What do these vacuum readings tell you (videos)? (1 Viewer)

MadMace

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Quick background on my FJ40:

1974 with stock 1.5F engine.
Head rebuilt by JimC (FJ40Jim). Manifold resurface/machined through him as well.
New distributor from City Racer (non-US distributor) running points. Points gap set to .018.
Original carb--it is Cali-spec. Rebuilt. I sent it to FJ40Jim so that he could dial it in on his engine. Idle solenoid working.
Timing is set to 12 degrees BTDC. Set here because this seemed to give me the best vacuum without pinging.
Valves adjusted then readjusted and then readjusted again to make sure that they are set to .008 and .014 (maybe a little on the loose side--like .009 and .015 because I don't want to be too tight). This was done when the engine was nice and hot.
All new gaskets--head and manifold. Manifold is OEM. I also used carb gaskets above and below the carb insulator.
OEM PCV valve--new. Using vacuum hose (not heater hose), no leaks.
Brake booster not leaking.
I have made sure that all the bolts and nuts are torqued to spec per the FSM--all head bolts to 90ft-lbs, rocker supports to 28 ft-lbs (10mm) and 18 ft-lbs (8mm), manifold nuts to 22ft-lbs.

When the choke is completely opened, idle drops to around 450RPM. She does not die--she will continue to run, but just barely. I have sprayed carb cleaner every where I can think of to try and find a vacuum leak--all around the carb base, intake manifold with no success in finding a leak.

I am assuming that there is a vacuum leak because of the way the needle flickers and the vacuum is too low (I am not at altitude).

Vacuum is checked through the brake booster hose.

Here are some videos:
Vacuum at 650RPM
2nd video vacuum at 650
Vacuum at 850RPM
Vacuum at 1000RPM

What do these readings tell ya'll. Is this consistent with a vacuum leak? Could a chunk of crud gotten into my idle circuit in the carb? I have spent the last 2 weekends trying to find the cause for this and I am coming up empty. Any and all help is very much appreciated.
 
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Pighead

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Re-torque your head bolts after a couple of hot/cold cycles, even the middle one. You will then, of course, have to re-adjust valves, because you have to pull the rocker arms to get to the middle head bolt.
Get back to us then.
 

MadMace

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Re-torque your head bolts after a couple of hot/cold cycles, even the middle one. You will then, of course, have to re-adjust valves, because you have to pull the rocker arms to get to the middle head bolt.
Get back to us then.

I forgot to mention that is what I did this past weekend--I had high hopes for this. I took off the rocker arm assembly so that I could get to the middle head bolt and torqued down all the head bolts to 90 ft-lbs. It was after this that I made sure the rocker arm assembly nuts and bolts were torqued down appropriately so that when I adjusted the valves they would stay appropriately adjusted. I made sure that the engine was hot when I adjusted the valves after this.

I have not yet re-torqued the manifold nuts though.
 

MadMace

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I put a new Toyota OEM gasket on the manifold. After researching, I think a Reflex manifold gasket would have been a better option. I figured after the manifolds and head were reworked/resurfaced, an OEM gasket would be best--maybe not though.
 

Pighead

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I couldn't recommend a Remflex manifold gasket, BTDT. Can you turn in your idle adjust screw to get your idle up to 750 or so? (without the choke)
Have you done a compression check?
 
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I'd be interested in seeing wet and dry compression numbers as well as cylinder leakdown percentages. Sounds like you have hit all the vacuum leak possibilities and the bouncing needle is concerning too.
 

MadMace

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I did a compression check before the head was rebuilt. I have not run a compression test since though.

Numbers were:
Dry:
1: 120
2: 135
3: 120
4: 122
5: 130
6: 130

Wet: I have written down that all 6 cylinders increased to 150. This was almost 2 years ago so probably time that I re-did them.

I have not done a cylinder leak down test. I have never done one on any vehicle for that matter so I probably should start learning.
 

MadMace

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I couldn't recommend a Remflex manifold gasket, BTDT. Can you turn in your idle adjust screw to get your idle up to 750 or so? (without the choke)
Have you done a compression check?

I have not yet turned the idle adjust screw. There are 3 reasons for this. First, and probably most significant in my mind, is that Jim dialed this carb in on his engine--it ran great on his 2F--I have figured that all the adjustments on the carb are good, if not ideal. Second, because my vacuum is not where it should be, I have assumed that changing the idle adjustment screw alone wouldn't get me out of the woods on this. Third is the needle flicker--everything I have read says it should be rock steady--so I again figured I am dealing with something more than idle speed. I will concede that this line of thinking could be flawed, but this has been the logic (or lack thereof) I have been following.
 

