Settings Tappets... Rule Of 9

[altezzaclub]

Ok, I set the tappets once I'd fitted the cam/SUs/extractors to Toyota's 10 & 12 thou, using my usual method of getting a cylinder to TDC firing and setting both valves.

 

Later I was reading Crow's paperwork and they said 16thou, so I opened them up. However they were noisy at that, so I've just closed them back down to 10 & 12 at TDC.

 

However, while doing that I noticed that the valve on another cyl had a larger gap than I had set it to. A quick think & I realised that at TDC neither lobe is right on its heel, so TDC settings are not at the largest gap you can get.

 

So.... if we set each valve individually using the rule of 9, would we be setting that gap on the actual cam heel, ie- at the maximum gap possible?? Perhaps Crows mean 16thou right on the heel.

 

It probably doesn't matter with stock cams, but I assume when they are cut the cheek changes shape and tappet gaps move very quickly with a few degrees crank rotation.

 

Who uses the rule of 9??

[greenmac80]

i've never heard of the rule of 9.. but jst say you have number 1 rocking you adjust number 4 and so on..

[altezzaclub]

Rule of nine is that when a valve is fully down, the tappet to set is the valve that adds up to 9.

 

So number three right down, set number 6..

 

number 5 right down, set number 4..

 

I think its because the nose of the cam goes over fully open so quickly you can easily pick that point, while the TDC point of inlet and exhaust crossing is a bit vague, but maybe its for exactly the reason here, that tappets set on TDC are a different gap to tappets on the cam heel.

[Mick E]

if its a ke series motor check a manual , you can withone valve downyou adjust four tappets, one full turn you adjust the other four .

[altezzaclub]

Gregorys manual says do them by TDC method....

 

but I've always figured Gregorys was just for starting fires on a cold night!

[Felix]

The rule of 9 is pretty much how I do it.

 

If the exhaust valve on cyl 4 (valve 8) is fully open, then you know for sure that the exhaust valve on cyl 1 (valve 1) will be in the middle of the base circle of the cam, and nowhere near the opening ramps.

 

Tighter valve clearances give you more cam, looser less cam.

[Evan G]

when got my cam back it said 16thou hot intake and exhaust.

 

do that or go a little bit tighter?

[altezzaclub]

Did you set yours to 16thou Evan?

 

Which method? TDC or rule 9??

 

..and were they noisy?

[Evan G]

Did you set yours to 16thou Evan?

 

Which method? TDC or rule 9??

 

..and were they noisy?

 

the note said "16thou HOT" so i set it at that cold, will adjust them again when i wear in the cam

 

how i did it was. turn engine over till a cylinder was at tdc (firing) then set it, turn it over do the next etc etc

 

i prefer doing 24valve straight 6 valve adjustments on trucks at work

[altezzaclub]

OK, so they will be smaller than the 16thou hot, as the pushrods lengthen as they heat up and the gap shrinks.

 

Take a measure of the gaps hot and post up what inlet/exhausts are. It will be intertesting to see how much it changes.

[Evan G]

OK, so they will be smaller than the 16thou hot, as the pushrods lengthen as they heat up and the gap shrinks.

 

Take a measure of the gaps hot and post up what inlet/exhausts are. It will be intertesting to see how much it changes.

 

will do!

[altezzaclub]

Just to add a bit more here- I ran them at 13thou using the rule of nine for a few months, but one was always a bit noisy and annoying. I couldn't find it and its a piss-off motor to check tappets on.

 

So a few weeks back I set them to 8thou hot using the usual 1-3-4-2 system and setting the cylinders one at a time. Nice and quiet, car ran fine.

 

Then I added the electronic dizzy and performance died. I chased the vac advance and got an advance curve that didn't show much vac advance, so when I borrowed a vac meter I checked and found low manifold vacuum.

 

Chasing more vacuum, I set out to adjust the tappets, but did a compression test first.

 

8thou tappets gave cranking compressions of 145-150psi and manifold vac of 10 to 12 inches of mercury.

 

Tappets were reset to Crow Cams recommended 16thou, and compressions went up to 170psi with vac up to (or down to..!) 14 to 15"Hg. They rattle like shit of course, well one or two do, and that is with re-faced followers. The extra bit of vac doesn't help the vac advance to any noticeable degree, but I saw that the Pintara pulls 18".

 

So.... tappet gaps on hot cams have a place to play with compressions, AND vac signal strength as well as altering cam timing..

 

Now I can get back to my search for a better advance curve with new weights and springs!

[love ke70]

this intrigues me.

 

is there a way to do this rule of 9 on a straight 6? 12 valve diseasal.

and a 24 valve 1g?

 

and you also reminded me i need to look into my vacuum i have no vac advance whatsoever at the moment

 

might do the rule of 9 on the 3tc this weekend maybe... see how different they are

[altezzaclub]

It would be good if you did love, just to make sure that there is a difference and I'm not barking up the wrong tree.

 

As for other motors, there is a rule of 13 for 6cyl motors, so I suppose every motor has a code. The multi-vavles that have valves moving in pairs would be just like a two-valve obviously.

[67Rolla-Ken]

I saw a squirrel, and it went like this :P:

 

 

Thank you for reminding me how little I actually know about mechanics.