4.3 lx issue I had.

[philbullet]

This is a resent rebuild we did.
After a 20-30 hour give or take of mostly 1900 rpm to 3500 on step.
I've notice a ticking from Port rear side and motor backfiring sometimes when getting on step and gust not running a smooth as it was.
So I decided to pull port exhaust elbow off because I noticed a Lil water leaking .Found gasket bad, I then proceeded to check push rod for bent, all good but then notice rocker arm broken on back (last) valve exhaust.Found the piece right below in head.
Wondering if the broken gasket could have cause this? I had some water down in the manifold so I soaked up with rag.
Also had to file the top of valve back flat.
Replace rocker arm and new gaskets on port and stb.
Running alot better, but had a hastation while on step at 3500 rpm and other rpms.
Changed all spark plugs and hastation went away.
Notice some plugs had white ish crud inside plugs.
Brother (mechanic) said looked like from running low octane fuel , also maybe from cheap gas.He said to start trying medium grade gas.
Just thought I'd share if anyone had these issue.
Sorry I forgot to take pictures of plugs and rocker arm.

 

[Rick Stephens]

Did you by chance get a compression test? That and a vacuum test would tell a lot about conditions under the head.


Rick

 

[philbullet]

No I hadn't, I did do it after the rebuild from some other isue s, it was all good then.
I have it running great now but I won't get much use out of it now.I pretty much done with its use till next May, But I'll still run it on muff from time to time through winter.

 

[philbullet]

Oh, I had isue s from begaining with heads not having enough lift on valves with the 262 cam ?, had to shim valve springs and Change valve keepers.If i remeber right i had .450 lift on valves and need .500, he has all tools to check for that and tools to change. Had a post about it here but that probably far down the list now.That had solved my isue of backfiring through intake back then.

 

[Rick Stephens]

I think I'd rerun the tests for peace of mind. Pretty easy and it tells the tale on valves and ring seat.

RIck

 

[alldodge]

Lil water leaking .Found gasket bad, I then proceeded to check push rod for bent, all good but then notice rocker arm broken on back (last) valve exhaust. Found the piece right below in head.

Notice some plugs had white ish crud inside plugs.

Oh, I had isue s from begaining with heads not having enough lift on valves with the 262 cam ?, had to shim valve springs and Change valve keepers.If i remeber right i had .450 lift on valves and need .500, he has all tools to check for that and tools to change. Had a post about it here but that probably far down the list now.That had solved my isue of backfiring through intake back then.

The white deposits could be running lean, if only on one or two plugs could be water

Having a .500 lift and a damaged rocker has me asking, were the tops of the valve guides cut down? Putting shims under the springs will also reduce the amount the spring can compress. Did you install roller rockers with the roller cam?

 

[Volphin]

What did your total lift measure out to be? You may have struck a valve guide, or if you are lucky, it's just a defective rocker. The total lift should have been addressed by your engine builder for the proper geometry and clearance given your cam, rocker and pushrod combo.

 

[philbullet]

I looked back at old post and it was .430 lift before.
Iam hoping it was a bad rocker, and no on the roller rocker arms.
The motor is a regular auto motor rebuild with a counter balance shaft with Vortec heads.The only thing used from the origanal boat motor block was the cam.That cam is in the converted auto eng..
That was the only thing used internal.
He also put some stiffer valve springs with spring guide, I believe they use these on racing motor.
I hoping these arn't a isue.we where trying that to stop the back firing.
But it has been doing good till the 1 rocker arm broke.

 

[alldodge]

I looked back at old post and it was .430 lift before.

OK this would be valve lift and not cam lode lift, which is stock. The cam lobe lift would be under .300 given the standard rocker ratio of 1.50

Now if he used a car cam and not a truck then your loosing low end torque, also the tighter springs are great for race motors and high lift cams but not so much for run around boat motors. Now if the springs are on the high end of tension, then the extra stress on the rocker/cam/lifter might be to much for the standard stamped rocker. Just my opinion and I don't know what the guy used

 

[philbullet]

No, the cam we used is from the boat motor 4.3 lx. And truck motor.
I believe it's a 262 cam.
I was thinking the same thing about spring tension but he said it shouldn't hurt anything, but my brother is a high proformance race car kind of guy, well not kind of.lol
He builds eng., transmission, rear ends, etc..has his own shop.
If I run into any more trouble on upper end, I guess I'll try to go back to stock spring sence we solved the backfiring isue earlier.
It's all running good now but only ran in the bayou a couple passes, may not get to put more hours on it tell next year.
Back to Bass fishing and speckle trout fishing now.lol
I iam sure impressed with the 4.3 Vortec compared to the 470.
Iam 5-6 mph faster at 3400-3500 and have more power to get on step.