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Old 06-01-2020, 03:43 PM   #1
Isaiah92260
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Need help with my first 350 sbc

So I have a 350 with a 350 automatic trans.
I am not sure what year it is. The alternator is on the passenger side and has that big alternator bracket/ shield.
Anyways I just got started. I tuned up the Hei distributor, and rebuild the 4 barrel Holley carburetor. So once I fired it up, the valves sounded extremely flattery.

I popped open the valve cover and the valves were sloppy as hell.

So I just adjust them, now it runs decent. It doesn’t smoke, idles on it’s on fine.

But I noticed the 350 shakes a lot.

I am not sure if it has a mild cam or not?

Also what timing do you guys think is the best degree and the right idle speed?
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Old 06-01-2020, 08:06 PM   #2
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Re: Need help with my first 350 sbc

How did you adjust your valves?
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Old 06-02-2020, 12:54 AM   #3
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Re: Need help with my first 350 sbc

They are hydraulic. Looked up the valve adjustment sequence and adjusted them until I felt slight resistance on the push rods and then tightened a 1/4 turn
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Old 06-02-2020, 01:02 AM   #4
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Re: Need help with my first 350 sbc

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How did you adjust your valves?
They are hydraulic. Looked up the valve adjustment sequence and adjusted them until I felt slight resistance on the push rods and then tightened a 1/4 turn
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Old 06-02-2020, 01:08 AM   #5
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Re: Need help with my first 350 sbc

My first thought when you said the engine is shakey was that maybe you got them too tight. Are you sure that each rocker was off of the cam lobe as you checked them? I usually do it with the motor idling backing off each one until it begins to clack then retighting just until it quiets then 1/4 turn more. As for the initial timing, I usually start at ten degrees and finesse it from there. The idle is different for an automatic transmission vs a manual but around 750ish will be a good starting point.
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Old 06-03-2020, 08:34 PM   #6
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Re: Need help with my first 350 sbc

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My first thought when you said the engine is shakey was that maybe you got them too tight. Are you sure that each rocker was off of the cam lobe as you checked them? I usually do it with the motor idling backing off each one until it begins to clack then retighting just until it quiets then 1/4 turn more. As for the initial timing, I usually start at ten degrees and finesse it from there. The idle is different for an automatic transmission vs a manual but around 750ish will be a good starting point.
That's how I do mine. I use those little clips so the oil doesn't squirt out.
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Old 06-04-2020, 12:56 AM   #7
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Re: Need help with my first 350 sbc

Did you get it worked out Isaiah?
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Old 06-04-2020, 01:13 PM   #8
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Re: Need help with my first 350 sbc

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That's how I do mine. I use those little clips so the oil doesn't squirt out.
Totally agree. Take of the cover on one side, start it up, back off the nut, tighten until no noise (and the final 1/4 turn). It won't be messy unless you rev it. I did my adjustment by the book and one was way too tight. Fixed immediately by doing it running. Then, check/set your timing.
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Old 06-04-2020, 10:26 PM   #9
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Re: Need help with my first 350 sbc

I would do it running too. I can twist those push rods in my fingers when the valve is open.
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Old 06-04-2020, 11:56 PM   #10
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Re: Need help with my first 350 sbc

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Old 06-05-2020, 12:25 AM   #11
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Re: Need help with my first 350 sbc

You don’t need clips.
4 inch tall piece of cardboard curved on both ends works fine.
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Old 06-05-2020, 12:50 AM   #12
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Re: Need help with my first 350 sbc

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You don’t need clips.
4 inch tall piece of cardboard curved on both ends works fine.
That's right, I forgot about that.
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Old 06-05-2020, 01:06 PM   #13
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Re: Need help with my first 350 sbc

Timing is always the first thing to set correctly because it is your engine’s foundation. If your foundation isn’t right, nothing else will be. GM engineers (and lots of racers) have found most SBCs run best at 36 degrees before top dead center total timing. Your distributor and vacuum advance also play a big role in this and must be setup correctly as well. What did you do for your “tune-up” on the HEI and do you know how many degrees of mechanical advance and vacuum advance it provides? What is your idle vacuum level?

