Vacuum test help

[btbuild]

73 fj40 desmogged, rebuilt engine, trollhole carb, new pertonix electronic ignition, stock dizzy, original coil with ballast resistor. New rotor, cap and wires.

I set timing at approximately 13 degrees btdc. BB at bottom of window. Idles great, starts great. Put load or rev engine it falls on it's face and sputters.

My question is when I hook up vacuum tester up I'm showing 18 inches vacuum. When I step on accelerater it will drop fast. Is this the correct response? Never done this before with vacuum tester.
I have my vacuum tester hooked up to brake booster port.

I'm leaning toward a vacuum leak somewhere but can't find with conventional ways.
I also did set idle mixture. I dialed in till started to run rough and then backed out till started to run even again. Idle is at 650 rpm with my tachometer gauge tester.

Yes I have been reading my head off in FAQ and other threads.

Please any help would be great.


Thank you
btbuild

 

[FF LC FREAK]

What's your altitude? That will determine how much vacuum you can pull. I pull a steady 21" of vacuum at just above sea level. However, falling flat on it's face when you rev or accelerate sounds more like a carb issue (accelerator pump maybe) than a vacuum leak. However, I'm no carb guru. Hopefully others will chime in.

 

[btbuild]

I'm at 82' above see level. The most vacuum I can get is 18"

 

[thebigredrocker]

Nice looking engine bay.

Do you have the vacuum port on the dizzy capped off? If not you could try that. You probably know a 73 dizzy retards timing when vacuum increases.

 

[btbuild]

Nice looking engine bay.

Do you have the vacuum port on the dizzy capped off? If not you could try that. You probably know a 73 dizzy retards timing when vacuum increases.

Actually I have a vac advanc dizzy. I tried hooking up there first but wasn't getting a reading. No the port is not blocked off. It is hooked up to carb port. Maybe we are on to something!! I still don't know what it is though. Haha

 

[thebigredrocker]

Did you get a different dizzy? The picture of the dizzy you posted awhile back is a vac retard.

 

[btbuild]

Now I'm really confused here! Is this vac advance or vac retard?

 

[thebigredrocker]

That is Retard dissy. To test it, pull the cap, apply suction. Retarding will turn the points plate clockwise. Advancing will Rotate the plate counter clock.

Here’s a pic of a extra small vac advance nippondenso

 

[Matt1260]

Considering that I'm trying to track down a vacuum problem on my own 73-74 and that it still runs and drives great, I'd forget about the vacuum reading and look elsewhere. My vacuum gauge is vibrating between 15-19" rather than remaining steady. There is also a tiny leak in my brake booster too.
When you give it gas the vacuum is supposed to drop almost all the way down and then go back up to above 20 when you let off before resolving back to 17-18.

Perhaps your distributor is not advancing the timing enough? Get a vac advance distributor if you don't have one.

 

[btbuild]

Considering that I'm trying to track down a vacuum problem on my own 73-74 and that it still runs and drives great, I'd forget about the vacuum reading and look elsewhere. My vacuum gauge is vibrating between 15-19" rather than remaining steady. There is also a tiny leak in my brake booster too.
When you give it gas the vacuum is supposed to drop almost all the way down and then go back up to above 20 when you let off before resolving back to 17-18.

Perhaps your distributor is not advancing the timing enough? Get a vac advance distributor if you don't have one.

That is exactly what my vacuum reading is doing. That was my first question on distributer. I just always assumed it was vac advance. i guess I was wrong.
So is the consensus I need a vac advance dizzy?

 

[btbuild]

That is Retard dissy. To test it, pull the cap, apply suction. Retarding will turn the points plate clockwise. Advancing will Rotate the plate counter clock.

Here’s a pic of a extra small vac advance nippondenso
View attachment 1582636

Is there a way to test and see if the retard dizzy is the culprit of my problem? Or do I just need a vac advance dizzy? I'm not sure where to go with this now. Feel kinda stupid.

 

[thebigredrocker]

You could try to cap the vac port on the dizzy and the port on the carb. I never ran my retard dizzy cause I read 65swb45 & FJ40Jim mention those are their least favorite Nippondenso’s. I run a early-68 dissy w/Pertronix from Mark’s Offroad on my 71 F. Gobs of power, no hesitation.

