Misfire - Cam? Help?

[swallet]

Having just splashed the cash on getting my new headlights fitted my engine has started to throw a hissy fit!

Has felt a bit down on power this week, nothing major but not the usual innards being rearranged feeling when booting it.
Also idle sounds rough/misfire like. Something not right.

First step, checked my manifold temperatures with my new IR thermometer gun (excellent toy BTW!). All manifolds quickly up to 300+C. Except cylinder 3 stayed at about 100C, cylinder 1 next door also a little below the others at around 250C . Good spark etc so not ignition.

Pulled plugs, as per the picture all look OK except cylinder 3 black and fouled as expected, so clearly bad misfire on this one:


Now compression tests:

(all dry and cold engine - I know should be hot but try putting the compression tester on with hot manifolds!)

.....BULKHEAD.......

(8) 170 ++ (7) 169
(6) 152 ++ (5) 168
(4) 170 ++ (3) 80
(2) 160 ++ (1) 75

......RADIATOR.......

From my basic knowledge two adjacent cylinders down would suggest head gasket blowing between cylinders (3) and (1). The again, I have not been loosing any oil or water and can't smell hydrocarbons in the coolant. Also why would only cylinder 3's plug be fouled?

Also tested the problem cylinders wet:

(1) 85 (3) 95. So doesn't look like worn piston rings as cause for these two. Interestingly also tested no (6) wet and pressures up to 172 from 152 so wonder if this piston ring may be worn.


Questions for the assembled gurus:

1/ Given the look of the spark plug is this really a head gasket failure or is this more indicative of a worn cam causing problems with valve opening on these two cylinders?

2/ What about cylinder (6)? Pressure was marginally down and improved with oil. Do you think bad enough to suggest piston ring problem?


Debating my next step... If I'm looking at a worn cam and another piston on the way out because of ring wear then wondering whether I'm better taking her off the road. Saving my pennies and getting the whole thing rebuilt. If it's just the cam/ head gasket then I'll just pay to get the necessary done.

Edited by swallet on Saturday 15th March 20:41

[jojackson4]

Simon look at leek down test on the gooogal or you tube
I don't think you can get a correct reading doing a comp test with hidrolic lifters they leek oil and don't give you the right reading
Am now getting ready to be down in flames

[QBee]

Question - if the gasket had gone between those two cylinders, exactly at the slimmest part, would you necessarily find water in the oil?

[jojackson4]

QBee said:

Question - if the gasket had gone between those two cylinders, exactly at the slimmest part, would you necessarily find water in the oil?

No

[QBee]

jojackson4 said:

Simon look at leek down test on the gooogal or you tube
I don't think you can get a correct reading doing a comp test with hidrolic lifters they leek oil and don't give you the right reading
Am now getting ready to be down in flames

Not shooting you down, but I had a compression test done on my 400 when I was considering supercharging it. My readings were similar to the six good ones.....but all 8 were good on mine.
A leak down test will check the piston rings IIRC, but I get this wrong on occasions. If you do one, a good engine will show around 1-4% leakage. Mine did.

[swallet]

Ok so I've just watched some youtube of leak down tests. This should tell me whether I have poor compression because of

Leak via the valves (i.e bad cam)
leak into coolant (head gasket)
leak into crank (worn rings)

Interesting! Not kit that I have though, so one way or another its heading into a garage for some diagnostics.

[swallet]

Just an update.

I have had the car looked over by Angelo at Ford-Tec in Huddersfield (does a lot of work for TVRCC members)

Leak down tests were pretty dire ! Over 50% on cylinders 1 and 3. And also some 20% on 5 and 7. Some air coming out of dipstick hole and exhaust manifold so clearly not just head gasket or cam.

Not sure what would give a whole cylinder bank figures like this but it seems pretty severe. Frankly I'm surprised it's still drivable. Things would appear to be getting worse as there is now very definitely a tappy noise at higher revs from this side.


Long story short we both agreed the way forward would be a full strip down and rebuild.

With this in mind I have taken a deep breath, sold my only child into bondage and made contact with TVR Power. Later this week the old girl will make the pilgrimage down to Coventry for a full rebuild and then "Taraka" tune. The promised boost in power and the three year warranty really sealed the deal.

I'll keep you updated.. Cost aside I am actually quite excited by the prospect of having essentially a new engine in the old girl and a pretty potent one at that. Every cloud...

[jojackson4]

Good luck Simon
I feel your pain

[swallet]

Cheers Pete,

I've been like a bear with a sore head around the house most of the week trying to swallow the cost implications, but reasoned that I have no option but to go for a rebuild as the car is worthless to me (or anyone else) with a shot engine.

