Welcome to our Site for MG, Triumph and Austin-Healey Car Information.
Triumph TR6 - timing gear installation
|I've got my '72 TR6 engine block at the machine shop getting the lower end rebuilt. Everything is together except that the shop cannot figure out how to properly install the cam and crank timing chain gears so that they are in time. The new gears don't have any marks on them.|
I told them that they might be able to get the positioning of the cam gear from an imprint of the cam on the back of the old cam gear. This doesn't help for the crank gear though.
There is an involved method contained in my old repair manual which requires setting and measuring valve tappet gaps on the #6 cylinder with the head installed on the block - which mine is not.
Anyone know of any simple approaches to this problem of installing these timing gears correctly?
I think I might be able to help you out..or at least give you an idea. First off the old sprocket gears should have "Dots" (punch marks) on them. The shop manual says that if new gears are installed (no dots) then align them and put dots (punch marks) on them (for future use). Alignment is 2 part: 1: both faces flush with each other as determined by staight edge. If not flush shims are added behind the cams (camshaft sprocket)((I will shorten crankshaft sprocket to cranks..I hate typing)).2: is the dot alignment and herein beith the problem. The manual says in the " timing chain and sprockets removal and refit" operation to do the following:"NOTE: Ensure the cranks and cams are not turned whilst the chain and sprockets are removed". Unfortunately it does not give the answer on...well they have been turned. So my thinking is that it is necessary to go back to what position the 2 cranks should be in. In the manual I go to "cams removal and refit".it takes me back to removal of the 2 sprockets and there makes this point:"Turn engine over until #s 1and6 pistons are at TDC with #1 on the firing stroke,check that the timing marks AandB .......all line-up"..back to square one.So we are at TDC of 1and6. We need to get TRUE TDC of #1.Going back to the rear of the engine and the fly wheel.. There should be a vertical mark on the engine rear adaptor plate. This eventually aligns with a mark on the fly wheel and in theory when alligned you have TRUE TDC #1. For TRUE TDC of #1 I will copy directly from the Manual and hope no one from the grave haunts me saying "hay..that is copyright material"
To obtain true TDC mark ON THE FLYWHEEL, attach dial gauge stand to the cylinder block top face and position a dial guage so that the stylus rests on top of #1 piston. Turn cranks in CW direction until the piston reaches the highest point as indicated by the dial gauge. Scribe a mark on the flywheel opposite the mark on the adaptor plate. Turn the cranks in CCW direction until the piston again reaches its highest point and mark the flywheel again below the mark on the adaptor plate. Scribe a line on the flywheel that bisects these 2lines and you now have TRUE TDCof #1.
At this point the 2 sprockets are "timed" with one another.
Scott I am not an engine mechanic but this sounds logical to me. There is also considerations for the reinstall of the distributor. I hope this helps and if anyone else sees a correction then please do so. Gotta go watch the Indy now. Have fun and let me know if this helps.
P.S. Love your town
|OOPS...Daytona 500...to many beer last night|
|Scott, I have the manual that Rick is using and you can use it. Call me at 888-6887.|
|I'm sorry to admit that I put some feelers out on this topic in several locations and forgot to check back with this one. I got a lengthy response from "Tirebiter" which was good and passed it along to the machine shop. |
I just got my block back this past Saturday. I still have my suspicions about whether or not they set the timing properly so I'll be checking everything again.
Rick, your methodology looks good and I'll check everything out accordingly. I certainly appreciate your feedback and am, again, sorry I forgot to check back on this BBS.
Allen, I tried to send you an e-mail last week to see if you were going to be at the car show this weekend at Delgado and if you'll have your TR6 there? I'm planning on checking it out and was hoping to meet you.
Thanks again for the feedback.
No arguement with the method, Rick, but here's a Mk2 method that does make it easier. It needs a circular protractor, a circle of card or plastic, marked with degrees, that most performance shops sell, or give away.
At TDC, by definition the piston stops and goes the other way. But before it stopd it goes slower and slower, for a given turn fo the crank. Bearing and bore clearances, and the limits of your measurement system mean that it will appear to stop BEFORE the actual TDC. That's why you look for the highest point in both directions. But it is hard to set the 'highest' point, as the piston moves so slowly for a given turn of the crank.
Make up a "stop" for the piston, that will prevent it rising any further up the bore than a definite point. A piece of angle iron, drilled for two head studs and with a central hole for a bolt will do. Position it over the piston, on the studs and fix it there. Self gripping clamps on the studs for instance, or a piece of tube over the stud with the stud nut on top. Fix the protractor on the crankshaft nose with the pulley bolt, and twist a piece of wire to an adjacent stud or bolt on the front face of the block, act as a pointer
Now do the same as you said, Rick, turn the crank one way, but until the piston hits the stop. Note the angle shown by the protractor. Turn the crank right round the other way (don't disturb the stop) and note the angle from that direction. As before, TDC is exactly between the two angles.
Two advantages here. First is that there is no need for a dial gauge, only a cheap protractor ($1?) and some bits from the scrap bin. Second, because you just turn the crank until the piston is stopped, there is no error from the clearances and no finicky adjustments of the crank angle.
The height of the stop is up to you, it doesn't matter, as long as it is exactly the same both ways. But too low down and you are measuring big angles, too high and the piston is moving very slowly. I find that about 1/2" below the block top is about right.
|Hay not my method..just coppying verbatium from the TR6 shop manual. If there is something easier (2002 technology) go for it.|
|You need to do more than just establish TDC, you need to make sure the cam is properly timed. There are some nice instructions on degreeing camshafts on-line from Crane Cams.|
Go toward the bottom of the page and pull up the degreeing a cam instructions in either HTML or PDF format. You will need to know some specification information on your camshaft to do this. If you are running an aftermarket cam it should have come with a cam card giving checking lifts and angles. If you don't have it from an aftermarket source, contact them and get one from them
If running a stock cam, the only information in the Bentley manual is for opening and closing positions, but it is a start if you use it in conjunction with instructions of section 12.65.08 in the Bentley manual. There is no information on the lobe centers, checking lift, total lift etc. What I have found is that the cams for these cars regardless of source typically have lobe centers in the 108 to 110 degree range. The outlyer is the early PI cam at 105. The Haynes manual only shows limited early PI cam information, no US early carb or Late PI/Late Carb (same cam), so no help there.
This thread was discussed between 16/02/2002 and 21/03/2002
Triumph TR6 index
This thread is from the archives. Join the live Triumph TR6 BBS now