The Triumph Dolomite Club - Discussion Forum

Just built up a "newish" TR7 engine.
I bought a barely used block/+40pistons and crank, all balanced etc. But been left, correctly wrapped/protected for some years.
Honed teh bores and fitted new rings. New bearings throughout, though not needed but as it was a fresh build.....
The head/jackshaft etc etc all supplied from my old, very tired engine. The piston ring lands were VERY worn!

New chain, one guide etc, I reused anything that was still in good condition, in fear of poor new parts.

Back together, and spun up on starter to get fuel up and oil pressure too. Plugs in, started first time. All good.
However, it became apparent that if I flick the accelerator, and let the revs drop back to idle, at about 1500rpm a rattle starts. Like a marble on a tin, coming from the centre 2 pistons sort of area. This stops as idle is reached.
I have checked the timing chain, no slack at all so the tensioner is working correctly? Valve clearances all around 8-10thou, so correct (according to some, a bit tight on exhausts according to the book). Plugs out and spin the engine, no noise.

This wasn't happening with the old engine. But teh distributor seems a bit short on advance, though mechanical is working. I have set it to 10 degrees at idle, vac disconnected. Getting an additional 6? degrees of crank advance up to 2000ish rpm. But teh dizzy plate seems to have a fair amount of slop when I took the rotor arm off, though my spare is the same. Seems the pin that goes though the baseplate can move in an oval hole? But to get such pinking seems wrong....

Any bright ideas? I have a feeling I need to investigate the timing chain tensioner....

To check if it's a piston noise under load, have you tried removing a plug lead one at time whilst it is making the noise Clive? It might give you an idea as to what cylinder is affected.

Tony.

dollyman wrote: ↑Mon Jan 06, 2020 6:45 pm To check if it's a piston noise under load, have you tried removing a plug lead one at time whilst it is making the noise Clive? It might give you an idea as to what cylinder is affected.

Tony.

Tony, it doesn't make the noise under load at all. ONLY as revs are dropping, and only then from about 1500rpm down to idle. Makes me think/agree that timing chain is involved...

cliftyhanger wrote: ↑Mon Jan 06, 2020 7:11 pm

dollyman wrote: ↑Mon Jan 06, 2020 6:45 pm To check if it's a piston noise under load, have you tried removing a plug lead one at time whilst it is making the noise Clive? It might give you an idea as to what cylinder is affected.

Tony.

Tony, it doesn't make the noise under load at all. ONLY as revs are dropping, and only then from about 1500rpm down to idle. Makes me think/agree that timing chain is involved...

Yes that does make sense, I had this on the Sprint, noise at low revs but disappeared as I reved it. It turned out I had incorrectly fitted the chain. It was also hard to find the position of the noise, I thought it was coming from the water pump area.

Bit of a strange one Sounds like the chain could be loose but it is'nt. Keep us posted when you find the problem Clive.

Tony.

dollyman wrote: ↑Mon Jan 06, 2020 10:39 pm Bit of a strange one Sounds like the chain could be loose but it is'nt. Keep us posted when you find the problem Clive.

Tony.

Hopefully it will be sorted tomorrow. A friend is popping over to lend a hand (along with his rattle gun and big socket set for the crank pulley!)
Otherwise there may be a bonfire

Hopefully it will be sorted tomorrow. A friend is popping over to lend a hand (along with his rattle gun and big socket set for the crank pulley!)
Otherwise there may be a bonfire
[/quote]

Hope not...

Today has not been good.
Essentially no progress.
The water pump and indeed dizzy seem to have excessive backlash, but the jackshaft has about 10thou of endfloat, so fine. No wear or ovaling of the jackshaft bore.Gears all in line, so no idea what is going on there. Ran engine with water pump removed, no change.

Ran engine without the chain cover fitted, so could see the tensioner was working correctly.

Noise definately appears to be from middle of the engine. But noises do travel.

Now had enough. Need to decide what to do. I could get the old block bored to take the oversize pistons, and swap the internals back into that. Tomorrow I will pull the cam, check there is nothing under the buckets or whatever. The ONLY thing I did to the head was to reshim the exhaust valves to close them up. So confident the head is not the issue, but I will check..

Clive, i would try removing one lead at a time to see if it makes a difference to the noise. Easy to do with insulated pliers.

Tony.

dollyman wrote: ↑Tue Jan 07, 2020 7:03 pm Clive, i would try removing one lead at a time to see if it makes a difference to the noise. Easy to do with insulated pliers.

Tony.

I'll give it a try tomorrow.

After I have double checked the exhaust isn't banging.
And before removing the cam.

Cheers
Clive

Are you sure that the chain guides are in the correct position, it is easy to have them slightly out of line. This will create a noise even if the tensioner seems to be working. If they aren't then the tensioner will have to be reset again.

Hello Clive,

Does the cooling fan has a viscous coupling?
It can also make a rattling noise when defect.

Regards,
Luke.

Hi Clive, Just as a try-out can you try resetting the exhaust clearances to 16 to 18 thou as per the manual. If the head has been skimmed the valves may be closer to the top of the pistons. If you need any shims let me know and I'll see what I can find.
Why the problem just occurs on running down I don't know.
As another try is the camshaft chain wheel flat on the camshaft ?
Tony.

Thanks for the replies.
I ran the car this morning after I had moved teh downpipe a smidge away from the body, and it didn't seem to have the noise until it had been running a short time and armed (no water in the engine, so it heats up quick!) I actually thought I had got lucky, but no.

I then ran teh car without plug leads 2 and 3 attached. No different.

Cam clearances are all fine. The inlets are all 8-10thou and exhaust range from about 10 -15thou. (based on Jeromes and others opinions that the exhaust clearances can be run tighter than book)

No fan fitted. Chain looks perfect to me.

Friday I have a friend popping by who has had many Dolomites, and knows how to build a cracking engine. Has done so for nearly 30 years. Hoping he may have an opinion.

Rest of the day was spent welding up a friends Vitesse front valance and doing a bit of real work.

Cheers
Clive

(please keep up with suggestions!)

(please keep up with suggestions!)

[/quote]

A very stiff drink

Tony,