2 Bent Pushrods in 350 SBC - Lateral-g Forums

Decline · #1 04-23-2015, 11:57 AM

1969 camaro with non orignal 350 SBC with iron heads a mild edlebrock flat tappet cam, crane stamped roller rockers and mystery valves, springs, push rods all done by previous owner..But it does have all ARP hardware so thats a plus

I heard some clacking under the hood. Car had been idling funny yesterday afternoon. I thought maybe my recently changed timing was causing pinging?
Pop'd the hood..Distinct metal chatter from valve cover..Opend to find the rearmost rockers all twisted. Further inspection revealed 2 bent push rods.

Question, what else should I inspect for damage? One of the valve ends is messed up a little/flattened and put some wear marks on the roller tip. I would have to remove the head to change it obviously? Can i get away with just replacing the 2 push rods and reseting the valve lash to get back up and running?

I feel like that should be fine for now until I decide wither to change the heads out for aluminum or just swap an LH6 5.3 aluminum truck motor in there. Ive had my eye on one on craiglist for $750 with no accesories. Prbly run it carbed innitially for $ reasons

**Sieg** · #2 04-23-2015, 12:36 PM

First thing you need is compression, as in no bent valves.

I'd want to know why it happened before going any further.

Decline · #3 04-23-2015, 01:25 PM

I can do a compression test on it to see if the valve is damaged on more than just the top..
My assumption is that rockers were loose and got out of alignment with the pushrods.
Does anyone else have any theories on what causes this?
Another friend of mine recomended taking a look at the lifters as well to see if there s damage..
I really wanted to avoid taking the engine apart

**GregWeld** · #4 04-23-2015, 02:58 PM

You may be able to get away with a "lash cap" on the messed up valve. But then this push rod length would need to be adjusted due to the now "longer" valve stem.

Now then. - this didn't just bend like that as you were casually driving down the road. My guess is you experience a severe backfire or you were getting after it pretty good.

My question would be: what was the timing? Why did you decide to adjust it? And what did you adjust it to? And did you adjust and or check the TOTAL timing?? And what was that number?

Decline · #5 04-23-2015, 05:27 PM

Quote:

Originally Posted by GregWeld

You may be able to get away with a "lash cap" on the messed up valve. But then this push rod length would need to be adjusted due to the now "longer" valve stem.

Never heard of a lash cap..i will look into it. This could be a possible band aid along with an adjustable pushrood[/COLOR]

Now then. - this didn't just bend like that as you were casually driving down the road. My guess is you experience a severe backfire or you were getting after it pretty good.

It happened as i was leaving work. I went a few blocks and heard the rattleing/clanking, so i turned around and came back. I thought it was just mis firing. A couple hours prior to that my buddy and I were in the parking lot attempting to check the timing again cuz the car seemed to be running rich and smoking covering my rear bumper with a thin film of black soot. The idle wouldn't settle down enough to check base timing..I rev'd it a few times at the carburator to try and get it settle. I heard some pings or pops during that time also.

My question would be: what was the timing? Why did you decide to adjust it? And what did you adjust it to? And did you adjust and or check the TOTAL timing?? And what was that number?

My engine has never really run right since after I got my suspension installed a few months ago. I've tried various fixes.
It is an AME front clip so the motor had to come out.
My old headers were "massaged" to fit which meant the shop beat one the tubes about 2/3rds closed..So I got the AME headers to clear control arms. That seemed to work for a while..
Performance was still spotty so I got new plugs and wires.. Was better.
Then it occured to me to check the timing..Well the distributor was loose so i thought id found my culprit.. I bought a timing gun watched a few youtube videos and set my initial timing to 12degrees, then i set my total timing to 36 degrees-ish.. I say "ish" because I had no tach to reference engine rpm so i manually rev'd it to what i figured was between 2500-3000..
It was actually running pretty good like that and i did the Del Mar good guys autoX a few weeks ago. Other than my high idle and crap gas mileage(10-12 down from 15-18) I thought i was in decent shape, just thought the carb needed tuning..

Che70velle · #6 04-23-2015, 09:26 PM

Solid or hydraulic cam? Do you know how to check and set valve lash?

**GregWeld** · #7 04-24-2015, 10:10 AM

An adjustable push rod is a checking/measuring tool.... there is no such thing that you could use to actually run the motor with.

At this point there is only ONE correct way to fix/diagnose your issue.

Drain your coolant
Pull the distributor
Remove the intake
Remove the head and fix the valve

There's something going on here that needs to be solved. My guess is you have a cam going flat.. which you'd be able to see if you remove the intake manifold. That would explain your running rough and inability to keep the car in a steady state of tune. The cam "going away" would allow the lash to open - pounding the pushrod - and stressing the valve train.

Vince@Meanstreets · #8 04-24-2015, 05:24 PM

Im with these guys, there's more than just push rods doing on. With possible mis matched stuff going on the best bet would be to replace the two bent push rods. Check ratio, check for coil bind and make sure your retainer isn't hitting the valve guide.

Did you over rev the engine recently?
Are you using coolant? Hydraulic that cylinder?

7&8 are the most common to go flat. Especially if you had just replaced an intake manifold and or gasket.

TheJDMan · #9 04-26-2015, 06:44 PM

The first thing I would do is run a compression test. You may need to borrow push rods from a neighboring cylinder to test #8. A push rod does not bend like that unless there is an underlying problem. As has been stated there is only one correct way to fix this and that will involve pulling the heads and doing some investigating. I would be looking at things like valve spring coil bind or rocker arm clearance issues and depending on the cam look at valve to piston clearance. Those heads don't appear to have guide plates which would help stabilize the valve train. You never stated if that engine is equipped with solid or hydraulic lifters. Let us know what you find.

Decline · #10 04-26-2015, 08:01 PM

I prbly should have tested the compression before I tore it apart. I was expecting to see piston to valve contact. There was none. How can I inspect the cam? Pull it out or just remove the #8 lifters?
The rest of the push rods on the even bank seemed straight by the roll method. The rockers on the other bank seemed pretty loose. Those push rods also seemed straight.
I would to get this engine back up and running while I decide on the future. Could it be as easy as 2 push rods and a valve and maybe a new flat tappet cam?
Also I need to figure out a better way to post pics. Should read that sticky about it posted somewhere.