help me

ok i have a 1990 gt with a cobra 302, the rocker arms are a little lose like i can wiggle them, i tryed to titen them more but one of them i guess i titened it to much because the stud broke off, first off are they sopose to be loose a little bit or what, second why would all of a sudden they come lose and dont tighten any more, i did take the cylinder heads off befor this happend to replace the valve seals, but i know i put every thing back the way it was soppose to be so im confused thanks.

What happened to the 393 or whatever?

First off what kind of rockers? What heads? Studs or pedestals?

I know on heads with studs and stock stamped steel rockers they will be somewhat loose but not sloppy loose. You can just feel them move a little. Hydraulic lifters have a preload spec that you tighten the rockers to, atleast that is with hydraulic rollers. Need to have more info.

Crackling sound!

My engine makes a crackling sound, cyclical, increasing with the RPMs. Sounds like a small diesel.
I suspect a broken valve spring. Am I on the right track?
Plesae help before I'll tore this piece of s... down
Thanx

Hard to pinpoint a "crackling sound". Is it coming from the motor of out of the exhaust? If you have a feelings its valvetrain related pop a valve cover off and see what you can find. If its a sbf then you only have 6 bolts and gaskets are cheap.

well im leaving for the navy in july and i wanted to just get her done befor i leave so i just went with a rebilt cobra carb engine, from what i know its got a after market performance cam dont know the specs tho, the springs are the ones that have two springs in one, the rocker arms are stud mounted and im not sure if there stock they look after market rockers they looke alot smaller and lighter then the ones i got off of my old 302, i think there Hydraulic lifters, it all started when i started the engine im pritty sure i had the timeing set right but when i started it at first a big cloud of smoke shot out the carb, i got a Aeromotive SS Series Electric Fuel Pump #11203 and a Aeromotive A1000 Carbureted Bypass Fuel Regulator 13204, a edlbrock 650cfm carb, i mean the rocker arms arnt that loose but there still pritty lose i know i can push on the push rod end and the rocker arm will come off of the spring, like i can twist the rocker arm off the spring just bye pushing on the push rod side of the rocker here are some pics

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Pics arent working but those rockers are too loose. You said you broke a stud off when tightening one of the rockers. Did the rocker ever tighten up? I know a friend of mine had some stock heads worked by a shitty machine shop and the guy left the stock press fit studs in the heads. His cam was a .510 lift hydraulic flat tappet cam and it started pulling the studs out of the heads. We had the same problem, could keep the rockers tight. Kept tightening and tightening, then we realised what was happening. Just something to look into. If I where you I'd take the heads to a reputable machine shop, have then install screw in studs, and buy some decent rockers. The motor if its a cobra motor should have roller lifters in it. You will have to pull the intake to get the heads off so you can find out for sure then. If they are hydraulic roller lifters then they should have a preload spec. I think my Crane retro fit link bar lifters where .030 - .050 or so on the preload. I just too a dial indicator and tightened the rockers down to the preload on the lifters and locked them in place (Comp pro magnum roller rockers). If all else fails take it to a shop and let the guys that do this stuff for a living get it running for you.

no the rocker did not tighten up that is why it broke off i kept trying to tighten it more, and i know befor i replaced the valve seals the rockers were not loose, but i put every thing back together just as it came off when i took the cylinder heads off, i know the engine is from a ford shellby cobra,

What year? I thought you meant like a '93 fox body cobra 5.0 motor. I dont understand what your trying to say...did the rocker stud break when you where trying to tighten it or did it break while running due to being loose? If thats so, you better check for bent pushrods. If they where tight before with the same exact set-up and you know you did everything right, then the studs must be pulling out of the heads. Sucks I know...but they will have to be pulled out and replaced with screw in studs. Cost a friend of mine $150 to have this done to a set of sbc heads.

yeah no i shelby cobra, the rocker stud broke when i was tring to tighten it. this is what would happen befor i checked the rocker arms, i was running about 10-13psi in gas, i would start it and a big puff of smoke would come out the carb then if you did not pump the gas it would just die, but if you pumped the gas for little while it would start to sound fine then you could let off of the gas and it would be run normal for about 35sec and then it would just die, so i checked the rockers, what would cause the big puff of smoke out the carb i was thinking it from the rockers being loose and the valves not opening and closeing right, that is just what i was thinking tho

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ok i was just messing with the engine and from what i can see, the only time when the rockers are loose is when the cam is not fireing that cylinder you know what i mean, like cam lobe is at the bottom,

It shouldnt really be loose there either. You do want the valve 100% closed when the lifter is on the heel of the cam. But you want the valve to open as soon and the cam begins to lift the lifter. There is a happy medium there. Just tighten the rockers down until they stop chattering. 10-13psi in gas? Do you mean your base fuel pressure was around 10-13psi? Thats twice as much as you need. Set fuel pressure at 7psi and leave it alone. Thats with a carb. Double check your timing. We had smoke coming out of the carb on my friends small chevy and that was also caused by the rockers studs coming out.

Hard to pinpoint a "crackling sound". Is it coming from the motor of out of the exhaust? If you have a feelings its valvetrain related pop a valve cover off and see what you can find. If its a sbf then you only have 6 bolts and gaskets are cheap.

Thanx,
I listened with the scope. Drivetrain sounds good. The only suspicious noise awas at the air pollution pump.
Also, it is plenty sluggish. For 3.8L it should have more kick. Once before the CAT rusted solid inside and I blew the gasket. I do not drive it in the winter, so it sits in the barn for 5-6 month every year. Not too good for corrossion, huh? I just pulled it out.
Should I replace CAT? Or... throw it away?

Is there a better TBI/manifold for this slug?
Thanx

ok thanks, alot