The Stovebolt Site Forums The Shop Area Engine Shop 235 Vacuum questions

Hi guys!
First post, still learning how to navigate the site.
1960 Chevy Apache10, I’ve had it just one month. It’s my first stove bolt. Im hoping to learn more about engine principles and this engine is just the ticket.
The truck has sat for the better part of 30 yrs. The “new “ keys have a tag with 2015 on it, and the fuel pump and distributor cap appear “new” also, so I’m guessing someone tried to get it going some years back. The engine is covered with oil and grime and the carb looked like a tar football until I cleaned it. The engine turned easily tho, so I poured marvel in the plug holes and rocked it around for a day, then poured gas down carb and I’ll be danged if she didn’t start up prettv easily. 30lbs oil pressure per aftermarket gauge. I’ve since dismantled carb (Rochester B manual choke) and thoroughly cleaned it and installed rebuild kit from Mike’s. It’s still not right tho so I’m doing some due diligence before I take the carb back off again again again.
First question: how much vacuum should I have? I pulled the vacuum advance line and pulled from there. It looks like it comes out above the throttle plate but the inner passageway in carb brings the vacuum from below the throttle plate, so i guess but should be manifold vacuum. But I only had 12 inches at idle ( no tach so rpm is unknown). It went into the low 20s with some throttle work. Then returns to 11-12. Adjusting the idle mixture screw had no noticeable effect. It’s currently ~1.5 turns out.
How do I remove the pipe plug in the intake manifold and install a vacuum port? Is this something I can find at my FLAPS?
Static compression test on semi-warm engine reads 115-130 so I’m happy about that. I adjusted valves and they were all pretty close to spec( .006” and .018” warm). I’m waiting on my timing light to arrive to check timing. What’s a good number of advance to start at?
Bonus question: my distributor sure does have a lot of up and down play. I was told it isn’t unusual but would that alter timing due to the helical cut of the gears?
Thanks for helping a new guy!

First, welcome to the ‘bolt! I’m sure one of the experts will be by shortly to help you with your questions. Spend a little time and introduce yourself in the “Welcome Center” forum. Tell us a bit about yourself and your truck.

And of course we bolters love pictures so include a few. Here’s a link to instructions on how to add pictures to a post.

Again, Welcome to the ‘Bolt!

You’re probably getting ported vacuum rather than manifold vacuum if you’re using the vac advance. Hard to make much of your results until you get a better signal. Gauges vary from one to the next, stability is more important than absolute number. But 12 is pretty low, my engine idles at more like 20. But again, you need to get a source of actual manifold vacuum before worrying about the number.

Are we talking about a 235 here?

There are a few different versions of the intake, but the hole there is just some sort of pipe thread (NPT). Should be able to remove the fitting and just go the hardware store and get either a brass tee or a barb with the right threads. Do that and report back.

Does it run OK? Will it idle on its own?

Lots of things we could explore to make it run better (vac leaks, ignition timing, carb issues, etc). Getting a vac gauge hooked up to a proper source is a good place to start that diagnosis. Sounds like you’re on the right track.

You mentioned timing. Before even worrying about a light, just verify the timing ball (visible through a little hole on the passenger side of bellhousing) more or less lines up with the pointer when your rotor is pointed at #1. From there, make sure wires are plugged in to create a 153624 firing order clockwise around the distributor.

That will be a good enough starting point. It’s probably not too bad in its current state if you got it running that easily.

The vacuum advance should not show much if any vacuum at idle. You need to remove the plug in the side of the intake manifold to check vacuum at idle. It should be 20 or a little bit under 20 and steady.

Thanks guys! Yeah the way the vac gauge was reading I suspect it is ported. I will remove the plug and head to the hardware store.
I’m still waiting on my timing light but it can’t be too far off . I have verified that the flywheel BB lines up when my rotor bug is pointing to number 1, using the eyeball gauge.
My newest concern is that the rockers aren’t getting oil. They are very quiet though so I never thought about it but I had the valve cover off again today and the holes on top of each rocker are dry as a bone. I know this is a common issue so I’m hoping there is a thread addressing it around here somewhere.
And yes it’s a 235.

You can remove the Distributor and I used a Cheap big straight screwdriver. Cut the handle off. Chuck it up in a drill..insert where diistributor piece connects to Oil Pump, spin away.. See how much oil flows. I did this several times before a start up.
Good luck.
Todd

Stovebolts will not shoot out gobs of oil like most other engines. It’s more like a slow drip. You just want to make sure the oil is reaching the furthest rocker a both ends.

I ended up cutting the tip off a long shank 3/8 spade bit to achieve the same thing. It was a cheapy.

To the OP - if you spin the oil pump like this and can’t get oil dribbling out of each rocker, need to disassemble the rocker shaft and clean things out. They get gunked up through the years.

The galley & lines that feed oil to the head might need a good cleaning.

This diagram might help 👍

How long did you run the engine? It takes a while for the oil to make it to the top of the engine if it has been sitting for a longish period of time.

Thank Guys!!
I got an hour to work on it today. Installed vac port in place of the plug in the intake, it’s pulling 17-18” at a high idle ( 1000 rpm? Tach install is next). The needle has an occasional flutter between 17 and 18 , so maybe I have a sticky valve. Hopefully once I get the rocker shaft all cleaned out then I can run it some more and let it work out the gunk.
I have run the engine for well over an hour over several different days and it’s making 30lbs pressure so the oil has had its chance to make it up too.
2 pumps on the gas pedal and choke mostly open and it lit up in a half crank today, I’m happy about that!

ApacheKid, Nice work!

👍👍👍

Post a pic 👍

Update: I removed and cleaned the rocker shaft ( see my other post). Idled engine forever to get it hot ( clutch was stuck so I couldn’t drive it) then set lash. Immediately my vacuum reading got higher and the flutter subsided some. Then I set timing as best as I could with my light, finally I just put it 4 degrees BTDC per the scale on the hold down clamp, or so. It was several degrees retarded from thst point before I started. Engine seems happier and I’m getting about 21” vacuum at a slow idle.
Got my clutch (mostly) unstuck and took some laps. Still has off idle hesitation inspite of my rebuild on the Rochester B.
Then I sprayed carb cleaner around the throttle shaft and sure enough it’s leaking.
So, I’m making progress thanks to you guys.

Depending on the degree of leakage at the throttle shaft, it might not be a big deal.

I’d guess that most/all Rochesters that have NOT had an intentional reaming/bushing job on the throttle shaft᠁..would fail the carb cleaner test. I strongly suspect my Carter YF would also fail that test.

If you can get it to idle down, run at a high and stable vacuum, and not puke fuel all over the engine᠁.you probably have bigger fish to fry than a throttle shaft that isn’t factory tight.

This sounds like my 62. I rebuilt the carb and it does ok for a 60ish year old carb. It leaks around the shaft too, but functions fairly well. My vacumn advance on the dizzy stopped working, so I capped the carb port off and Ive ignored the slight hesitation for so long its now normal to me 😅. I have been driving it almost daily for a while, so I just putt on down the road 👍🇺🇸👍.