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#578356 - 12/28/14 11:26 am 6T ENGINE REBUILD - T110 Barrels 6t Head??  
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666Thunderbird Offline
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Hi Everyone...

Finally getting close to engine assembly time on my 1955 Thunderbird. Some of you may remember the bike as it had an 18 foot holly tree growing through it!

I have saved the casings which are big bearing type.
The cylinder head looks ok and is a 4 fin one.

I have 2 barrels... First I have a 3332 T110 one with pistons which I was just going to fit but.. not sure if this will work with my head??

Everything I have is 6T camshafts, crank/rods, pushrods etc etc but the barrels are T110

Does anyone know any reason why I shouldn't fit these


2nd barrel option is a 6T one bored to +60 but I have no pistons yet and this seems more hassle not to mention expense.

Thanks

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#578358 - 12/28/14 11:41 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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666Thunderbird Offline
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For those that don't remember my bike this is the story so far......

https://www.flickr.com/photos/116301631@N02/

#578365 - 12/28/14 11:56 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Another "silly" question... Why are all the old 6T pistons so flat looking on top yet all the pistons I can find for sale seem far more dome shaped.. The pistons in my T110 Barrels are a lot rounder than the flat ones which were welded into the original barrels by 43 years of English weather!

#578384 - 12/28/14 1:24 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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T110 barrels and 8 stud 6T are the same.

The domed pistons you are seeing commonly for sale are probably 9:1 compression ratio, standard on late Unit 650s.

They probably work ok in a 6T. I've never heard of any problems and I'd bet loads of owners have fitted them.

They do work in an iron headed T110. The measured compressipn ratio with "9:1" pistons in mine was just under 8:1.


Last edited by triton thrasher; 12/28/14 1:26 pm.

Amateur Loctite enthusiast.
#578392 - 12/28/14 2:33 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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'59 Bonnie Offline
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Just looked, you doing a great job. No you should not have any issues using the higher compression pistons etc.

Last edited by '59 Bonnie; 12/28/14 2:35 pm.

"We are "motorcyclists" & "historians" our hobby includes the research & preservation of motorcycle history. What we are doing in the research & preservation of iconic bikes is, an important part of its history & value".
#578517 - 12/29/14 7:51 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Thanks for the advice so far..
Does anyone know why the 6T and T110 Barrels have different part numbers if they are the same?

6T E2895
T110 E3332

Seems unlikely they would be the same. I have cross refd a lot of other parts and they use the same part number if they are the same so why not on the barrels?

Thanks

#578521 - 12/29/14 8:23 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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i would do a volume measure to get accurate comp , you do not want 9:1 in a all iron 6T , it will run but not as sweet as this engine should be

#578523 - 12/29/14 8:39 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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http://britishbikebits.com/cylinder-barrel-8-stud-triumph-650cc-pre-unit#.VKFLNYoN8

Quote:
8 Stud Cylinder Barrel

Suitable for Triumph 650cc Pre-Unit Models circa 1954-62

T120 Bonneville
6T Thunderbird
T110 Tiger
TR6 Trophy

Triumph Part number E3332, 70-3332

Can also replace E2895 (70-2895) This just has a different fin style


2895 may be older, from when the only 650 was a 6T.

Can you see a difference in the fins?

Last edited by triton thrasher; 12/29/14 8:49 am.

Amateur Loctite enthusiast.
#578524 - 12/29/14 8:51 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: craig]  
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Originally Posted By: craig
i would do a volume measure to get accurate comp , you do not want 9:1 in a all iron 6T , it will run but not as sweet as this engine should be


Have you tried it?


Amateur Loctite enthusiast.
#578526 - 12/29/14 9:34 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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i have built and own several pre unit triumphs (i still have a 6T) setting comp via volume measure is the only way and on petrol have tryed upto 10.2:1 and they will run , 9:1 will run but still to high for a sweet running all iron engine , if you want a easy starting very nice running 6T 7.5 to 8:1 is perfect , they still go well and top end is almost the same but takes a little longer to get there . if you combined this comp with a SU carb you will think your riding a jap bike they really are that good .

#578559 - 12/29/14 1:23 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Both numbers quoted are from the 1955 Parts Cat.

All my parts are 6T apart from the Barrels and Pistons which are T110

I might try and find some flat topped +60 Pistons for the other barrels just to be on the safe side.


Thanks for everyone's input.

#578578 - 12/29/14 2:33 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: craig]  
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tbird649 Online content
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Originally Posted By: craig
i have built and own several pre unit triumphs (i still have a 6T) setting comp via volume measure is the only way and on petrol have tryed upto 10.2:1 and they will run , 9:1 will run but still to high for a sweet running all iron engine , if you want a easy starting very nice running 6T 7.5 to 8:1 is perfect , they still go well and top end is almost the same but takes a little longer to get there . if you combined this comp with a SU carb you will think your riding a jap bike they really are that good .


