I understand the family and health issues all to well, I deal with them on a daily basis and get little else done lately.

This may be a far out idea but the G heads and 1:54 rockers used 56-59 used a shorter push rod then the 60-64 heads. I watched a demonstration video at one time that showed the effect on rocker arm ratio and valve opening when push rod length is changed. If you reused the longer push rods from the 64 engine I don't know how much effect that would have and possibly effect the vacuum. I didn't want to throw another wrench in the works but something to consider, don't shoot me

 

Actually, I did reuse the cam, lifters & pushrods. Have you got a link to the demo video you referred to?

 

No, I'm sorry I don't and wish I did. I'll try to find it. At one time I wanted to install the longer 60-64 push rods as an experiment just to see what difference it makes. Maybe some of the YBlock guys will comment on this.

Doing some further research it seems using the different length doesn't have any major effect.

 

Jim,
I'm not a cam guy but I did some measurements when I was trying to figure out what cam I had.
Valve retainer to the bottom of the valve set. Intake .427 / Exhaust .3685
Measurement of the pushrod movement Intake .256 / Exhaust .2435

Unfortunately I didn't do something as simple as measure the cam lobes while the cam was out and in my hand.

 

A lobe measurement would have been helpful but it is what it is now. Hopefully it's not the cam and a more simple solution.

 

The measurements of the lift don't really match any stock cam and the valve lift of the intake is quite a bit off based on a 1.54 ratio. If you check 2 or 3 others you will get a better idea of the actual numbers.

That said, if they are in the ballpark, then it is not at all a big cam and should produce very good vacuum. Things that can reduce idle vacuum are retarded ignition timing, incorrect idle mixture setting, retarded cam timing, overall poor condition of the engine. If you haven't taken it out for the ring break in, then that definitely could be contributing. You should do that the first chance you get. Cam break in does not equal ring break in. You have to drive it and put a load on it for proper ring break in.

Also, the adjuster screw position does have quite a significant effect on the rocker ratio, about a 4-8% change depending on where you start. It doesn't amount to a huge gain in overall power by itself but it is one of those things that is almost free if you do it when the engine is first built. Correcting rocker geometry should be done at the same time, to get the most out of it.

Eaton Balancing » Altering Rocker Arm Ratio By Varying The Length Of The Pushrods

Eaton Balancing » Rocker Arm Geometry

 

Charlie, how much do you think valve lash adjustment might contribute to the vacuum indication at idle? A point or two?

 

I actually had the valves adjusted to .016 and thought that was the problem so I loosened up to .019. Didn't seem to make a difference in vacuum.
I forgot to add I had an old spacer that seemed to be made of some sort of pressed board that I thought might be contributing to the problem so I bought a new plastic one with 2 new gaskets. But no change in vacuum.
I installed the cam straight up (no advance or retard) 12 links apart both dots at the 3 O'clock position.
I can check other valves once I get back out to the trucks.
Charlie,
What kind of lift should I be seeing and from where?
Not sure when I'll get to drive since I'm still figuring out the column and automatic transmission shift linkage. But listening to several folks advice I'll not run it a lot until I can drive it.

 

Most stock cams are in the neighborhood of .260 and intake or exhaust will vary by only a few thousandths.
That doesn't matter a whole lot. You just want to be sure to check a few to make sure they are all in a similar range. If one is significantly smaller than the rest, then that can contribute to your problem.

Did you degree the cam or simply install it on the Keyways, by-the-book? If you did not degree the cam, then you have no idea where it is and it may be retarded. The reason being that the crank, cam, and gears all have machining tolerances. If they all stack up one way or another, then the cam can be significantly retarded or advanced, even if it is installed in the "straight up" position.

Another thing I forgot to add, a friend had a car with a pretty decent cam and only 9" hg at idle. He ran power brakes off that and it seemed to work. I'm not saying it's correct or ok, but it worked.

 

The dreaded degreeing the cam.... No I didn't degree the cam I just installed it like the sprocket set described to Zero. Normally I would just pull it all down but a truck Y block is much more involved and then changing a cam & lifters requires an engine pull.
Since it seems to run OK I'm going to risk it and give it a drive to see what shakes out.
JIM Brought up the point about long vs short pushrods. I used the 64 292 pushrods with the 1.54 rockers. Does anyone think this could cause my vacuum issue?
I'd hate to buy 57 pushrods to "SEE" if that makes a difference.

 

I'm not sure if using the long push rods will change the rocker ratio enough to effect the vacuum that much? It was just a wild thought on my part. I'm in the same boat, I think my push rods are to short but I don't want to buy a set to find out. They are suppose to be the correct ones for the G heads and 1.54 rockers but they seem to short to me, mine have the ball on the adjuster about 3/4 down. Do you remember where yours were?

 

Not the clearest of pictures but they look to be about 3 threads from all the way screwed in.

 

In my eye it looks like more then three, they are a fine thread and it looks better then mine. Now I really want to try the longer push rods.. The difference between the two lengths is .195 if I calculated correctly.

 

Yep 8.320 vs 8.125

 

We'll I believe I found the problem. I finally bit the bullet and pulled the intake manifold. The gasket was stuck everywhere but #4. Cleaned everything up, checked intake and head mating surfaces for straightness, all was good. So I MODed my "B" manifold to two ovals and put it back together, with new gaskets. Now I have 19-20 inches of vacuum. Of course in the meantime I exchanged the old original axle for a 9", had a new drive shaft made to fit the 9", and changed out all the rear spring hangers with the poly ones from MidFifty.
Now that the engine is running well I'll install my new two speed electric fan and wiring kit to keep her cool.