AndyR100 Posted May 6, 2020 Report Share Posted May 6, 2020 Top job! the cuppa will taste even better ........ Andy Quote Link to post Share on other sites
BigBogan Posted July 10, 2020 Report Share Posted July 10, 2020 On 4/16/2020 at 11:18 PM, Motorsport Mickey said: Why do the pistons have holes in the middle !! To be honest I've never thought about it, probably because I can't remember seeing them before ! My guess would be the hole is used in the location of the piston (for a machine tailstock centre to centralise) in it's production process. Also Bob might be an idea to measure the liners top and bottom checking for taper and of course checking for a thrust face wear ridge. Mick Richards Hope this doesn't constitute a thread hijack, but what is the general engineering consensus as to what is the acceptable tolerance for taper? I have measured a vertical taper in the bores at around 1.8 - 2.3 thou using a digital bore calliper. There is a lip at the top which can be felt with a fingernail. Not sure whether the liners need changing. They aren't out of round that I can find. This is for a normal road-use 64 TR4 for weekend joy rides. I'm putting in new pistons and rings, but debating whether new liners are needed. I'm looking at an 89mm piston and liner set from Rimmers, but they are a bit of a strain on the back pocket in the present circumstances.. Quote Link to post Share on other sites
Motorsport Mickey Posted July 10, 2020 Report Share Posted July 10, 2020 If the engine was working fine before you removed the head why are you even considering the taper ? If you want to button it back up it will work fine for thousands of miles yet, especially if you are using it as a weekend time machine only. If you are "putting in new rings and pistons" the rings will need a ridge dodger top ring (it has a step in the top ring top face... not large about 10 thou) so the ring doesn't hit the liner ridge and break. I would always check the liner protrusion height over the top of the block, straight edge and feelers is ok for a rough check (measure around it in 4 positions and write the numbers down on the top face of the liner). You are looking for 3.3.3.3 or 4.4.4.4 or 5.5.5.5 heights above the block, typically the liners lean in all directions like Ken Dodds teeth, the last 50 years having stress relieved them allowing them to be displaced. Beware 3.3.2.3 measurements, they are so close but yet offer a chance of a head gasket problem in the future, the "crutch liner" on the outside edge of the head prevents the head deforming and giving the same clamping force on the gasket. Depending upon how you've broken down the engine (retained the liners position with washers before removing the pistons is good and the appropriate way) then the new pistons and rings can just slip right on in there, minimum of work. If the liners have not been retained in position it's possible (vaguely ) the piston removal has disturbed the bottom Figure of 8 gasket seal and if just rebuilt without removing and resealing the liners a future water leak into the sump and then strip down to the position you are now beckons. If you are going to replace the Fo8 liner gaskets on the original liners you may as well rotate the liner 90 deg so the thrust face on the piston has a fresh bit of liner to attack for the next 20 years. There are over 80 posts on liner removal and reworking (at least 8 of them from me) use the search box on any of the 4 cyl forums and you get all the guff on it. Mick Richards Quote Link to post Share on other sites
John McCormack Posted October 1, 2020 Report Share Posted October 1, 2020 On 4/9/2020 at 2:26 AM, Lebro said: 'tis off, much energy exerted, & much vandalism with crowbars etc. but seem to have got away with it. Think I can probably re-use the gasket ? no sign of bad erosion on No. 3 Exhaust valve, but will see properly tomorrow when they are all out. Interesting there does not seem to be the usual crack in the centre. Bob (knackered) I use a thin bread knife between the head and block. Hammer it in gently but firmly all around the join. It is broad so spreads the load and lifts the head enough to break the seal between the head, studs and gasket. Quote Link to post Share on other sites
Lebro Posted October 1, 2020 Author Report Share Posted October 1, 2020 That definately would not have worked for me John, it was well stuck on the rearmost RHS stud. I'm too embarassed to describe what was required to finally get it off, it wasn't pretty Bob Quote Link to post Share on other sites
stillp Posted October 1, 2020 Report Share Posted October 1, 2020 47 minutes ago, Lebro said: I'm too embarassed to describe what was required to finally get it off Oh go on Bob, you're among friends here. Pete Quote Link to post Share on other sites
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