350 Uneven Cranking & Won't Stay Running After Break In

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evilws666
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350 Uneven Cranking & Won't Stay Running After Break In

Post by evilws666 »

Before I start rambling..

Rebuild specs:



350 4 bolt main bored .030 over

10:1 CR

Stock Cast Crank turned .010

SCAT Forged 5.7" I-beam Rods

Sealed Power Flat Top Pistons w/ 4 valve reliefs

Vortec 906 Iron Heads

.016 Steel Shim Head Gaskets

Jones Cam's Hydraulic Flat Tappet: 110LSA 224/232 @ .050, .501"/.504" with 1.52 rockers

Cloyes Heavy Duty Double Roller Timing Set (set to advanced keyway while degreeing cam)

Melling 10552 HV Oil Pump

Holley 4160 600cfm Vac. Secondary Carb

Edelbrock Performer RPM Vortec Intake

Stock GM HEI Distributor

NGK TR55 Plugs

Factory replacement Taylor wires

High Torque Mini Starter

Rotating assembly was balanced during rebuild



Well fellas, I'm currently stumped. I just recently rebuilt my 350, and broke it in a few days ago.. used PennGrade break in oil. Break in went pretty well.. I set distributor in at 14* before starting it. It started right up, bounced around a little for a few seconds, then smoothed out as I raised the RPM's. I varied the engine speed between 2000-2500 for 20 minutes. After 20 minutes, I started to back the engine speed down. I eventually got to the point where I could no longer unscrew my curb idle screw any further. I snapped the throttle a few times, but it didn't come down. I pushed the throttle lever forward a little to make sure it wasn't the cable, when suddenly the idle dropped, I heard a clack, and it shut off. I started it again, heard clacking, and shut it right off. After removing the valve covers, I found that my #3, 5, and 6 intake rockers were loose. They weren't making a single sound until I pushed the throttle blade forward and the car died. I started turning the engine over by hand to readjust these valves.



I turned the engine over by hand while watching the corresponding cylinder's exhaust valve. Once the exhaust valve started to open, I adjusted the intake valve, and gave it 1/2 turn past zero lash. I did this for all 3 that loosened up. Then, like a complete idiot, I forgot to take the breaker bar and socket off of the crank pulley, and blipped the ignition. I heard the breaker bar rotate clockwise, hit my frame rail, and then fall to the ground. I went and double checked that the crank bolt didn't loosen up, shook my head at myself and then started the car up. It was running terribly. The engine was bouncing and running very rough, and it wouldn't stay running unless I held the throttle open. The second I let go, it would die. Now I noticed that while cranking, it was "galloping" rather than a steady crank. You could hear it crank fast, then slow, fast, then slow. Before adjusting the timing, I marked the distributor cap location so I could go back to my starting point. I tried advancing it further - didn't help. Tried retarding it a bit, didn't help. Eventually I got it to where it would at least stay running well enough that I could pull it in the garage. Out of curiosity, I checked where the timing was at this point, and it was somewhere near the 30's at idle with the vacuum advance plugged! I retarded the timing, and it shut off. Lined up with my original reference mark on the distributor cap, it wouldn't stay running again. Before taking a break, I pulled my plugs - they were black, sooty and fouled. Smelled like gas.



Today I went back to the garage and swapped another working carb onto the engine. I installed brand new plugs, and relashed every single valve. I jiggled the pushrod up and down until I felt zero play, and this time, I gave them each 1/4 turn. Rotated the engine until I saw the exhaust valve open, and fully close - right on TDC on my timing tape. Rotated it one more revolution to TDC. Adjusted my distributor to line the #1 terminal up with the rotor, as close as I could get it. Turned the key, it fired up and died. Held the throttle open a little, turned the key again, and it's struggling to start. Keeps firing off but dying. I tried adjusting the timing a little, but once again it didn't help much. Try giving it more throttle, backfires out the carb. It still has that "gallop" present while cranking. I checked my plug wires numerous times, and aside from them currently being a little messy and strung about, they are in the right positions. Verified that I have 12.4 volts at the ignition wire at the distributor, and 10.4 volts while cranking. I removed the distributor cap, and it was spotless inside. No signs of arcing. I couldn't find any noticeable rips or tears in my wires either. I cranked it again with the ignition disabled, and it sounded exactly the same.



I am completely stumped at this point. I keep asking myself if I wiped the cam, but it made it entirely through break in with zero issues, and no valve noise until the RPM's dropped and it died out. I was hoping my initial valve adjustment wasn't consistent, and maybe those few were just a little loose. But why didn't they make any noise until the engine died out when I closed the carb? The other thing I'm wondering is.. when I hit the ingition with the breaker bar still on the crank bolt, did it hit the frame and jump timing? The bolt didn't loosen, so either it fell right off, or something else had to give. I double checked my timing chain slack, and it only moves 2 degrees before turning the rotor if I turn it counter clockwise.



