The Triumph Dolomite Club - Discussion Forum

Nice work. Shame about the bottom end problem but at least that's sorted now.

You're using a different sump than standard...just wondering, 5000rpm, obviously accelerating fairly hard, what looks like a loss of oil supply....

Where is the pick up in that sump and was it well baffled? Also, did you check the clearance between the pickup and the bottom of the sump?

Just thinking out loud...you don't want it happening again. Or did you find the cause?

Thanks for the comments.

I have had the same feedback from 4 different sources now referring to loss of oil supply. SBD quoted this straight away and indicated you get it on conrod number 1 1st which is where I had my failure. (By the way I have to say the help I got from SBD was exceptional, they were more than happy to discuss problems and clearly have a vast experience to draw upon - very professional) So my initial approach has been to ensure the oil system is functioning correctly by doing the following

1. New oil pump
2. New oil filter
3. Clean out sump, block and head - sump was full of shades of bearing!
4. Clean out pick up pipe, again full of shades of bearing. Don't belive it actually became blocked though.
5. Fit oil pressure gauge
6. Fit oil temp gauge with sensor in sump plug
7. Check clearance of pick up pipe to sump bottom. It had about 12mm which I have increase to 20mm. Also checked for any pin hole leaks in the pick up pipe as it was modified to suit the front bowl sump - it's sound, no holes found.
8. Refit crank and conrods, new ARP bolts (these did not fail), torque bolts as per spec with calibrated torque wrench.

With all this done the oil system appears to be functioning fine, 5 bar cold, 4 bar hot 2-3 bar hot idle. Operating temperature seems to be around 50 degree C.
Also water temperature seems fine with the needle on the sprint temp gauge reading between 1/2 - 3/4 without the need for the kenlowe to kick in. Opening temp of thermostat is 92 degree C for the redtop whilst the Sprint opens at 82 degree C. I have read that the redtop happily sits at 100 degree water temp so my gauge reading between 1/2 - 3/4 seems fine.

With the above in mind I am still concious that a root cause hasn't been established. So your note has prompted me to capture possible causes below. First here are the symptoms as I recall them.

1. Bang heard at highish rpm (between 4-5000 rpm) but not under significant load. Suspect this was the initial bearing failure when it first spun.
2. 30 seconds later at around 3000 rpm knock heard from block
3. When engine next went to idle, oil light switch came on and would only go out above around 1500 rpm.
4. Engine shut down.
5. Inspection of conrod bearing clearly indicates loss of oil wedge to spin it. But only on number 1.

Possible causes

1. Oil pump failure - inspected this and it seemed fine. Replaced with new.
2. Oil filter blocked - possibility but I will never know, i clearly had oil pressure when the initial failure occurred as the oil light only came on afterwards
3. Oil relief valve stuck open - unlikely as I would have seen low oil pressure before the bang.
4. Incorrect torque setting of ARP conrod bolts - unlikely, I was maticulous on the original engine rebuild and when I dismantled the bottom end I used a torque wrench to estimate the breaking torque of the bolts and they were all the same.
5. Loss of oil wedge on bearing - this obviously happened but why?

So my thoughts now are moving away from the oil system being the root cause.
Other area of interest - ignition timing.

I am running MEGAJOLT mappable ignition with a conservative initial map.

Following the recent rebuild I believe I am getting pinking at rpm's above 4500rpm. It's difficult to determine with the induction noise present as well but there is something there that doesn't seem right. I also haven't been above 4500 rpm much. Power and torque from idle to 4500 is very impressive though.

The engine itself has high compression pistons with deeper valve cut outs, 276 degree sports cams. So I have done a compression test and got 230 psi on each cylinder. Obviously high, so I compared with my track BMW M635csi which runs at 220 psi so given gauge inaccuracies it's pretty close to the BMW engine and not wildly excessive.

I don't know much about pinking but given it will stress the conrod and bearing it's got to be considered as a possible cause of oil wedge depletion and hence the failure.

I can't think of any other root cause that I haven't already taken action on.

So next thing to do is to feed the motor with some super dooper high octane juice and retard the iginition above 4500 rpm to see if I can eradicate it and then progressively increase iginition advance to get the power back. I am tempted to start off at a low 10-15 degree setting above 4500 to be on the safe side. Timing at idle has been confirmed at 10 degree as per the MEGAJOLT requirement.

Thoughts welcomed on all the above.

Thanks

Ian

Another thing.

My exhaust manifold is a homemade unequal length jobby so I would expect to see alot of back pressure at high loads and high rpms. Could this be causing poor combustion and pinking?

Ian

The manifold will not be doing you any favours as far as power is involved, especially top end power but as for causing detonation (pinking), I wouldn't have thought so. Its probably down to compression ratio and not so good petrol. I would also be reluctant to blame the engine failure on the pinking, yes, pinking will put an additional load onto the crank but it's far more likely to burn a hole in a piston than cause the problem you had, and neither is likely in such a short timeframe. Regarding the failure and reading your symptoms above, I would tentatively rule out both oil pump and pressure relief valve failure as either of those would put the oil light on immediately. I am reminded as others have been of your sump quandary and its solutions, is it possible that your home made dipstick is giving you a false (lower) level? I realize its probably a bit late now but I have a spare Carlton oil pickup, dipstick and tube available, all for front well sump apps if you're interested. Steve

_________________
'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.

Thanks for the comments. Engine was filled with 5.5 litres of oil when rebuilt so I could record the level on the modified dip stick. Going for the original set up would be a good idea though! I have a sump gasket oil leak as well so I might have an opportunity to swap things out soon, i'll pm you re beer tokens for them...