I agree, my 1956 6T has 8:1 pistons, and SU carb, it is a very smooth and sweet engine. When I first got it it had bloody great domed pistons in it, +60's , I think maybe a few years ago these were all that were available in that oversize. New barrels, and lower compression was a big improvement.



#578586 - 12/29/14 3:25 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: craig]  
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Originally Posted By: craig
i have built and own several pre unit triumphs (i still have a 6T) setting comp via volume measure is the only way and on petrol have tryed upto 10.2:1 and they will run , 9:1 will run but still to high for a sweet running all iron engine , if you want a easy starting very nice running 6T 7.5 to 8:1 is perfect , they still go well and top end is almost the same but takes a little longer to get there . if you combined this comp with a SU carb you will think your riding a jap bike they really are that good .


Yes, a real 9:1 might be high. Have you tried the pistons that are nominally 9:1 with an alloy head, in an iron headed 6T?

They give me just under 8:1 measured, in the iron T110. Could be different in a 6T and the OP can't measure before buying and fitting.

They are the commonest and cheapest Triumph 650 pistons. The low measured compression in the T110 makes me wonder whether pistons labelled as 7:1 or 7.5:1 might turn out to be 6:1 when used with an iron head.


Amateur Loctite enthusiast.
#578589 - 12/29/14 4:08 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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I just bought some flat topped pistons (with the correct part number) for my old +60 6T barrels.. hoping this is going to prove a good move.. 7:1 seems a bit low but the part numbers are the same as the 1955 parts book... fingers crossed :-)

#578598 - 12/29/14 5:28 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Just had another look at your pictures. At least mine didnt have a tree!



PS Keep the SU carb.



#578602 - 12/29/14 6:04 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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The tree is very under-rated.. I think it was holding mine together ;-)

Well actually it was just holding it in place for me... The tree must have been older than me. My bike was there when I was born.. and all the way through my life it was just sitting there. At one time I even lived just 9 miles away from it. Every single day of my life, through every event the Thunderbird was just sitting there.. makes you think really.

And yes I will keep the SU... I still have the tree trunk too :-)

#578606 - 12/29/14 6:19 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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At .060 over, you might be in for some problems. The max overbore on pre units is stated by the manual to be +040. You might get away with it or you might have cylinder wall distortion when you torque up the head bolts. I would test the cylinder with head bolts and spacers torque to spec, measured with a bore gauge or just blue up the cylinder and pass a hone once through it to see if the cylinder walls are bulging at the head bolt holes. I have done this and honed the cylinder to get it round again, but I'm not really proud of that since it is a bodge after all.

Cheers,
Bill


Bikes
1974 Commando
1985 Honda Nighthawk 650
1957 Thunderbird/T110 "Flying Tiger"
Antique Fans: Loads of Emersons (Two six wingers) plus gyros and orbiters.
#578613 - 12/29/14 6:51 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Thanks for the advice. Seems like a minefield whichever way I go.

#578660 - 12/30/14 2:00 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: tbird649]  
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'59 Bonnie Offline
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Originally Posted By: tbird649
Just had another look at your pictures. At least mine didnt have a tree!



PS Keep the SU carb.


That looks really great, hope you don't mind me posting this.


As to the differences between the T110 and 6T barrels exactly what they are I am not sure but one reason would be for mag motor compared to coil/ distributor motor. With Triumph if it had a extra hole it had a different number........ Nice bikes.


"We are "motorcyclists" & "historians" our hobby includes the research & preservation of motorcycle history. What we are doing in the research & preservation of iconic bikes is, an important part of its history & value".
#578664 - 12/30/14 2:50 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Top job. If mine ends up half as nice I'll be more than happy.

#578672 - 12/30/14 6:32 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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+60 rebores have always worked for me, but I can see how they might not always. The bore is close to the head bolt holes.

That is a handsome bike.


Amateur Loctite enthusiast.
#578686 - 12/30/14 9:25 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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are the cam follower blocks the same ? as the lower end of the push rods tubes are different did they alter the setting arrangement , very nice 6t , I changed mine to mag as I like control of the ignition adv/ret but that's ust my age as the dizi worked fine

#578690 - 12/30/14 10:03 am Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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Slight change of topic, but now someone has mentioned ignition, I kept the points for some years, then took the plunge and sent my distributor off to www.kirbyrowbotham.com and had it machined to take Pazon EL. Best mod I have made! Just saying, so if you go that route, send it off in plenty of time as mine took a bit longer to come back than was originally stated .



#578707 - 12/30/14 1:16 pm Re: 6T ENGINE REBUILD - T110 Barrels 6t Head?? [Re: 666Thunderbird]  
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tbird, thanks for the information on the Rowbotham conversions.
If I can never find a really competent magneto rebuilder, that's what I will have to have done.


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