The V8 Owners Forum -

I'm writing hoping someone has a idea what may be wrong with my SD1 3.5RV8. fitted to my TR7.

Basically it has a knock which only appears when it is hot (after driving 5 or 6 miles), the bulk of the noise seems to be coming from the top of the engine, at one time removing one spark plug (cyl2 on rh side) seemed to quieten it down a bit but now it seems to be there all the time, it is worse at lower engine speeds and comes and goes (at idle it will go for a few seconds then come back etc) I have so far done the following:

New cam followers (cam looks perfect), removed heads all pistons / bores look perfect except one (cyl 2 on rh side)which had a non symetrial wear pattern and turned out to have a very slightly twisted con rod, repaired this (lightly honed bore replaced rod and piston)and also checked big ends which all look like new, valves springs etc are all fine with no play in the guides .

The only issue I have found is one rocker shaft was assembled wrongly shaft in wrong orientation and the shaft is now a bit marked, (cylinders 2 and 3)

The history of the engine is that it was re-built run for a while and then stood for some years, internally it is very clean and there is little wear.

The other thing I have noticed are, for some reason it has been fitted with low compression pistons.
The knocking started after I removed the overun valves in the carb butterflies because it would not idle evenly (it now idles very smoothly). In the past it has suffered from a similar noise which was solved by tightening the RH exhaust manifold (std sd1 part), this had no effect now though.

Appart from the noise it is fine, 20 psi oil pressure hot at a 600rpm idle and 45psi at 1500 rpm plus, no smoke or oil consumption pulls really well wih no misfire etc and never shows any signs of overheating

Suggestions I am going to try this weekend are to check the lifter preload
as the heads look to have been skimmed and valve seats re-cut but there are no shims and try another rocker shaft.

Anyone else any other ideas?

What sort of knocking sound is it? Thudding? Tinking? Pinging? (excuse my poor impression of engine sounds but you get the idea!)

Does the knocking disappear when yo refit the overrun valves? If it is then it is some problem directly related to either the carb or the induction mixture - eg. overly lean and causing pinking.

If the sound doesnt go away if they are refitted then it was likely a coinsidence.

However I am sure someone more experienced will know the answer.

It's a metalic knock, not heavy like big ends etc more like a loud tappet on a engine with solid lifters (I don't have any real experience with hydraulic lifters).

Is the frequency of the knock proportional to engine speeds?

Yes the knock is proportional to engine speed

Perhaps check that things like pushrods arent hitting the holes they pass through and that nothing else is touching when it is turned over by hand. Did you try refitting the overrun valves and see if the noise goes?

Kevin,

If you think it may be a lifter bleeding down then remove the rocker cover on the suspect side of the engine and at tickover just put your finger tip on the rockers and you should be able to feel which one is faulty, or put a large screwdriver on to the bolt heads of the bolts that secure the rocker shafts and use it as crude stethoscope.

You cannot check the preload when the lifters have oil in them, they have to be removed, drained, and replaced in the same lifter bore that they came from otherwise the cam will wear excessively.

kevin.!

kstrutt1 wrote:I'm writing hoping someone has a idea what may be wrong with my SD1 3.5RV8. fitted to my TR7.

Basically it has a knock which only appears when it is hot (after driving 5 or 6 miles), the bulk of the noise seems to be coming from the top of the engine, at one time removing one spark plug (cyl2 on rh side) seemed to quieten it down a bit but now it seems to be there all the time, it is worse at lower engine speeds and comes and goes (at idle it will go for a few seconds then come back etc) I have so far done the following:

New cam followers (cam looks perfect), removed heads all pistons / bores look perfect except one (cyl 2 on rh side)which had a non symetrial wear pattern and turned out to have a very slightly twisted con rod, repaired this (lightly honed bore replaced rod and piston)and also checked big ends which all look like new, valves springs etc are all fine with no play in the guides .

The only issue I have found is one rocker shaft was assembled wrongly shaft in wrong orientation and the shaft is now a bit marked, (cylinders 2 and 3)

The history of the engine is that it was re-built run for a while and then stood for some years, internally it is very clean and there is little wear.

The other thing I have noticed are, for some reason it has been fitted with low compression pistons.
The knocking started after I removed the overun valves in the carb butterflies because it would not idle evenly (it now idles very smoothly). In the past it has suffered from a similar noise which was solved by tightening the RH exhaust manifold (std sd1 part), this had no effect now though.