Ta

Ian

I'm tending to think that it was foreign object damage causing oil starvation to number 1 conrod now as this was the only bearing damaged in the engine. Another possible root cause that I will never be able to prove

Ian

I'm tending to think that it was foreign object damage causing oil starvation to number 1 conrod now and with the oil light coming on AFTER the bang and knocking the fault would appear to be specific to this bigend and not related to system pressure. Another possible root cause that I will never be able to prove

Ian

Hello Ian.

What make of bearings do you use? The bearings had no oil OR could not withstand the pressure. When having a higher compressio ratio the pressure on the bearings is much more and maybe by coincidence no1 was first. There's a lot of quality difference in bearings./oil.

Can it be that the first big bang was piston/head contact?

Jeroen

_________________
Classic Kabelboom Company. For all your wiring needs. http://www.classickabelboomcompany.com

I would be very surprised if ignition or compression caused that failure.
Those bearings look like they ran out of oil.

Were you cornering hard at the time?

I've had to rebuild the bottom end on 4 of my own personal engines on different cars, 3 of the four were directly down to oil surge.

I hate sumps.

They were quality bearings - UCL I belive supplied by SBDevelopments.

Piston to head contact - could have been but there was no damage to piston or head when I took it apart.

Ian

No not cornering hard at the time. With the oil light coming on AFTER the bang and knocking I don't think I lost system pressure, just possibily lost oil flow to number 1 bigend.

Ian

Of course it is POSSIBLE that the rod was a little bit out of tolerance in the first place. Another theory you'll never be able to prove or disprove! Or did you check them for ovality while it was stripped and i'm trying to teach my grandmaw to suck eggs? Steve

_________________
'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.

They were checked originally by me and then again by the engine machinist and found to be ok so just polished up. I checked them again when they came back after the failure, good job I did as they went straight to second undersize! even though I instructed them to go to 1st undersize. They even recorded on the invoice that they had gone to 1st undersize. Precision Engineers my arse. I wont be going back there.
Ian

Quick update.

Now done about 200 miles on the rebuilt motor.

Oil system looks good, just less than 4 bar at revs when very warm, oil temp gauge only seems to record up to 60 degree C but the sensor is in the sump which may account for this. At least it gives me a reference point. Water temp bob on at between 1/2 to 3/4's without the need for the kenlowe to kick in. Didn't find the actual root cause of the failure, the evidence looks lost in the failure itself.

I also filled it up with Sheel V max and some NOS octane booster. Drives much better as you might expect, don't think I am getting pinking at high rpm, just general mechanical noise! I do pretty much have solid mounts to the chassis so I should expect some transfer to the body!

Power is great upto 5000 rpm and it feels like the motor is loosening up a bit. No more oil vapour from the head breather so it's not breathing as much as it was.

Plan now is to get about 1000 miles on it and then get the exhaust manifold sorted so I can start to release the power higher up the rpm range. Then gradually lift rpm to 7000 and beyond...

Still, a very impressive engine, pulls well from 1000 rpm, get's into it's stride after about 2,700 and then pulls harder, hopefully it will pull hard to the redline eventually. Gearbox seems well suited to it, drops nicely into the power band when changing up. Completely different to a normal sprint engine.

I'll probably do a final write up of the conversion with costs and things to do in the next few weeks with some pics to suit.

Cheers for now

Ian

Well done mate, sounds like its all coming together nicely. I noticed when stripping my spare Carlton engine for that pickup that theres no baffle at all in the standard sump and that the pickup is right at the front, which would indicate the possibility of oil surge on hard starts, however mine has had an oil pressure guage from day one, has done more than a few very hard starts (I dont mess about on the dragstrip when the red mist descends!) and so far not so much as a flicker so I would say you can rest easy on that score. I think the manifold is surely what is restricting performance over 5k rpm, my car, with its cast manifold and partsbin (part Skoda!) rather small bore exhaust system runs out of puff quite abruptly at 4500. Swapping out the ecu for an uprated Cav one made almost zero difference to it! I'm now on the hunt for a Sprint sports system but will probably delete the rear box in favour of a bit of drainpipe! I may have to bite the bullet and buy just the front box and cross axle pipe from the folk in Lincolnshire, Dammit! Steve

_________________
'73 2 door Toledo with Vauxhall Carlton 2.0 8v engine (The Carledo)
'78 Sprint Auto with Vauxhall Omega 2.2 16v engine (The Dolomega)
'72 Triumph 1500FWD in Slate Grey, Now with RWD and Carledo powertrain!

Maverick Triumph, Servicing, Repairs, Electrical, Recomissioning, MOT prep, Trackerjack brake fitting service.
Apprentice served Triumph Specialist for 50 years. PM for more info or quotes.