Need help on a tune

[vlad01]

even the old lifter often jam up at the proload they run at becoming solid beyond that point, I found this to be about 50% of them once they get a few ks. So a further down pushrod will open the valve.

[krusty]

If the lifter was jammed depressed I'd think it less prone to hold a valve open but yeah I guess depends how much preload was on it to start. If it was preloaded solid then well, anythings a possible scenario hahahahahah

[vlad01]

Reason i say that is with heads shaved a heap and aftermarket rockers, it well could be further down the lifter preload range but they often jam at what they were set in the factory.

I've tried to free some destructively using an old pushrod and a hammer with only some success. they do jam really well, more than enough to act as a solid lifter below that preload. I guess varnish and carbon deposits cause them to jam at that.

[krusty]

Reason i say that is with heads shaved a heap and aftermarket rockers, it well could be further down the lifter preload range but they often jam at what they were set in the factory.

I've tried to free some destructively using an old pushrod and a hammer with only some success. they do jam really well, more than enough to act as a solid lifter below that preload. I guess varnish and carbon deposits cause them to jam at that.

Lifter preload isn't related to rocker style or type though? Lifter preload relates to the lifter itself. You may set it up at different ends of the scale depending on desired rpm band, spring pressure, cam lobe lift or oiling system pressure characteristics but push rod length variation to control rocker tip contact patch to the valve tip is secondary to lifter preload other wise it would all be futile and stick a valve open or let a push rod escape the lifter and stick a valve into a piston which I've had the displeasure of seeing

Anyways, I'd be keen to see the results of where lifter preload is at because it sounds like someone has thrown heads and cam in without checking and now a valve may have had a moment and touched a piston. usually when it's at the limit of acceptable piston to valve clearance and preload is fudged 1 valve may tag a piston during an event and drop power which settles the valvetrain. Seen it many many times from diy blokes and shops that were previously unaware sadly

[siktrk]

I'll get my heads taken off this week just to see what the problem is and find out what is the compression ratio and how much has been shaved off

And I think the cam has abit of lift compared when I had the stock heads cause I hear abit of grinding when I give any acceleration what so ever

Other than that I'll change the lifts,get gaskets suited for the heads and make sure if I can get cosmetic ones
Might even change the cam suit for the heads so at least it runs better
better

I'll let you guys know how it goes and if it runs good

Thanks for your help

[vlad01]

Reason i say that is with heads shaved a heap and aftermarket rockers, it well could be further down the lifter preload range but they often jam at what they were set in the factory.

I've tried to free some destructively using an old pushrod and a hammer with only some success. they do jam really well, more than enough to act as a solid lifter below that preload. I guess varnish and carbon deposits cause them to jam at that.

Lifter preload isn't related to rocker style or type though? Lifter preload relates to the lifter itself. You may set it up at different ends of the scale depending on desired rpm band, spring pressure, cam lobe lift or oiling system pressure characteristics but push rod length variation to control rocker tip contact patch to the valve tip is secondary to lifter preload other wise it would all be futile and stick a valve open or let a push rod escape the lifter and stick a valve into a piston which I've had the displeasure of seeing

Anyways, I'd be keen to see the results of where lifter preload is at because it sounds like someone has thrown heads and cam in without checking and now a valve may have had a moment and touched a piston. usually when it's at the limit of acceptable piston to valve clearance and preload is fudged 1 valve may tag a piston during an event and drop power which settles the valvetrain. Seen it many many times from diy blokes and shops that were previously unaware sadly

I know what you mean, what Im getting at is the preload likely to have changed due to installing parts without checking or adjusting for them. I know you are saying preload isn't related in the sense it shouldn't be set to a rockers etc.. but they will change the preload if different ones are install than what the factory used. Also cam base circle and head shaving would have effects changing the preload, thus why we need to alter pushrod length to set it correctly based on the lifter specs and rocker geometry.

[krusty]

Reason i say that is with heads shaved a heap and aftermarket rockers, it well could be further down the lifter preload range but they often jam at what they were set in the factory.

I've tried to free some destructively using an old pushrod and a hammer with only some success. they do jam really well, more than enough to act as a solid lifter below that preload. I guess varnish and carbon deposits cause them to jam at that.

Lifter preload isn't related to rocker style or type though? Lifter preload relates to the lifter itself. You may set it up at different ends of the scale depending on desired rpm band, spring pressure, cam lobe lift or oiling system pressure characteristics but push rod length variation to control rocker tip contact patch to the valve tip is secondary to lifter preload other wise it would all be futile and stick a valve open or let a push rod escape the lifter and stick a valve into a piston which I've had the displeasure of seeing

Anyways, I'd be keen to see the results of where lifter preload is at because it sounds like someone has thrown heads and cam in without checking and now a valve may have had a moment and touched a piston. usually when it's at the limit of acceptable piston to valve clearance and preload is fudged 1 valve may tag a piston during an event and drop power which settles the valvetrain. Seen it many many times from diy blokes and shops that were previously unaware sadly

I know what you mean, what Im getting at is the preload likely to have changed due to installing parts without checking or adjusting for them. I know you are saying preload isn't related in the sense it shouldn't be set to a rockers etc.. but they will change the preload if different ones are install than what the factory used. Also cam base circle and head shaving would have effects changing the preload, thus why we need to alter pushrod length to set it correctly based on the lifter specs and rocker geometry.

Ummm yeah. In other words preload should be checked before heads are removed and once verified a leak down test would be the next step . Pulling heads may be a waste of time at this stage but probably not

[siktrk]

ill do a leak down test tomorrow and find out what i need but if its major ill get the heads taken off and just do it again and find out that way how much has been shaved and work from there

[Charlescrown]

I am a firm believer in four basic tests. Power balance, manifold vacuum, compression and cylinder leakage and then analyse the results and you are sure to work out whats wrong before you do any work at all. I had a student who went into business and he came in to see me saying he had a problem "Audi with no compression" he pulled the engine down and couldn't find anything wrong. I asked about the cylinder leakage results and he looked at me funny and said "that wouldn't tell me anything" so I said "well you now have an even bigger problem". You can't diagnose a problem with an engine in bits. I never found out what it ended up being.

[krusty]

I am a firm believer in four basic tests. Power balance, manifold vacuum, compression and cylinder leakage and then analyse the results and you are sure to work out whats wrong before you do any work at all. I had a student who went into business and he came in to see me saying he had a problem "Audi with no compression" he pulled the engine down and couldn't find anything wrong. I asked about the cylinder leakage results and he looked at me funny and said "that wouldn't tell me anything" so I said "well you now have an even bigger problem". You can't diagnose a problem with an engine in bits. I never found out what it ended up being.

I've not read a wiser comment in a long time . Basic mechanical principle is don't fix it until you know the cause