At this point, the only things I haven't really checked are my ignition coil, ignition module, and my timing set. I've also yet to drain the oil to check for metal particles. Either way, it sounds like the valve event timing and ignition timing is not occurring when it should, or something happened with my compression. I'm not sure, this is my 3rd engine rebuild and I am stumped and defeated at this point. Any help would be greatly appreciated, and if you read ALL of that, thank you - lol!



Here are 2 videos. The first shows what it currently sounds like while cranking, and the second is after 20 minutes of break in when I started to back the idle down. You can hear that it's running nice and smooth during this time.



https://youtu.be/Ax5LUXwVt1k



https://youtu.be/L5lPrKtQ_8A


Any guidance is much appreciated. Thank you
1980RS
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by 1980RS »

Hate to say it but you may have lost the cam already if the rocker are loose after break-in.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by Nut124 »

evilws666 wrote: Wed Nov 30, 2022 2:19 pm
...Rotated the engine until I saw the exhaust valve open, and fully close - right on TDC on my timing tape...
^^ I'm trying to understand the statememnt above. Did you time the cam to close the EX at TDC?
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

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1980RS wrote: Wed Nov 30, 2022 4:13 pm Hate to say it but you may have lost the cam already if the rocker are loose after break-in.
Or I pulled out my press in studs. The Vortec's are basically completely stock, except for Comp Cams 787-16 retainers and LS6 beehive springs. Or maybe I bent valves..
Nut124 wrote: Wed Nov 30, 2022 4:19 pm
evilws666 wrote: Wed Nov 30, 2022 2:19 pm
...Rotated the engine until I saw the exhaust valve open, and fully close - right on TDC on my timing tape...
^^ I'm trying to understand the statememnt above. Did you time the cam to close the EX at TDC?
I was stating the procedure my engine book shows to find TDC on compression stroke before installing the distributor: Rotate engine, watch exhaust valve open and fully close. Check damper. Should be close to TDC. Rotate the crank one more revolution to TDC. This is TDC on the compression stroke.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by 1980RS »

evilws666 wrote: Wed Nov 30, 2022 4:43 pm
1980RS wrote: Wed Nov 30, 2022 4:13 pm Hate to say it but you may have lost the cam already if the rocker are loose after break-in.
Or I pulled out my press in studs. The Vortec's are basically completely stock, except for Comp Cams 787-16 retainers and LS6 beehive springs. Or maybe I bent valves..
Nut124 wrote: Wed Nov 30, 2022 4:19 pm
evilws666 wrote: Wed Nov 30, 2022 2:19 pm
...Rotated the engine until I saw the exhaust valve open, and fully close - right on TDC on my timing tape...
^^ I'm trying to understand the statememnt above. Did you time the cam to close the EX at TDC?
I was stating the procedure my engine book shows to find TDC on compression stroke before installing the distributor: Rotate engine, watch exhaust valve open and fully close. Check damper. Should be close to TDC. Rotate the crank one more revolution to TDC. This is TDC on the compression stroke.
That is very possible to have that happen. I raced 2 sets of Vortec heads on a 406 and did not pull any studs out yet and in all the years never have one stud come out either, but a lot of my friends sure had them pressed in studs come out. Next set of Vortecs will have screw in studs for sure, as my luck will run out one day.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by Tom68 »

Seem to be doing the valve lash and dizzy install the hard way.

Split the firing order for lash adjusting.

Air coming out number 1 plug hole is on the way to TDC.
Or just check number 6 rockers are rocking for number 1 TDC.
Last edited by Tom68 on Wed Nov 30, 2022 6:25 pm, edited 1 time in total.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by steve cowan »

Hopefully you have not killed the cam or lifter.
The engine sounds like cam timing is retarded by the video and on the cranking video sounds to me like it has no compression on a cylinder or 2.
A couple of questions -
Did you degree the cam and set up as Mike recommended?
When using the exhaust open/ intake closing method for setting rockers you will find the exhaust valve has to be close to full lift and intake valve nearly closed to be on opposite base circles.
There might be a possibility you are keeping the valves open with to much preload on the lifter.
I would do a compression test first.
I have no issues with ignition timing around 34 - 36 total on initial start up because if ignition timing is retarded the engine will get hot,headers will glow red etc.
Hopefully with the rocker deal it has not pulled studs or wiped cam.i would mark pushrods with white paint and see if they spin when engine is been cranked over with spark plugs out and crank on starter .
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by BobbyB »

Watch Ellisons Machine Shop YouTube video on valve adjustment and follow his procedure exactly. Hopefully you were just a little out of adjustment on the 3 loose rockers. Good luck!
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by Racer97 »

