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1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#1
Quite a regular
Quite a regular

hynesjm
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Hi All,

I have a 1941 180 with a recently rebuilt 356 straight 8 cylinder that has hydraulic lifters (I believe, see attached picture) that I have never been able to get to idle smoothly or have acceptable vacuum. No matter what I have done with Carburetor or timing, I struggle to get 13 inches of vacuum at idle of ~570-600 RPM.

I have been trying to find a major intake manifold leak that would explain this, but
can't seem to find an obvious leak. I am now wondering if a valve train with a misaligned cam or without sufficient clearance (~.03 to .07") is to blame?

From the build sheet, the following camshaft information was listed (note that engine builder was not Packard specific, but was a very sharp guy):

Cam Lobe Separation: 110.38
Centerline set to: 107.25

I have done compression and leak down checks, and while they look a little low (101 psi avg with 97 on the lowest , 7% leak down avg on each cylinder, highest at 9%), I don't think that would explain the very low vacuum readings?

cyl-Comp-Leak Down
1-102-6.3%
2-98-9.2%
3-100-7.9%
4-97-8.0%
5-101-6.6%
6-104-6.5%
7-103-5.3%
8-105-8.0%
Average:101-7.2%

Is there a way to check valve lash on an assembled engine? Everything I have read is checking and grinding valves to achieve the desired .03" to .07" clearance, but I haven't seen much on checking an already assembled engine.

Attach file:



jpg  IMG_8889.JPG (2,658.04 KB)
160461_613e9cec0e5e7.jpg 3264X2448 px

Posted on: 9/12 19:49
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Re: 1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#2
Quite a regular
Quite a regular

hynesjm
See User information
Update: The Manifold IS leaking.

I made an adapter with a tire stem, piece of a tin can and a silicone coupler with hose clamps so I could slightly pressurize the intake manifold. I then put about 5 PSI of air to it and sprayed the intake ports with soapy water and could see at least 3 of the 4 inlet connections blowing bubbles.

I will R&R the manifolds and report back to see if that improves the situation...a good case of K.I.S.S right here :)

Posted on: 9/12 23:41
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Re: 1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#3
Home away from home
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Wat_Tyler
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Good luck with it. Sounds like a pain in the hind parts to sort out.

Posted on: 9/14 5:11
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Re: 1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#4
Home away from home
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Dell
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Need gaskets, check ebay 165066392039 you will have an extra supply

Posted on: 9/14 9:37

35-1200 touring sedan
42-110 convertible coupe
48-2293 station sedan
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Re: 1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#5
Quite a regular
Quite a regular

hynesjm
See User information
Thanks for the ebay listing. I currently have installed and another set of the ~4 port interconnected Metal Faced/paper gasekts that seem to be advertised for the later 8 cylinders.

I ordered copper ring gaskets that are individual and have a single 2 port connected piece like you show in the 165066392039 listing you mention.

Posted on: 9/15 12:38
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Re: 1941 Packard 356 8 cylinder - Low Vacuum After Rebuild
#6
Home away from home
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Dell
See User information
Did you check the surface with a straight edge? Might need to be surfaced. They sell the paper ones because the correct metal jacketed one are very hard to find. Max get $95 a set I believe

Posted on: 9/15 19:12

35-1200 touring sedan
42-110 convertible coupe
48-2293 station sedan
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