Appart from the noise it is fine, 20 psi oil pressure hot at a 600rpm idle and 45psi at 1500 rpm plus, no smoke or oil consumption pulls really well wih no misfire etc and never shows any signs of overheating

Suggestions I am going to try this weekend are to check the lifter preload
as the heads look to have been skimmed and valve seats re-cut but there are no shims and try another rocker shaft.

Anyone else any other ideas?

Sounds like my problem, I have the tapping noise that only happens when the engine is hot and idling. Engines had a full rebuild and is on it's second set of tappets and its tapping worse than ever. Hope you find a cure

Hi
You said you have replaced the tappets but not the cam, the result of doing this will be very accelerated wear of the cam lobes (did it myself on on my first rover rebuild because, I thought I had a dud lifter, result I killed the cam in about 100 miles). the cam lobe and lifter have to be run to in together to build a hard surface layer, bringing new metal to this strips the run in layer of the old surface and forms a wearing layer on the new, result magically dissapearing cam lobes.
Second you don't say what oil you are using, but I'll bet it isn't 20/50 use anything but 20//50 and the lifters blead down when the engine gets hot resulting ticking tappets. There are a good few threads on the subject on here, worth a read.
Mike

[quote="kiwicar"]Hi
You said you have replaced the tappets but not the cam, the result of doing this will be very accelerated wear of the cam lobes (did it myself on on my first rover rebuild because, I thought I had a dud lifter, result I killed the cam in about 100 miles). the cam lobe and lifter have to be run to in together to build a hard surface layer, bringing new metal to this strips the run in layer of the old surface and forms a wearing layer on the new, result magically dissapearing cam lobes.
Second you don't say what oil you are using, but I'll bet it isn't 20/50 use anything but 20//50 and the lifters blead down when the engine gets hot resulting ticking tappets. There are a good few threads on the subject on here, worth a read.
Mike[/quote

My cam was about 3 months old and has done about 1000 miles .when i changed the lifters.The tapping was just the same after doing the lifter change. Changing from 10w-40 to 20w-50 halfords classic oil hasn't helped in my case either.

I am using 20/50, I also tried 15/40 which had no effect.

The followers were fitted around 1000 miles ago and I checked the cam lobes last week and they look perfect, just a slight wear pattern on one side.

I have also checked the prelods which were miles out, and changed the rocker shafts but fixing these has had no effect. (except it runs even smoother at idle)


Listening with a pipe it it definitely sounds like top end valve gear noise, so I guess it must be a faulty tappet, perhaps dirt or something stoping the ball seating completely and allowing them to bleed down. As well as the idea of listening with a rod I thought about sliping a feeler gauge between the rocker and valve with the engine running to see if I can change the noise, any thoughts on this?

Looking at Smoker's thread it does seem a very similar story.

I couldn't make any effect with feler gauges so I removed the inlet manifold and took a close look at the cam, none of the followers look to bad but one of the lobes is worn worse than the rest (it's more rounded over and has sharp edges) So I guess I am going to need a new cam.

The good news is it looks like it will come out with the engine in the car (TR7), so is'nt too big a job. and not too expensive (around £100 in parts)

I'm planning to fit a standard cam as I'm not realy interested in ultimate performance, the engine was originally a 9.35 CR but at some time has been fitted with a 8.25 pistons (I believe to compensate for skimming the heads). I plan to use a standard 9.35 cam can anyone see any reason why I can't use this with the 8.25 pistons?
Also a couple of sites list a metric 9.35 cam, is this just the threads for the cam wheel that are metric?

I've just been looking throught the internet and another option appears to be a 3.9 camshaft, anyone any idea what the differences are?

kevin

Kevin

The 3.9 cam does give a bit more power and can be got from V8 Tuner for a good price, do fit new lifters and break in the cam for a total of 20 minutes using the cam lube and not letting the engine idle or you will be back to where you started.

Try and set the preload at 30-60 thou. only use shims if absolutely necessary.

Also do carefull check the cups in the rockers to make sure there is not excessive wear.

Use tin gaskets to maintain compression and lifter preload, composite valley gaskets are better in my opinion.

kevin J

Thanks

It looks like 3.9 cam then.

I came to the same conclusion ref gaskets, it has tin heads and composite manifold.

Looking closely at the parts I don't think the knock was the worn lobe, all of the followers except one (including the one with a worn lobe) have a circular wear pattern, one though has a star shaped pattern of pits layed over the circular pattern, I suspect this is the cause of the noise as the follower has failed and is loosing contact with the cam. I Also suspect the excessive pre load may have lead to the failures

Anyway the bores in the block and rockers looks very good so I will fit new cam and followers, and set the preload, hopefully this will finaly fix it.


Kevin