Valve Guide Loose in Head - Options?
Discussion
stevieturbo said:
This engine seems to have had a hell of a rough time.
Who built it and what sort of usage has it seen ? Has it ever been tuned correctly ?
Normally aspirated or has someone added boost ?
This particular engine?Who built it and what sort of usage has it seen ? Has it ever been tuned correctly ?
Normally aspirated or has someone added boost ?
When I bought the car seven years ago it was the perfect example of deferred maintenance
I have run it on a budget since then, gradually replacing parts as and when I could
It was over pressurising the cooling system when I bought it, so the first thing I did was pull the heads
The most of the liners have several tide marks so the engine has sat with coolant the the cylinders several times
This correlates with the low recorded mileage between MOTs when I bought it
Also most of the intake buckets were dished because the valve clearances had closed up and the shims had'd been replaced
After replacing the head gaskets the first time, it was mapped primarily to try to address a pinking issue at 2k
It produced healthy figures on the dyno and is absolutely standard apart from short induction (because the standard hoses cost over £500, and the short kit was half that - I am on a budget)
However I suspect the fuel injector was already faulty, but I didn't discover that until I had them flow tested three years later, the next time I had to pull the heads
The car has been regularly tracked since I bought it, and the engine is routinely red lined, so yes it probably has had a hard life
Since the engine has about 60k on it, I am now coming to terms with the fact I will have to replace all valves and springs, which means my parts cost for this job is going to be about a grand, and that doesn't include any of the engineering work
GreenV8S said:
The internet suggests they designed in just about every other problem you could imagine in the valve train so it shouldn't be too surprising if they included this one too.
Perhaps you are thinking of the Speed Six and the poor Finger Follower quality controlAs far as I'm aware the AJP8 has no valve train issues
In fact the very light 16v design means it is pretty robust and revs freely to 7600
The only proviso is that the shims need to be checked and adjusted more frequently than the official 12k service interval
I do it twice as often, and there is always work to do on the Intakes as the valves stretch
Exhausts are far more stable, they don't seem to wear the valve seats
Interesting about valve clearance disappearing, where does it go? Does the inlet seat on the insert recess or does the insert move up towards the valve guide, maybe the valve itself mushrooms over? To be honest the seats look in very poor condition for a modern engine. As these engines get longer in the tooth problems associated with longevity will come to light. You say ex valve side fairs better than inlet side. We see this with the extremely high revving single cylinder four stroke bikes, ex valves fine but inlets mushroomed over, purely because they weigh more than the ex valves! Both inlet and ex valves are titanium with a coating so seats can only be blued or run out gauge checked for concentricity as the coating, once ground off reduces the life of the components to a couple of hours!
Peter
Peter
PeterBurgess said:
Interesting about valve clearance disappearing, where does it go? Does the inlet seat on the insert recess or does the insert move up towards the valve guide, maybe the valve itself mushrooms over?
The new intake valves are shorter than the ones I've removedI presume that means they have stretched (it also seems to be the consensus of the TVR crowd)
I had to drop them off as soon as I bought them so I haven't been able to measure them, but I did compare lengths very crudely while sat on the dash in the car
Are the new valves the same make/part number as the ones you are replacing ?
That could account for height differences.
Although if the height difference on your current valves are not all identical, then yes stretching, tuliping, whatever could well be likely.
Not something that should ever be happening with small light valves on a n/a engine with a relatively low rpm range.
That could account for height differences.
Although if the height difference on your current valves are not all identical, then yes stretching, tuliping, whatever could well be likely.
Not something that should ever be happening with small light valves on a n/a engine with a relatively low rpm range.
stevieturbo said:
Are the new valves the same make/part number as the ones you are replacing ?
That could account for height differences.
With a cursory glance I couldn't see any etched markings on either new or old, there are only a couple of suppliers of AJP8 parts, I suspect they all come from the same sourceThat could account for height differences.
Several years ago I tried to find out where the buckets come from, assuming they were not AJP8 specific, I didn't get anywhere at all
However I did find that some used ones I acquired were a few grams different in weight, I made sure I used a set that all matched
This is obviously one of the ones I eventually threw out
In 30 years of building race engines I've never seen a valve stem stretch. The grades of steel used are industry standard all over the world and the dimensions and strengths required for a given rpm and spring load are well known. However looking at the pics of inlet valves on the tvr parts website the valve heads do look a tad flimsy with not much land depth but I've seen worse. I suppose it's just about conceivable the heads could distort a bit so the seat area pulls away from the stem end but I'd think that seat recession is a more likely cause of tappet clearances closing up. It's an easy enough thing to measure before and after a stripdown if anyone really wanted to get to the bottom of it.
ukkid35 said:
Perhaps you are thinking of the Speed Six and the poor Finger Follower quality control
No, my comments aren't specific to the Speed 6 engine, although that's certainly got it's fair share of issues. I'm referring to the whole AJP engine family - the engine that broke TVR.
