Manifold vacuum test

[wally426ci]

 

Just did a vacuum test. I ran the engine and tied directly to the manifold through my brake booster nipple (direct to manifold) I adjusted the vacuum to the highest. I was getting a reading of 15-17 (bouncing back and forth) The only problem is that starter now does a slow crank and then cranks out a normal speed. So, anyone think i should back it off a little even if i lose a little vacuum?? I was reading 12 lbs with it @ 34 degrees @ 2600 RPMS.. now i get a wopping 52 so my balancer must be off.

[422STROKER]

The 52 is when you hook the vac advance back up.  Recheck the timing after you get you best idle.  See what it is at initial now.  I assume you turned the curb idle screw down after you got better idle?  Just make sure you aren't too high on the initial.

Tom

[wally426ci]

Thanks Tom. Im not one for patience and after my ride to and back from Fort McHenry today, Im hanging up the towel for a little while. Very frustrating. When i went with the highest vacuum, the car would sit and surge badly at red lights, stalling 3 times. Almost like it needed a larger stall converter. Then, i took it back with the 34 @ 3000 rpms. It was fine across town, but when i got to the highway (70mph) it was missing pretty bad to keep it at that speed. so, im at a loss. I cant help but make a big deal of it, even though its probably something im over looking.. 

[422STROKER]

Easy Wally, What kind of vacuum are you getting in gear?  At idle.  Have your girl hold the brake and check it.  Maybe you have a small vacuum leak.


Maybe a reset to factory setting are in order.  Grab you edelbrock instructions and reset the idle screws to baseline like you just bought it.  Get it running and adjust the idle.  Then check the timing with the vac disco'd and plugged.  Shoot for 12-14 advanced.  I use a bit of white out on the damper to see it well(TDC mark) also the timing cover mark at 0 degrees.  Then after you get the carb to idle clean by adjusting for best vac re adjust the curb idle down to acceptable levels all the while.  It may take a few tries.  now bring the engine up in revs and see what the total advance is.  Hopefully it's around 34-36 or so.  Reconnect the vac adv when done.  If you want leave it off and drive around see how it acts.  Now if you hook it up and it starts acting funny you may have to adj the vac can with a 3/32 allen wrench IIRC.  This adjusts the total adv with the vacuum. 

The 34 was that with the vac adv hooked up?

Also you could need a larger converter depending on your cam.

What kind of compression are you running?

Make sure you are using the ported vac source(passenger side) on eddy.


Tom

[Changin Gears]

Never heard of adjusting advance by the highest vacuum reading.  I thought idle mixture was done that way.

[422STROKER]

I think thats what He's doing(idle mixture).  At least I hope so.

Tom

[wally426ci]

  well, i ws sort of aiming at solving it all that way. I just heard that vacuum should be around 17lbs. thanks for the input guys, im done with it for a little while. Ive never had this much trouble. And just think, this all started when i tried to go with electic choke.... 

[422STROKER]

Wally I get about 10" of vac at idle750rpm in gear, 18" in park/nuetral900rpm.

You'll get it.

Tom

[Chryco Psycho]

the missing on the highway is over advancing , leave the inital timing where ti is & either disconnect the vacuum advance or dial it back off with an allen wrench, take it counter clockwise until it it clicks & turn it back clockwise 2-3 turns you highway miss will disappear

[BIGSHCLUNK]

 

I had a very similar problem w my pontiac at hwy speeds. too much advance. 

[wally426ci]

Thanks guys. I assumed it was something like that. can anyone explain why it was surging so bad when i had the timing adjusted otherwise sitting at redlights? Ok, i will be sure and mess with it again. I may disconnect the advance temporarily to make sure thats where the problem lies.

On another note, this morning on the way to work, i was thinking of throwing my old Racer Brown cam back in. I had taken it out last year b/c i was convinced something was up with a lifter and i figured if i was buying lifters, id go all the way. Now it could just have been a collapsed lifter and the cam may be fine. I just thought of changing it up again. I may have it degreed in and gone through again when i pull it to paint the engine bay. But, if i were to change out the cam, would there be any problem using my current lifters? ive heard the myth of putting lifters in dif locations could have catastrophic results.....

 

[Chryco Psycho]

it is always a possibility of wiping a cam using old lifters , at least both the lifters & cam were broken in already you probably have a 75 % chance that everything will be ok

[wally426ci]

If i do it, i thought about getting a new set, but still not sure i will change it out.

I assume that while i was messing with the timing, and the car would drop down when id got to 12-14 initial that i need to mess with A/F mixture again? sorry ive never had to make all those adjustments at once...

The car is really just to radical to enjoy right now, i need to quiet it down........ The lady isnt into it... 

[moper]

You can put new lifters ona used cam. You cannot mix up posotions and run usd lifters on the used cam. If they broke int he same, and were kept in order, you're fine. If they were mixed up, buy a set of new ones, and then follow the cam break in procedures with them. If the best percentage one can get for camshaft success is 75%, one is missing something important in the setup.

[Chryco Psycho]

I was just saying that by running used lifter on a used cam he probably has a 75% possibility of success & may have to replace the cam if he takes a chance , doing things correctly the success rate better be above 75%