Perform a leak down test with all spark plugs out . Check for air coming out of the next cylinder. Possible blown head gasket between cylinders. Place straight edge on rocker studs to check for pull.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by Nut124 »

evilws666 wrote: Wed Nov 30, 2022 4:43 pm I was stating the procedure my engine book shows to find TDC on compression stroke before installing the distributor: Rotate engine, watch exhaust valve open and fully close. Check damper. Should be close to TDC. Rotate the crank one more revolution to TDC. This is TDC on the compression stroke.
If the EX fully closes at or near TDC following that method, then your cam would apprear to be way retarded in timing. Should be somewhere 30-35ATDC. Or the TDC mark could be off.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by cgarb »

Leakdown test the motor if you can. If not crank the motor over till the cylinders you lost lash on the valves are both closed and put compressed air in the plug hole and listen for air going past the valves. Possibly you bent a few valves somehow. That might explain the uneven cranking and the clacking noise you heard.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by evilws666 »

Here is the cam card for anyone wondering:

Image
Tom68 wrote: Wed Nov 30, 2022 5:51 pm Seem to be doing the valve lash and dizzy install the hard way.

Split the firing order for lash adjusting.

Air coming out number 1 plug hole is on the way to TDC.
Or just check number 6 rockers are rocking for number 1 TDC.
I actually did the "split firing order" method this morning before I made this post. I used EOIC on the stand, but tried this other method to see if I got different results.
steve cowan wrote: Wed Nov 30, 2022 6:01 pm Hopefully you have not killed the cam or lifter.
The engine sounds like cam timing is retarded by the video and on the cranking video sounds to me like it has no compression on a cylinder or 2.
A couple of questions -
Did you degree the cam and set up as Mike recommended?
When using the exhaust open/ intake closing method for setting rockers you will find the exhaust valve has to be close to full lift and intake valve nearly closed to be on opposite base circles.
There might be a possibility you are keeping the valves open with to much preload on the lifter.
I would do a compression test first.
I have no issues with ignition timing around 34 - 36 total on initial start up because if ignition timing is retarded the engine will get hot,headers will glow red etc.
Hopefully with the rocker deal it has not pulled studs or wiped cam.i would mark pushrods with white paint and see if they spin when engine is been cranked over with spark plugs out and crank on starter .
1. When I was degreeing the cam, I had it on the zero keyway. I checked valve event timing, and it was off by a few degrees. I tried calling Mike, but he was actually on vacation. After reading up a bit, I switched it to the advanced (triangle) keyway, and the valve events were spot on with the cam card. That is how I left it.

2. I thought maybe I was doing the EOIC method wrong as well, so I did the "split firing order" method this morning, and gave 1/4 turn instead of 1/2.. that was before I made this post.

3. After I got it to stay running and brought it in the garage, the 30'ish timing mark was INITIAL timing at idle. That's how far advanced it was to stay running.

I'll be doing a compression and leak down test once they arrive. I have to go check the studs as well. I'll verify that the pushrods are spinning too. If one doesn't spin, that's a wiped lobe/lifter, right?
BobbyB wrote: Wed Nov 30, 2022 6:47 pm Watch Ellisons Machine Shop YouTube video on valve adjustment and follow his procedure exactly. Hopefully you were just a little out of adjustment on the 3 loose rockers. Good luck!
I'll take a look, thank you!
Racer97 wrote: Wed Nov 30, 2022 7:16 pm Perform a leak down test with all spark plugs out . Check for air coming out of the next cylinder. Possible blown head gasket between cylinders. Place straight edge on rocker studs to check for pull.
I have the tester on the way. Will report back, thank you.
Nut124 wrote: Wed Nov 30, 2022 9:27 pm
evilws666 wrote: Wed Nov 30, 2022 4:43 pm I was stating the procedure my engine book shows to find TDC on compression stroke before installing the distributor: Rotate engine, watch exhaust valve open and fully close. Check damper. Should be close to TDC. Rotate the crank one more revolution to TDC. This is TDC on the compression stroke.
If the EX fully closes at or near TDC following that method, then your cam would apprear to be way retarded in timing. Should be somewhere 30-35ATDC. Or the TDC mark could be off.
I checked TDC mark accuracy once I got the damper on, so that should be good. I'll double check the valve timing event.
cgarb wrote: Wed Nov 30, 2022 9:34 pm Leakdown test the motor if you can. If not crank the motor over till the cylinders you lost lash on the valves are both closed and put compressed air in the plug hole and listen for air going past the valves. Possibly you bent a few valves somehow. That might explain the uneven cranking and the clacking noise you heard.
I'll have the tester here in a few days. Will report back.

