Glowing headers
Thread Starter
Instructor
Joined: Jun 2012
Posts: 212
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Thats what the previous owner said it has a Blue Racer .488 lift
I have 16* advance initial at idle without vac advance connected altough the hose is plugged, and i have recently redone the valve timing.
I managed to get a constant 11* before tuning the idle mixture, since changing the main jet size bigger i get the fluctuating, the bigger issue is the fluctation, i can then work on tuning it to get better vac.
Here are the details of the cam.
Deg. Dur. @ .050 Cam Lift Int./Exh.
234
234
Deg Adv Dur Int Ex
300
300
Deg lobe seperation
114
Lift
.488
.488
I have 16* advance initial at idle without vac advance connected altough the hose is plugged, and i have recently redone the valve timing.
I managed to get a constant 11* before tuning the idle mixture, since changing the main jet size bigger i get the fluctuating, the bigger issue is the fluctation, i can then work on tuning it to get better vac.
Here are the details of the cam.
Deg. Dur. @ .050 Cam Lift Int./Exh.
234
234
Deg Adv Dur Int Ex
300
300
Deg lobe seperation
114
Lift
.488
.488
Last edited by brady5885; May 5, 2013 at 09:30 PM.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
So i changed the jets to #74 and it seems to be better and want to put miles on it to get a true representstion of the way it is running.
But im having issues with the brakes and the power assist not working. I checked all is working, and lastly checked the vacuum. Im only reading 10 but it is fluctuating very quickly between 8-12.
i have a .488 cam installed if that matters
But im having issues with the brakes and the power assist not working. I checked all is working, and lastly checked the vacuum. Im only reading 10 but it is fluctuating very quickly between 8-12.
i have a .488 cam installed if that matters
There is something seriously wrong to make a need jump like that at idle. Even with a huge cam (which you don't have), it shouldn't be jumping around that badly.
Appears you may have valve issues- leaking/not closing properly etc.
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
Thats what the previous owner said it has a Blue Racer .488 lift
I have 16* advance initial at idle without vac advance connected altough the hose is plugged, and i have recently redone the valve timing.
I managed to get a constant 11* before tuning the idle mixture, since changing the main jet size bigger i get the fluctuating, the bigger issue is the fluctation, i can then work on tuning it to get better vac.
Here are the details of the cam.
Deg. Dur. @ .050 Cam Lift Int./Exh.
234
234
Deg Adv Dur Int Ex
300
300
Deg lobe seperation
114
Lift
.488
.488
I have 16* advance initial at idle without vac advance connected altough the hose is plugged, and i have recently redone the valve timing.
I managed to get a constant 11* before tuning the idle mixture, since changing the main jet size bigger i get the fluctuating, the bigger issue is the fluctation, i can then work on tuning it to get better vac.
Here are the details of the cam.
Deg. Dur. @ .050 Cam Lift Int./Exh.
234
234
Deg Adv Dur Int Ex
300
300
Deg lobe seperation
114
Lift
.488
.488
Thread Starter
Instructor
Joined: Jun 2012
Posts: 212
Likes: 0
I did a compression test not so long ago. And got consistent readings of around 135 give or take 5-10.
I played with the idle screw, I'm at pretty much 1 turn out on both sides
I have had it with a fairly steady needle showing 11in vac, the only thing done to the engine since then is out bigger main jets in.
Maybe I should do it again and re-check the valve adjustment?
How do you free up a sticking valve?
I played with the idle screw, I'm at pretty much 1 turn out on both sides
I have had it with a fairly steady needle showing 11in vac, the only thing done to the engine since then is out bigger main jets in.
Maybe I should do it again and re-check the valve adjustment?
How do you free up a sticking valve?
Last edited by brady5885; May 5, 2013 at 10:30 PM.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
I did a compression test not so long ago. And got consistent readings of around 135 give or take 5-10.
I played with the idle screw, I'm at pretty much 1 turn out on both sides
Maybe I should do it again and re-check the valve adjustment?
How do you free up a sticking valve?
I played with the idle screw, I'm at pretty much 1 turn out on both sides
Maybe I should do it again and re-check the valve adjustment?
How do you free up a sticking valve?
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
if your compession is consistent between all cylinders,, then its not a bent or burt valve..and since the motor is new, doubtful its a sticking valve.. thats usually caused by build up in an old engine ...you can put a detergent like SeaFoam in the oil, if you like .. but ,I doubt thats the problem..I m sure the heads were redone with the engine.. have you checked the valve springs thoroughly? you could have a broken spring.. recheck your valve lash ..make sure you don t have one too tight
Thread Starter
Instructor
Joined: Jun 2012
Posts: 212
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Static test? .... I pulled all the plugs, attached pressure gauge and turned the engine over approx 5 strokes.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
Sorry, a bad choice of words.
I'd suspect something with the valvetrain.
Adjustment too tight, broken spring, valves not seating properly etc.
Even though your heads/motor are new/rebuilt, that doesn't mean whoever did the work did it right. I've seen a lot of poorly done heads in my day....
