Technical Top Dead Center According To Bruce Lancaster

[Ryan]

So I've heard the mark on a Flathead crank pulley coordinates with top dead center. I've also heard at times that it coordinates with 2-degrees before top dead center and yet other times I've heard it coordinates with four degrees before top dead cen...

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[cactus1]

Wow! Bruce is the man.

[Lazer5000]

I like the "Heads on Method". Now I just have to find an apprentice to hold the thing.

Great info though.

[Tman]

Simple and to the point. Always read Bruces replies, feel smarter from them!

[Slick Willy]

"Mug an eighth grader..." !
Man, kids must be smarter in PA!...Around here I'd have to beat up a 5th year senior to get his compass and protractor!

As always, Bruce has wonderful information!
Thanks for posting, Ryan.

[need louvers ?]

An eighth grader around here had a compass once, but I think he ate it...

[choprodinc]

Bruce's bulb burns bright! U don't mug anyone in Texas... we're ALL packin'!

[Asphalt Outlaw Hero]

This is the same technique I use for timing motorcycles.

Here is a link to a degree wheel you can print and glue to cardboard or the front of the pulley.

http://www.tavia.com/free_degree_wheel.html

[Adam.Perrault]

Originally Posted by Asphalt Outlaw Hero

This is the same technique I use for timing motorcycles.

Here is a link to a degree wheel you can print and glue to cardboard or the front of the pulley.

http://www.tavia.com/free_degree_wheel.html

this is fantastic... the 8th grader i tried to mug must of been from Texas! It was only a flesh wound though.

[caseyscustoms]

Originally Posted by Adam.Perrault

this is fantastic... the 8th grader i tried to mug must of been from Texas! It was only a flesh wound though.

yea down there they all know a shot below the waist isnt attempted murder, less time served.

[choprodinc]

you're right! down here we'll shoot you just for kicks... you gotta really piss us off to make us kill you!

[MIKE47]

Join the Bruce Lancaster Fan Club group!

[GMC BUBBA]

Ryan,


Good material for sure AND it would apply to any engine ever made not just the flathead. For a accurate timing of the engine we must know where we are at all the time.
I would give the small block chevrolet the worse rating here as a typical "hot rod " build is a mixture of parts. IE : Balancer from one engine, timing cover from another etc, short water pump vs long pump etc...
Last year i put together a complete test stand engine from parts, complete engine with heads was purchased from machine shop ( a 283 customer never came back for) at a deal, timing cover was from the wall just hanging there and the balancer was a new degreed unit from ebay. Fired the engine up and couldnt get close to any of the marks with timing mark.
Used a piston stop in plug hole and marks were way off from any marks we had. ( 15-20 degrees etc) Made up new pointer for correct mark, set timing and has ran well every since....

We need to know correct TDC on every build ..

[Steve Hedke]

Easier on 59AB: just bolt it up. Old Henry figured it would be too confusing I guess. Besides, timing lights only get you close, because published numbers are for stockers. Every engine is different: fuels, compression ratios, head designs, etc. I always use 'tune by ear' for final adjustment. Warm it up, then lug it down in 2nd: if it pinks, dial it back. If not, dial it up. No rocket science here.

[Nads]

A poet he is, that Bruce.

[HOTRODSURFER]

learn something new every day..Thanks Bruce !!!

[flt-blk]

Simple and affective......good job sharing it with the masses.

[Bruce Lancaster]

On early flatheads, no marks. There are methods using distributor machines, simple fixtures, and just straightedges (I have posted simple timing methods for '32-41 and '42-8 engines and also a simple dwell device built out of Home Depot components) which time the distributor OFF the car, essentially by registering the tab that fits the cam.
You do not need to add a timing mark to set initial timing pretty accurately to spec if you own a ruler, but you still want timing marks.
The reasons...first, of course, you can jack around the initial to experiment, but no big deal...the distributor itself has a timing plate to do that, and flathead always seem to end up right around the stock 4 degrees by preference.
The real reason is being able to check the whole curve, as moving initial moves it all. Especially important with pre-41, which is a bit conservative for 1930's octane, and aftermarket, which frequently has entirely inappropriate curves.
If decoding the centrifugal on a flathead on a new installation...remember, once the vacuum is added in the compexity gets up around infinite...you can first rotate the dist cam by hand and try for a rough measurement of total advance (remember to multiply by 2 to get crank degrees!) or maybe trust the spec...maybe not.
Then revvitup with a tach, timing light, and newly marked pulley. Most flatheads are going to want full advance by around 2,000 or not far from there, so if your full advance isn't coming in (brake backed off on earlies, vac disconnected on conventional systems)) by thenabouts stuff is sticking or springs are too heavy.
Typically a good curve starts moving right off idle and finishes in the rough neighborhood of 2,000, and you can see what's happening right on the engine. Remember the brake; with brake dragging heavily, curve is much slower at full throttle, ending maybe above 3,000 somewhat, brake released curve peaks around 2,000.
This gave less full throttle/more part throttle advance with bad antique gas octanes, but on decent modern octane levels most engines seem happy with brake way off. You do need slight drag to stabilize brake disk according to those with proper machines. Start off with brake adjust turned all the way out BY HAND, then screwed in just a turn or so. Crank it down more only if your rig pings.
Once you know what distributor is doing, hit the road and see how it goes, hook up the vac and see what happens, try experimenting by TEMPORARILY jacking the initial setting to boost or reduce upper ranges of curve. At least you know the basic numbers to think about what is happening.
Good advance curve is serious stuff...getting it right gives more seat of pants improvement than any finned aluminum stuff, getting it wrong makes car slow, breaks parts, and causes overheating. NEVEREVER assume a new distributor out of the box is doing anything at all right.

[JeffreyJames]

I heart Bruce.

[hotrd32]

There is NO substitute for experience.....period