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View Full Version : TR4/4A Cam Timing with Head Still On HELP!



jeep937
12-10-2015, 12:39 PM
I've been building motors for about 10 years. Mostly chevy stuff with a few model A Fords in there. I'm a bit gun shy in this situation because the 1965 TR4 ran stellar. I only pulled the motor to fix the oil leak and replace the clutch. I left the head on and pistons in. Had to pull the crank because of a broken dog bolt in the snout. It's all going back together now only I can't see to understand the marks and set up for putting the timing gears and chain all back in sync. It sees to say put the motor at top dead center (cotter key down) and the dot on the can gear at 11 o'clock. Well there's two dots. One on the gear and one on the front of the cam. They are in the same area but not real real close to each other. Maybe one at 11 and the other at 10:30.

My question is when I put the crank at TDC and the cam at around 11 o'clock, it seems that there would be a few teeth where it would all fit but could still be off by a couple. These motors have a large dwell cycle so the piston is at TDC for a good amount of time and where exactly does the **** cam need to be? Just before opening of the intake valve? I should have just drawn a sharpie line when I took the gears off. I really don't want to take the head off and degree the cam. Is that the only way?

Darrell_Walker
12-10-2015, 12:56 PM
You should be able to degree the cam with the head in place. Use one of those spark plug hole piston stops to get the precise TDC for the pistons, use a lifter and pushrod to find the lift on the cam.

CJD
12-10-2015, 02:06 PM
Use a straight edge laid over the centers of the crank and cam. There is only one position the cam dot will line up with the crank dot AND the straight edge. If there are multiple dots on the crank sprocket, then set top dead center on the crank and one dot will stand out as correct.

sp53
12-10-2015, 05:29 PM
What John said, I am curious how are you going to seal the rear main after pulling the crank? do you have the engine out and flipped over?

titanic
12-10-2015, 06:52 PM
There is a procedure in the WSM for checking/setting the valve timing that can be used for fitting unmarked sprockets with the head on.
1. Set valve clearance on #7&8 valves to .040", using rule of 9-set #7 valve with #2 fully open and set #8 with #1 fully open.
2. Turn the cam until the clearances on #7&8 valves are equal. One valve will be closing, the other opening.
3. Turn the crank until pistons #1&4 are at TDC. Install the chain&sprocket, taking care not to move the cam. You may have to try different holes in the sprocket or turning it front to back. It is better to have the valve timing slightly advanced 2-3 deg.as chain/sprocket wear will retard it.
Berry

bobhustead
12-10-2015, 08:11 PM
I just replaced the crank sprocket, cam sprocket and chain on mine. On your already marked parts, the crank sprocket has a chisel mark and the cam sprocket has a chisel mark on its perimeter, These two marks and the crtank and cam centers are the alignmen t reference points. They probable wont line up as four points on a line, but the straightest alignment is the one you are looking for. Not possible to get it wrong using the closest possible line approach in that a one tooth error will be a glaring number of degrees and obviously out. The punch mark on the cam needs to be visible thru the open hole in the cam sprocket so as not to get the cam 180 out.
Bob

glemon
12-10-2015, 11:20 PM
If you don't trust the timing marks, or they just seem wrong there are many methods for degreeing on the cam on the web. Some made more sense to me or seemed easier to follow than others. I picked out the one that made sense to me and then also had another guy I knew with some experience double check the work before I buttoned it back up.

KVH
12-11-2015, 02:26 AM
See my pic below. I just did all this. Unless someone replaced your sprockets, each will have a line struck in the metal. The one on the crank sprocket is hard to see because it's on one of the teeth. When those are lined up, you're in the correct place. As Berry says, the cam lobes for valves 7 and 8 must be in balance. You can't see the cam with the head on, so you have to watch the valves, and when one starts to close and other starts to open, simultaneously, that's the point of balance and when you're at TDC "on the compression" stroke. Those marks should line up, and if not, maybe the punch holes will approximate what you see in my pic. You'll note that I marked the tiny punch hole in white. Note also the alignment of the other holes. Again, you can barely see the sprocket score marks.https://www.britishcarforum.com/bcf/attachment.php?attachmentid=40282&stc=1

jeep937
12-12-2015, 02:28 AM
Thanks guys. I replaced the rear scroll seal. The dog fan bolt was also broken in the crank so I had to take it out anyway. Also everything was leaking. I just went over and threw a bottom end kit at it. Bearings looked good. Found the marks on the timing gears and put it all back.