Pighead

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Well, Jim C. rebuilt my carb too, i don't think he minds too much if you adjust it just a little bit to your engine. I think you need to get your idle up to 750 or so without the choke when warm. I'm thinking either advance your timing some, but not if it's gonna ping, or turn up your idle speed screw. Or something else that I don't know. You can always turn the idle speed back down if it doesn't work. You're searching for answers right now and minor adjustments might help, couldn't hurt.
Tighten up your valve adjustment, see what happens. You're not gonna burn a valve at idle.
One more thing, common knowledge, maybe even paraphrasing Jim C. himself, the further you get away from the factory, either in time or modifications, the less you rely on factory recommendations. You tune your own engine to run it's best when and where you are. Do not be afraid to twist an adjusting screw. It's easy to undo.
I can quote Jim C. by memory here: :"It's a 1F, it's too stupid to die"
OK, you got a 1.5 F. Just like mine started out as. Sure, I put a bored & balanced 2F block underneath, but I'm still running the original head and original carb.
Play with it, go outside the box.
I don't know what degrees mine is timed at anymore I can't even see the BB in the window, I Time by my (indash) vacuum gauge and seat of my pants. And ear.
Check your carb hold down nuts & studs, those studs like to strip in the intake manifold...

Edit: sounds like you're doing everything right. Keep at it.
 
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MadMace

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Well, Jim C. rebuilt my carb too, i don't think he minds too much if you adjust it just a little bit to your engine.

I do have to say that the needle did smooth out as the RPM went up. You are right—making the adjustment is a good idea—if no change just set it back. I’ll do it slowly, maybe quarter turn at a time, give the engine time to adjust and go from there.

Also, I will re-torque the manifold nuts. Do dry and wet compression testing. Probably also not a bad idea to do a leak down test. I’ve never done one of those before—no time like the present to learn something new!!
 

thebigredrocker

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I would be curious to leave the carb as-is for now and see if adjusting valves to spec raises/smoothes vacuum. At 650rpm my 71 F engine has a steady vac of 18.
Set the timing whenidling at or below 650 RPM, vac hose disconnected just to be safe. After timing and dwell is set, adjust idle speed & mixture to preference.
 

John McVicker

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@MadMace I know you’ve sprayed carb cleaner around the base of the carb, but are you certain the bottom of the carb insulator is in good order?

if not certain, the only way to find ou unfortunately, is to remove the carb & insulator and take an actual look see.
 

MadMace

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@MadMace I know you’ve sprayed carb cleaner around the base of the carb, but are you certain the bottom of the carb insulator is in good order?

if not certain, the only way to find ou unfortunately, is to remove the carb & insulator and take an actual look see.

I am pretty sure it is in good shape. I inspected it closely and didn't see any cracks. It didn't look like it had been abused--i.e. scraped to get the gaskets off. That being said, it was hard for me to tell if there was still gasket material on it so I went ahead and put this gasket between the insulator and the intake manifold and this gasket between the insulator and the base of the carb. I know that I have read that they are not needed but I figured they couldn't hurt. Again, maybe flawed thinking?
 
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I sound like an ass in my head as I type this... but what the hell... Dude, adjust your idle correctly!!! Jim may have "dialed it in", but he did not do it on your rig. Carb settings are not "set" in stone. Chasing all this without setting your engine to the correct idle speed is one hell of a wild goose chase.

Set the speed where it should be. Then tune your idle mixture and timing to the best vacuum and reset the idle speed screw as/if necessary (not exceeding 13* BTDC). Every carb need to be tuned for the engine it s on. It is not rocket surgery or brain science and judging from your comments in this thread it is well within your capabilities. Whatever Jim may have set it too is not meant to be regarded as the ultimate configuration.

THEN see if your vacuum readings are worrisome and THEN chase the problem (which may not actually be a problem at this point).

BTW, just as data points, Toyota says that 113psi is the minimum acceptable cranking pressure in the F/2F. Personally I consider 120 the minimum that I find acceptable. The FSM calls 149psi nominal. I like to see about 160-165 in a fresh engine.


Mark...
 

MadMace

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I sound like an ass in my head as I type this...

You don't sound like an ass at all--I very much appreciate the help/advice. Telling me what I need to be doing is exactly what I appreciate. If I'm being a dumbass I don't mind hearing so as long as I am being helped to NOT be a dumbass. I certainly know in my profession what I learned in school and from textbooks frequently does not match up with what I see in practice.

I think the order that you outline to do things is a great one.
 
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