Jump to content

Advise on head rebuild


Recommended Posts

Hi all,

 

After one and a half years I still do not have my TR7 on the road. I have been fixing small things until I found out it has a broken exhaust valve. I have the head off now and I am wondering if there are other things I should take care of.

 

I will change al valves as a matter of course, but I am wondering, are they prone to failure?

 

I was thinkng in changing the timing chain and sprockets. I looked at RB and they offer a standard and a more expensive german chain, so I googled a bit to see what the difference is and read some comments saying they are no better and that the sprockets on sale now will break quickly, would it be better to keep the current ones which seem to be OK?

 

Thanks!

Link to post
Share on other sites

Why has the valve broke. I had a bucket break on a newly rebuilt engine, from now on I will only use original buckets. Obviously it broke the top of the valve and wrecked the NOS cylinder head.

Link to post
Share on other sites

Do not know about the quality of TR7 chain but there is a big difference

between the replacement cheap chain and the one from German IWIS at TR6.

As there is no tensioner on the TR6 you can see a huge stretch after short use.

Although there might be a tensioner the timing will get worse.

 

When valves fail beside poor quality and no reason to be found there are some reasons, that should be checked:

 

First there is the poor valve clearance that prevents the valve getting rid of the heat when to tight.

The valve can not rest on the seat what would allow to pass the heat from valve to head or when

getting more worse will allow the hot gas to pass the slit between seat and valve and fry the valve.

 

One more reason that should be checked is if the seat is in line with the valve guide and

allows the valve to seat nice and full on the seat all around.

Link to post
Share on other sites

Andreas,

There is, or should be a tensioner on the timing chain of a TR6!

See: http://www.canleyclassics.com/triumph-tr6-late-timing-cover-details

Part No. 145866

 

John

Edited by john.r.davies
Link to post
Share on other sites

Hi John!

That funny sheet of metal is not worth being called a tensioner.

It smoothes a little bit the tendency of the chain to swing on the

powerless side but not more.

 

I tried that with a fixed timing advance from my Megasquirt

picking the trigger from the distributor that is welded for fixed timing..

You can see the timing jump at some lower revs and

timing going backwards at very high revs from the chain

riding higher on the teeth.

 

I believe responsible for that is the play in the chain and from that

I would try to get a chain very tight that keeps being tight fit over the mileage.

So one has not to rely on that the tensioner does its work.

 

But another argument for the IWIS is that the sides of the chain

feel noticeable smoother and from that will not wear the "tensioner" that much.

Edited by TriumphV8
Link to post
Share on other sites

Thanks for the responses,

 

I have no idea how the valve broke. When I bought the car it didn't even start after 10 years storage, but it was already broken.

 

Good point about valve seats, they seem to be Ok, but will be lapped together with the valves so if this was the cause hope it does not happen again.

Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

Loading...
×
×
  • Create New...

Important Information

Please familiarise yourself with our Terms and Conditions. By using this site, you agree to the following: Terms of Use.