Timing an 8ba flathead

A few years ago, I set the timing on my '51 flathead by ear, no timing light. Basically I just rotated the distributor until the idle was smooth. I recently installed a demon 98, and I beleive the Barry Grant literature says to start with 10 degrees initial advance.

I recently decided to pick up a timing light, and it appears that when I set the timing by ear a few years ago, the advance ended up being about 34 degrees. That seems like a lot. So I set it to 10 degrees, but the engine doesn't idle quite as smooth. Is this normal? I'm wondering what other's set as the initial timing on their flatheads?

 

4 degrees BTDC works well for my car.

I use a combination of the timing light and a vacuum gauge to set my timing.

 

It probibily jumped a few teeth over the years, go with the 'by ear' method.

 

Max of 6 degrees initial and 27 total.

 

If I do it by ear, and I am off, what symptoms can I look for? ie, if it is too advanced will it run hotter, or if too retarted will it have less power... etc.

 

Flatheads don't jump teeth, they shear them off.

 

If too far advanced it'll ping under load; if too far retarded it'll run hotter. Just use a timing light or use a vacuum gauge. Twist it for the highest vacuum reading at idle and back it off 1" of vacuum.

Jim

 

The original 8Ba markings is 4 degrees BTDC.
And NOT TDC.
And 4 degrees BTDC there where it should be on an original engine.

 

Thanks. I think I'll pick up a vacuum gauge. I set it to 10 degrees initial with my timing light, wich was apparently about 25 degrees less than before, and it sounded better before. This evening I advanced it by ear and it sounds like it idles much better now, and the idle speed went up fro 650rp to 950rpm, as I advanced it by hand, so now I've unscrewed the idle screw a bit to get it back down to 650rpm at idle. The timing light says it's at 24 degrees advance, so I'm still a little confused as to why it's so far off from what people have recommended the advance should be. Someone suggested the timing gear skipped a tooth or two, but I don't see how they can just skip like that, maybe they are just not aligned properly.

I'll hook a vacuum gauge up and see where I can get the max vacuum at idle.

 

If you're going to advance it by ear; give it all the timing it can stand without pinging, and still hot start. Then back it off slightly. May not be "correct," but it will run good. I suspect that's where you had it anyway. Go figure...

 

Note that if you have stock distributor with demon carb you probably have either no or totally incorrect advance...what distributor??

 

Yes, it's currently a stock distributor, so it won't have any vacuum advance. I'm guessing that because the distributor isn't hooked up to any vacuum line, the only advance would be the initial advance set by rotating the distributor counter clockwise.

 

thats probabaly not good, find someone who can make a sbc or mopar dizzy for you, or contact GmcBubba here on the hamb.

I can tell you from personal trials and tribulations that a good mechanical advance dizzy will make a whole different animal out of a flathead. (more like a kangaroo, less like a wallaby, still cute and fuzzy just bigger and badder!)

Runs much cooler, starts easier and pulls a lot further into the rpms.

 

Yes, do yourself a favor and get rid of the stock distributor. It's probably the worse designed part Ford ever made. GMCBubba here on the HAMB sold me a Chevy conversion with mechanical advance (around 130 bucks)and it really helps the old flatmotor come alive.

 

I put a pertronix unit in the stock distributor, and it's been ok until I switched to the demon which doesn't have a vacuum advance. whish it did. I've been thinking about getting an msd or mallory distributor specifically for the flathead...

 

I run a Mallory dual point on my other flathead. The advance wasn't set properly out of the box but since it has been OK and I've driven it all summer. The new ones quality control isn't that great.

 

I won't be going with points. I'll use an electronic type.

 

I replaced my stock dizzy equipped with a Pertronix Ignitor II for a Mallory UniLite when I went to dual carbs, and it is EXCELLENT. All centrifugal (mechanical) advance. No points. Set it and forget it. If you are running any carb set up other than a single Holley 94, you really need to upgrade.

 

The MSD I installed works great!

 

Thanks for all the info. On my 50 ford v8 I can't advance enough because the vacuum hits thermostat. What to do? gto57

 

The 8BA markings are really 2 degrees BTDC.

 

Proper advance curve will do more for driving performance than any amount of finned aluminum and stuff...

 

Pull the distributor out and move it a tooth and stick it back in. Happens a lot.

 

Yes as said above.
Sometimes you’ll find your spark plug wires won’t allow you to turn the distributor enough.
Just change the plugwire location on the distributor. Doesn’t matter which holes they are in as long as they are in the proper order.

 

A slight hi-jack here , where do you get a Demon 98 these days??

 

My issue is ... my CR is 9:1 with 175 pounds of compression. Where it wants to run and start beautiously she pings unless I use 96-97 octane. What would you guys do?

 

What is the total timing and what RPM?

 

9.1 is a heck of a lot compression for a street flathead.

At idle set the timing with a light with pointer on the dot. That's stock spec. The ear can fool you.

What distributor?
As RPMs increase the timing will advance.
The original distributor must be matched to a single Ford 94 otherwise, you have no functioning advance.
No advance would cause pinging under load.

 

Will let you know, just backed it down.