Just wanted to say thank you to everyone, I really appreciate it.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by Tom68 »

Don't do a leak down on all cylinders, too much messing around.

Crank it over with the rocker covers off and watch that all valves have full travel.

If no... you stuffed a cam or there's no oil getting to your lifters....fix it.

If yes... Compression test all cylinders.

If major variations...get worst cylinder to TDC and attach airhose to spark plug hole, listen through Exhaust, intake and oil fill to see where the majority of air is escaping.

If inlet valve....you've f'd up and bent a valve.

If Exhaust valve....similar crap to above.

If it's roaring into the sump....somethings not been done right with bore, or piston, or rings.

But I'm hoping you've got some basic fuel feed problem and the carby isn't filling up or the opposite and you have too much fuel pressure.


Loose valves may be your interpratation of what is loose, they can feel loose when they're closed and there's no oil pressure (engine not running) holding load on the valve train.

You may be over thinking things and missing something simple. Engine sounded good for the video at least, was it hesitating when cracking the throttle ?

Don't worry about the 30 degrees at idle, 50 degrees works to.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by HQM383 »

evilws666 wrote: Thu Dec 01, 2022 1:04 am Here is the cam card for anyone wondering:

Image
Should be easy enough to put a dial gauge on #1 intake pushrod and verify at .050” lift the balancer reads 5* BTDC. If that is way out some investigation into why. I’d also pull the distributor to check nothing is loose and everything where it should be including roll pin in gear. Fuel smelling plugs, backfire through carb, the cranking video seems like when firing order is way out but that has been confirmed? Are those plug leads resting on the exhaust in the run-in video?
I’m a Street/Strip guy..... like to think outside the quadrilateral parallelogram.
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Re: 350 Uneven Cranking & Won't Stay Running After Break In

Post by evilws666 »

So I just went out to the garage to check a couple things. Distributor cap, rotor, and coil all look/tested fine. I was rotating the engine by hand to make sure the distributor was lined up properly, and I noticed something...

I was cranking it over by hand with the distributor cap and the valve covers off, watching the rotor and the rockers. I had all the spark plugs in. It was (of course) a bit more difficult to turn. I was able to hear the air hiss as I rotated the crank - building compression I assume? Sounded like it was in the crankcase. Then I got to a point in the rotation where the engine turned much more easily, and I heard no air. I kept rotating it around, same thing happened every time right around the same spot - near the #3 firing position when looking at the rotor. I then observed the #5 rockers at this time - exhaust opened, closed, then intake open and closed during this area of "easier rotation." What's interesting is that the rockers that loosened up for #3, #6, and #5. All of which are in succession in the 18436572 firing order. I wonder what could have happened that affected all 3, one after the other.

Anyway, if the air/hiss sound is in fact just compression being built while I turn the engine, there is definitely an area where compression isn't being built. I guess I'll confirm with the testers when I get them.
Tom68 wrote: Thu Dec 01, 2022 1:24 am Don't do a leak down on all cylinders, too much messing around.

Crank it over with the rocker covers off and watch that all valves have full travel.

If no... you stuffed a cam or there's no oil getting to your lifters....fix it.

If yes... Compression test all cylinders.

If major variations...get worst cylinder to TDC and attach airhose to spark plug hole, listen through Exhaust, intake and oil fill to see where the majority of air is escaping.

If inlet valve....you've f'd up and bent a valve.

If Exhaust valve....similar crap to above.

If it's roaring into the sump....somethings not been done right with bore, or piston, or rings.

But I'm hoping you've got some basic fuel feed problem and the carby isn't filling up or the opposite and you have too much fuel pressure.


Loose valves may be your interpratation of what is loose, they can feel loose when they're closed and there's no oil pressure (engine not running) holding load on the valve train.

You may be over thinking things and missing something simple. Engine sounded good for the video at least, was it hesitating when cracking the throttle ?

Don't worry about the 30 degrees at idle, 50 degrees works to.
I really wish it's something that simple, but I doubt it. I had the same result with 2 carbs, and it's just not right while cranking. I have a feeling it's going to be a valve or cam/lifter issue.
HQM383 wrote: Thu Dec 01, 2022 1:46 am
evilws666 wrote: Thu Dec 01, 2022 1:04 am Here is the cam card for anyone wondering:

Image
Should be easy enough to put a dial gauge on #1 intake pushrod and verify at .050” lift the balancer reads 5* BTDC. If that is way out some investigation into why. I’d also pull the distributor to check nothing is loose and everything where it should be including roll pin in gear. Fuel smelling plugs, backfire through carb, the cranking video seems like when firing order is way out but that has been confirmed? Are those plug leads resting on the exhaust in the run-in video?
I'm going to do exactly that, and check lift at whichever cylinders come back with an issue.. which I'm betting there will be at least one.
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