Has anbody run into this before? Pushrods touch valve cover rail

[turbodave231]

On a recent build, I removed the valve covers after running the engine. I found that the pushrods were rubbing on the gaskets and in several spot were making small witness marks on the cover itself.

These are GN1 heads w/ T&D individual shaft rockers and GN1 valve covers

I corrected the situation by carefully marking the contact areas and grinding the valve covers. I RTV'd the gakets to the cover and then trimmed the gasket away using an razor knife. I'm glad I caught this before this engine got installed in the chassis.

 

[Mike T]

I had that same problem with 8445 heads and 1.55 rollers. The first set of Cometic gaskets I had to clearance, the second set of gaskets were the black rubber type that after a run in period I found that they rubbed as well. I did call Cometic and they said that they were not aware of the problem.

 

[pacecarta]

i just went thorugh setting up a set of GN1 heads on the bench with the same Jesel setup for kidglock. we are a little bit away from final assembly on motor but with pushrod in place on rocker i noticed the very same thing that edge of the vavle cover could be an issue with pushrods
he is also running the cometic valve cover gaskets and they have no give so they will need some trimming

 

[Mike T]

I have 1.55's and they rubbed. Wouldn't 1.65's have more clearance since they are closer to the fulcrum?

 

[FHW]

I have 1.55's and they rubbed. Wouldn't 1.65's have more clearance since they are closer to the fulcrum?

Yes 1.65 give you more clearance but still req. checking as they are still tight. With 1.55 not only did we notch valve covers the pushrod holes of the heads had to be milled for more clearance. hth.

 

[earlbrown]

I had to put my 8445's on the mill and clearance them for 5/16's pushrods with stock rockers. It would seem pushrod clearance problems often go overlooked with these engines.

For a few years I've been wondering is a lot of 'lifter noise' is actually pushrods hitting stuff they shouldn't be hitting.

 

[Mike T]

I had to put my 8445's on the mill and clearance them for 5/16's pushrods with stock rockers. It would seem pushrod clearance problems often go overlooked with these engines.

For a few years I've been wondering is a lot of 'lifter noise' is actually pushrods hitting stuff they shouldn't be hitting.

Earl I'm thinking the same thing. I have been chasing a slight random upper end noise myself.

 

[turbodave231]

I have had to correct pushrod clearance issues on several engines built by some high priced vendors (not mentioning any names). I've learned to be very careful about all valvetrain clearances. Those things can bite you hard if left uncorrected.

 

[bison]

I've had to mill pushrod holes on all my engines with aftermarket castings when trying to use aggressive valve train components.

 

[bison]

 

[TTipe]

On a recent build, I removed the valve covers after running the engine. I found that the pushrods were rubbing on the gaskets and in several spot were making small witness marks on the cover itself.

These are GN1 heads w/ T&D individual shaft rockers and GN1 valve coversView attachment 208629 View attachment 208630

I corrected the situation by carefully marking the contact areas and grinding the valve covers. I RTV'd the gakets to the cover and then trimmed the gasket away using an razor knife. I'm glad I caught this before this engine got installed in the chassis.

Dave Tom (at Champion) suggested that a slight rub in the pushrod tunnel was very possible. I have not seen a rub in my GN1's pushrod paths. I have 1.6 T&D shaft rockers and have a very minor rub on the gasket but saw nothing on the valve covers. Likely stack up issues / dimensional change in the Champion rocker cover gasket rail has occurred. I just went out in the garage and looked.

 

[kidglok]

i wish things just "bolted together".

Building heads like these are not for the faint of heart.

 

[turbodave231]

Brian,

When I disassembled this engine, All the pushrods were rubbing the cylinder head (along with a long list of other problems). The heads went back to Tom at Champion for repairs and a full CNC port job. While the heads were there, I had him mill the pushrod holes as you have displayed. He cut slightly into the valve cover rail and the pushrods are still close to the head, but no contact. I've run into this before with GN1 heads. On this engine, I saw the valve cover problem on the passenger side head only. I did not expect the GN1 valve covers to be a problem. I'm glad I checked.

The valve covers do have a little slop before I tighten the bolts. The covers will move away from the pushrods or toward the pushrods. This is probably why I saw the problem on only one side. I gave both covers/gaskets the clearance you see in the picture above. Someone in a hurry would miss the problem completely.

Thanks for the input.

Dave

 

[pacecarta]

another thing noticed was i measured the height of the rocker nut at full lift of cam ( ~ .630 at valve) and the rocker height was taller than the cover depth with no gasket . it definitely would not work with a stock felpro cork gasket after a crush , the comitic should work but its close

and the supplied bolts to attach the stand bridge to the head were too long even with .125 shim under it ,
if you have any bolt holes that breached unto the intake ports (for the bolts that attach the bridge to head ) you should use sealer on them

im sure before we get get done ill have to adjust the headlamps to get this valve train to fit perfect

 

[TurboTdr3.8]

im sure before we get get done ill have to adjust the headlamps to get this valve train to fit perfect

Paul did you learn that at Hard Knocks School ? LOL!!!!!!!

 

[pacecarta]

nope , i learned long ago ..look before you leap

 

[SS/GN]

I am surprised the holes are not elongated on a performance head like that. I have used this tool on many engines I have done
http://www.summitracing.com/int/parts/cca-4710/overview/

 

[earlbrown]

The only downside to that tool it is assumes the holes are in the right place to start with. When I modified mine, I put layout die on the VC rail area and scribed the actual pushrod location. They were waaaaay off compared to the factory holes.

 

[SS/GN]

The only downside to that tool it is assumes the holes are in the right place to start with. When I modified mine, I put layout die on the VC rail area and scribed the actual pushrod location. They were waaaaay off compared to the factory holes.

I don't have enough room in my garage for that but I have done many sets of heads at home with that tool and it works pretty good on small block chevys but I have not tried it on Buicks

 

[earlbrown]

sbc's seem to be a little more centered and roomy. Angle milling or changing the rocker arm ratio will put you into interference. (and of course incorrect geometry can't help either)

I couldn't find a shot of how far off my Buick heads were off, but my notes mentioned two of them were way off. It was left to right that was the problem with mine. Since I had a mill in the next room, I went ahead and made sure I had room since the heads had to get dirty again.