Initial Timing via Vacuum

Anteek29

Anteek29

Well-known member
Been discussed on the forum before but I decided to try the technique on my stock '55 272. Patched my gauge gauge into maniford vacuum, disconnected the vacuum advance line, ran engine at warm idle, turned the dissy until I achieved maximum vacuum, then turned back dissy until vacuum dropped
a tiny bit. Secured the dissy. I had noticed the engine ran smoother as the vacuum increased.


I then checked the timing using my strobe light. Instead of the recommended 6 degree static advance, I now have approx. 14 degrees using the max. vac. technique. (I have read that Y-blocks like more static advance). I also verified that the re-connected ported vacuum timing advanced with increased RPM to approx. 38 degrees. I chalk marked the damper according to these latest readings and will road test tomorrow.
 
I’m used to running 10-12, even on fairly high compression yblocks. Premium fuel. If you hear pinging under heavy load, and hot, just back off a couple degrees at a time.

I’ve had other engines that would pull thru 1st and 2nd but ping in 3rd as heat built up in the chambers. Just what to watch for. And your gearing and fuel choice effect this.
 
A lot depends on whether it's an older Y-block with the Holley Load-O-Matic or a 1957 or later set up with the better distributor. The Load-O-Matic was an all vacuum system designed by Holley that includes the carburetor and distributor. It worked OK for the flatheads but the OHV engines needed more advance and better load control. It took Ford three years to finally get a system that worked fairly well for the Y-blocks.
 
I have a 54 customline. It does not like a 3-4 degree advance as per the spec. Runs much better at 10 degrees. I too use the vacuum method. Works for me. It's almost impossible for me to test and change the spring tension in the dizzy, so I gave up now that it runs strong at 10 degrees. I also changed jets in carb from 56 to 55 and car ran better.
 
I read this thread with interest. My 239 with a Fordomatic pinged when cold, timing set at 8 BTC, then ran smooth after it warmed up. Hoping that a Pertronix ignition would be an improvement I installed one. Now it pings even when at operating temp and very loud. Sounds like a rod knocking but it is intermittent. With the vacuum port on the carb plugged and no vacuum to the distributor I've increased and decreased the timing from 0 to a estimated 15. The rpm changes but the pinging will no go away. After hooking the vacuum line back up the pinging is worse at all settings. While I'm disconnecting the vacuum hose to the power brake module to measure engine vacuum with a gauge I'm hoping someone will give me a little input. The gas in the tank is premium but I'm sure it has ethanol in it.
 
Using vacuum the timing ended up at 10BTDC. As soon as I hooked the vacuum tube to the carb it will only idle. Any gas peddle and it backfires and/or dies. I'm about to put points and condenser back into it. Where can I get some reasonable quality?
 
Is there another distributer that will work with my 6 volt system or maybe a rebuilder? I really tried hard to keep the car original so would not like to go through the expense of converting to 12 volts.
 
Your stock mechanical distributor will function just fine on either 6 volts or 12 volts. Personally, I am not a fan of electronic ignitions. I've had good success with points and condensers from NAPA. Oh, were you able to observe ignition timing advance with increase in RPM? Sometimes the vacuum cans develop leaky diaphragms.
 
The Load-O Matic system has a special valved vacuum port directly off the carburetor venturi that feeds vacuum to the distributor for advance after start up. The ported vacuum increases as the velocity of the air increases with higher throttle settings. If it was manifold pressure then the vacuum would decrease with more throttle so it works opposite of how a more modern distributor that uses centrifugal advance with a vacuum port for load control such as all distributors had up into the early 1970s.

Most of the aftermarket distributors such as a Mallory performance type would be mechanical advance with centrifugal flyweights only. They work OK but they were for performance so they had no load control. Fuel mileage suffers due to that but they will run pretty well.

I'd consider using a 1957 or later distributor and convert it for use on the earlier engine and likely change the carburetor to one that could provide load control if possible.This and the larger CID 292/312 engines was why Ford changed over in 1957. They needed better stock performance than the old system could provide.

Electronic ignitions can be tricky on the older engines. They have to be set up just as the manufacturer recommends or electronic components will suffer. Some are better than others.
 
The infamous Load-O-Matic distributor system came out in 1956 and I believe was only for one year? 1954 and 1955 stock distributors were vacuum advance only - no mechanical advance.
 
Loado’s were around on flatheads, and hung around on at least some 6’s after they were gone on y blocks. The dual diaphragm on yblocks was (I think) a 1 year only. Never an optimum solution for performance or mileage. But they worked, like most of the stuff Henry did.
 
Anteek29 said:
Your stock mechanical distributor will function just fine on either 6 volts or 12 volts. Personally, I am not a fan of electronic ignitions. I've had good success with points and condensers from NAPA. Oh, were you able to observe ignition timing advance with increase in RPM? Sometimes the vacuum cans develop leaky diaphragms.
Click to expand...

