise direction stop turning about 10 degrees BTDC. Then set the distributor so that the rotor lines up with number one on the cap. Even just a touch before to help it start.

by 77mali Sat Jul 06, 2013 3:45 pm

I worked on my motor today & decided to try & verify where TDC was since I've had some firing issues (among others LOL). I saved the little paper plugs the engine builder placed in the spark plug holes when painting the motor (so they'd pop out as the engine turned in each cylinder). When the paper plug in the #1 popped out on the compression stroke I noticed that the alignment mark on the harmonic damper & the corresponding "tab" on the rear main seal are @ 12:00.

Shouldn't the mark on the damper be close to the "0" on the metal timing tab @ TDC?

by driveit Sat Jul 06, 2013 3:50 pm

Do you have it on the correct stroke? Maybe you should make another revolution and check it. Seems like I remember I had to do something like that, but it was 2003 when I built my engine.

by 77mali Sat Jul 06, 2013 5:24 pm

It's at the top of the compression stroke, which is correct when lining up the Dist for an initial fire-up. I just thought it was a bit odd to be that far away from the tab. The cam & timing gear are set @ zero which means it's not set at either 4 degrees before or after TDC. I'm about to tear it down & sell the parts...there's a nice 2 bbl 350 for sale near me for $350.00 Laughing

by pila Sat Jul 06, 2013 9:36 pm

Depending on how fussy you are about checking for TDC, a piston stop in #1 spark plug hole, on compression stroke, will stop the piston a bit down in the hole. Mark the balancer. Then rotate engine the other way ( backwards) until piston stops again, against the stop.
Mark the balancer again. Halfway between the marks you made is is TDC. You will also know if the outer ring on the balancer hasn't slipped etc. if it doesn't read TDC ( 0 on the tab) If the ring has slipped a bit on the rubber damper, at least you have a new precise mark anyway.

by 77mali Sun Jul 07, 2013 9:23 am

I do want to make sure the timing mark is correct- it's a new balancer but probably was rebuilt. I think I can make one from an old plug- how long is the adjustable part that should go into the chamber supposed to be? Do you want to make it so that it'll rest on the center of the piston? Thanks Bill!

by ant7377 Sun Jul 07, 2013 5:06 pm

Paul,usually I do the same as you. Get it to pop a piece of paper out of the plug hole then go with a wrench and bring it to zero. Do you have an oriental chrome timing cover? Maybe the marks are little off on the pointer. Or maybe you had something in your eye, like the sun or bird poop. Go with the 2 barrel 350,you'll be better off.

by ant7377 Sun Jul 07, 2013 5:07 pm

Proform makes a neat harmonic cover which I have and makes it easy to set timing. Also if you have a balancer that turned its easy to correct with the cover.

by 77mali Sun Jul 07, 2013 6:35 pm

I'll check into the cover- thanks Anthony.

Bird poop...LOL, but seriously- I looked @ my Cam card to see when the valve closes on the compression stroke & it's like @64 degrees before TDC. I think that makes sense, seeing as the timing mark is @ 12:00.

The timing cover lines up perfect but I might also spring for a better timing tab. Mine only goes to like 12 degrees BTDC & even less ATDC.

by pila Sun Jul 07, 2013 6:48 pm

A piston stop can be fabricated with a spark plug body like you mentioned. That's what I use. I used a 3/8" bolt with the hex head rounded off on a grinder or belt sander, to where it will fit in the plug hole, and sit in position to contact the top of the piston. It's welded into the spark plug body. Length isn't critical as long it keeps the piston down in the bore a bit when the engine is rotated, from one direction, then the other.
I could have made a fancy piston stop on the lathe, but this one has worked fine for decades now.

by 77mali Sun Jul 07, 2013 6:54 pm

Cool. Thank you.

by Bruisr Mon Jul 08, 2013 12:37 pm

Remember the oil pump shaft will have to be turned accordingly or the dizzy wont drop down completely. You could if you are certain where you want the dizzy to be set at, put it down as far as it will go then turn the engine by hand and the dizzy and oil pump drive will mate themselves. Or climb on top of the motor look into hole where dizzy goes and use a long screwdriver to turn the oil pump. Good Luck!

by pila Mon Jul 08, 2013 11:09 pm

X2 on what Bruiser said...you will figure it out when you notice how far the distributor turns as it drops into the oil pump drive, Like if it goes too far, pull it back up, & turn the dist shaft backward to make up for how much it moves when engaged with the oil pump drive shaft. Sometimes it drops in just right, and other times it can be a PIA Very Happy

by 77mali Tue Jul 09, 2013 6:01 pm

Got a piston stop tool today ($10.00 @ Indy Auto Parts & on the shelf)!

It turns out that the mark on the tab is off by 2 degrees...I don't think this would make a huge difference, what do you guys think? Regardless, I made a mark on the crank @ 2 degrees BTDC which is where it should be, so it's on there now & the dist is pointing right @ #1.

BTW- Phil did you & your ever get your brothers Monte squared away?

by ant7377 Tue Jul 09, 2013 10:15 pm

77mali wrote:Got a piston stop tool today ($10.00 @ Indy Auto Parts & on the shelf)!

It turns out that the mark on the tab is off by 2 degrees...I don't think this would make a huge difference, what do you guys think? Regardless, I made a mark on the crank @ 2 degrees BTDC which is where it should be, so it's on there now & the dist is pointing right @ #1.

BTW- Phil did you & your ever get your brothers Monte squared away?

AHA! I knew it! Chinese parts! Conspiracy!

by 77mali Tue Jul 09, 2013 10:24 pm

Probably...although most of the SBC stuff is Taiwanese..."crose enuf" I guess rabbit

by Cale11 Tue Jul 09, 2013 10:37 pm

Marisa Tomei knows the answer, I dont Sad

by ant7377 Tue Jul 09, 2013 10:37 pm

Yup ,but could be croser! The guy flying that plane that crashed in CA probably said "crose enough too" -butt hole.

by pila Wed Jul 10, 2013 10:40 pm

The plane at SFO was using the auto-approach gizmo, according to what the pilots said.
Heck, they were ONLY 150 feet too low. DUH !!
Not too sharp it seems....
The triple 7 is a good airplane too. A friend flies one on the Hawaii run from here, for American.

by 77mali Mon Aug 12, 2013 10:14 am

Getting ready to do this again & was reading more about this subject. Here are some good links too for anybody going through this as well as Distributor & timing related information & a couple of Video's.

http://www.crankshaftcoalition.com/wiki/Determining_top_dead_center

http://www.crankshaftcoalition.com/wiki/How_to_install_a_distributor

http://www.crankshaftcoalition.com/wiki/Hot_rodding_the_HEI_distributor

http://www.crankshaftcoalition.com/wiki/Timing_tabs_and_damper_TDC_lines_SBC

by dynchel Mon Aug 12, 2013 10:58 am

Cale11 wrote:Marisa Tomei knows the answer, I dont

here you go, more just an excuse to look at marisa tomei. Leg Hump

by ant7377 Mon Aug 12, 2013 4:10 pm

How did ya make out. Spill it!

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