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Triumph TR6 - New Pistons
|After taking all the bore and piston measurments I'v determined that the standard bores in my engine are in good shape and don't require a rebore. The pistons, however, are worn out for a couple reasons; primarily the ring lands are worn badly with 400% too much gap between the ring and the lands themselves. Pistons are also scuffed on the sides and pitted from detonation on top. |
So - I'm planning to purchase a set of standard pistons and see that the prices vary quite a bit between the big suppliers such as Victoria British and the smaller outfits like "British Parts Northwest".
Does anyone out there know about who the piston manufacturers are (Hepolite, others?), is there a big difference in quality etc.
Any advice would be appreciated.
|John-The pistons I have purchased from BPNW (I live quite close and have done business with them for many years) are AE brand (I think it is the same as Hepolite) and are probably sold by the "big 3". You could have your present pistons knurled and GI, in which the skirts are expanded by knurls and the ring grooves are machined&shimmed to compensate for the wear. However, it might cost almost as much as new pistons. At this point, I think it would be false economy to buy new std pistons, instead go for a .020" oversize and rebore.|
|When I was looking at pistons (in the end I didn't need them), I asked Garry Altwasser (formerly lived in Windsor, Ont and Calgary - now Penticton) where he bought his pistons for his very fast red and white TR3A. He told me about Hastings. Check out:-|
They have a full page on pistons for Triumphs. They also have a tech person - you can ask e-mail questions as well.
Don't let the fact that her name is Dawn trouble you. She really seems to know her pistons.
They also have a Canada Customer Service No. 1 800 430 3109
Don Elliott, 1958 TR3A
|Don - the hastings website "service tips page" is excellent. Piston page is temporarily out of service. Thanks for the lead.|
Berry - on the "false economy - should re-bore" comment - I don't disagree but in my case the car is up on blocks with no way to get it into a machine shop. The bores are good and within spec; not even a ridge so I don't see a problem.
Thanks guys. Good advice.
|I disagree about reboreing. If the bores measure up OK I would just fit a new set of standard pistons- cheaper and much less work. My motor ran for over 200,000 miles using about 10 replacement pistons before a rebore was needed.|
|John - I found the Hastings Triumph page under "International".|
P. Cobbold (Peter isn't it ?)
As for 10 pistons in 200,000 miles, how many times did you open up your motor ? I hope it was only twice - to change 6 pistons on the first "operation", and 4 the second ?
I ran my TR3A from 1958 to 1972 on the first original set of pistons (80,350 miles) and since 1990, I've driven over 70,000 miles on a full piston/rings/liners set I bought from Peter Hepworth in Yorkshire - with no trouble. Any predictions about pistons for me and for "TRusty" ?
BTW, my Grandfather was born and raised in Criccieth, but moved to Wigan in 1892 to learn English and take up his trade as blacksmith. Here we are today doing much the same, but with more modern "horses".
Don Elliott, Original Owner, 1958 TR3A
|John, Click on the Hastings home site:-|
Click on Catalog, then on International, then scroll down to TRIUMPH, then click on "SELECT" at the bottom.
There it is.
|In defense of reboring, my rational was that the cost of reboring is only about $10 per cyl.plus hot tanking and the inconvenience of removing and disassembly. On the other hand, you would be starting with a round and straight honed bore. Perhaps it seems like a waste of block material, but at the present rate of use, we will all be "pushing daisies" long before the block would have to be replaced or sleeved.|
Being a firm believer that the best engineering is the cheapest, I changed four individual original fitment pistons over the first 100,000 miles as each developed a split across the crown and down to the end of the oil-drain slot. After the fourth I got fed up, and fitted a whole new set( Hepolite I think). These had the ends of the oil drain slots opened up into a 'comma'shape (someone had learned from the original design fault). After the rebore I holed a further two pistons when the supercharged engine took a disliking to the fuel- pistons and detonation don't mix. I replaced just those two, the compression etc being OK on the four remaining pots. I'm keeping the 4 spare pistons for the day when I get 12 psi boost rather than present 9psi....