Idle spec for auto trans is 600 rpm in gear with foot on brake. Works out to 750 rpm in park or neutral. Also, for the choke (not that you’ll really need it in Whittier lol), fast idle speed spec is 1500 rpm.

The best way to adjust valves is the EOIC method: https://www.youtube.com/watch?v=Prj0GUZ7nes

If it shakes a lot, could be a vacuum leak you need to find. Or maybe your idle mixture screws need to be adjusted with a vacuum gauge for best vacuum & rpm. You need to get a calibration kit for that carb so you can dial it in well.

Just some ideas....
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Old 06-06-2020, 11:16 AM   #14
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Re: Need help with my first 350 sbc

if the shaking smooths out ie goes away at higher RPMs say 1500 or higher than most def it's a vacuum leak, you can plug all the ports on the carb with rubber plugs just as a test, but then it can leak from the base plate especially a crack in the back where the big port is for the brake booster
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Old 06-06-2020, 11:21 AM   #15
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Re: Need help with my first 350 sbc

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Originally Posted by Isaiah92260 View Post
The alternator is on the passenger side and has that big alternator bracket/ shield.
I recently went through the short water pump / long water pump circus and here's what I remember

alternator on the passenger side means late 70s long water pump aka more modern V8, sure way to tell is if your alternator actually bolts up to a bunch of holes / bolts on the water pump itself

long water pump = alternator on passenger side

alternator on the driver side / short water pump, older V8 from late 60s
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Old 06-10-2020, 02:10 PM   #16
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Re: Need help with my first 350 sbc

shaking can indicate a dead miss in one or more cylinders as well
you may need new plugs and plug wires
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Old 07-03-2020, 12:19 AM   #17
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Re: Need help with my first 350 sbc

Hey fellas thank you for your reply’s and answers.
It’s been rough few weeks because of this damn covid, I work for the state.

I did have the motor running good, then the timing mark went 2” off ATDC.

So I replaced the balancer because the ring went bad and got loose, and Now

I havnt adjusted for valves while running since I can’t get it to idle well.

It’s idling very rough.

I checked if I was at TDC.

#1 spark plug out, distributor pointing at #1.
Cranked the motor to check if air coming from #1, which it blew air out, and my timing mark was pointing at 0. So I’m pretty sure TDC is set right?

Then started the engine. She idles very rough, I then set the timing at 12 before TDC. And it still idles bad.
I tried raising the idle speed screw and nothing happens when I raise it.

I have a 4 barrel holley, I set the idle screws starting at 1 1/2 Turns back out.

I checked to see if I have any vacuum leaks but I can’t find any around the manifold. Or the hose that goes to my automatic trans I’m stumped again.

Responding to the question, When I did the distributor I bought a tune up kit from Accel, I’m not sure what the specs sure, I know I should have checked... it was a brand new coil, cap, rotor, metal plates, the little springs, and the harness, and my spark plugs and wires are brand new, I set the gap on the spark plugs at 45

After when I fest set the valves and installed the new carb and set the timing at 12 the first time, it was running fine, great actually, but now this, I’m sure you all could tell I’m pretty frustrated, a little pissed too.

I checked everything I could think of

Lastly here is a picture I took of my vacuum gauge
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Old 07-03-2020, 10:03 AM   #18
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Re: Need help with my first 350 sbc

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I havnt adjusted for valves while running since I can’t get it to idle well
You need to. This may be very much the cause for your bad idling. Read what that gauge is telling you in red.
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Old 07-03-2020, 11:20 AM   #19
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Re: Need help with my first 350 sbc

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You need to. This may be very much the cause for your bad idling. Read what that gauge is telling you in red.
Yes I did see that’s it says late valve timing?
So that pretty much says the valves are not
Lifting when they should?

