Hi.

I carefully opened the vacuum can with a small screwdriver.
I then went to a company that sold different springs, and found one in same length, but a little weaker. Closed the vacuum can again. And then you are ready to go;)

I will try to post some pictures later.

This is the only way you can achieve to get the vacuum can to work probably. And by this you will achieve a high timing in idle, just the way your BIG cam wants…. It will also produce a steady idle with very little fuel. By doing this will allow you to close the throttle plates a little more, giving you a little more vacuum.
And if you have any stumble on acceleration, this will hopefully disappear as well.

Forget about switching intake. I went from a Torker II (Single plane) to a Edelbrock RPM (Dual plane) and this only gave me about 0,5 Hg….


Best regards Søren

There are several different vacuum cans available over the counter with varying opening rates and amounts. Or you can use an adjustable can available from many sources.

Vacuum advance can help...but I don't count on it to add lots of advance. I would prefer to set more initial and limit vacuum to 6-8* max depending on the combo. My reasoning is that it is idling all nice and clean, then when you open the throttle, vacuum drops, timing drops and you can have a stumble. This assumes using full and not ported vacuum. Now sometimes that's exactly what you want to help eliminate off idle ping...but not usually needed.

I would work on the dist curve itself to add initial, limit total and limit vacuum as needed.


JIM

I have a Crane adjustable can, and last night I tested it with a vacuum guage, and can get a fair amount of travel with 7 inches.( This is with the adjustment screw all the way in.) I put it on,but didn't have time to play with it running. I also made my own limiter bushing, that I may end up trying as well. I'll have to pull the distributer to put it on, but I'm guessing it will allow for a 20-21 degree initial, and still keep the 36 total. I can't find an MSD bushing bigger than the black one I'm running now, and that only limits 18 degrees.

I'll play with it some this weekend, but from what I hear it's supposed to rain.

I tried my home made limiter bushing, now I have 21 degrees initial, 36 total, and I still have the idle issue.Response is very quick. I still have not tried the timing locked out, but at this point I'm out of ideas other than that.

Any thoughts?

I'm considering tossing my RPM intake back on for a test, but since the "season " just started,may put it off till fall. Then I may down size the cam a notch, and swap back on the RPM intake.

1 thing i'd like to try is using a $4 solenoid to close the choke just right, only at idle. a microswitch would open the choke as soon as u give it gas.
this way idle enrichment would be controlled by choke adjustment and not hurt cruise mpg.

You need to just start over. Remove that herbert wonder cam. They use simular roller cams of that duration in circle track motors that idle at 2000 rpm

how many ci do you really have?

It's a 406, and the last cam I ran was a Comp XE-284 flat tappet hydraulic. It had 240/246@.050, and a LC of 110 installed at 106. I read that a solid to hydraulic equivilent conversion would need 10 degrees more for the solid to match a hydraulic, so I thought the match was fairly close. (Isky has 254@.050) The main cam difference is the Isky runs 108 LC, and is installed at 108.I also swapped to the Vic Jr. at the same time, so I have a manifold design change as well.

I am overall happy with the combo, with the exception of the idle problem. I unfortuately crossed the perverbial "line" when I picked this cam, and have been trying to tune around it.:smash:

I'm sorry, I thought this was a suggestion for me. JP-80, I tend to agree, that is a monster cam for a smaller engine.

Hi again...

Heres is a picture of the can. This is a VCR 1862 like yours, and the can that needs the less vacuum to operate. In my sistuation it wasent enough. I tried the adjustable as well, but this I could not adjust low enough....

http://i90.photobucket.com/albums/k2...p/P4130082.jpg

Try this, I think it would help you. I running a Satuday Night Special Cam thats running in 3500-6500 RPM range...:D

Best regards Søren

I opened up one of my Crane adjustable cans just to see how difficult it would be, and see the spring you changed. Mine measures 1 3/4" long, and has wire .075 diameter.I'm going to check around to see if I can find a lighter spring and use the adjustable can. This will give some tuning ability once I get the spring rate close.

Money Pit - I know it's a monster cam now. Didn't know much about it when I ordered it (engine builder suggested it). But I would really like to try tuning it and getting it to run before swapping out cams. What sping combo are you using to set your advance curve?

I printed off MSD's instruction manuel and I fooled around with it this weekend and got it to idle really well (without vacuum hooked up) at 18* and around 1000 rpms. Shot up to around 32 with vacuum hooked up and around 1500 rpms. What exactly does the vacuum do? Do you really need it? I tested the vacuum at idle and it was around 5.5.

My MSD HEI Pro Billet is set up with the combo "C", I think it's the heavy silver/light silver spring.

The vacuum can adds additional timing to the base under high vacuum conditions. Idle,and cruise. But under heavy throttle, drops out the added timing, so the engine doesn't ping.

I can't believe you got a decent idle. I'm still messing with mine, and I even made a custom limiter bushing to give me 21 degrees initial.I was running the black limiter,which is only 18 degrees.

I drove it to work this morning,and I'm not happy with it yet. Now it surges at low speed, I guess from too much advance, and still wants to stall at the stop signs.Man does it pull though when I get on it.

My problem is I get a decent idle at 1200 in park, but the idle becomes un stable in gear.

Are you running an automatic or standard trans?

I switched out to combo "C" this weekend before I started messing with it. I'm currently using the black bushing. How did you make your custom one?

I wouldn't hold my breath on it being a winning combination though. I didn't really get to drive it that much after setting (wife thought dinner was more important:crazy: ). I did drive it for a while before I set it so that the engine would be hot and idling like it normally did.

You get your 1200 with the vacuum hooked up right? When I hooked it up it shot up from 1000 to ~1500. Is that normal? Is that just a carb setup?

I running an auto trans.

I found a nylon bushing at Lowes that was 1/2" in diameter,and had a hole about .190" I stuck in in a drill press at work and turned the OD down to .400". This I cut off to be the same thickness as the MSD bushings. Fits perfect. Not sure it's a winner though.

My 1200 rpm idle is with the vacuum can connected. (VC1862) This with the 18 degree limiter would give 34 degrees advance at 1200 rpms in park. (The vacuum can pulls an additional 16 degrees with 8 inches of vacuum.)

What stall speed is your converter, and are you able to idle in gear?

3500 stall converter.

Idle in gear... Yes and No, it will but it really wants to die. Since I didnt' get to drive it much I'm not sure if it will actually continue running or stall out. I'll try and put on a few test laps around the neighborhood this evening and see what it does.

Is your vacuum source ported or manifold.

Full manifold.

I would suggest only backing up in your driveway and trying to pull forward in gear till you get a feel for how it runs.

When I got my front end aligned, I almost shot off the lift ramps trying to keep it running with one foot on the brake,one on the gas. It would run like Godzilla one second,then feel like stalling the next.

I just set the timing to 18* with vacuum disconnected and it idled at 1000 rpm consistently out of gear and 800 in gear and it didn't try to stall. I drove it around the neighborhood several times and it ran fine (no lag, pinging, etc.) and kept the above rpm's.

With that being said, is it really necessary to run the vacuum advance??? I don't have anything else hooked up to vacuum (no A/C, heater, brakes).

good work!
in your case i'd try ported. it will only advance at crusie and help it run cool and get good mpg.
.
some guys report good results without it.