Dic Doretti Posted July 22, 2024 Report Share Posted July 22, 2024 I plan to take the head off my TR2 and carry out some tuning work over the winter, it really needs a respray but that can wait. Turning to Kastners book he recommends a 0.090" head skin as a good way to release more power on a road engine (TR4) but then I turned to my well thumbed copy of Technicalities where Ian Cornish states a maximum of 0.050" for a TR3A head. I am carrying out this work on a low port head so how much should I take off? I have had a tuned low port engine years ago and it went well as did the Jabbeke TR2. Any help appreciated, I will be using the original H4 carbs on a Wilen manifold. Cheers Richard Quote Link to post Share on other sites
Lebro Posted July 22, 2024 Report Share Posted July 22, 2024 90 thou sounds a lot. I took 60 off mine, but that was after removing quite a lot of metal around the inlet valve. Bob Quote Link to post Share on other sites
Dic Doretti Posted July 22, 2024 Author Report Share Posted July 22, 2024 I would agree Bob which is why I am on the Forum to see what the experts think. The British Leyland Competition Preparation Manual written by Bob Kastner for the TR4 recommends taking 150 thou off to give a 12.6 compression ratio for a racing engine and 90 thou to give a 10.2 compression ratio for a fast road engine. I would be scared to take that much off so perhaps 60 thou would be a good compromise. Cheers Richard Quote Link to post Share on other sites
2long Posted July 22, 2024 Report Share Posted July 22, 2024 (edited) One thought is that measuring the low-port head precisely before you skim would reveal how much has already been taken off. Most heads have already been skimmed by now. One of my TR2 low port heads had about as much taken off as it could stand, and I had to use thicker head gasket to get to the stock compression, which was my goal. Cheers Dan Edited July 22, 2024 by 2long Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 22, 2024 Report Share Posted July 22, 2024 (edited) Agree with Dan Get it off. Do not get all carried away reshaping the chambers unless you are prepared to make a gasket that fits the chambers once you have removed the overhang above the valve. That overhang goes the moment you shave too much off the head face. Leaving it thin (1mm or less) means it glows red hot and sets up pre ignition issues. Gaskets are available with the modified shape from Racetorations or others will sell you a sheet of copper that will need shaping and annealing. That is only needed if you remove the overhang pocket over the valve. Simply check the old gasket on the head before fitting, the gasket must not intrude into the combustion chamber. Kastner covers all this. Special shaped gaskets are not cheap compared to the standard item. Information you must have to get the CR at the level you want. The broad target is over 9 but under 10 to work with today’s fuel. The last couple I have done I aimed for 9.5-1. You will need that sort of ratio to get a sports cam to deliver improvements if you are changing the cam. The Newman PH1 is a nice improvement without loss of flexibility. So….. Measure the chamber capacity and the head gasket thickness and bore size ( the one you intend to use and compare to the one you removed) and the distance the piston is down the bore at tdc from the top of the liner (deck height) Also what bore size you have. Crank throw is 92 mm unless it has really been got at. The tech data in the service book tells you the fixed sizes like bore and crank throw in both imperial and metric. Armed with the info do a compression ratio check using one of the many online sites. Here is one I use. http://www.csgnetwork.com/compcalc.html Edited July 22, 2024 by BlueTR3A-5EKT Quote Link to post Share on other sites
Lebro Posted July 22, 2024 Report Share Posted July 22, 2024 Another consideration is the gap (or lack of) between the bottom of the thermostat housing (on the head), & the water pump. Later heads had a different shape here to allow for some machining. On my TR3 high port head I had to grind the bottom of the head in this spot, & also the top of the weater pump to get a clearance. Bob Quote Link to post Share on other sites
Dic Doretti Posted July 23, 2024 Author Report Share Posted July 23, 2024 Thank you, wise words. I will measure the combustion chamber volume before I proceed any further. There is a section in Technicalities which looks very useful giving a comparison between combustion chamber volumes and compression ratios. Who stocks Newman cams? Cheers Richard Quote Link to post Share on other sites