I’ve been researching and now I’m starting to hope that my camshafts lobes are not worn the heck out.

So far I already have the new radiator, water pump, and 196 thermostats in and she still idles at 180-200 even though it isn’t running right.

I’m going to pull the valve covers next and try to get it running again and adjust the valves.

Turn till the clicking goes away and then 1/4-1/2 turn on each one correct?
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Old 07-03-2020, 03:59 PM   #20
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Re: Need help with my first 350 sbc

Valve timing refers to the cam being advanced or retarded. That’s a function of when they open/close and not how much they open.
If it won’t idle well you’ll need to adjust running differently.
Loosen rocker until it clicks, tighten Until it gets quiet then leave it alone. Then do the next one the same. Continue until you’re done all 16. At that point all will be at zero lash. Shut the motor down and go back and give each nut 1/8 turn. Wait ten minutes after all are done.
Fire it up to see how it runs.
If all is well slowly turn each another 1/8 turn.
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Old 07-03-2020, 05:07 PM   #21
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Re: Need help with my first 350 sbc

Might try advancing the timing another 10 and see if things improve. Doesn't require you to open anything or replace things.

If the only thing that changed between the motor running good and now is the replacement of the harmonic balancer, bad timing is a leading suspect. The 'air comes out, I am on compression' is good for finding the compression stroke but not for exact TDC. Very possible the mark on the balancer isn't matched to your timing indicator. Parts QA isn't always what it should be. You could still be very much ATC on your timing.
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Old 07-04-2020, 12:33 AM   #22
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Re: Need help with my first 350 sbc

Okay so this is what I found.

#3 cylinder intake rocker arm was loose and the valve was not even opening!! I believe the pressed in stud is starting to pull out from the head, because I started to tighten the rocker down, and got it to start clacking, then tightened it some more until it stop clacking then I did a 1/4 turn
Then I went back and adjusted all of the valves that’s way while running, the engine smoothed out A lot.
It still was a little tough,
So then I started playing with the timing. It did not run so go at 2•-12• degrees.
It was only pulling about 10” of vacuum.

So I then retarded the advance down and watched the vacuum gauge until it went up to around 20” of vacuum under the “normal engine” green area.

And at that point my timing mark was 2” out again.

Why is it doing that?

Maybe the engine builder previously made it 180 out?

Anyways I set that carb in park at 750 and the engine seems to run smooth.

It has glasspcks so it sounded a little choppy in the back end
But besides that, I feel I have some things to figure out.

The picture with the balancer and timing mark is while it was running and my timing light on it
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Old 07-04-2020, 12:52 AM   #23
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Re: Need help with my first 350 sbc

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Might try advancing the timing another 10 and see if things improve. Doesn't require you to open anything or replace things.

If the only thing that changed between the motor running good and now is the replacement of the harmonic balancer, bad timing is a leading suspect. The 'air comes out, I am on compression' is good for finding the compression stroke but not for exact TDC. Very possible the mark on the balancer isn't matched to your timing indicator. Parts QA isn't always what it should be. You could still be very much ATC on your timing.
Oh I see, How exactly can I find TDC?
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Old 07-04-2020, 12:54 AM   #24
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Re: Need help with my first 350 sbc

Also see how far the stud is sticking out? It was like this when the rocker arm was loose.
That can’t be from a worn cam shaft right?
And if so is it possible for just one cam love to be worn like that? Because all the other valves looked, and sounded fine even when operating
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Old 07-04-2020, 01:47 AM   #25
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Re: Need help with my first 350 sbc

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Also see how far the stud is sticking out? It was like this when the rocker arm was loose.
That can’t be from a worn cam shaft right?
And if so is it possible for just one cam love to be worn like that? Because all the other valves looked, and sounded fine even when operating
That absolutely could be from a flat cam lobe.
could be a collapsed lifter or a bent push rod too.
I would check the push rod first (fingers crossed)
if the push rod is straight, check the lifter, if the lifter checks out, good news:
You get to upgrade your camshaft
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