TR7 Piston to Valve Clearance

[Ecosse]

Hello All,

I am currently rebuilding my 7 engine and would appreciate some advice / reassurance from any members 'in the know' for 7 engines. Would I be correct in my assumption that when a piston is at the top of its stroke, neither of the associated cylinder's valves are fully open. The head and block have had minimal resurfacing and prior to refitting the head I have noticed that when a piston is at the top of its stroke if either of the cylinder's associated valves were fully open they would make contact with the piston. The answer may seem obvious, but reassurance is required, particularly as there are valve shaped cut outs in the pistons.

Thanks for any comments.

Cliff

 

[BlueTR3A-5EKT]

if the cam is timed correctly no contact should happen.  How much has been shaved off the block and head?    There were thicker head gaskets available to replace the material removed.   
 

Sanity check.  

find TDC on the crank with one piston without rings fitted and mark it.  Remove piston.   Fit head and cam timing bits.   Happily turn the cam and crank knowing there is no piston to contact valves.   Satisfy yourself the valves will not strike the pistons with the valve timing you have set.   Mark everything, strip head and timing gear from engine fit pistons and carry on.
 

Put your cam timing figures in here and rest assured by the visual cam lobe positions when related to the piston/crank position.

https://www.blocklayer.com/degree-wheel

You will get something like this that you can print out and stick to an old cd to attach to your crank.

Edited February 27 by BlueTR3A-5EKT

[Ecosse]

Hello Peter,

Thanks for your reply, as previously your input has been really helpful.

A cumulative total of .005" has been removed from the block and head just to clean up the surfaces. Since my enquiry on Sunday I have been advised that there should be circa .060'' clearance between the valves and pistons at their closest point and obviously there has not been a problem with contact as the car has done 70,000 miles. It was more a case of the jitters prior to fitting the head. Your sanity check would be the ultimate, but would be time consuming given that the 7 is OHC, but I may do a simplified check with the head off based on valve opening and closing points if I can find that data. I guess that if there are any issues with contact the engine would lock up whilst being turned over by hand.

Perhaps a beer would be in order if we ever meet up.

Cliff

 

[BlueTR3A-5EKT]

7 hours ago, Ecosse said:

Hello Peter,

Thanks for your reply, as previously your input has been really helpful.

A cumulative total of .005" has been removed from the block and head just to clean up the surfaces. Since my enquiry on Sunday I have been advised that there should be circa .060'' clearance between the valves and pistons at their closest point and obviously there has not been a problem with contact as the car has done 70,000 miles. It was more a case of the jitters prior to fitting the head. Your sanity check would be the ultimate, but would be time consuming given that the 7 is OHC, but I may do a simplified check with the head off based on valve opening and closing points if I can find that data. I guess that if there are any issues with contact the engine would lock up whilst being turned over by hand.

Perhaps a beer would be in order if we ever meet up.

Cliff

 

Do not forget you need to have an head gasket fitted as that extra thickness lifts the head and valves away from the pistons. The height also changes valve timing to some degree.

 

 Use a cleaned. Up old one rather than possibly ruining a new one.    I keep a couple of old head gaskets on the shelf for this purpose on the wet liner engine.

Edited February 27 by BlueTR3A-5EKT

[Andy Moltu]

You should be fine if the cam timing is correct.

The important thing to check that the engine turns over by hand before cranking it over on the starter.

[BlueTR3A-5EKT]

Does your piston look like this?

Then I guess it’s cattle trucked.