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#1
09-29-2020, 03:22 PM
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SD 455 vacuum reading
My question is on a stock SD455 engine what should I see for vacuum at idle?
I have a steady reading about 14"hg vacuum is this correct? |
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#2
09-29-2020, 03:49 PM
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Should be around 17 to 20 with a stock engine. Check your timing and idle mixture.
My bad. A sd 455 has a 230 @ 050 cam, stock. So, 14 not too bad. Check the above anyway and see if you can get a higher reading. Last edited by PunchT37; 09-29-2020 at 03:55 PM. |
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#3
10-01-2020, 10:27 PM
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Altitude has an effect on vacuum readings. What elevation are you at?
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#4
10-01-2020, 11:35 PM
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14hg is about right, actually very good
for a 230 duration stump puller type cam, more like 16-18 if it has 068 cam maybe 18-19 with an 067?
__________________
1974 Lemans Sportecoupe GT (daily driver) "Well the girls out there knock me out, you know Cruisin' around in my GTO" Rock 'n' Roll High School Ramones |
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#5
10-02-2020, 05:25 AM
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The stock 455 S.D. uses a cam with 224° intake duration and 236° exhaust at 115.5° LSA. same as the 744 Ram Air camshaft.
I have the 744 cam in my 462 and 14 in/hg@650 rpm in Drive with a std converter and properly tuned Qjet. |
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#6
10-02-2020, 08:15 AM
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I don't know if it should be higher then 14!
The idle specs say it should idle in gear at like 500 rpm if I recall right and with 13 degrees of advance. That same 744 Cam as used in the 69 and 70 manual trans RAIII 400s with same 500 rpm idle would have pulled more vacuum even with there smaller cid due to the smaller chamber of the high comp heads they used and there smaller D- port head runners.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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#7
10-02-2020, 10:10 AM
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There are too many variables that affect the vacuum reading. Tuning is a big player. Elevation is another as already mentioned.
With the stock cam and a 455 if you are somewhere in the mid teens I'd say you're doing fine and I wouldn't suspect anything out of the ordinary. |
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#8
10-02-2020, 06:19 PM
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Hopefully it doesn't have the 041 cam. In traffic, that cam is misery at its purist form..
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#9
10-03-2020, 06:06 AM
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The 041 Cam would not pass a smog test and the factory had to use the 744 Cam, so there never was a production SD455 with the 041 Cam.
__________________
Wernher Von Braun warned before his retirement from NASA back in 1972, that the next world war would be against the ETs! And he was not talking about 1/8 or 1/4 mile ETs! 1) 1940s 100% silver 4 cup tea server set. Two dry rotted 14 x 10 Micky Thompson slicks. 1) un-mailed in gift coupon from a 1972 box of corn flakes. Two pairs of brown leather flip flops, never seen more then 2 mph. Education is what your left with once you forget things! |
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