Rather than resurrect my original thread, that started about Twin Carb needles and devolved into general engine problems... Seems more appropriate to start a new thread to continue the saga.
So, I spoke to the original engine builder (from 20 years ago) and as soon as I described my problems (low compression, lack of power, mis fire etc....) he immediately said "Sounds like your Cam timing is out by a tooth"! Shocking.
I mean I have gone through everything but the cam timing. Now that I have a dial indicator and base, a big ass wrench to get the crank bolt off.. I now have the timing chain exposed... good times.
So, I have educated myself on cam timing and how to dial it in... printed a degree wheel and low and behold... this is what I found.
VP7 cam spec sheet says that ATDC #1 inlet (max lift) should be about 103 to 104... mine reads 129!!
Lobe centre should be 106... mine times in at a whopping 127!! And yes, I measured this several times... :-[
At TDC the dots on the gears are nowhere close...
So, I guess the next step is to set it up again... and see how I can reset the timing. The Saga Continues...
BTW... how much movement (side to side) can I expect in the timing chain (no tensioner version)?? Seems like there might be too much slack...
Great find! Good luck getting it sorted.
I like how the engine build expert knew right away what the problem likely was. Learned that lesson by experience no doubt.
Is this a pre A motor? A+ have a chain tensioner, early cars don't. Make sure you haven't sheared a key.
There will be some slack, but if there's enough to skip a tooth something is really worn out. Check for excessive wear on the cam and crank gears.
I always start setting the cam timing by aligning the marks on the gears, then use the dial indicator to set it where the cam mfr wants it to be. I use offset keys to set it when not using a vernier adjustable cam gear.
Another way is to get the cam in general starting position is to set the lobes on cyl 4 in rock, where moving the crank back and forth slightly will open and close both valves.
Remember, the #1 intake pushrod is the second one, the first is the exhaust .
Also, once you have the crank set at TDC using the dial indicator, recheck it with the dial indicator - don't just go off your pointer - after you've measured the valve gear settings before checking the cam position again.
Definitely not an A+ (its 1979/80).
I think the chain might still be good, but I will replace anyway and see if there is a big difference. As for the teeth on the gears, they are in mint shape, so I don't think they skipped at all... I think it was just a bad install when they put it together most recently.
On the plus side... I'm hoping to save some $ by doing this myself, and getting more comfortable. I have another 998 that I may tackle as a rebuild project...
More to follow!
So it's been changed since the original build? Who did that?
You can't go wrong lining up the marks first and then seeing what it measures out to......
See if you can get an Iwis chain, they're supposed to be the best.
So crazy this thread shows up. Had a long conversation with Dave about this. Question is was the motor out of the car and was the head on?
You can do it with the head on, just set your dial indicator on the top of the screw on the rocker arm.....
Quote from: MiniDave on December 15, 2020, 06:33:18 PM
So it's been changed since the original build? Who did that?
You can't go wrong lining up the marks first and then seeing what it measures out to......
See if you can get an Iwis chain, they're supposed to be the best.
I guess I should have been more clear. The timing chain and gears were not changed when the engine was "put back together" most recently. At the time we figured that it had low miles overall but sitting so long it needed new seals etc... I think they just re-installed the timing gears and chain incorrectly. The motor was completely out and the body was restored. I think the chain is ok... but cheap enough to simply replace it now on spec.
Right now the motor is in the car with the head etc off while I mess with the timing.
OK, so it's just a matter of putting it back together correctly and you'll be good to go. 77.gif
Quote from: MiniDave on December 16, 2020, 03:40:56 PM
OK, so it's just a matter of putting it back together correctly and you'll be good to go. 77.gif
Thats the dream...
Just curious, I'm not fluent im cam timimg or installation but i beleive it's a factor in setting valvees. My qyuestionn of the experts here is why wasn't the cam clocking apparent when the valves were set?
If you use the "rule of 9" method to set the valves, then no it wouldn't be apparent.
Yeah rule of 9 wouldn't expose it but TDC should.
So, I have messed with the timing set up a bunch and now have it reset to time in at about 109 instead of the 106 that the VP7 needs... I need a 3 degree woodruff key...
Looking at the crank end from the front of the engine... which direction (left or right) would the key sit?
You want to retard the timing, so the offset goes to the right as you're facing the front end of the engine. So, when the points align the cam won't have moved quite as far, retarding it.
