How To Fix Late Valve Timing
Low just steady vacuum gauge reading - belatedly valve timing?
- Thread starter Michael Sammy
- Beginning date
- #1
So I believe the 400 sbc motor I have does non accept a large cam since it sounds pretty much stock when idling, notwithstanding it has very low vacuum at idle like nine in-hg where I remember stock motors had effectually xx. The vacuum is extremely steady though, to the indicate I though the guage was stuck but it works just low. Also, I did check and make certain I was using total manifold vacuum port on the carb. in my opinion, the engine does feel weak for being a fully rebuilt 400 equally I have iv.56 gears in the rear, and in third gear on my th400 the motorcar does not accept much take off until about 2000-2500 rpm where it wants to shoot off. It feels kind of hasty.
the gauge says that my valve timing might be late. Is there a mode that I can bank check the valve timing without taking autonomously the front of the engine?
- #2
Practise your feel the vacuum gauge is accurate? You have to pull the timing cover to change valve timing. Most rebuilders and engine shops install the cam straight up, information technology's uncommon that someone would install it otherwise without a reason.
How many degrees are in your base ignition timing?
- #3
Don't check for vacuum on the carb, find a port on the back or port of the intake to check it. Been downward that route chasing my tail on issues like that in the by. Bump your initial timing up 6 or 8 degrees and encounter if the vacuum goes up. 9" is pretty low for a 400, perchance the cam gear is off a tooth.
- #iv
For Ha-Ha'due south...maybe exercise a pinch check on a cylinder? Peradventure the rebuild isn't as good every bit idea. (Not throwing stones, it'due south an easy check that could eliminate i aspect of the equation for you).
- #five
For Ha-Ha's...mayhap practice a compression check on a cylinder? Mayhap the rebuild isn't as practiced as thought. (Not throwing stones, it's an easy check that could eliminate 1 aspect of the equation for you lot).
Tin I exercise compression exam with the car after its been sitting for over a week? Or does it demand to be done with the engine warm? I live in NJ and its in the 40F-50F now in the evenings.
- #6
Don't check for vacuum on the carb, find a port on the back or port of the intake to check it. Been down that road chasing my tail on problems similar that in the past. Bump your initial timing upwards half-dozen or 8 degrees and see if the vacuum goes up. 9" is pretty low for a 400, maybe the cam gear is off a tooth.
I am using a performer RPM and exercise non see any vacuum ports on it. My carb is hooked up the air breather. Will that lower vacuum? Should I cap that off? I simply have information technology hooked upwardly because people say oil will get through the breather and brand a mess in the engine bay
- #vii
You hateful a breather on the valve embrace runs to the air cleaner, similar stock?
- #eight
You mean a breather on the valve cover runs to the air cleaner, like stock?
The hose from the sabbatical cap is running into the big vacuum port in the front of the carb
- #nine
- #10
No PCV valve. It simply runs from the breather on the rider side into the carb. Was like that when I bought the car.
Source: https://nastyz28.com/threads/low-but-steady-vacuum-gauge-reading-late-valve-timing.321751/
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