Here’s cool page
Dizzy FAQ

^ What he said. ^

Vac retard is useless for us. Leave it disconnected and run the dissy as mechanical advance only. Retard dissy has a lot of mechanical advance, so they work OK in this configuration.

That is a '71 carb.

Do not connect any vac hose to the '71 vac retard distributor. Just set base timing to 10*BTDC and run as mechanical advance only.
Cap off manifold vac fitting (#3).

Cap the giant hose fitting on the air cleaner lid that used to feed clean air to the AIR pump. It's just letting dirty air right into the top of the carb.

Install large diameter oil-proof hose between currently capped air cleaner barb and fitting on valve cover. Maybe available from Toyota?

There is a rubber seal that should be in the neck of the air cleaner to seal it against the carb air horn. Get a new one from Toyota.

Back the idle mix screw (#1) out 4 or 5 turns to get a decent idle. Adjust the idle speed screw (hidden on back side of carb) to get the desired idle speed. If it will idle at 6-700RPM, then turn in idle mix screw until idle speed starts to drop, turn back out to achieve peak/smoothest idle.
If it will not idle correctly, then it likely is running too lean due to:
-manifold vacuum leak
-plugged carb idle passage
-warped carb body &/or air horn.

HTH

Yes, that is the ported vac fitting on carb base. Connect it to a vacuum advance dissy. Do not connect to a vac retard dissy.

 

[btbuild]

You could try to cap the vac port on the dizzy and the port on the carb. I never ran my retard dizzy cause I read 65swb45 & FJ40Jim mention those are their least favorite Nippondenso’s. I run a early-68 dissy w/Pertronix from Mark’s Offroad on my 71 F. Gobs of power, no hesitation.

Here’s cool page
Dizzy FAQ

Thank you very much! I have always assumed it to be vac advance. Always learning...

 

[thebigredrocker]

See how your dissy vac nipple points toward the rear of the vehicle and mine faces forward? That’s my understanding of how to quickly decifer retard from advance dissy’s.

Does the Trollhole carb have a “ported vac” fitting right by the idle mix screw?

I’d just cap it for now.

 

[btbuild]

Yes it does. here is a pic of what I have. Does this tell you I should be running a vac advance dizzy?

 

[thebigredrocker]

Yep, that is “ported” for a vac advance if you decide to go that route.

For now I think you can just put a cap on it. Or a short chunk of hose doubled back and zip tied so it doesn’t leak air. I read where FJ40Jim has said your style dissy has lots of mechanical advance and can be made to work Might be worth a try.

 

[btbuild]

Yep, that is “ported” for a vac advance if you decide to go that route.

For now I think you can just put a cap on it. Or a short chunk of hose doubled back and zip tied so it doesn’t leak air. I read where FJ40Jim has said your style dissy has lots of mechanical advance and can be made to work Might be worth a try.

well I think I will just cap off the port on carb and dizzy for now and see if I can get it to run any better. I will start looking for a new vac advance dizzy. Do you think that will be much better in the long run? Marshal sells those also, he is just so hard to contact.

Thank you so much for your help! I've been driving myself crazy the last couple weeks.
Barrett

 

[4Cruisers]

I decided to go with an FJ60 electronic ignition in my '76 FJ40 with original 2F, am very happy with the way it turned out. It's vacuum advance. Will be setting up my '71 FJ40 (with a '76 2F) identically.

 

[btbuild]

I decided to go with an FJ60 electronic ignition in my '76 FJ40 with original 2F, am very happy with the way it turned out. It's vacuum advance. Will be setting up my '71 FJ40 (with a '76 2F) identically.

is that pretty much a drop in swap? And where did you buy your fj60 dist?

 

[ducktapeguy]

I did the same swap and it's a nice improvement. It's almost a drop in swap, you will need a new "dented" side cover to clear the larger dizzy and I believe there was a wire that needed to be changed or lengthened. There's a few writeups on here about it.

Also, check your advance (or retard) diaphragms to make sure they're not leaking. Mine were bad and caused a vacuum leak.