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Camshaft / distributor drive failure - advice


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Today, car going well, noisy tappets, engine revving at about 5000 (redline 6500 on new motor) suddenly noise like running over cans or metal hoops and all power goes & motor dies

 

much investigation later , no spark, replaced coil, pulled cover off dissy & its not rotating when motor cranking over, so pulled dissy shaft and it rotates when free

 

suggests the teeth on the diisy drive or the camshaft have sheared or some other failure on the cam

 

any ideas pllease

 

car towed to workshop, wont know more till next week

 

Graeme

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Graeme I would have thought it more likely it's the woodruff key on the shaft of the dizzy drive which can be a bit of a sod to get fitted right rather than the cam gear, although your noise description is pretty scary.

Just pull the complete drive gear out, you'll soon know

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Trying to think what failure could cause the noise you describe.

Must be the cam-to-drive gear teeth - can't see much else that

could fail. Must be something loose to get into that gear.

 

I don't think the top end of the drive gear connection to the dizzy

would cause such a noise.

 

So - not much encouragement - any gear failure is going to wreck

both dizzy drive gear (cheap s/h fix) and the cam (NOT a cheap fix).

 

Hoping for better news from the garage when they strip it down.

 

AlanR

 

(Agree with Chilliman that it's easy enough to pull out the dizzy

drive gear and see what's up)

Edited by TR 2100
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Alan, john

 

thanks

 

also no oil pressure when trying to crank it over so suspect that the oil drive shaft also not engaged

 

I guess any "bits" from the gear shredding would end up in the sump? - might be another spot to look next week

 

will get dizzy pulled out next week

 

was at the point of buying new cam anyway as the one I had ground for it appears to be out of round on the back of the cam and is causing very noisy tappets so can do ita ll at once

 

Have just ordered a fast road cam from Kent cams

 

will report back

 

Graeme

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Hi Graze,

if the drive shaft woodruff key shears then you lose oil pressure and all other things.

Big-end will start to clatter along with other things.

 

If it is only the key then you will need to drop the sump to check the BE shells.

 

Roger

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Roger

 

yes lets hope its not too serious at the bottom end

 

will advise when I know

 

thanks

 

Graze

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Is camshaft turning, a broken timing chain would make a hell of a noise ?

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Hi Graeme

 

Wondered if you have checked your timing chain and sprocket assembly , as the clattering noises you describe are quite pronounced?

 

If you haven't already done so, might be worth removing rocker cover to check for camshaft rotation. I wouldn't have thought a broken dizzy drive would make the noise you describe, but no way of telling without a strip down. If it's a newly built engine, pulley bolts could have been left loose?

 

Kevin

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Having suffered a catastrophic Dizzy failure at Castle Combe 2 years ago, I would also be suspecting the Mills Pin, between the Dizzy drive shaft and the dizzy......labelled part 35 in the current Moss catalogue on Page 18. This would allow the cam to drive the oil shaft but not the dizzy.

 

Whilst my dizzy literally disintegrated internally and broke holes in the casing, the failure of the Mills pin saved the engine. Two hours later and with massive thanks to Eric Mobley, we were back on the track. :D

 

Good luck lets hope its the simple stuff.

 

Iain

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Chris, Kevin

 

I hope (for my hip pocket) you are on the wrong track and when cranking the motor there were no unusual noises - at first we just thought the coil had died and we weren't getting spark but after swapping coil realized distributor not turning, hence current diagnosis. Guess we need to start pulling bits off to know more

 

Graze

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Had a similar problem: dropped oil pressure and when looked at bearings found shards of metel

Found the cam gear driving the dizzy/oil pump were grinding each other away with shards of metal not picked up by the oil filter

Only after grinding mains down to +10

Still investigating the cause and thinking of how to increase oil supply to the cam/dizzy gear drive

Michael

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Was this a new cam blank?

