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Triumph Repair/Spitfire MarkII valve timing

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QUESTION: Hello Again Howard

About a week ago you were kind enough to reply to my request for help in setting  cam gear/ chain on my fresh engine. I might add that I am not a pilgrim to mechanical things, but this situation is driving me crazy. I have meticulously followed the given procedure (several times), and always end up with same results "test failed". I am repeatedly doing something wrong and getting the same results. My guess at this point is that I am a tooth off but do not know how to adjust in order to correct. Have you ever considered a house call near Los Angeles?

Thank's
William

William

ANSWER: Hi William,

I sometimes assume some things when I write and sometimes I do it late at night and am half asleep so I will look over what I wrote and see if I can clearify it some.

I am taking for granted that the cylinder head is on the block.

Rotate the crank until you see that #1 and #2 rocker arms are BOTH moving when you rock the crankshaft back and forth. (This is close to TDC (Top Dead Center) of pistons #1 and #4.
Now set the valve clearance of #7 and #8 valve to .050" or you can use .080" but be sure both are accurate. Now rotate the crank so that #7 and #8 are in the rocking position and set the crack pulley so that it indiacates EXACTLY TDC. (It is also best to loosen the bolts on the cam sprocket so they can easily be removed without moving the cam or crank)

I found it best to assemble the front cover on with just two screws and put the front crank pulley on without the big bolt. This enables you to set the crank at EXACTLY TDC (Top Dead Center of #1 and #4 piston. (sometimes the pulley is tight on the crankshaft so it is difficult to get the pulley off without moving the crankshaft but it MUST be done so that the crankshaft is EXACTLY at TDC.
Now remove the cam sprocket and chain being careful NOT to move the crankshaft nor cam shaft. If you loosened the cam sprocket bolts like I said this will be easy to do without moving either the cam nor the crank.

Now, check the valve clearance of #7 and #8 valve being very careful not to move the camshaft. They MUST be exactly the same clearance. If they are not, move the camshaft a very slight bit in each direction until BOTH valves are exactly the same clearance no matter what that clearance is. This positions the camshaft in an exact position to match the TDC of the crankshaft and you must be careful not to move it at all after that. This procedure only applies to a stock cam. A competition cam can not be set this way, they must be set by the racing cam manufacture's procedure.

Note that the cam sprocket has 4 holes but the cam only has two bolt holes. The 4 bolt holes in the sprocket are not square. The reason for this is to give you an option of a half tooth adjustment using one side of the sprocket to get the cam exactly correct.

Slip the chain on the crank sprocket and put the cam sprocket into the chain and slip the cam sprocket up on the cam and look in the bolt holes to see if they line up perfectly. If they are a tooth or two off, move the cam sprocket around in the chain until they line up and then push lightly on the slack middle of the upper strand of the chain to duplicate what the chain tensioner would do if the front cover were on and look into the bolt holes to see if they line up EXACTLY. If they seem to be about half a tooth off. Remove the cam sprocket from the chain and rotate the sprocket ONLY 90 degrees so as to be using the other two bolt holes. And look again remembering to take the slack out of the upper strand of chaine. If it looks like it is now only 1/4 of a tooth off, then remove the cam sprocket again and flip it over so the back side of the sprocket is facing forward and check it again using the same proceedure. This gives you 4 possible settings between one tooth off.

Now, once you can see in the bolt holes that they line up perfectly (with the slack taken out of the chain) you can snug up the cam bolts and put the cover on with just a couple of bolts and snug up the crank bolt but none of them torqued tight yet.

Now to test it, rotate the crank until you have #1 piston at exactly TDC (of the compression stroke both valves closed) and check the valve clearance of #7 and #8 valve of #4 cylinder. If both valve clearances are the same or very close to the same you can remove the front cover and tighen all the bolts to specs and finish assembling.

Let me know it that works better for you. This system of setting is so strange that it often trips up even highly trained domestic car mechanics.

Sorry, no house calls. I am in middle TN, so a house call would cost you the price of another car. ha! Plus my doctor taught me to never do house calls ha!

Let me know,

Howard

---------- FOLLOW-UP ----------

QUESTION: Dear Howard-Please excuse me for not getting back to you sooner. I became so frustrated that I thought it best to take a break from project. The good news is that with your help I finally got timing gear and chain properly installed.The bad news is that while engine sort of runs, it is blowing fuel vapor out of carbs when running. I have never seen an engine do that! All valve adjustments and ignition timing seem to be near perfect. We are getting close! Any Ideas?

Thanks Again,
William

Answer
Hi William,

That sounds like either the cam timing is off or you have leaking intake valve on one or more cyliders.

Neither of these are difficullt to test. First pull the valve cover and the all 4 plugs. Check the valve clearance accurately on #1 cylinder. Put the gear in 4th gear and brake off. Roll the car until you get both valves on number one cylinder in the rocking position. Set the pointer at TDC and note that both valves are slightly open (no valve clearance) Now, slowly roll the car so that one of the push rods just starts to spin free. go down on the pulley and make a mark on the pulley across from the TDC mark. Now roll the car in the opposit direction untill the other push rod just gets free. Now put another mark on the pulley opposit the TDC mark. Now rotate the crank back to TDC and measure the two marks you put of the pulley to see if they are the same distance from the TDC mark on the pulley. I think your pulley had a notch in the rim for it's TDC mark. If your magic marker marks are evenly spaced on each side of the notch in the pulley then the cam timing is corect.  It would have to be far off to cause fuel to spray out the intake. If it is ok then you for sure have a leaking intake valve or a stopped up exhaust pipe.

First test is a compression test (throttle wide open) and at least 5 or 6 revolutions. Should read from 135 PSI to 170 PSI and only a little difference between cylinders. If that is also ok you need to either remove the exhaust pipe and muffler to check for mice nests.

There is a test you can do on the exhaust without removing it. You will need a short piece of steel brake line about an inch and a halve long and a drill bit slightly under the size of the piece of brake line and you wiil need to drill a hole in the exhaust pipe just below the exhaust manifold. Then sharpen the piece of brake line and drive it into the hole you drilled but leave about an inch showing outside. Now get a low pressure gauge like a fuel pressure gauge and slip the hose of the gauge onto the piece of brake line sticking out of the pipe. Have someone start the engine and set the RPM up slowly to about 3000 RPM and hold it there. Watch the gauge and it should never go over 1.5 PSI. (5,6 or 7 PSI) is a 100% clear indication of a stopped up muffler. GM claims their cars can hamdle up to 3 PSI but I tested a lot of British cars, MG, Triumph and Jaguar and none can handle more then 1.5 PSI. When finished remove the piece of brake line and screw in a short screw to seal the hole. You don't need to run it long so you don't have to worry about the hose on the short pipe melting.

let me know.

Howard

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Howard M. Fitzcharles III

Expertise

Triumph TR-4 up & Spitfire, and Engine theory

Experience

Dealership line mechanic on MG, Triumph, Jaguar for 15 years, Instructor in commercial mechanics school 2 yr. Product information manager for piston and valve manufacture, Instructor & hotline answer man for import car parts importer 15 yrs.

Organizations
Associate member SAE EAA member

Publications
Import Car magazine

Education/Credentials
ASE Master Auto with L-1 certification up to 2000

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