Can you suggest the best procedure for hi performance 510-65 [old 1060 and 51060] cams in a 1967 Triumph Bonnie Twin 750 engine. I have the following information:Intake Open 47 btc Close 68 abc Exhaust Open 72 bbc Close 43 atc .
Best procedure to install and time using timing figures supplied (@.020" lift). a. lobe center timing b. open - closing timing. c. lift at TDC. or Best procedure to find hidden HP in the cams. or Best procedure?
My question is, how doo I time these cams in a Triumph engine assembled and in the bike? How different would the timing be compared to stock 650 cams? Can I set these cams without loosening the head bolts? I have never set up valve timing on anything but stock cams.
Originally posted by Hopper Tom: My question is, how doo I time these cams in a Triumph engine assembled and in the bike? How different would the timing be compared to stock 650 cams? Can I set these cams without loosening the head bolts? I have never set up valve timing on anything but stock cams.
The simple answer is yes, but it is not practical. Megacycle has provided lift figures at TDC. So it is just a matter of putting the piston at TDC and setting the cam lift to the figures provided and you are done.
BUT the valve springs will constantly fight you as you try to: 1. keep the piston at TDC. 2. and try to rotate the camshaft into position so you can slide the pinion on the camshaft.
Given enough hands, the patience and skill of a very experienced Triumph mechanic, and cam wheels that have been modified to allow them to slip onto the camshafts. Yes, it can be done... but then we did send people to the Moon.
I would advise that you at least remove the rocker boxes, as this will remove the valve spring pressure which tend to rotate the crankshaft just when you think you have things lined up.
You will need: 1. a degree wheel and adaptor to mount on crankshaft. 2. Pointer for degree wheel. 3. Piston stop to align the degree wheel with the crankshaft: Degree wheel TDC and crankshaft TDC. 4. A cam wheel extractor and installer - unless you remove .001" from the inside of the cam wheel which will allow it to slip on (typically I only do this on racers where in search for HP the cam timing is changed often). 5. And someone else with more time than I have at the minute to explain how it is done and I already have tried explain the easy way to time a gearbox and no one listens anyway... so RF have at it.... john
When presented with timing a new set of Megacycle cams you will need some special tools: A degree wheel and adaptor to attach it to the crankshaft. A hex spacer to put in place of the rotor to turn the cranshaft with a wrench. A piston stop to help align the degree wheel and the crankshaft so degree wheel reads 0° when crankshaft is at Top Dead Center (TDC). A dial indicator with at least .500” (1/2”) travel, a modified push rod, and adaptor to mount it to engine. Camshaft pinion removal and installation tool. Timing Card that cam with the camshaft.
SETTING UP THE DEGREE WHEEL All we are setting out to do is connect the rotation of the crankshaft to the rotation of the camshaft so we know where each is located as each goes through its 360° of rotation.
The main tool we use to tell us where we are is the degree wheel. It must be securely attached to the crankshaft. The time spent securing the degree wheel to the crankshaft will make the job a lot easier. One the adaptor secures the degree wheel you will have to attach a pointer and set the degree wheel to 0° when the crankshaft is at TDC.
I have made a short length of 1 1/8” bar stock into a spacer that is broached for the alternator key. I place this behind my degree wheel and in place of the alternator rotor and use it to turn the crankshaft during timing.
The easiest way to locate the degree wheel is to use a piston stop. A piston stop can be as simple as a bar laid across the top of the cylinder. The bar will only allow the crankshaft to rotate so far until it comes to a stop. We will use this to align the degree wheel with the crankshaft
Lay the bar across the cylinder and rotate the crankshaft bringing the piston to a stop at the bar. Now look at the pointer at the degree wheel and read the number on the degree wheel. Let’s say it is 80°. Now rotate the crankshaft in the other direction until the piston hits the bar again. Read the number on the degree wheel. Let’s say it is 120°.
Now to align the degree wheel with the crankshaft add the two figures 80 + 120 and divide by 2. (200 / 2 = 100). All you have to do is to be sure the degree wheel reads 100° when the piston is against the stop - Both ways: 100° Before Top Dead Center (BTDC) and 100° After Top Dead Center (ATDC).
REMEMBER the figures you read on the degree wheel when your piston stops at the piston stop (in our case a bar across the cylinder) will be different. You will have to go through the drill to get your own figures. Once you set your degree wheel you remove the bar across the cylinder.
SETTING UP THE DIAL INDICATOR
We will need a method to measure the tappet “lift.” This is typically done with a dial indicator. You will avoid a lot of frustration if you are able to securely mount the dial indicator. Typically it is mounted to a head bolt with a nut added to lock the head bolt to the cylinder. This keeps the bolt rigid and locked to the cylinder. Standard dial indicator accessories available from machine shop supply companies easily adapt the dial indicator to the head bolt.
I like to use an old push rod which I have removed one end. I shorten the aluminum shaft and reinstall the push rod end. I use this to connect the top of the tappet to the dial indicator. With the indicator and the push rod in place we will now be able to measure the tappet lift as we rotate the camshaft. Be sure to check that the dial indicator will not “top out” as you rotate the camshaft. This will upset you when you are timing your cams.