Reboring seems to me to involve a huge amount of work, stripping the engine, removing it etc., so only something to be done if absolutely necessary. On other hand fitting pistons is easily done in a weekend, dropping the sump and removing the cylinder head. However I gather large diesels can be rebored in situ. Anyone rebored a TR block without removing the engine?
|Peter-I was looking at the situation from the perspective of rebuilding the engine once and not even having to remove the head for many years.|
Odd that you should mention reboring in situ. I was just reading an old Car&Driver from 1961. There was an article about a TF being rebuilt and the auto machinist made a house call to rebore the engine while still in the car. I have also heard of machines that can grind a crankshaft in place. It seems that either operation would make it impossible to remove all of the swarf.
|Berry, Nice idea, restoring the engine fully and not having to open it up for many years. It's something I hoped for every time I finished a piston-repalacement job, particularly when the TR was my daily driver. But I suspect that head removal will become more commonplace in future- valve seat recession being the new problem with the demise of leaded fuel. I'm using a manganese-based additive to try to delay things, but the blower addds about 50 degrees C to combustion chamber temperature sothe dope may not work. I think the stuff was banned by Canada years ago!|
|Peter-Some people think the valve recession issue is over blown(no pun intended )and is not a problem under normal driving conditions. I went the hard seats-bronze guide-stelite exh. valve route at the last overhaul. It probably wasn't necessary given my drving style, but seemed like cheap insurance. You might try the other TR6 email@example.com. At least one person-Dick Taylor has experience with a turbocharged TR6.|
|In 1987 I rebuilt my engine. In 1990, Canada banned leaded petrol. What was I to do ? The car was now finished and on the road in 1990. So I decided to run unleaded as long as I could to see how many miles I could go before recession would happen. At about 36,000 miles on the valves and head (some of my valves were original with 116,000 miles on them by this time) I started to notice that I had to re-gap my exhaust valves every 3,000 miles - the gap was down from 0.012" down to a few thou (0.002") so after 3 more re-gaps, and at 42,000 miles after my rebuild, I removed the head and put in new guides, 8 new valves for unleaded and had inserts put in for the 4 exhaust valves.|
Since then, I've driven a further 28,000 miles and check the valve clearances once a year. I have never needed to adjust them during the last 3 years.
I drive at 70 to 75 mph when I can and do long trips. Since the new inserts and valves, 7220 miles from Montreal to Portland Oregon and back.
5220 miles to Colorado and back. 2200 to Baltimore, Washington and back and so on. With overdrive, the tach usually sits about 3200 to 3400 rpm.
So, the conclusion of all this is that the seats in the cast iron head will have a severe recession and the valves will become razor sharp on the edges after about 40,000 miles for an engine which is normally aspirated, not supercharged.
Don Elliott, Original Owner, 1958 TR3A
|Found the Hastings Piston Page.|
One thing I noticed about the pistons and rods I'v just pulled out of my motor - the PO did a lot of machining. Rods are lightened (griding and polishing at each end) and the pistons have been on a lathe with material removed from the insides up to the wristpin area. The "old" guy I purchased from said at one point "this is a racing engine". Well, it isn't but I have to admit, at redline there isn't a hint of vibration etc.
So I guess I have to follow suit with the new pistons and send them out to the machine shop along with the rods for balancing and lightning.
(I was talking to my wife about forged pistons and and carrillo rods... after all, she keeps reminding me the six is "our car" not my car!)
The point of all this being - where does one stop.
|John - One stops before the mods get to the point that you can't afford to repair it every 2 months of driving when you have exceeded the point where it has now become un-reliable and you can't have any more reasonable fun without all the trouble you have caused yourself.|
Don Elliott, 1958 TR3A
That's very encouraging as I now drive the TR only ca 2000 per year , so your 36000 miles before signs or recession appear is good news. The manganese dope also raises the octane of the fuel, needed when the motor is under full boost, so that's my insurance. And it also revs at around 2700 rpm at 75mph, a little lower than your 3, which will help too. The only uncertainty is the rather higher combustion temp due to the blower.
Mind you, around here 40-50 mph on the relatively empty scenic roads of N Wales is a more usual speed- about 1500rpm in O/D top. Criccieth is about an hour away- its a seaside resort, opened up when the railway reached there. Your grandfather I guess would barely recognise it now. You ever been there? ( respell my email address before trying to send)
This thread was discussed between 13/11/2002 and 18/11/2002
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