I think the writing was already on the wall when I borrowed your Roverguage the other month - that persistent high Lambda on the passenger bank was clearly not fuelling but a mechanical misfire.

TVR Power reckon on a 6 week turn around so hopefully back in time for some running in blasts into the Dales!

The car has always felt quick - God know what it will feel like with a proper engine in it!!

[Alun450]

Dom built mine and after 5000 miles its sweet as a nut. Here's what it looks like all clean and new looking. Taken a month or so after I picked it up. Its loads of money but boy it feels and runs good.
Onwards and upwards. Goodluck

[jojackson4]

It looks like mine has been built by a baboon and I don't think mine would have done
Much better on the leak down test
From what I have learnt this week I have had a good chance my valves have never shut
But by the end of the week every thing should be good

[ChimpOnGas]

Alun450 said:

Dom built mine and after 5000 miles its sweet as a nut. Here's what it looks like all clean and new looking. Taken a month or so after I picked it up. Its loads of money but boy it feels and runs good.
Onwards and upwards. Goodluck

For the first time I dropped in at TVR Power today, or what ever they've been forced to call themselves these days.

Wow what a machine shop Dom has!

There are some very good Rover V8 engine builders out there, and there are good machine shops that help them achieve great results.

But very very seldom do you find both in the same building, with one guy who has the talent, environment & the very expensive equipment to take total responsibility for the whole process of building an engine from start to finish.

Unusual to say the least, but I can see why he has the confidence to offer the guarantees he does.

It's a very very impressive operation indeed, zero outsourcing is the holly grail of engine building in my book

Fortunately Dom seems like a very friendly bloke too

[swallet]

Thanks for all the positive feedback on TVR Power guys - Really helping me justify my man math's to Mrs Swallet!

Booked the trailer tonight so there's no going back!

[swallet]

Resurrecting this thread to update it.

Just spoken to Dom at TVR Power. Turns out the failure was a blown head gasket. I am imaging between the two poorly compressing cylinders. SO turned out to be a pretty straightforward job for Dom and the boys.

Debate now is either to put it back together as a standard 500 rebuild at around £3500 or continue with the Taraka build at £4500?

Could do with saving the £1000 in all honesty. Then again the lure of more power??

Decisions!

[KateV8]

I've no experience of the Taraka engine-build but lots of experience of the 'upgrade now or later' scenario usually to my cost. I'd say go for it, you will want the power eventually and it will cost much more to revisit at a later date.

[jojackson4]

You have saved a grand in vpower go for it
It's all in bits you don't whant to pay again to get it to this stage

God it's good spending other peoples ££££!!!
What ever you go for it's going to be better than what it was

Just don't show up at my house with more than 300 bhp

[blitzracing]

Ask your self one simple question- how often and how long did you ever hold it flat out? If its was hardly ever, or not long then why spend the extra for just a few seconds of "faster flat out" on the public road? A cars dynamics can be improved in many whys apart from pure BHP. (There speaks a man with a Ginetta chassis made of pipe cleaners where a couple hundred bhp is quite enough in a 800kg car).

[wuckfitracing]

blitzracing said:

Ask your self one simple question- how often and how long did you ever hold it flat out? If its was hardly ever, or not long then why spend the extra for just a few seconds of "faster flat out" on the public road? A cars dynamics can be improved in many whys apart from pure BHP. (There speaks a man with a Ginetta chassis made of pipe cleaners where a couple hundred bhp is quite enough in a 800kg car).

I agree. Extra power is good but not always the best way to be any quicker.

[EGB]

My compression according to Gunson. All in the middle green OK area.

Radiator

173.3. 166.8 ...............a bit down on no 2 cylinder.
170.4. 168.2
172.8. 169.7
170.4. 171.1 Average: 170.3

Bulkhead

After 56,000 miles, I'm happy. I don't know how 170.3 PSI equates to a 10.1 compression ratio for a 500.

At steady 70 on motorway with some roudabouts and traffic light hold ups, my exhaust manifold decat 500 did 23.6 miles/gallon on V Power. Vitally Important to measure at the same V Power fuel pump at tank fill up and after a measured road trip. All done on same day.
An interim fill up at a tesco fuel pump gave me nearly 50 mpg !!! The tesco pump under filled to stop setting.

Edited by EGB on Thursday 1st May 22:52

[swallet]

Those look like good figures EGB.

Saving a £1000 would be great. Could get a new hood or update shocks and get full alignment both probably more important than head work and port polishing etc.
Then again I'm viewing the car as a long term keeper and it is more economical to get it done now and of course I'm a man and more BHP = more bragging rights.