TIMING THE CAMS
What we are setting out to do is to get the cam to lift the tappet, which will open the valve, at a predefined point in the crankshaft’s rotation. So lets look the timing sheet that cam with our camshaft. It tells us the inlet cams opens the valve 35° BTDC. It also tells us that this 35° figure is given at .020” tappet lift.
So we rotate the crankshaft until our degree wheel pointer indicates the crankshaft is 35° BTDC. The we rotate the camshaft (clockwise) until the cam lobe lifts the tappet .020”. All we need to do now is connect the crankshaft to the camshaft. We do this with the gears and pinions in the timing cover.
A SIDE BAR
Because the camshaft pinions are a light press fit on the camshafts a special cam tool is required. The tool adds another dimension to doing the job. If it was a simple matter of locating the crank and camshafts and slipping on the pinion the job would be a lot simpler. It is further complicated by the locating key in the camshaft which must be aligned as you press on the pinion.
You will notice that most Triumph pinions have three key way slots. The standard slot, used with factory camshafts is adjacent to the timing mark on the pinion. The three key ways allow you to juggle the 15° you get when you move the pinion one tooth in to 5° increments. This will allow you to get the final cam timing within a couple of degrees of the figures on your timing card.
The 2 1/2 degrees error is ok for the typical street application, but if you are looking for a particular performance parameter you will need to get the timing closer - less than 1 degree. To do this you take the typical variation of key way locations in the camshaft pinions and juggle pinions until you find one that will give you the exact timing you require.
Because you will be doing a lot of juggling of cam timing, when I am setting up a racer I use a 7/8” reamer and open up the pinion’s hole .001” which allows it to be slipped on the camshaft. This allows me to set the crank and camshafts into position and slide the pinion onto the cam. With a stack of pinions at hand I keep offering them until I get one to slide onto the cam at just the right point.
When I use the timing tool, I first offer the inner part of the puller that screws on to the camshaft nut’s threads onto the camshaft. I then confirm that the o.d. of the puller will allow the cam gear to slide over it. If it binds I reduce the diameter of the tool until the pinion slides over the shaft easily.
To start the timing process I randomly place the center “idler” gear on its shaft. Then I locate the crankshaft at the desired 35° and rotate the camshaft (clockwise) until I have .020” lift. Then slide the pinion over the tool looking through the pinion’s key way slot to visually align the camshaft key with the slot. Then using the tool I press the pinion onto the camshaft.
During this process of installing the pinions I will have inadvertently moved the crankshaft. Rotate the crankshaft until the cam lifts the tappet .020” and the pointer should be pointing to 35° BTDC on the degree wheel. If it is off by more than 2 1/2 degrees I start over. I continue until I get the desired results.
When I think I have the opening figure set correctly I slowly rotate to motor, hrough max. cam lift, until the lifter is once again showing .020” lift (only a few degrees away from closing the valve). I look at the figure on the degree wheel and it should the same as the closing figure on your timing sheet. Which will be for our example 68° After Bottom Dead Center (ABDC).
NOW WE HAVE TO DO THE EXHAUST
Timing the exhaust camshaft is the same as the intake except YOU MUST be sure the cams are timed to each other: When the inlet camshaft you just timed is opening when the exhaust cam you are timing is just closing (these are the overlap figures often given on cam timing cards). When you first start doing this it is easy to get confused and have the exhaust camshaft timed 360° degrees out of time or one full rotation of the motor.
You want one cylinder to be in its overlap period when the other when it is at the top of the compression period. With Triumph’s individual intake and exhaust cams it is possible to get their timing crossed.
Now I do not have any pictures handy and am running out time before I have to get absorbed with grand children, chicken wings and burgers. Time also doesn’t give me time to edit this properly so if you see a glaring mistake please comment.
There are two other ways to time cams. One used on all of Triumph’s racing camshaft’s and and listed on some Megacycle timing cards. LIFT AT TDC and lobe centers.
Lift at TDC and lobe centers also use a degree wheel and dial indicators and are preferred by some tuners. Especially when the real HP timing figures for what you are doing are found. Then it is simply a matter of duplicating lift or lobe center readings to dial the power back in.
Because the “area under the lobe center” can vary because of uneven opening and closing ramps a slightly modified method of setting up the camshaft is used. It requires rotating the cam to lower the tappet to a fixed figure on each side of max. lift and noting degree readings. Lobe center timing is half way between the two readings. Lobe centers should not be confused with cam centerline figures.
While most camshafts have symetrical opening and closing ramps the lobe center and cam centerline figures will be the same. If the opening and closing ramps of the cam's lobe aren't symetrical, the lobe center and cam centerline figures will be different... but that is only for those who are interested in such things. John
Morn'n Prof John, You never fail to impress me with the way that you are able to put these complex issues into words that can be easily understood!!! One would think that you had done a bit of cam timing in your day. Dick
I was hoping no one would see this until I got a chance to edit it a bit... Used a laptop and a word program that kept moving the cursor back and inserting what I was typing in the middle of previous text. i spent a minute with it last night trying to clean it up and will re-post it, with some corrections.
What a great explantion John, you are truly generous with your knowledge I am in the process of learning how to time valves with the first method you have verified what I have worked out so far thanks I owe you a few beers oneday.