Ok... WTF.
I ordered a 3 degree offset woodruff key to time in my cam. I presumed... it goes on the crankshaft?? but the key that came out of the crank is huge compared. See pic.
Does this go on the cam as the offset to bring the timing back in?
If not... what the hell did I get?!
8.gif 9.gif
EDIT: Sorry... the pic is very large... not sure why...
The offset key goes on the camshaft....
:-[
huh... kinda feel dumb now....
Ok, so like you said before, its around 110 now, so add the key with the off set toward the right (looking from the front) and simply adjust the cam so the gear slides on remaining dot to dot (ish).... stop me if i'm wrong here...
Cheers...
yes. then recheck it.....start over from the beginning
Got it! Thanks...
Any tricks to getting the old key out of the cam?? Or is it a matter of brute force and ignorance?
I use a pair of side cutters (dikes) grab it on one end and lever it up
alright... not sure why, but now that I have everything set up... the best I can do with the 3 degree woodruff key is to get the timing in at 109... I thought that I was at 109 already, but now that I have tried again with the new timing chain, the best I can do is 109... and I checked and rechecked. clearly I needed a 6 degree key.
The VP7 cam says it wants 106. My timing is still retarded by three degrees.
Question is, if I leave it here... what are the issues? Calver article says that slightly retarded ends up losing down low, but gain peak, but then suggests that Minis like to be advanced slightly (maybe on the other side of 106?)
Welcome thoughts on the above...
Also wondering if I simply tried the old chain again... Its in great shape... can't imagine that would be an issue...
If you're at 109, you're advanced, not retarded.....106 is retarded from 109 or 110 if I understood what you wrote. (it's possible I didn't my brain is a bit foggy these days) was 110 with the standard straight woodruff key in the cam drive?
Just for the experience of it, turn the woodruff key around and recheck it....it should in theory go to 112 or 113, that will confirm you had it in correctly. Don't skip a step, set it at TDC with the dial indicator on the piston, then set your degree wheel to TDC, then measure the valve lift.
You're measuring the intake valve at it's most wide open point at so many degrees after After TDC.....you don't want it open too soon or too late.
Thanks Dave.
However, what you say seems to contradict the following from Calvers website;
ADVANCED cam timing means that the valve events are occurring BEFORE the recommended point. Your measurement will therefore compute a reading LESS than 106. Generally this increases bottom and mid range outputs, but losses a little peak output. To correct this the cam will need turning counter-clockwise (anti-clockwise).
RETARDED cam timing means valve events are occurring AFTER the recommended point. Hence measurements and computations will give a value MORE than 106. Generally this increases peak outputs, but will lose bottom and some mid range output. To correct this the cam will need turning clockwise.
If 109 is advanced, I think that might actually be ok... other places I've read, including calver, suggests being slightly advanced at the cam helps...
Thoughts?
OK, semantics at play here......I never run them over 106 as it kills the bottom end and I like the torque, since I'm rarely running consistently about 5K.
Depends a lot on what you're after.......
Oh man... totally got myself confused... At 109 i'm still 3 degrees retarded... So i'll need to acquire a 6 degree offset key to get this down to 106. Damn... cause that 3 degree key was expensive and 30 days from the UK! 50.gif
If I remember right, a six degree key is kind of risky. It is so thin on the offset portion that it can, and does, break. Somebody correct me if I am wrong. If you need six degrees of offset you might have to buy a vernier sprocket. Ask some knowledgeable pros if they used a six degree offset key successfully or if they recommend going to a vernier adjustment system. Alternatively, you can use a 3 degree key and just accept being 3 degrees off.
Having looked at the 3 degree key... being a very slight off set... I can't imagine that the offset for a further 3 would be that big. Given the width of the key I suspect it should work. That being said, I've never used one. A 9 degree key would be something else...
Great thought though...
I don't think it's heavily stressed at the key anyway, while the key locates the cam it's the nut that's torqued on the front of the gear that holds it in place.
I believe MiniSpares has up to 10* offset keys.
Did you turn the key around and retest?
Offset keys are available from Mania or 7 Ent......I think in their demo video they use a 5* offset to get theirs into time, I would not hesitate to use a 6, just torque the nut down correctly when you're done and tap over the lock tab. If you don't want to cross the border because of cost, Steveston in BC might have them
Yup... tried the other way... went to 112. Like Magic!
