No compression in #8 cylinder - 454 Magnum

[Mike Phillips]

Wow! that would do it.  Have any salvage yards near you?

Local NAPA store has a brand new on in stock.  I'll pick it up tomorrow and install it tomorrow night and baby the engine till I figure out the root cause.

[eventhorizon66]

Local NAPA store has a brand new one in stock.

Brand new and fresh from China.

Once you sort out what is causing it, why not upgrade to these?  They're cheap, strong (as long as open spring pressure is under 350 lbs), and reduce wear on valve guides.  Of course, you would have to switch over to studs as well.

[VileZambonie]

Go with a full roller.... The heads you have allow for no rocker arm adjustment. Are your pushrods the correct length? did you swap in a bigger cam?

[Mike Phillips]

***Update***

First, I was recommended to a local machine shop that works on a lot of marine engines.  I explained what happened to the owner of the shop and showed him the broken rocker arms and the first thing he said was, (after looking at my truck),

What kind of valve covers are you running?

I said, some tall Ansen aftermarket valve covers. 

He then said that was the problem, the factory engineered valve covers were designed to keep the rockers well lubricated and the tall valve covers I installed were reducing the proper oiling of the valve covers.

He told me to go to the local auto parts store an order a replacement rocker for a newer Gen VI 454 and put the stock valve covers back on.

I called Tim Briggs, one of the best engine builders I've ever known and he said what the shop owner said was probably true.  Tim's going to look into a high performance replacement option for my valve train because if the tall valve covers are the root cause then it's likely even though not all rockers have broken they may already be affected.  He'll make sure they'll fit under the stock valve covers.

I did order a single replacement rocker arm kit from Advanced Auto parts and also one from NAPA here in Stuart, Florida basing off a 1998 Chevy Suburban with a 454.  Keep in mind, I have know idea what this motor came out of but I do have a picture of what it was slated to go into and it could be it came out of this boat too, I just never received a concrete answer to that question.




Here's a shot of the stock valve covers, I still have them but they're in Apple Valley, California and I'm having them shipped to me.



Anyone agree with the shop owner's assessment that the root cause is the tall valve covers?

Anyone disagree?

[VileZambonie]

As you can see there is plenty of oil on the rocker arms. I disagree that your valve covers are the problem. You didn't answer my previous questions. Please answer them. Lack of lubrication in these points would cause galling and I see very little from your pics. Either your rocker arms were over tightened or you have a binding condition. You have a roller cam, but is it stock? What valve springs are on there? Are the valve rotators installed? Keep in mind they will be UNDER the spring. Rotate the engine by hand and watch the actuation of the rocker arm. The torque spec for the rocker arm bolts is 40lb-ft

[Mike Phillips]

As you can see there is plenty of oil on the rocker arms. I disagree that your valve covers are the problem. You didn't answer my previous questions.

Usually I'm pretty good about breaking posts up via the quote format and answering questions, it was along day yesterday so after my previous post I logged-off and hit the hay... sorry...

Please answer them. Lack of lubrication in these points would cause galling and I see very little from your pics.

Correct, everything looks clean and smooth.

Either your rocker arms were over tightened or you have a binding condition. You have a roller cam, but is it stock?
 

This is a non-adjustable rocker arm system, you torque the rocker arms down to 40lbs and all the play is adjusted by either grinding the valve stems or changing the push rod length.  At least that's what I've been told.  I've only worked on adjustable valve trains myself so this is new to me.  I actually wrote a how-to manual called,

"How to adjust the Chevrolet Valve Train using the EIOC method.

So I'm very aware of how to adjust the normal or old school style Chevrolet valve train both hydraulic and solid lifters.  This Gen VI engine is alien to me.

What valve springs are on there? Are the valve rotators installed? Keep in mind they will be UNDER the spring.
 

I bought this from a friend that was storing the motor and the boat for a friend that flaked-out and left the state.  He sold the boat to someone else and I bought the motor.  It was supposedly rebuilt in a SoCal engine shop with a good reputation but that's about all I know.  I'll send the link to this thread to Steve, the guy I bought the motor from but in the past I haven't got much more information about the engine than what I've already posted.  As such, I don't know what valve springs are on the engine, I don't know if the rotators are or were installed, the engine was wrapped in plastic and a new rebuild when I bought it.

I tool this photo when I was looking at the motor initially.  Steve is a reputable business man and a car guy like the rest of us.