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Instructor
Joined: Feb 2013
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Just a guess, and (admittedly) an echo of what another member posted recently, but I've been wondering all along if the cam is not timed correctly.
But then I think, wouldn't that have shown up when confirming that #1 cylinder was at TDC and both valves were closed? Or could the duration/overlap of the cam allow both valves to be closed, but valve timing still off a tooth or more?
But then I think, wouldn't that have shown up when confirming that #1 cylinder was at TDC and both valves were closed? Or could the duration/overlap of the cam allow both valves to be closed, but valve timing still off a tooth or more?
Melting Slicks
Joined: May 2006
Posts: 3,303
Likes: 14
From: Lynn MA
as mentioned prior, need to make sure cam, cam gear, crankshaft gear are aligned correctly, make sure it is on number one compression strong with timing mark aligned correct, as well as both valves on number 1 when you are setting it up from scratch...
I really think it is valve timing/ignition timing and adjustment
keep us posted
I really think it is valve timing/ignition timing and adjustment
keep us posted
Drifting
Joined: Aug 2009
Posts: 1,346
Likes: 160
From: new iberia la
Brady, what I was talking about earlier is valve timing in relation to crankshaft.. there are marks on the crank gear and cam gear that must be aligned during assembly...only an absolute retard would get that wrong, but its possible ....they are behind the timing chain cover..waterpump and timing cover have to come off to access.. late valve timing will cause low manifold vacuum, but will not cause the fluctuation you have..but, check your springs and valve lash first, and once more, spray starting fluid or carb cleaner around edge of manifold and base of carb to check for leaks, before tearing off the timing chain cover
Melting Slicks
Joined: May 2006
Posts: 3,303
Likes: 14
From: Lynn MA
It stinks to start from scratch, but you likely will need to....
The timing chain crank gear and cam gear are exposed when the timing chain cover is off.
I agree with fishslayer, check all this other stuff first....buit IF and when you need to, check this out.
The timing chain crank gear and cam gear are exposed when the timing chain cover is off.
I agree with fishslayer, check all this other stuff first....buit IF and when you need to, check this out.
Thread Starter
Instructor
Joined: Jun 2012
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Ok I will be checking all the first things this evening, and I'm going to do tdc with a piston stop and not off the balancer mark.
One more thing that's happened since the needle shake occurred. I put the old side pipes on, I think they are reverse flows, VERY RESTRICTIVE as apposed to my hooker max flows... Just while I'm working on it. Would this cause the needle to shake like that?
Or could too bigger jets in the carb do it?
One more thing that's happened since the needle shake occurred. I put the old side pipes on, I think they are reverse flows, VERY RESTRICTIVE as apposed to my hooker max flows... Just while I'm working on it. Would this cause the needle to shake like that?
Or could too bigger jets in the carb do it?
Last edited by brady5885; May 6, 2013 at 11:23 PM.
Thread Starter
Instructor
Joined: Jun 2012
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Ok so i checked TDC balancer mark is actual TDC of #1, and its correct.
Initial timing is at 16* and its still looking the same (shakey needle -/+ 5inhg)
I pulled the plugs for the first time since putting in bigger jets and they were very black, obviously too rich. Originallly had #70, i went to #74, i will drop it to #72 tomorrow.
I was just thinking, if it was very sooty if that could cause the valves not to seat properly due to the build up?
I need to check the springs are good. (they should be as the are brand new whe he did the rebuild)
Im pretty certain the valve lash is correct i did it 3 times a little while back just to make sure, with the engine at temperature and running i backed off the rocker nut until it was tapping, tightened it down till it went away then an extra 1/4 turn in.
The original owner assures me that he did the cam timing correctly.
Initial timing is at 16* and its still looking the same (shakey needle -/+ 5inhg)
I pulled the plugs for the first time since putting in bigger jets and they were very black, obviously too rich. Originallly had #70, i went to #74, i will drop it to #72 tomorrow.
I was just thinking, if it was very sooty if that could cause the valves not to seat properly due to the build up?
I need to check the springs are good. (they should be as the are brand new whe he did the rebuild)
Im pretty certain the valve lash is correct i did it 3 times a little while back just to make sure, with the engine at temperature and running i backed off the rocker nut until it was tapping, tightened it down till it went away then an extra 1/4 turn in.
The original owner assures me that he did the cam timing correctly.
Drifting
Joined: Aug 2005
Posts: 1,443
Likes: 65
From: Wauconda IL
Carb jetting wouldn't produce the fast bouncing vacuum reading, only valve related issues will. Even having the cam off a tooth wouldn't produce that type of reading-
You have valve closure issues of some sort.
Either weak/broken springs, bad valve grind (valves not sealing properly), bad guides etc.
You have valve closure issues of some sort.
Either weak/broken springs, bad valve grind (valves not sealing properly), bad guides etc.
Thread Starter
Instructor
Joined: Jun 2012
Posts: 212
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I understand that it wont effect it directly but what I mean is a very rich engine produces carbon build up, could it have excess carbon build up on the valves/valve seats hindering the valve to close with a good seal, thus making the needle shake?