Ordered one from Hunter Classic Sports Cars in Victoria BC... Cheapest within Canada...
I'll let you all know how it goes!
Good, I'm glad it gave the right result, more experience is always valuable.
You'll get it sorted, I'm sure. 77.gif
Maybe I'm over thinking this... or inducing some sort of error.
I started fresh, used a 0deg key and timed it at 112. I am looking for 106.
Now, I use a 6 degree key to advance the timing and now I am at 108. Now I may just be a pilot, but I do know that 112-6=106... 8.gif
I may be inducing some measuring error, but I don't think so... as I am doing things the same each time.
If it is an error, perhaps I'm closer to 106 than I think. Either way, I'm thinking of leaving it as is and see how it runs once back together. AFAIK the engine always had a 0 deg key, so any closer to the ideal should have the car running better anyway whether advanced or retarded by about 2deg.
Thoughts?
Chain stretch/wear retards the timing, I would want to start slightly advanced.
I've had the same issue with keys sometimes you have to get a different key than you think to get the result you want. I know 6 degrees should be 6 but sometimes they don't work out that way manufacturing tolerance of the keys I guess?
I agree with Jeff, and I would go ahead and put it in also.
One other thing you might try is to put it back a tooth on the chain then use your offset key to advance it back and see where you land.
It can be a frustrating process......
If I advanced it by a tooth... then retarded it back, about how many degrees would that tooth distance be?
No idea, that's why I suggested trying it - might work, might not.
I guess you could count the number of teeth on the gear, that should tell you how many degrees each is.
According to google its 13degrees. So if going advanced to 99 then retarding by 6 should get me to 105... maybe 104 depending on if the key is off a bit... Gonna try it... have nothing to lose!!
Cheers.
There you go!
Let us know what happens...... 77.gif
Well... I advanced by a tooth... and retarded it by a 6 degree key... now I get about 101 in the end...
5 degrees advanced seems too much to me...
Thoughts?
You have me very confused - if you're at 101 you're retarded, not advanced.
When you had it at 108 you were advanced, and both Jeff and I thought that after wearing in a bit you'd probably be right where you want to be. Or get one more offset key 2* more than you have and get it to 106.
Remember, as you face the water pump end of the engine, the crank rotates clockwise.
I'd have stayed at 108 and been 2 degrees advanced, anticipated chain stretch, and set my all in timing at 30 degrees and called it a day.
Ok... now I'm super confused. Everywhere else I read they are saying that a number larger than your target is retarded from the ideal, and a number less is advanced of the target. So advanced would mean that the valve opening is happening earlier (in advance) of the ideal. Looking at the UK Mini forums they are all setting something like 104 when they are targeting 106.
The following quote is from Calvers website where he talks about timing...
"ADVANCED cam timing means that the valve events are occurring BEFORE the recommended point. Your measurement will therefore compute a reading LESS than 106. Generally this increases bottom and mid range outputs, but losses a little peak output. To correct this the cam will need turning counter-clockwise (anti-clockwise).
RETARDED cam timing means valve events are occurring AFTER the recommended point. Hence measurements and computations will give a value MORE than 106. Generally this increases peak outputs, but will lose bottom and some mid range output. To correct this the cam will need turning clockwise."
https://www.calverst.com/technical-info/cam-timing-introduction/
I'm still learning all this, so would love to continue hearing your thoughts...
Lol, I have all winter!! 77.gif
Good thing I don't build engines cause I assumed 108 was 2 degrees advanced.
I see his point, like I said before it's all semantics....set it at 108 with what you have or get another offset key and get it to 106.
My point of view is that the 106* is how many degrees past TDC the valve is fully opened - so I want it fully open by 106*, call it what you want! ;D
You are opening it later and holding it open later in the cycle - so I do see your point.
I think pretty much all the engine builders agree that 104-106 is the sweet spot for a street motor.
Thanks MiniDave... appreciate it... I'm back on the same page.
However I just saw on theminiforum in the UK that the cam sprocket is 18 degrees per tooth (makes sense). 112-18=94+6=100 (which is exactly where I am... damn).
Anyone know where I can get one of those crank sprockets with the 2 degree increments? and not be part of a whole set?
Gonna start over from scratch... again... but we'll get there.... I might just accept the 108 and see how it drives in the spring if it comes to that...
