Griff engine problems: please help!

[gerjo]

Ever since I had an engine out job last year (a moving cylinder lining) the Griff (500) has been a bit lazy above 4.500 rpm, so I thought a RR session should clear this.

Thus last week I went to Mark Adams. However, after several hours Mark couldn't figure out why the engine wasn't performing (250 bhp/298 lbs for a 500 with ACT's twin plenum isn't very good). He suspected a worn camshaft or bad valves after a compression and leakage test.

So I went back home and today brougth the Griff to the dealer. They performed the leakage test twice and came up with a normal (so they say) 12% leakage for all cylinders. They will inspect the camshaft tomorrow but they are almost certain it's o.k. since they had a thourough look when the engine was out last time.

So I am stuck. All seems well with the engine but it isn't performing as it should. In my opinion it is running brilliant untill 4.500 rpm and then is struggling to get to 5.500/6000 rpm where it used to race to that point.

Any ideas? Is there anything they could have done wrong when putting the engine back together again last year? They checked the cam timing and they are very thourough, but still....

Please help, thanks guys!

[douglasr]

I had a similar problem with an old Golf - it was because the fuel filters were filthy and I was suffering fuel starvation at high revs.

[2 sheds]

Gerjo.
What a pain !
Does sound like cam problem to me, especially as Mark couldn't sort it.
Uprating the induction will only make it seem worse if it is a worn /out of adjustment cam,
i must admit to being supprised that it wouldn't "rev out" after you had fitted induction, meter & chip,
Tim

[gerjo]

guys, thanks very much for your thoughts:

Douglas: I'll ask the dealer to check but this is probably not it since Mark thought it was even running too rich at high revs

Tim: cam is indeed suspect but Nimag (and they are pretty reliable) inspected it 6 months ago and said it was as good as new. We'll hear tomorrow. I might call you to discuss.

Macdeb: liner moving caused a hard pounding noise, getting worse over time. Mind you at the time it ran like hell, hasn't been that fast since!

[apache]

6 months is enough for the cam to go once it starts, I've heard that they degrade rapidly.
You are lucky the liner didn't cause major damage (or did it?) I had an old Rover 2.6 SD1 that dropped a liner into the crankcase, sudden loud crunchy noise, lots of warning lights, total silence, luckily still under warrenty. Keep the faith mate

[gerjo]

You are lucky the liner didn't cause major damage (or did it?)

no , it was moving only a few mm when they discovered it, so no major damage

could be the cam but the thing is that all of a sudden it didn't perform as it used to, so that would mean that the cam was damaged during the engine out job which isn't likely

I must say it is getting quite frustrated: open up engine, put it together again, result: you've lost 15-20% power, what on earth can it be?



>> Edited by gerjo on Thursday 22 May 06:39

[griffman]

dont know if it will help but i had a similar problem a couple of years back. had loads of work done on the engine and it turned out that the pipe between the air filter and the air flow meter and started to disintergrate.it was restricting the amount of air to the air flow meter which made the car run lean. once replaced at a cost of £10 the car flew.

[GreenV8S]

Are the inlet and exhaust manifolds and gaskets lined up with the ports correctly? If these are out of line, it'll all run OK but the step will cause a restriction which will sap top-end power. Which leads to the question, how do you check? Don't know, the only approach I can see is to be extremely careful when putting it all together in the first place. Maybe Tim or one of the other engine specialists can advise on a better way to check?

[2 sheds]

You can only check manifold alignment & gaskets by taking them off, have they been off/ replaced recently ?
Tim

[gerjo]

dealer has checked camshaft and it's like brand new.

they indeed will check the air inlet tube.

manifolds have been off during engine out job, I will ask dealer to check.

Mark suggested to check the valve lift but according to the dealer it is not adjustable, so jury is still out on that one.

any other ideas?

thanks guys!!

[gerjo]

reply from dealer:
- inlet tube is o.k.
- manifolds/gaskets: gaskets have holes in them, so you can't fit them wrong
- valve lift: still unclear, TVR Power says the engine doesn't have any?

they will also check the exhaust and the main cat to see if anything is blocking it, but I'm running out of options and the car is still down on power

any thoughts?

thanks, Gerjo

[2 sheds]

Only options left that i can think of ( knowing that mark has eliminated the ignition air metering / fuelling)
Blocked main cat, or cam timing out of adjustment.
Tim

[gerjo]

2 sheds said: Only options left that i can think of ( knowing that mark has eliminated the ignition air metering / fuelling)
Blocked main cat, or cam timing out of adjustment.
Tim

yep, they will check the main cat and exhaust
indeed, ignition air meter and fuelling was checked by Mark

keep my fingers crossed it's the cat/exhaust

thanks Tim

[2 sheds]

Gerjo could you email me the dyno graph.
tim

[gerjo]

2 sheds said: Gerjo could you email me the dyno graph.
tim

o.k. I just did

[350matt]

Sounds suspiciuously like cam timing to me, What is the low -end torque like?

Matt

[gerjo]

low end torque is "normal", 270 lbs at 2000 rpm, rising to 298 lbs between 3000 and 4000 rpm
it is quite a flat curve, dying too soon right after 4000 rpm. (see graph below)



cam timing was/is suspect, however Mark ruled it out by looking at the graph. Still under investigation though. All others things were checked by the dealer and were A o.k.

This is driving me nuts!

[GreenV8S]

Did the power loss definitely occur when you had that work done on the engine? What was changed? What parts were disturbed?

[gerjo]

GreenV8S said: Did the power loss definitely occur when you had that work done on the engine? What was changed? What parts were disturbed?

yes, it did occur right after the repairs, although I only noticed it after a few hundred miles, since I had to take it easy running in the new liner.

Changed: that's the million dollar question. Dealer says nothing was changed, only a new cylinder liner was fitted. Advance timing changed, but that was corrected on the RR session. Cam timing wasn't changed according to dealer and was checked with Blackpool spec's. We can't think of anything else that was effected by the repairs.

[GreenV8S]

Any idea what they had to remove to do the work? Did they take the engine out? Presumably the heads and induction all had to come out? Did they need to take the front cover off? I assume that Mark will already have checked the ignition timing and mixture was right, that plus the cam condition and timing seems to rule out all the easy options. Is it possible there's something really silly going on like wrong thickness head gaskets dropping the CR, trumpets knocked out when they took the plenum off or something like that?

I still think there's a small chance that the exhaust manifold or gasket are misaligned or the wrong size for the ports and this is restricting the exhaust. I know your people said it's lined up by the holes but the holes aren't a perfect fit, and I reckon there's always scope to get a gasket with port cut-outs that don't quite match the heads.