Rotate the engine by hand and watch the actuation of the rocker arm. The torque spec for the rocker arm bolts is 40lb-ft

I'm going out of town for the weekend for some car guy stuff, when I get back I might have the following Saturday off and at that time I can probably get my hands dirty and get some work done.


Thanks for the follow-up, I appreciate your help.  I need to get this engine bullet-proof.

[VileZambonie]

Show a pic of the bottom the rocker arm too please

[Captkaos]

I disagree that the covers are causing your problems also.  It looks like it binded up and broke in two.
Are there any numbers on the cylinder heads?

[joesgarage71]

I disagree that the covers are causing your problems also.  It looks like it binded up and broke in two.
Are there any numbers on the cylinder heads?

Maybe too much cam for the stock valvetrain

[VileZambonie]

Yes I am aware you have non adjustable rocker arms, that is why I initially asked what you had and gave you the torque value. Yes they can be overtightened still. You do not adjust the clearance by grinding the valves, you need the correct push rod length. Once you determine that you do not have coil bind and that the rocker arms are correct along with the pushrods you won't have any issues. The Gen V BB's and crate motors also had this style cylinder head.

[HAULIN IT]

Mike, I also don't buy the valve cover theory. Not all BBC's had the drippers, plus MANY BBC's have been run without them on non-factory valve covers. One of the ones I saw this happen to had factory covers...One had Aluminum M/T's without drippers.
 Have you done a compression test yet?
  I would also like to see the bottom, the pivot, ect. from that rocker & a few other rockers, pivots, ect. from a couple other cylinders also. It's hard to tell for sure in the pictures because of the shadows/glare, ect. but I see no signs of gulling, ect. from lack of oiling. I would take apart a couple "unfailed" cylinders & look for witness marks. It would be helpful if you knew if all of the failed rockers were intakes. Are the springs single or dual? I'd be checking allot more just to be safe before just sticking another rocker on there. Lorne

[Mike Phillips]

Hey everyone,

Thanks for all the ideas and questions, I'm in Dallas, Texas for the next few days so I can't get any picture or doing any wrenching till I get back home, as soon as I do I'll pull a couple other rocker arms off and get some good close-up pictures.

Mike

[joesgarage71]

 Hey Mike whats up with the BB

[Mike Phillips]

Hey Mike whats up with the BB

Sorry for such a late reply... my job keeps me very busy... here's the update...

***Update***
 
One of my mechanic friends said he was told by that there were some rocker arms Chevy put out that were defective and/or weak and that breaking like mind did is a known problem. I don't know if this is accurate or not and quite frankly don't care as I've found out the root cause of the problem.
 
The problem is the non-adjustable Chevrolet design for their modern heads. My boat mechanic Tim Briggs said this design is used so valve trains can be assembled at speed on assembly lines without the need for a second step, (valve adjustment). While this might be fine for assembly line work it doesn't work anytime any modifications to the engine are made that affects the valve train.
 
Here's what I know. I'll never buy a Chevy Mark VI engine again unless a Pro shop has went through it and upgraded the heads to quality aftermarket heads as the stock heads are JUNK due to the thread size for the "bolt" that holds the rocker arm in place. The thread size that hold the rocker arm in place for the Gen VI engines is a 3/8" diameter thread hole while old school heads, (the good stuff), is 7/16" diameter threads.
 
There's a conversion kit by Comp Cams to install a 3/8" stud with a 7/16" diameter stud on top for "Normal" high performance parts. So I'm going to order the bolt to stud conversion kit and a set of Pro Magnum Roller Rocker Arms and this should solve all the rocker arm problems and fix the Chevrolet Engineer's mistake. While this engine is in a Pavement Pounder, you would never want to use a head like this in any kind of performance situation, including High School Drags. So learn from my experience, spend the money up front for a quality engine with quality heads. My next engine will be built by Tim Briggs. Whatever the cost, it's a money saver, not a money pit.
 
Pro Magnum Roller Rocker Arms

 
The Good News and the Bad News!
 
The Good News is it will be easier to install the conversion kit and the new rocker arms after I remove the engine.
 
The Bad News is on December 10th my truck was rear-ended by an young man with a suspended driver's license in a 1996 Ford Truck. The Allstate Adjuster has evaluated the condition of my truck after the accident and has totaled it.
 
Thanks for everyone's help....
 
You can see pictures of the damage and the crime scene here,
 
Just was rearended... 1975 Jimmy RIP
 
 
Mike