TR6 GP3 Camshaft won't turn

[nichola]

I've run into a problem with my engine build.

This is a '73 TR6 with:
head milled .140;
the GP3 camshaft:
valve springs per Goodparts recommendation for that camshaft;
pushrods .140 shorter than the originals;
new lifters;
block bored for cam bearings, which are installed;
new standard ratio rocker arms;
new rocker arm shaft;
Payen head gasket;
head and rocker pedestals torqued per spec.

I am trying to rotate the camshaft so that I can do an initial valve adjustment. Without the rocker arm assembly, I can screw a couple bolts into the end of the cam and use a screwdriver to rotate it. Once the rocker assembly is bolted down, I need an 18 inch lever to rotate the cam, and even then it's darn near impossible. In fact, I bent the bolts screwed into the front of the camshaft when I applied leverage to rotate it.

What the heck is going on? Have I forgotten something? Arrgh.

I did send an email to Goodparts and left a voice message, but maybe someone here can help me out.

 

[bobhustead]

I've never tried to do what you are doing in the way you are trying. You are using a very short lever to try to compress a number of valve springs at once and, with respect to valves that are closing, overcome the friction on the cam faces applied by the springs. You could well be wallowing threads in the cam via the deflection of the bolts. Consider the radius of the flywheel x2 as the length of the lever that usually moves the system from static and the torque of the starter, not your forearms, as what is pressing that lever. In short, I don't think you have a problem except the possible damage to the bolt holes.
Bob

 

[glemon]

Based on your list it sounds like you are following the right steps/know what you are doing, so I apologize for the basic question, but assume you have plenty of assembly/cam lube on the cam lobes and bearings. I agree about the torque factor, I have never done it except through cranking the motor, with the big sprocket and chain attached. That said I wouldn't force anything. I think there is a cam retainer plate on the front of the motor, make sure that isn't too tight. Sounds like you got special springs so shouldn't be any spring bind.

 

[nichola]

Bob, thanks for the response. I was sort of wishful thinking along the same lines. Richard Good responded within a half hour of my message to him, which I appreciated. To give a little more background, my first attempt at installing the GP3 cam was unsuccessful as the cam made it through the first three bearings no problem but then would not go through number 4. So I pulled the cam and installed the old one, which had no problem slipping all the way in. I then took both cams back to the machine shop and they polished the new cam down to the same spec as the old one. That allowed me to push the new cam all the way in by hand, but with a little more resistance getting past number four than the front three bearings.
So, the upshot of my conversation with Richard is that I probably need to waste another head gasket, remove the cam, and use a dial indicator on the bearings to make sure I have three thou or so clearance. Or, I guess I could wing it and just polish down the number 4 and 5 bearing journals on the cam a little more and try again. Richard says he removes the cam without taking the head off, but I guess I'd rather buy another head gasket than risk dropping a lifter into the oil pan and having to redo that.

 

[nichola]

Based on your list it sounds like you are following the right steps/know what you are doing, so I apologize for the basic question, but assume you have plenty of assembly/cam lube on the cam lobes and bearings. I agree about the torque factor, I have never done it except through cranking the motor, with the big sprocket and chain attached. That said I wouldn't force anything. I think there is a cam retainer plate on the front of the motor, make sure that isn't too tight. Sounds like you got special springs so shouldn't be any spring bind.

Everything is nice and lubed up. And the cam end play is at spec. I am following the Leyland shop manual on reassembling the engine. They set initial valve adjustment by rotating the cam before timing gears are attached, then the cam is rotated to proper position with pistons 1 and 6 at TDC, and then timing gears and chain installed. Like I said... arrgh.

 

[TRMark]

Many years ago while doing a few mods to my TR4, I ran into a bad batch of valve springs/improperly matched collars.

 

[nichola]

Many years ago while doing a few mods to my TR4, I ran into a bad batch of valve springs/improperly matched collars.

Everything looks correct on mine, Mark.

 

[nichola]

Defeated the problem with leverage, seems easy now.

 

[nichola]

Final camshaft update... it is installed and timed! BIG tip of the hat to Richard Good at goodparts.com for being so responsive and helpful through the process. Multiple exchanges with him helped assure me that I was on the right track. Timing ended a little advanced from the GP3 spec sheet which called for 6 degrees BTDC at .050 lift. Richard said “In my tests 2-4 degrees advance was all gain.” Mine ended up at 9 degrees BTDC, i.e., 3 degrees advance. The owner of the machine shop that got my block and head ready also said every single engine he builds is advanced at least a couple degrees.