no vacuum

[acfd813]

Hey y'all I've done some searching but can't find a whole lot. I got a 73 f100 with the 240 inline 6. I did a tune up Friday and found out that someone has already converted it over to a Mallory pointless ignition. That was a nice surprise. I pulled the vacuum Jose off the vacuum advance and noticed it wasn't pulling any so we unplugged it from the port on the carb and still nothing. Not even right at the carb. So we pulled it off and rebuilt it. We also put a new vac line on cause the old had a bb stuck in the carb end of it. Started the truck up and still no vacuum coming off the carb. The truck runs OK feels like its lacking something while its driving but otherwise it runs OK. Do I need to try to fix this or is it an issue or any ideas what's going on. Do Ieven nneed the vac advance with the converted ignition?

 

[Ronzi]

The vacuum advance for the distributor runs off a ported vacuum source from the carb. It does not pull any vacuum at idle but it will at speed and advance the distributor at higher rpm's

 

[acfd813]

Oh OK gotcha how can I tell if the vac advance is doing what its supposed to? Thank you for replying

 

[jebadiah04]

When u give it a little throttle you can feel vacuum.

If u just want to test your vacuum advance. Unplug it from the partial vacuum port and attach it to a full vacuum port. It will make it advance significantly and u will hear and feel the difference.

A second test you can do is unplug the vac advance from the carb and suck on the hose. Pull real hard then quickly release. You should hear the vac advance snap back closed

Third test is pull the cap and do the suck test, u should see it move.

If you get air from the dizzy then u need yo replace the vac canister
Sent from my mudwhistle via Lemmiwinks.

 

[Ronzi]

Vacuum advance is primarily used in an effort to improve economy, therefore you won’t hear much about vacuum advance when discussing performance and racing. There is little to no vacuum during wide open throttle which means no vacuum advance any way!

A vacuum advance canister provides a way to advance the ignition timing during moderate and part throttle conditions. This is when the load on the engine is less and vacuum is higher. There is a diaphragm inside the canister which is connected to a linkage connected to the pickup plate in the distributor. When vacuum is applied, the plate is pulled which advances when the trigger signal is created. When the engine accelerates, vacuum drops so the advance returns to the original position.

When connecting the vacuum advance, most applications connect to a port above the throttle plates. This is called ported vacuum compared to manifold vacuum which comes straight from the intake manifold. The difference here is that manifold vacuum is there constantly while the ported source provides vacuum only when the throttle blades are open. The amount of advance that occurs varies by application but generally ranges from 10°-15°. Some companies even offer an adjustable vacuum advance canister. This lets you set the exact amount of vacuum advance that your engine requires.

 

[acfd813]

Thank u for the desceiption. I was a little confused as I haven't ever worked on an older truck before. From the description it sounds like there should be a way to delete it. Can u delete it or did I miss something. Also mine has 2 ports. On points up and the other points to the firewall. The only one hooked up is the one going to the firewall and the one pointing straight up is left open is this right?

 

[acfd813]

Anybody? If I can't delete it I just need to know if it is connected right. Is that port pointing straight up supposed to be open?

 

[dustybumpers]

You need the vacuum advance, so hook it back up.
If you have a vacuum port open, it needs to be capped. That very well could be a reason for it not to feel right when your running. They sell the small rubber caps in any help section of an auto parts store

Another thing to remember when you say it don't feel powerful, it's a 240. That's 240 cubic inches

In modern terms it would be something like a 3.3 liter.
Not a huge engine to push around a 5,000 lb truck

 

[acfd813]

Yea u gotta point I will definantly plug that up. Will a 300 i6 bolt to my tranny

 

[jebadiah04]

Yes.

Sent from my mudwhistle via Lemmiwinks.

 

[acfd813]

Awesome Im pretty sure my 240 needs a rebuild but iI'd rather rebuild a 300 or a 302 but I don't wanna change the tranny

 

[dustybumpers]

Block is the same. both bolt up to the same trans.
If you go the build a 300 route, use the head off the 240. It will give you a higher compression ratio

 

[acfd813]

OK cool I'll remember that BTW dusty I love ur signature that's awesome

 

[dustybumpers]

Thanks. It is a true fact!!!!

 

[acfd813]

My uncle said instead of a 300 I should just do a 302 rebuild. He said that since its a 2 wheel drive truck the mpg won't be bad. Is he right? What do y'all think? Will I have to change my tranny or will it bolt up as well?

 

[5.0Flareside]

My uncle said instead of a 300 I should just do a 302 rebuild. He said that since its a 2 wheel drive truck the mpg won't be bad. Is he right? What do y'all think? Will I have to change my tranny or will it bolt up as well?

It'll bolt up. But you'll have to change quite a bit of other stuff I can link you a thread showing the basics..

Mpg will be better with a 300.


Smokin' Tires with my 5.0 on Tapatalk

 

[dustybumpers]

Some like small blocks, some like big sixes.
I have both

It depends how you drive, how your fuel mileage goes.

I have a 95 4x2 with a 4.9, it gets 25 mpg on the road.
My 82 with the high performance 300 gets about 11 mpg.

Big difference in the two, The 82 spends most of it's time with the throttle to the floor. Holleys get thirsty when you keep the secondaries open

 

[acfd813]

5.0 I'd love to look at that link
And Yea dusty I know what u mean I like to feel the power when u know u got it but this will just be my everyday driver

 

[5.0Flareside]

www.fordtruckfanatics.com/forum/showthread.php?t=13676&highlight=5.0+Swap


Smokin' Tires with my 5.0 on Tapatalk

 

[acfd813]

Wow I think I'll stick with the 300 lol where is the best place online to buy parts. Like all part from engine to interior to electrical OEM and aftermarket. I said in another thread I wanna do a modern restoration on it but still keep it as an everyday driver. I'm not concerned with keep on stuff original or stock as long as it functions and looks good.