96 replies to this topic

[JakeJakeJake]

now youve said that, im thinking at a longshot that the cam lobes may be worn if it wasnt a new cam, did you check to see that the pushrods were straight when you changed the head gasket?
And did the misfire gradually come along or was it sudden?

because the only thing im thinking right now, is that you have good compression, that the cause of the misfire is due to bad fuelling, if you can eliminate the carb from the equation, then it may be that the valves arent opening properly

I did not check them specifically, but I did not notice anything. I just need to pop the rockers off to get them out to check?

It happened in about 50 miles, from driving like it was just a but cold too barely running. Which later turned out to be because it was firing on 2 cylinders.

[Carlzilla]

Yeah, just drop the rocker assembly off and pull them out one by one, and replace them where they came from as you probably know, if theyve been under too much stress, youll see the bottoms of them where they meet the cam worn, or possibly slightly bent. id look for the wear where they touch the cam more importantly.

[JakeJakeJake]

Yeah, just drop the rocker assembly off and pull them out one by one, and replace them where they came from as you probably know, if theyve been under too much stress, youll see the bottoms of them where they meet the cam worn, or possibly slightly bent. id look for the wear where they touch the cam more importantly.

Yeh when I took the all out to change the HG I made a sort of map of where they all went. If one is worn or bent how do I go about replacing it?
Will I have the same problems as I would if I put them back in the wrong order or just replace them all and everything's OK?

[Carlzilla]

if ones had it, the others are under the same stress, youd fit new pushrods, slacken off the nuts for adjusting the valve clearances, fit the rockers then adjust all the valve clearances again.
Oh, and im not sure if you have to, bit id oil up the pushrods too before you put new in, if thats part of the cause.
What do you take the rev's to? If you dont go past say 5.5k rpm, you wont need the strong springs, put standard valve springs back in. My engine gets valve float after 5.6krpm, but its never taken that far anyway, so no point in me buying uprated valve springs, if you get where im coming from

Edited by Carlzilla, 09 January 2011 - 11:13 PM.

[JakeJakeJake]

if ones had it, the others are under the same stress, youd fit new pushrods, slacken off the nuts for adjusting the valve clearances, fit the rockers then adjust all the valve clearances again.
Oh, and im not sure if you have to, bit id oil up the pushrods too before you put new in, if thats part of the cause.
What do you take the rev's to? If you dont go past say 5.5k rpm, you wont need the strong springs, put standard valve springs back in. My engine gets valve float after 5.6krpm, but its never taken that far anyway, so no point in me buying uprated valve springs, if you get where im coming from

OK I will check them this evening. Did not expect them to be so expensive. What would have caused one to bend?

I have a 544 camshaft so power band is 2500 - 6500, so sometimes I do go all the way to just over 6500, but not very often

[JakeJakeJake]

Not taken the push rods out yet but I had a thought, if they were bent/worn and not opening and closing the valves correctly would the compression test not have shown something?

[Carlzilla]

They would be closing properly and sealing, but not opening properly, because the pushrods may be shorter, and the valve springs are that strong, itll be whats causing the wear on the pushrods/cam. Which is why the thought popped up in my mind. Extra strong double valve springs are only really needed on race motors id have thought, where valve float needs to be eliminated, as theyre at the top of the rev range most of the time
As i said though, it may not be this at all, but if you can check, its definately worth checking as were all running out of ideas

Edited by Carlzilla, 10 January 2011 - 05:04 PM.