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Manifold vaccuum question

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T

Tinster

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I was with a Triumph mechanic yesterday and he
asked if I had checked my manifold vaccuum pressure.
I told him yes - 17# to 19#

He asked me to test the engine again at 3500 RPMs.

Why is this important?

thanks,

dale
 
Vacuum gauges were considered as part of basic Mechanics 101 when I was growing up. They can tell you a lot about potential or existing problems in an engine and were considered a necessary part of properly tuning an engine.

If you get a lot of fluctuation at a steady higher RPM, it could indicate sticking or leaking valves or possible valve guide issues. Or weak springs or cam or a lot of other things. This is a tool to be used in conjunction with a series of tests, not a stand alone test that can be counted on at ALL TIMES to provide a finite diagnosis of a problem. That is why I said it was used AS PART OF a properly executed tuning package, not a panacea for every ailment possible.

Here is a site that has various scenarios that can occur when certain vacuum readings are present.

https://www.users.bigpond.com/ergoff/vac2.htm
 
Thanks Paul- good to know: I have a similar graphic
chart that indicated my engine in good condition but
with a header present. Turns out I do indeed have a header.

regards,

dle
 
That is certainly a header in the pictures that I've seen of your engine.

Were you ever in doubt about that?
 
That's what happens when you walk into a kid's play area and forget the door height is only 5' high
 
DNK said:
That's what happens when you walk into a kid's play area and forget the door height is only 5' high
Click to expand...

<span style="color: #660000">Dang!! All these years I thought a header was the monolithic
piece of lumber over a door or window opening.

:winner1:</span>
 
Tinster said:
Yes!

I'm still not sure what a header is.

d
Click to expand...

A header is an exhaust manifold. Over the years the definition has come to mean a performance exhaust manifold.
 
I still don't understand what this has to do with a vacuum reading at 3,500RPM???

You can see if you have a header just by looking at it. It either is, or it isn't by virtue of it's design.

Do these new Triumph mechanics in your hood enjoy seeing your can with the hood up in the garage or watching you drive it to the beach?
 
The only concern that I can envision that would happen with some other car(specifically, Hondas, and other catalytic equipped cars) would be loss of vacuum.. Which we know would be exhaust restriction.
 
Brosky said:
I still don't understand what this has to do with a vacuum reading at 3,500RPM???

You can see if you have a header just by looking at it. It either is, or it isn't by virtue of it's design.

Do these new Triumph mechanics in your hood enjoy seeing your can with the hood up in the garage or watching you drive it to the beach?
Click to expand...

<span style="color: #660000">Drivers one and all!! Beach guys. Just giving my car a look-over and
telling me what I've got. They know ALOT about Triumphs.

They picked up immediately that I have a vapor lock problem wit my carbs.
(I did NOT have my insulated carb bowl heat fixture installed when they saw the car.)

Thanks shawn- it appears my car has Monza headers on it

d</span>
 
Paul Rego hit the nail on the head! Vacuum gages will tell you a lot about an engine, if you know how to decipher it. When you take a low RPM reading then a higher RPM reading, a comparison of how the gage reacts between the two readings can can give a world of info. Again, if you know how to decipher it. It can also be used to check vacuum controls, distributor's vacuum, cracked hoses, etc. I wouldn't be without one.
happy0034-1.gif
 
Thanks Paul !!

I have an oil leak from behind my flywheel.
Probably the engine rear oil seal.

Jose believes a high RPM vacuum test might yield
some information concerning the oil seal condition.

Paul Rego- The header and request for a vaccuum test
were two seperate comments not related. Sorry for the
confusion.

d
 
<div class="ubbcode-block"><div class="ubbcode-header">Quote:]They picked up immediately that I have a vapor lock problem wit my carbs.[/QUOTE]

Was that diagnosis before or after this comment?

<div class="ubbcode-block"><div class="ubbcode-header">Quote:]"Strong and fast" they said.[/QUOTE]
 
Comment was while they were inspecting the engine.
BEFORE they drove it.

But they are correct- without my carb heat shield,

I do get get brief vapor locks. Tony was with me during
a brief vapor lock sputter.

dale
 
What happened to the heat shield? I know that you fabricated it and went to great lengths to insulate it. I thought it was on the car, but should have noticed that it wasn't showing in the linkage photos.
 
kodanja said:
HEY DALE EVER CONSIDER THIS?

FOR DALE!!!!
Click to expand...

<span style="color: #660000">And have YOU ever considered what
you might look like with carbuncles and pustules
covering your entire body?

:lol: </span>
 
only joshin' Dale

Youve come so Far, just a few more replacement parts
and yer car will be brand new!
 
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