Thanks all!
crank sprockets with 2* increments? did you mean a 2* crank key?
since you bought a 6* offset key and it didn't get you where you wanted to be, I don't know whether it's better to buy another 6 or get an 8* and chance winding up at 104? If it were me, I would buy a 6,7 and 8 - that way I'm bound to get there!
Update.
I used the original timing chain this time (only about 3 years use), still in nice shape... Anyway...
0 degree key got 112... 6 degree advance key... bang on 106. 17.gif
Presumably this is due the chain having been already stretched a bit with use as expected?
Well there you go!
Yeppers!
Button it up, run compression again and I'll bet things are where they should be. So, go take it for a drive!
Way too much snow and salt up here for that... but I'll recheck the timing and start putting it all back together for sure..
Can't wait for Spring!
Thanks for all the help
Ok guys... I need a serious sanity check. Now that I have everything locktabbed and torqued, timing cover on... etc...
I seems that when I timed the cam, the distributor was pointing 180 out, away from the #1 point... if that makes sense. So, I rotate the engine and my timing marks line up right and now the dist is pointing in the right direction.
Question is; If timed this thing at the wrong TDC using #1 inlet lobe... Do I still have it timed correctly?
9.gif
Take the valve cover off, rotate it to #1 TDC firing according to the valves, then see where the rotor is pointing. If it's pointing at #1 or #4?
I think I see what your getting at. The head is off. I'll use the pushrods in place and see. I might just be overthinking this.
When I did the cam timing I clearly had #1 inlet open... and can that only happen on the intake stroke right?
Exactly
I wish I was coming to you all with great news... but I'm not. 50.gif
I have put everything back together and simply can't get the car to fire. Not one pop or fart. Allow me to recap a few things.
1. I re-timed the cam to the crank at 106. In doing so naturally I was using the TDC that starts the intake stroke (with #1 inlet opening yadda yadda....)
2. Head back on, valve clearances checked and rechecked, carbs reset and back on.
2a. Cold compression check has 1-4; 130, 135, 135, 130 (big improvement from the 99 psi with the cam way off)
3. I moved the engine to TDC on compression (power stroke). I have confirmed that I am on compression on #1, both intake and exhaust closed, #4 just rocking.
4. At this point I have the Dist rotor aiming directly at #1 lead on the cap, and the dist cam lobe (under the magnetic pick up) is pointing at the module. (BTW its a Accuspark 45D4 type). Further, the dist drive gear (after removing the dist to look) is in the correct alignment per the haynes manual and google etc. (vacuum advance removed and capped at the carb).
5. The coil tests well on a multimeter, the various wires and leads are getting 12V where they should with the ignition on... and I am getting sparks at the main HT lead, and each lead for each cylinder. So I can only assume that when the dist is in the right position for each lead it is doing what it should.
This is where it gets odd. I hooked up a strobe light to #1 to see where it is firing as the engine is cranked over and over. I was expecting to see a flash at TDC markings on the pully wheel... but it doesn't seem to me that this is happening. I get spark, but not at the TDC (or slightly before) like the engine is set up??
If the crank, camshaft, and dist are all showing me a correct installation what the hell have I missed? Obviously fuel is the only other part to this equation, but as far as I can tell its getting gas (inside of the carb jet is wet) and I confirmed that the pump works...
Is there a chance that the dist is going full advance on cranking? and so missing all the leads?
Everything that I have read so far (and all your amazing advice) says that this should run first crank.... but alas... I am stumped again, and the weather up here is finally nice.
9.gif
For reference mark location of distributor and then loosen the distributor hold down and advance and/or retard timing until it fires? Dump a shot of fuel into the carb throat in case carb is not delivering fuel.
Also may try timing light lead on the other three spark plug leads in turn to see if spark is on the wrong cylinder.
Update;
It runs... pulls like a freight train!
I finally got the distributor in the ball park and after much cranking, it finally fired and over some time it began to run better and better (lots of unburned fuel I guess). It seems I was simply overthinking it...
Used the strobe to bring the ignition timing back to about 10 BTDC (it was about 5ATDC initially) and she ran around the block like a maniac!!
Apparently the rotor arm was incorrect, it was a 25D instead of 45D... swapped that, and seems to have been a major issue of mine all along!!
Now to get the twins tuned properly... and on we go...
Happy Easter!! 4.gif 77.gif 62.gif
Excellent news! Glad you got it all sorted - you're now an expert on cam timing! 77.gif
Happy to hear it worked out so well!