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Old 11-15-2013, 03:31 AM   #1
'59
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Default Triumph 750 Cam Question

got a set on order from the bay to fit in pre unit cases with Morgo top end. It just occured to me, will the exhaust cam need re working to remove the end where the advance / retard unit would fit so it doesn't foul on inside of pre unit timing cover?

thanks
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Old 11-15-2013, 04:33 PM   #2
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Default Re: Triumph 750 Cam Question

I have run a unit exhaust cam on my 500cc pre-unit Triumph for 8 years and never had a problem. Problem comes when you wanna add a tach drive cover. No way to drive it.
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Old 11-15-2013, 08:01 PM   #3
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Default Re: Triumph 750 Cam Question

T140 exhaust cam isn't the best choice.A 3134 cam from a late 650 ('70 onward) is a better choice and has about 10 degrees more duration and 0.009" more cam lift.

Watcha going to do about the breather holes in the intake cam?Are you going to drill the T140 intake cam?The nitriding is fairly hard for about 0.020" depth.You could get through that with a carbide drill.
Time the intake cam to 100 degrees ATDC lobe centre +/- 2 degrees.Take measurements at about 0.080" lift to find the lobe centre.

Last edited by Mr.Pete; 11-15-2013 at 08:10 PM. Reason: "Take measurements - - - - lobe centre."
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Old 11-15-2013, 08:22 PM   #4
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Default Re: Triumph 750 Cam Question

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Originally Posted by fouraceswes View Post
I have run a unit exhaust cam on my 500cc pre-unit Triumph for 8 years and never had a problem. Problem comes when you wanna add a tach drive cover. No way to drive it.
that's not true Wes, I have a pre unit tack drive somewhere that is tapered to fit into a unit cam. I got it in some parts from Danny Macias .
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Old 11-16-2013, 02:51 AM   #5
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Default Re: Triumph 750 Cam Question

I wanted a nitrided cam and grabbed a 71-7182. Without being able to measure up a '3134' cam it seems from what i read that everyone and their dog will look at the casting number interpret it as the magic 3134, charge top $ , and you can end up with any one of a dozen different grinds that were done using that blank.

Thanks for the heads up on the breather hole, i'll look out for that. For some reason my machine shop man hates working treated metals, i guess it knocks the sh1t out of his lathes and eats bits so i'll need to invest in some carbide drill bits and get out the trusty black & decker.
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Old 11-16-2013, 04:05 AM   #6
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Default Re: Triumph 750 Cam Question

Try EDM , If you cant find a shop with that equipment or one that will do the job you can do it yourself ! The equipment itself aint expensive but requires you to learn how to use a different approach !

www.instructables.com and www.HomemadeTools.net are good resources for this if you want to diy or just learn a bit about it !
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Old 11-16-2013, 04:46 PM   #7
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Default Re: Triumph 750 Cam Question

I guess I should have been WAAAAAAAY more specific so I could not be called on the carpet by the ghost of Danny Macia, (properly channeled by Tony Dunn of course). Danny was the creater and maker of all sorts of ONE OFF parts that are unavaiable to most mortals here in jockey journal land. Danny probably forgot more about the Triumph motorcycle than this board and all of its members collectively will ever know.

Let me be less brief and more specific for all who give a shit. A STOCK unit exhaust camshaft is incompatible with a STOCK pre-unit tach drive timing cover without some sort of specialized work on the end of the camshaft or the drive of the tach cover or the addition of some widget that mates them up. In my estimation, combined with my clearly WAAAAAAY more limited knowledge than the experts on here, it seems to me that the stock pre-unit tach drive will not bolt directly to a lower end equipped with a stock unit camshaft and make the tach go roundy round.

However, since I began racing at the Bonneville Salt Flats 8 years ago I have run a stock unit construction exhaust camshaft in my 500cc pre-unit lower end with a "normal" non-tach drive cover with many many successful runs. I should add a disclaimer here that I have not run every timing cover ever made with every unit camshaft ever made in a pre-unit lower end so I cannot be 100% sure of what I am saying here. I am 99% sure however that I am not at least 50% full of shit.
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Old 11-16-2013, 10:17 PM   #8
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Default Re: Triumph 750 Cam Question

woah....what'd I do piss you off ?

All I was saying that I got this cool little deal out of some of Danny's parts that allows a unit cam to drive a P/U tack drive.

I thought it was a great idea.

sorry.
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Old 11-17-2013, 05:41 PM   #9
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Default Re: Triumph 750 Cam Question

For those of you who might be wondering about this "controversial" part . . .

It's just an adapter to allow you to drive a mechanical tach (like a Smith's) comparable to what was used on the pre-units. They are, as far as I know, one off fabrications. When Tyler was getting his pre-unit salt flat Triumph together (I'm sure Wes recalls this very well ), he wanted to run a nice old mechanical tach. Only one problem - the later unit cam wouldn't accept the tach drive and no adapters are available on the aftermarket. I made up a couple of the adapters, one went to Tyler and the other went to a guy in Europe. Here is a picture of the adapter prior to threading. Actually, I rejected the one in the picture because I felt the slot was too wide, but anyhow, it will give you an idea of what the part is and what it looks like.



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Old 11-17-2013, 06:15 PM   #10
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Default Re: Triumph 750 Cam Question

A skillful guy could make that from an auto advance bolt with weld added the head and hand ground to rough shape and then"turned" to shape in a drill press. and the slot cut with a hacksaw.
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Old 11-17-2013, 07:02 PM   #11
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Default Re: Triumph 750 Cam Question

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A skillful guy could make that from an auto advance bolt with weld added the head and hand ground to rough shape and then"turned" to shape in a drill press. and the slot cut with a hacksaw.
Yes, you sure could.
I turned them on a lathe out of O-1 drill rod and then I actually did cut the slot by hand because it was kind of fussy trying to hold the part solid enough so I could slot it with a mill. I wanted to make sure I used some material that I could be confident that it would hold up under any circumstances, and the O-1 was just what I happened to have on hand. The last thing I would want to see happen would be one of my parts causing a failure when somebody is trying to make a record run .

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Old 11-19-2013, 02:51 AM   #12
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Default Re: Triumph 750 Cam Question

WTF! is wrong with these people, so the 'usable' cams arrive from fleabay seller. Staining i can live with, pitting on the lobe is just totally FUBAR.

'call if not completly satisfied, don't post negative feedback', Damn right you'll pay return shipping if you want this piece of crap back.

J*sus f*ckin' H Chr*st these tw*ts give me the dry rots.

rant over.
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Old 11-20-2013, 06:06 AM   #13
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WTF! is wrong with these people, so the 'usable' cams arrive from fleabay seller. Staining i can live with, pitting on the lobe is just totally FUBAR.

'call if not completly satisfied, don't post negative feedback', Damn right you'll pay return shipping if you want this piece of crap back.
Did you use PayPal? If so just complain and you'll get the money returned..
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