[danny427]

Need help:
I have a shelby csx 4000 cobra with a shelby 427 aluminum block with edelbrock aluminum heads,comp cam roller rocker on solid lifters.
On two occasions the rockers have broken apart (as if peeled back and split from the bottom belly). The car has a tendancy to knock when I shut it off. I am running pump gas (premium 94 octain), the comp is 11 to 1.

The first break occured pulling into my driveway at almost no speed, the other time I think it may occurred when shutting off the engine. I have heard that the spring tension may be too high or is it possible the rocker is just not strong enough, possibly not enough oiling. I don't like the fact that the raw aluminum rocker is riding on a metal shaft (these rockers have no bushing or needle bearings).
My engine builder wants to make the car hydrolic roller being a street car. He insisted we make the car a solid lifter car a few years ago. Changing to hydrolic does not explain or cure the reason for rocker failure. Can someone please help. This is become a real pain and at times I want to just get rid of the car. More time being repaired than driving.

 

[arnoldtx]

What cam and specs? What valve springs? What type of rockers? Many things could cause it. Spring bind could be a cause, has it been checked?

 

[82GT]

I dont know the answer to your problem but I don't think 94 octance fuel is enough for 11:1 CR

 

[Motorhead]

82GT: Depends on the cam specs, chamber design, spark advance, and a lot of other variables. It may be marginal, but we already know it's an aluminum head which is supposed to help. A big cam will lower the dynamic compression ratio making it more tolerant to static compression. However all that being said, I don't think the compression would have any impact on this particular problem.

I agree that it seems odd that the rocker has no bearing at all, it pivots right against aluminum. What brand/model rockers are they? Still, for it to split open like you say, I agree with Arnold, seems like something would have to be binding up. Maybe inadequate piston-to-valve clearance? Seems like you'd see bent valves if that were the cause though... Definitely need more info, like cam specs and springs used. The engine builder should be able to give you those, or else he shouldn't be building such pricey engines.

BTW awesome car, if you get too tired of it, I'll be first in line to take it off your hands (at significantly below market value, since that's all I can afford)!

 

[n2omike]

There are some bright people here, but there are a TON of very experienced FE guys at the FE forum. I'd also post my question there. 332-428 Ford FE Engine Forum You may also want to contact Barry Rabotnik at Survival Motorsports. He is a former Federal Mogul engineer, former street racer, FE specialist that campaigns FE engines in the Engine Masters dyno challenge, is super helpful, and most of all honest. He knows pretty much everything there is to know about the FE. He sometimes visits the forums here. He is at the FE forum on a regular basis, and has his own site. Survival Motorsports Home Page

Good Luck!

 

[shiftthis]

What cam and specs? What valve springs? What type of rockers? Many things could cause it. Spring bind could be a cause, has it been checked?

+1
spring bind would be the first thing to check.