Reground cam with approx 2000 miles on it. The tappets were getting noisier and had proven impossible to set due, I think, to the back of the cam being out of round

 

Graze

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well the reason the dizzy wasnt turning is the timing chain isnt connected any longer - havent pulled it all down to identify the extent of damage but its new motor time again

 

Graeme

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well the reason the dizzy wasnt turning is the timing chain isnt connected any longer - havent pulled it all down to identify the extent of damage but its new motor time again

Speaking as someone who has already built two this year you have my full sympathy and understanding, but each time you build - you learn and build it better - now is the time to rip it apart and add the new cam you were looking for.

 

Sh*t happens Graeme and we learn & move on. - no-one hurt which is always a good thing.

 

J

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John

 

And it was a lovely day, I was with four good mates, we had a bunch of laughs and as you say I can fix the cam, the oil leaks and fit the overdrive I've got

 

Cheers

 

Graeme

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Well i now know what happened

 

one of the cam followers disintegrated, the pieces jammed into the cam lobe & froze it in position long enough to shear the two bolts holding the vernier cam gear on the camshaft, which dropped the cam gear and the chain to the bottom of the timing cover. Probably brought on by the strength of the valve springs which were supplied by a reputable source in the US - although they always seemed too stiff! This also explains why the tappets were so damn noisy as the cam follower was disintegrating on the cam meaning it was impossible to set the gaps.

 

the lobes on the cam were worn and the other cam followers showed signs of breaking down with pitting on the faces

 

then to the bottom of the engine, severe wear of the crankshaft, bearings, rear oil seal etc from oil starvation - not sure why yet - rocker oil feed?, faulty pump?, blocked galleries? but need to find out

 

all of this in 2800 miles

 

 

Graeme

post-12376-0-73651000-1464085075_thumb.jpgpost-12376-0-87752300-1464085094_thumb.jpgpost-12376-0-86448300-1464085144_thumb.jpgpost-12376-0-55364900-1464085157_thumb.jpgpost-12376-0-73817800-1464085024_thumb.jpgpost-12376-0-98057400-1464085040_thumb.jpgpost-12376-0-33063000-1464085109_thumb.jpgpost-12376-0-79187000-1464085128_thumb.jpgpost-12376-0-92610800-1464085010_thumb.jpg

Edited by Graze
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Graeme,

 

Very very nasty.

 

The cam follower failure - were the cam followers new, or used?

 

Was the cam new or used?

 

Either way, the wear on the crankshaft and bearings doesn't seem to be linked,

although if there has been oil starvation, then ALL the problems found could be

attributed to that. (except maybe cam lobes that are not lubricated by oil feed)

 

So, two problems,

What to do for a proper lasting repair? ('cos I'm sure you took care last time)

And who/what to blame for the various faults you have discovered.

 

AlanR

Edited by TR 2100
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Very sorry for that!

Understand the disappointment because I had to work

on a friends TR4 who lasted similar miles and engine was

about 6000 GBP. If the wrong things are combined thats the result.

 

Too often the self employed experts recommend stiff springs and they

do not know that spring pressure is also significantly increased from the

increased valve lift of the sportscam.

 

It might be helpfull to start engine life with poor spring load and a limiter

lets say at 3000 rpm to allow a nice running in.

 

Did you add ZDDP or was this sufficient in the oil?

Was the cam smeared with with some lubricant for running in?

 

I think the whole disaster was started from the metall scrapped from the cam & tappets

and was not fully absorbed by the oil filter.

 

Would refurbish all the included parts and cam bearings and oil pump and give it a

severe clean with opening the oil pipes in the block.

 

We just had cranks refurbished by Peter, price was fair and quickly done.

3x TR6 and one TR4, all nitrided. Picture in the front is the TR4 crank with case.

 

post-13092-0-65377200-1464095499_thumb.jpg

 

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What was the spring's seat pressure? Pressure over the nose? Tappet source / diameter ? Cam numbers?

 

Even what the fastest racing TR4s run for springs, will not wipe a cam flat if broken in correctly and used with the proper parts.

Edited by hoffman900
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Ouch !

+1

 

 

Peter W

 

PS

What is the debris in the lower segment of inlet ports?

What caused the marking on the rear oil seal - flywheel bolts too long?

Edited by BlueTR3A-5EKT
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