If you ever wondered what happens if you try to produce a high performance engine with about a thousandth of the expertise, research and development that mainstream manufacturers put in to achieve modern mass production reliability levels, there is no need to wonder any more because TVR have found the answer for us: it's the AJP.
I've lost count of the number of died-in-the-wool TVR enthusiasts I know who had been in the habit of trading up to a new TVR every year or two as each new model came out, eagerly bought the new top-of-the-line TVR and found themselves a few thousand miles later with a five-figure repair bill and a car off the road for months waiting for TVR to return the broken engine. And routinely, the replacement engine also failed, often before it had even finished being run in.
The cars with this engine in are superb to drive and extremely desirable. If I owned one, my main concern would be to sell it before the engine blew up. The idea of owning a car with this engine that hasn't been maintained properly would fill me with dread. Maintenance and repairs were always expensive on this engine, even when you could get the parts.
Edited by GreenV8S on Sunday 11th March 11:24
Mignon said:
The marks on that lifter bucket look like it wasn't rotating properly. Cam lobes should be offset from the lifter centre by a few mm to create rotation. Maybe some design engineer messed this up.
They definitely do rotate, you should see the ones where the shims have never been checked/changed - they are very literally dished all the way round to a depth of a mil or twoFortunately mine was never that bad
Mignon said:
Maybe some design engineer messed this up.
RND published some information about the AJP6 heads at http://www.rndengineering.co.uk/tvr_all/page_p6_tv... in case you're interested.GreenV8S said:
If you ever wondered what happens if you try to produce a high performance engine with about a thousandth of the expertise, research and development that mainstream manufacturers put in to achieve modern mass production reliability levels, there is no need to wonder any more because TVR have found the answer for us: it's the AJP.
There are only two design flaws that I am aware of with the AJP8- Cranks that snap - this only affected early 4.2 engines, journal size was increased on later engines
- Aux drive shafts failures (driving water/oil/PS pumps) - again the shaft was uprated on later engines (possibly not mine though)
I am intrigued like Dave, which part of the valve stretches? I have seen mushrooming of the seat which isn't imminent failure and I have seen collet grooves stretch which is imminent failure.
It may well be aftermarket valves are shorter to take into account valve seats going up in the head or severe wear because of seat material? If you asked the suppliers do you think they would tell you why the valves are shorter? Seats moving towards the guides shows up as a new looking tiny band of alloy where the seat meats the port. Sometimes all the way round sometimes more one side than the other depending on support. This sort of problem is very common on heads where the short side of the port has been ground back too much, many Rover V8 and Vauxhall 2 litre 16v heads can be like this!
I don't think anyone is trying to criticise the engine as such. It is a high rev engine which will wear fast. It is also an engine that was not years in the design and operation so inherent problems have not been addressed and may not have been known about when production ceased. My main love is B series BL engines, they were modified to take into account problems which showed up over the extremely long evolution time of the engine.
Peter
Edit....meets, not meats, I must have been longing for my Sunday luncheon
It may well be aftermarket valves are shorter to take into account valve seats going up in the head or severe wear because of seat material? If you asked the suppliers do you think they would tell you why the valves are shorter? Seats moving towards the guides shows up as a new looking tiny band of alloy where the seat meats the port. Sometimes all the way round sometimes more one side than the other depending on support. This sort of problem is very common on heads where the short side of the port has been ground back too much, many Rover V8 and Vauxhall 2 litre 16v heads can be like this!
I don't think anyone is trying to criticise the engine as such. It is a high rev engine which will wear fast. It is also an engine that was not years in the design and operation so inherent problems have not been addressed and may not have been known about when production ceased. My main love is B series BL engines, they were modified to take into account problems which showed up over the extremely long evolution time of the engine.
Peter
Edit....meets, not meats, I must have been longing for my Sunday luncheon
Edited by PeterBurgess on Sunday 11th March 13:12
PeterBurgess said:
I don't think anyone is trying to criticise the engine as such. It is a high rev engine which will wear fast. It is also an engine that was not years in the design and operation so inherent problems have not been addressed and may not have been known about when production ceased. My main love is B series BL engines, they were modified to take into account problems which showed up over the extremely long evolution time of the engine.
It is worth bearing in mind that the AJP8 is possibly the lightest v8 engine of its capacity ever built at just 121kg (flat plane crank helps)Not only that, but it is tiny!
Apparently it fits in a 2 foot square cube...
PeterBurgess said:
It may well be aftermarket valves are shorter to take into account valve seats going up in the head or severe wear because of seat material? If you asked the suppliers do you think they would tell you why the valves are shorter?
You may well be rightThe length of the only used valve I've checked is exactly 120.50mm
I remember seeing the length of a new intake specified as 120mm
I am not sure I'll get anywhere by asking questions, but you never know
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