4a problem, maybe Broken/damaged valves???????

[4A-GE Power]

Oh woops. i just assumed you were talking bout a ge. You wouldn't think they run the same cranks. I know the main and big end journals are the same size

[gunbz-r]

so slyda ur tellin me on a 4ac, that the cam runs straight on top of valves? they have arms.

oh u said ge, i know they dont have arms, most twin cams dont.

[gunbz-r]

not being patronising or whatever, but how'd u test what cylinders are running? check and make sure all the shims are there, tho that'd make noise down low, but check it. and feel all the rockers for play.

u'd have to be unlucky to snap a crank, and i would imagin it would of made a fair bit of noise when it let go. i see it as a bit odd for a crank to sheer driving normally at 60ks, could happen but i dont see it as likely, if u were revin it hard or had it really loaded up yeh but cruisin at 60?

[maxhag]

If it is the headgasket, what is the 'Rattle' when throttle suddenly applied?????????

I can understand losing compression, but whats the noise?

[gunbz-r]

cause its not your headgasket, have u checked comp yet? pull the rocker gear out, go over it make sure nothings bent or worn, then look in all the cavaties in the head for any debree, check your valve springs, make sure they are all sitting square and are all the same height. maybe theres been a hotspot or a dry one, and a valve or two have grabbed in the head, and are stuck partionally open, theres your comp lose, and would explain a rattle sort of noise uptop, if the pistons are tappin the valve, then the noise is louder at the higher speed due to the higher frequincey it would make.

another thing, maybe the valve springs have sagged/gone soft, then at a highr rpm valves have come in contact with piston tops, which would kill comp, and cause the rockers not to sit right in the shim.(this one happened to my b6 single cam)

the latter is more likely, but somethins let go in your head

[maxhag]

Compression test results:

CYL
1 - 60
2 - 62
3 - 158
4 - 156

The head is now coming off....

[maxhag]

Just got the head off...... The headgaskt was rooted between 1 and 2 cyl........

[gunbz-r]

ah yeah thats good, still why was it rattling?

[maxhag]

Toymods boyz reckon the noise was 'detonation'........

[slide86]

<div class='quotetop'>QUOTE (Maxhag @ Jan 1 2008, 05:59 PM) </div>
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