Lebro Posted July 23, 2024 Report Share Posted July 23, 2024 Buy direct from Newmans. http://www.newman-cams.com/camshafts/ Bob Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 23, 2024 Report Share Posted July 23, 2024 29 minutes ago, Dic Doretti said: Thank you, wise words. I will measure the combustion chamber volume before I proceed any further. There is a section in Technicalities which looks very useful giving a comparison between combustion chamber volumes and compression ratios. Who stocks Newman cams? Cheers Richard You need a syringe, some paraffin, a sheet of perspex with a hole in it and a smear of grease to adhere the perspex to the head. Simply see how much volume of liquid you can get in each chamber Quote Link to post Share on other sites
Andy Moltu Posted July 23, 2024 Report Share Posted July 23, 2024 22 hours ago, Dic Doretti said: I plan to take the head off my TR2 and carry out some tuning work over the winter, it really needs a respray but that can wait. Turning to Kastners book he recommends a 0.090" head skin as a good way to release more power on a road engine (TR4) but then I turned to my well thumbed copy of Technicalities where Ian Cornish states a maximum of 0.050" for a TR3A head. I am carrying out this work on a low port head so how much should I take off? I have had a tuned low port engine years ago and it went well as did the Jabbeke TR2. Any help appreciated, I will be using the original H4 carbs on a Wilen manifold. Cheers Richard Were the compression ratios on the USA spec cars lower which may have influenced Kastner's measurements. Not sure when Triumph started sending different spec engines to the States. Quote Link to post Share on other sites
john.r.davies Posted July 23, 2024 Report Share Posted July 23, 2024 Dic, May I humbly recommend to you my article "How To Raise The Compression Ratio, Safely And Effectively" over on the Sideways board? See: https://sideways-technologies.co.uk/forums/index.php?/topic/7551-how-to-raise-the-compression-ratio-safely-and-effectively/#comment-99739 Therein, I explain the volume measurement procedure (use a glass sheet - easier to use than Perspex! A local glazier can make you one from offcuts and drill two holes in it for you) and the calculation to estimate the chamber volume, the CR that will result and how to calculate how much to skim the head to achieve a desired raised CR. JOhn Quote Link to post Share on other sites
iain Posted July 23, 2024 Report Share Posted July 23, 2024 Another consideration is that if you skim the head significantly it lowers the exhaust manifold and this can then catch the ribs on that side of the block.....result is a manifold air leak. Iain Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 23, 2024 Report Share Posted July 23, 2024 25 minutes ago, iain said: Another consideration is that if you skim the head significantly it lowers the exhaust manifold and this can then catch the ribs on that side of the block.....result is a manifold air leak. Iain Also, with an early head the underside of the water outlet casting where the thermo housing sits conflicts with the water pump housing. This was resolved on 4A heads with a chamfered casting. Quote Link to post Share on other sites
Lebro Posted July 23, 2024 Report Share Posted July 23, 2024 16 hours ago, Lebro said: Another consideration is the gap (or lack of) between the bottom of the thermostat housing (on the head), & the water pump. Later heads had a different shape here to allow for some machining. On my TR3 high port head I had to grind the bottom of the head in this spot, & also the top of the weater pump to get a clearance. Bob I think I mentioned this ! Bob Quote Link to post Share on other sites
BlueTR3A-5EKT Posted July 23, 2024 Report Share Posted July 23, 2024 59 minutes ago, Lebro said: I think I mentioned this ! Bob You did, my fault for not reading Quote Link to post Share on other sites
Dic Doretti Posted July 23, 2024 Author Report Share Posted July 23, 2024 Thank you everyone. I have ordered a burette and will check out the Sideways site. I will also be modifying a high port tubular manifold to fit the low port head, I did this many years ago on Robbie Coltrane's TR2 after a misunderstanding with Moss. Had a great run out in the TR2 today to take advantage of the sunshine so will not be stripping the engine anytime soon. Cheers Richard Quote Link to post Share on other sites
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