One thing im worried about with this problem is that replacing the cams & followers will only sort resulting damage caused by the real problem which still needs to be identified - the cause of the lack of lubrication.
I think im going to have a dig around on a couple of toyota forums to see if this has cropped up elsewhere, after all this is a pretty common engine, and as far as i know it has not been modified by lotus apart from the ECU.
Does the stage 2 Piper cam (285) not suffer from a lump tickover ? has anyone fitted them yet ?
Phil, apparently Dan from Jude Performance in Newcastle has fitted the Piper cams to a customers Exige and has reported very good results - a big increase in mid range torque. Not too far to go from Cumbria…
We’re all scratching our heads at the moment. I forgot to bring my cam cover into work, I was going to blow some degreasant through the spray bar and see what the flow distribution looked like.
One thought is that the cams which are failing have not been fully case hardened? Otherwise its not so easy to say why Phils has gone on cyl 1 and mine on 3 and 4?
Mines booked in the dealers week friday but I dont expect any miracles (but DVA is just 2 miles form my dealer…)
Hi Chris, yep its annoying for sure. Depending what the Lotus dealers say I may may getting those Pipers we were discussing at the last meet after all.
Sean, you are very correct regarding the effect of oil spray jet modifications, I will have to put some thougth into it. I dont mean to sound arrogant but I’m actually an analysis engineer dealing in engine lubrication for the company who used to be called Cosworth Engineering (we’re called Mahle Powertrain now and and we still own the intellectual rights to the YB engine design). It just such a bizarre coincidence that you should use that example! Cheers guys
BC
No problem Bob, I like hearing from people who are really in the know!!
On your case hardening comment, I have had problems in the past with case hardened parts, in my experiance it seems that if you actually wear through the case hardening the metal underneath is sofetre than it originally was before the case hardening process and its wear rate is greatly accelerated. Following a bit of research and I’m sure you know more about this than I ever will, I found that there seems to be quite a few different processes for case hardening and that some base metals take to the process better than others.
I have seen YB’s where the follower has been worn right through and the cam was actually pushing on the top of the valve!!! Obviouly the engine did not sound to sweet at that stage.
Surely another thought for you S2 boys must be oil contamination. All of those little bits of cam and follower have to go somewhere!!! ALthough I’m sure the filter is catching 99% of them.
Cheers Sean, I’m not really that well informed about cam surface treatments. I do remember we had a few issues a few years ago when we did the Focus ST170. We tried three different methods before we found something durable.
Regarding all the sh1te/grinding paste which must be in the oil now … well I hope the filter has caught it all but it will have had to go through the oil pump first to get there… and if the filter blocks then the relief valve may open and blow its contents straight into the gallery… Time for a good flush out asap. The oil itself looks okay though. Finger crossed.
I dont see why in theory the VVTL system would interupt the oil flow to the spray bar. I can see that the VVTL solonoid is situated at the same end as the spray feed though. I cant find any decent schematics in the engine manual, just scary procedures on how to strip the whole thing to pieces…
The wierd thing is that many OEMs are delecting cam spray jets and finding they dont have a problem. Audis used to have sprays mounted in the roller rocker ball joints but they’ve taken them out now and not found any issues. I know BMW mount a spray bar across the top of the cam caps but they all but block up after the engines run in…
It points more towards a case hardening issue than a lubrication now?
I dont see why in theory the VVTL system would interupt the oil flow to the spray bar. I can see that the VVTL solonoid is situated at the same end as the spray feed though. I cant find any decent schematics in the engine manual, just scary procedures on how to strip the whole thing to pieces…
IIRC the VVTL solenoid closes the feed to the spray bar to give oil pressure for pushing in the 2nd cam pins. the VVTL-i mech was described on a SAE paper, again IIRC.
I dont see why in theory the VVTL system would interupt the oil flow to the spray bar. I can see that the VVTL solonoid is situated at the same end as the spray feed though. I cant find any decent schematics in the engine manual, just scary procedures on how to strip the whole thing to pieces…
IIRC the VVTL solenoid closes the feed to the spray bar to give oil pressure for pushing in the 2nd cam pins. the VVTL-i mech was described on a SAE paper, again IIRC.
Yeah, I’m reading the paper now (2000-01-0671?). It mentions about how the oil is fed into the rocker shaft at all times to lubricate it but then at high pressure to lock the high speed rockers.
I can see that the spray bar flow comes out of the solonoid so I’m not saying your wrong.
It also mentions that the low speed rocker is a roller type which I hadn’t noticed (same as an Audi whcih lives fine without a spray) but it also says
“Special care was taken to control the initial wear of the high speed cam” - What??? Control it to a high level??
It then says that the slipper type follower (high speed) “NEEDS to be lubricated”…
Quick thought on this. I have heard that the Yota engine can suffer from a temporary drop in oil pressure during hard cornering on left (or is it right??) bends which I believe has caused major failures on a few engines. Is it possible that this wear on the cams is another manifestation of the same oil pressure problem? Or is the wear too localised for that?
Nightmare scenario would be that the oil flow to my crank has been interupted whilst cornering on track (maybe a previous owner) and that the crank worn–> reducing oil pressure–> reduced spray flow–> worn cam?
That fact that the engine still runs sweetly at low rpm and no MIL lights have come on to say the VVT is unable to mover etc suggests that oil pressure is still good…fingers crossed.
Yeah Bob, I would have thought that if the big ends were worn to the point that there was a significnat drop in pressure to the head, you would hear that tell tale rumbling from the bottom end. Fingers crossed!!!
Have you had chance to measure the wear on the cam follower?
I haven’t seen the followers yet, I’ve got to wait for Lotus to have a look at it. If they say get stuffed then I’ll be getting the spanners out.
If so I’m hoping that the lost motion assembly can be lifted out of the high speed follower and replaced (doubtful) as you have to remove the chain case and slide the rocker shafts out of the side of the head (which will probably be a clam off job - although the clam is coming off when it goes to the menders…)
The jets are firing horizontally so they do curve down, there wasn’t any noticeable difference in flow rate between the jets though. The only difference was inlet 3 and 4 were skewed towards 1 and 2
This is funny I should come across this thread.
I just removed an engine here in the states from one of our few 240R Cup cars that we have been blessed with.
The car had covered only 680 miles before the owner missed a down shift and spun the motor to 10101 rpm, catastrophic failure of #4 cylinder valve train followed.
I did notice during disassembly that one of the high cam lobes (#1 intake) was worn just as the pics in this thread.
The car was fitted with an Accusump oil pressure accumulator system so a drop in oil pressure would probably not be the case of the failure. The case hardening angle seems plausible.
Hi Bob,
Have just noticed that my engine no. is 2ZZ0143xxx so I will be removing my cam cover this weekend to carry out an examination. My car has done 5000 miles now. I will post my findings at the weekend.
![http://i90.photobucket.com/albums/k252/Bob_Corbishley/crash/camsprays.jpg[/image]](http://i90.photobucket.com/albums/k252/Bob_Corbishley/crash/camsprays.jpg%5B/image%5D){kind=link}