23-26 Inches of vacuum in E440----Whats up?????

[saccyclone]

Ok, i just bought this 70 Sport Satellite a few months ago and found that someone had changed out the 383 for a E440 motor. They left the 727 trans in it. I replaced the Edelbrock carb with a new Holly 850 dual feed and vacuum secondaries. It has a cast iron 4 bbl manifold with these numbers 2806178 and dated 4-1-69. I am running a 1 inch spacer plate because the carb linkage hits the cast iron intake without it. New fuel pump with 8 lbs of pressure. Stock chrysler electronic ignition with 14 degrees of initial timing and 34 degrees total. I found that once i got it running i hear a lot of engine noise from the carb but it just does not pull very hard at full throttle. Placed a vacuum gauge and found that i have 23-25 pounds of vacuum at idle (700-900 rpm) and when i rev it up i can get over 30 pounds. I don't know what cam i have but it is very smooth at idle. I think that the excessive vacuum has something to do with how poorly it performs. car has dual exhaust with log type manifolds and turbo mufflers. Any ideas on the intake manifold vacuum????? Thanks for all of you help...

 

[PurpleBeeper]

With that much vacuum I'd say two things....First, the engine is running very well (no vacuum leaks, valves seated well & piston rings sealed well) & Second, your cam is very small. Even for a stock 440 hp cam that is a lot of vacuum. Don't get me wrong, high vacuum is a good thing, but that does seem high. For comparison, my 440 with a pretty big hydraulic cam only gets about 11" at idle and 15" maximum.

With a small cam that carburetor is way too big IMO. If you want to go fast, put in a much larger cam & maybe even step down to a 750 carburetor. If you want a little improvement in performance and keep some "decent" mileage, then maybe step down to a 600-650 cfm carburetor (vacuum secondary) and keep the cam you have. Just my 2-cents.

 

[daredevil]

Are you sure the chokes opening and the throttle blades are opening

 

[RustyRatRod]

No such thing as 30 inches of mercury. 28 inches is considered a "perfect" vacuum....think outer space. My guess is you have a cheap gauge that reads too high.

 

[saccyclone]

All good thoughts....several people that i have talked to locally said that the cam is way too small and may be some type of industrial 440 motor and cam....so changing the cam is going to be something i will have to look at.
The choke is adjusted so that it never comes on....this car starts up fine on even our cold mornings which is not all that cold. All the throttle plates are opening fully, at least by hand.
I will check the vacuum with another gauge that i have...my friend used his gauge last week that gave us those numbers.
Thanks again to you all for the input.

 

[MikeyT]

LOL, I got to agree with rustyratrod on this one!

Mike

 

[Meep-Meep]

No such thing as 30 inches of mercury. 28 inches is considered a "perfect" vacuum....think outer space. My guess is you have a cheap gauge that reads too high.

I agree about the potentially misleading gauge!

Actually, one atmosphere is 29.92 in-hg absolute or zero gauge (you're thinking gauge pressure). I use Torr units when testing my high vacuum pumps and those get to outer space levels of vacuum, which can't be measured with a bourdon gauge but rather must be measured electronically.

 

[lewtot184]

No such thing as 30 inches of mercury. 28 inches is considered a "perfect" vacuum....think outer space. My guess is you have a cheap gauge that reads too high.

bingo!

 

[67 B-body]

LOL... Yep,,,, it's not going to have that much vacuum..... If it did, you could use it to pump down A/C units... You could have a mobile refrigeration repair service....
Just kidding,,,,
Try another gauge and make sure your hooked to manifold not ported vacuum....

 

[ply64post]

High vacuum

Saccylone

I will take a guess and I would check the exhaust for restriction.
Heat riser froze shut,critters carrying debris up the exhaust???



Jeff

 

[saccyclone]

Thanks to you all for the input...tomorrow i will check with another gauge and also check for back pressure. The exhaust has the old log type manifolds and the mufflers and pipes look like they have seen a ticket or two from Adam-12. I will update you all...Thanks again.