All Small Six SCV Check Ball

[FuzzyDriver]

The 1964 Comet service manual does not show a SCV check ball. The Mike's Carburetor tech guy says all Autolite 1100's with AT and SCV have check balls. I've seen threads where posters say that cars never have an SCV check ball, citing parts lists with SCV check ball sizes for trucks only. The Mike's guy sent me a service manual drawing for a different year (different model, too, maybe?) It clearly shows an SCV check ball. This is driving me nutty. The carburetor that was on my engine when I got the car did not have an SCV check ball. I bought an identical, remanufactured Autolite 1100 on eBay. It DOES have an SCV check ball.

There's no way that everyone is right. Or wrong. Does anyone know FOR ABSOLUTELY CERTAIN whether a 1964 200-6 Comet should have the blasted SCV check ball?? Here's the 1964 Comet service manual drawing (no SCV check ball):

 

[TrickSix]

I happen to have 1966 and 1969 Ford shop manuals. Both of them show only 2 or 3 check balls in an 1100 for manual or automatic transmission cars. I've put many carb kits in the 1100s I've had on my car over many years, and they always had extra check balls left over. Not once that I remember did those many iterations of instructions instruct me to use all 4 balls. I don't assign equal validity to every source I see online. The many mistakes I've made on here are a clear example of why doing so may be a bad idea... Perhaps Mike's Carbs has discovered that the 4th ball does indeed have a beneficial effect with the modern gasoline blends we use today. Or something. But without an explanation for why the factory manual put out by the factory engineers is wrong I'd be skeptical of alternate recommendations.

 

[sixtseventwo4d]

the question you are asking may be more pertinent as to the altitude that the carb is being used or built for.
Also consider the check ball may serve as protection in case of backfire; so the SCV doesn't get damaged?

 

[FuzzyDriver]

Not once that I remember did those many iterations of instructions instruct me to use all 4 balls. I don't assign equal validity to every source I see online. The many mistakes I've made on here are a clear example of why doing so may be a bad idea.

I hear you, TrickSix!

The Mike's Carb guy provided me with a real, Ford service manual exploded view showing 4 balls, so it's certain that some 1100's use 4 balls. The part that got me was when he typed that he's never seen one without 4 balls. I've got both (one with, one without), you've never seen one with 4, and Mike's never seen one without 4 balls???

Per Ford instruction sheet 50-465-1, the van gets a .223" ball; the truck gets a .262" ball. It may well be that 1100's in cars aren't supposed to have one, and larger vehicles are supposed to get one (to alter distributor advance).

Just as an aside, the 15253A Walker kit I got had 4 balls, but they are all the same size (.1875").

I'd love to hear from a ninety-year-old Ford carburetor engineer! And Bubba...we miss you!

 

[TrickSix]

My impression from rebuild kit instructions is that the 223 and 262 refer to the older truck/van six-cylinder engine families. The numbers are engine displacement in cubic inches, not check ball diameters. Maybe they don't have a LOM distributor, so no SCV, so it needs a check ball there instead. I don't know.

 

[FuzzyDriver]

My impression from rebuild kit instructions is that the 223 and 262 refer to the older truck/van six-cylinder engine families. The numbers are engine displacement in cubic inches, not check ball diameters. Maybe they don't have a LOM distributor, so no SCV, so it needs a check ball there instead. I don't know.

Yeah, looks like what we usually see as ci they just put quotes. My misinterpretation. The spec literally says:

223" eng. PARCEL DEL.,
262" eng. TRUCK

hmmm...and that reinforces that those engines get the fourth ball. If all engines get it, then it wouldn't make sense to specify anything different for the SCV check ball. The drawing doesn't specify anything different WRT the SCV, BTW.

 

[gserafini]

Wanted to follow up here, is it confirmed that with this application we should not use a 4th check ball at the SCV? I just did a mild rebuild of my 1100. The 4th check ball was not there (above the SCV). I added it. The car is running wayyy better after the rebuild. However, I seem to not be getting any advance when I rev in park, the balancer stays at 12 degrees. I used to get advance before this. I did notice my vac advance canister isn't working quite right, so i'm replacing it. But i'm unsure if the issue with lack of spark advance is because of the canister, or the 4th check ball addition above the SCV. This is a 66 mustang 200 with LOM system stock btw

 

[DON]

I think you are touching on the way to solve the issue. What do they actually do? What is their purpose??

 

[gserafini]

I think you are touching on the way to solve the issue. What do they actually do? What is their purpose??

Well my guess is the check balls are there to regulate the flow of either air or fuel. In the SCV port i'm guessing it keeps it closed when theres lower vacuum, and as the vacuum raises it rises to open the valve and activate advance. I'm only confused because that seems reasonable, but i'm not getting advance with it in there. And on the manual that check ball (#29) is listed for Parcel Delivery trucks with a larger ci engine. But on Mikes Carb instructions that port is shown to use the check ball if you have spark valve

 

[gserafini]

Ok I thought about it more and read the manuals again. Since LOM and the spark valve use a mixture of manifold and venturi vacuum, I think that 4th check ball is used as a restrictor. I found this schematic that shows a "restrictor," but it doesn't say if that is for the parcel delivery truck models or not. But the exploded view notes that this is for trucks? I read in an 1100 manual that the autolite models for parcel trucks had an extra passage below throttle plate to allow for constant manifold vacuum, but that models for cars shouldn't have this. So, it's still unclear (to me) if the restrictor is necessary for a stock mustang application or not

 

[gserafini]

Thought I would reply again, and apologies for hijacking this post. It appears there's no public answer for this 4th check ball question (that I can find). I found one more expanded view of the manual for 1100s on 223" and 262"trucks specifically. It's another source that shows this SCV check ball is labeled for parcel and delivery engines. It also confirms the check ball on the anti-stall dashspot for automatic transmissions. There is a lot of conflicting information on this subject, even between Ford and Autolite manuals. I'm fairly convinced that the SVC check ball is not used in mustangs/ car setups. I'm going to pull it apart and take that ball back out. I just hope my 1100 doesn't have the extra manifold vacuum chamber meant for these trucks. Cheers!