Yes, it does advance but it dies soon after. I've given up on this distributor, I'll start a search for a better one.
 
rotorwrench said:
The Load-O Matic system has a special valved vacuum port directly off the carburetor venturi that feeds vacuum to the distributor for advance after start up. The ported vacuum increases as the velocity of the air increases with higher throttle settings. If it was manifold pressure then the vacuum would decrease with more throttle so it works opposite of how a more modern distributor that uses centrifugal advance with a vacuum port for load control such as all distributors had up into the early 1970s.

Most of the aftermarket distributors such as a Mallory performance type would be mechanical advance with centrifugal flyweights only. They work OK but they were for performance so they had no load control. Fuel mileage suffers due to that but they will run pretty well.

I'd consider using a 1957 or later distributor and convert it for use on the earlier engine and likely change the carburetor to one that could provide load control if possible.This and the larger CID 292/312 engines was why Ford changed over in 1957. They needed better stock performance than the old system could provide.

Electronic ignitions can be tricky on the older engines. They have to be set up just as the manufacturer recommends or electronic components will suffer. Some are better than others.
Click to expand...

I was aware of most of that. I dove into it again today and decided to cut my losses on the Pertronix. It starts and pings at idle. As designed there is zero vacuum at the carb. A little throttle and the vacuum climbs to 5 inches. The book calls out 6 1/2- 7 1/2 but the fitting I was using wouldn't seat correctly. My conclusion is that the spark control valve is working correctly. After reattaching the vacuum line to the distributor the engine would start and idle but a little throttle and the engine would die. Timing would increase a little before dying.

Could you expand on converting a '57 or later distributor? And considering the shape of the base of the carb what are my choices to upfit it? I'm assuming the hotter coil from Pertronix will work with points and condenser or should I reinstall the stocker?
 
Anteek29 said:
The infamous Load-O-Matic distributor system came out in 1956 and I believe was only for one year? 1954 and 1955 stock distributors were vacuum advance only - no mechanical advance.
Click to expand...

Ford went with the L-O-M system in 1948 for the first of the 8BA family of engines beginning with bonus built trucks. It worked fine for the different flathead engines produced through 1953 in the US. The design was updated for the Y-block engines in 1954. The early Y-blocks started out the same CID as the the flathead V8s, so the engineers figured it would work OK but they quickly found out that it wasn't working as well as customers wanted. They clung to the 1st Y-block design for another year while redeveloping it to hopefully get better performance for the newer larger CID Y-blocks. If you study the redesign that came out for the 1956 model year, it's not hard to conclude that just adding another vacuum can and complicating it further wasn't going to do the job. They finally chucked it for the 1957 model year when they caught up with the industry and went to the combination of centrifugal and vacuum advance with way better load control and they never looked back. Those 1956 units are complicated and they still didn't solve the problem since even larger CID engines like the 312 Thunderbird & 352 FE engines were coming out with even newer and larger MEL engines in development.


For the question in the previous post, I can only think of the possibility of using a base plate adapter to fit the early manifold if the difference in the carburetor base and plate size is great enough to require that. A person may have to play with the advance weight springs or use an adjustable vacuum can for the vacuum system if needed to get the just right amount of advance. I've never attempted a conversion but I'm sure that Y-block fans have or know of others that have. Plenty of flathead lovers have modified older GM distributors to work on their hot rod engines with multiple carbs and such. The first 3-deuce Y-blocks would have been changed as well.
 
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It was an easy swap to a HEI distributor in the SBC I have in my old Chevy pickup. I'm wondering if the base, shaft and gear of a '57 distributor will easily slide into my 239 and if not, what needs to be changed.
 
I put an ad in the wanted section. Hopefully it gets more interest than the ad for the parts car I want to sell.
 
Just to get you started. The early 239-256’s used a different cam,cam gear and distributor gear than the 272-312. I believe the oil pump drive was a tang, rather than a hex shaft. So, the later model distributor requires a change of the oil pump for the hex drive, and a transfer of the drive gear from the existing 239 distributor. I’m told there were some late model 239’s with the later cam, etc. but I’ve no idea of those details.

There’s a lot of discussion about distributors in general and 239-256’s on yblocksforever. If I could run the search function I’d post a link, but I can’t get it to work. My fault, not the sites. But that might be worth a shot for you. Parts or info.
 
Miker is correct. "The early 239-256’s used a different cam,cam gear and distributor gear than the 272-312. I believe the oil pump drive was a tang, rather than a hex shaft. So, the later model distributor requires a change of the oil pump for the hex drive, and a transfer of the drive gear from the existing 239 distributor."


This was known as the EBU version of the 239.


In the 1955 model year (and maybe late in the 54 model yea), Ford came out with the EBV version of the 239. This block had all the points of the 272/292/312 version of the Yblock. Smaller cam bearings and cam, hex oil pump drive oil pump and the drive gear with the different number of teeth..
 
I have an EBU block, and I assume EBU cam since the distributor fits well. So besides a later model distributor I need a later model oil pump. No chance the '54 shaft will fit into later model distributor?
 
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