I am thinking of renewing the pushrod tubes can it be done with the engine in and do you have to remove the head .Also I am going to do a compression test and can anyone give me the average readings . (its a 650cc engine )

If you have the standard Fiat push-rod tubes,whether the collapsible type or the 'straight' variety, the cylinder head normally has to come off to renew like-for-like. If you go to the 'sprung' tubes, although more expensive, they do have the advantage of being able (just) to be removed/fitted with the head still in situ. If you don't want to remove/refit the head (might depend on your compression readings) remove the push-rods, cut/bend the old tubes out (it will destroy them beyond further use) and replace with the 'sprung' push-rod tubes. I have used the thicker of the push-rod tube seals on my 'sprung' tubes.
Neither the Factory w/shop manual or Haynes give a compression test 'poundage'. but I would have thought that 110/120psi would be a good figure, with preferably,no more than 10% difference in readings. Hopefully, some other Forum member can give us a more pertinent reading.

Just read through my old 'Haynes' w/shop manual (pre-decimalisation--it cost just £2 !) and it does have how to carry out a compression test---it states that a compression reading on a 500 should be between 100 and 107psi (7-7.5kg cm sq) and should be have no more than a 5% difference. I would expect a 650 '126' engine (with a higher compression ratio) to show slightly more---but my suggestion of 110/120 psi might be a bit high--maybe 105/110psi.

I think it best to point out that before you rip out the pushrod tubes with the head in place you do need to remove the rocker assembly and lift out the pushrods and oil feed pipe otherwise you will have a few more problems to deal with.

Just take the engine out...........only takes 15 minutes ..........

Yes I am going to remove the engine, clean the head and pistons and lap the valves in . It will also give me a chance to repaint the tin work .I have already bought the tubes and a gasket set because I don't know what is going to happen about Brexit .

If you are going to fit 'normal' push-rod tubes (as against spring-loaded tubes) I would suggest that you have 2nd pair of hands available when re-fitting the head the help align the push-rod tubes.
I wish that I could remove an engine in 15 mins, and with respect, I have possibly removed more 500 engines that most ( but not all) Forum members have; must be my age!

Hi I have purchased the spring loaded type .

the hobbler said:

I wish that I could remove an engine in 15 mins, and with respect, I have possibly removed more 500 engines that most ( but not all) Forum members have; must be my age!

Click to expand...

Mr Hobbler, purely tongue in cheek and quoting a previous post.....

I am curious though how long it would actually take so watch this space