Adjusting adjustable cam gears.. 130-95?

[Celica RA45]

joel your problem with your engine is .
you have changed the inlet length ,on the std motor it had longer runners ,more torque down low versus short inlet no torque to higher in the rev range
also you made up a exhaust its most likely longer or shorter from the factory specs ,
thats why most engines should be left as they are ,because most poeple drive with in a certain rev range about 1000rpm to 4000 max ,so toyota make their torque around the lower part to say around 5000rpm
yours starts at 5000 and and most likely goes to 7500 ,
short inlet it moves torque higher up in the rev range
the sierras in the 80s were the same power starts from 4500 up to 7500 in the rev range
the bathurst cars made 50hp up to 4500 and after that 5000 made 550 hp and my mate that raced there said they were a hand full mainly in the wet ,but a big push in the back

[TurboRA28]

Howdy.. I got around to checking the cam timing tonight. Wow talk about being a long way out!

The inlet cam is around 130 deg on the crank when the valve is fully open. The exhaust cam is around 95 deg on the crank when valve is fully open.

So I assume when people say like get cams to 110 - 110. Youd say mine are 130 - 95?

This might account for it making no power until 6000rpm or so?

Cheers
Joel

[StuC]

wow, this is probably one of the most helpful posts ive read on these forums. keep the info coming

[Starfire]

When playing with cam timing you really can't overstate the value of dyno runs.

Do a baseline run. Adjust. Do a power run. Compare. Repeat.

It will cost more to do it that way, but it will give you very well defined results that can be repeated. Rather than "it feels faster" you will know that you get 10hp more at this rev range and lose 2 at that one.

Another point worth mentioning is that if the engine is standard leave the cam timing pretty much where it is. Toyota spent a lot of time and money working out the best timing for the engine. You may get some gains changing it if you want it to suit your particular driving style or want a little more power at the expense of economy and so forth.

New cams from a half decent manufacturer should come with suggested timings. Start from there and then fine tune them.

Don't forget that the ignition system in most twin cam engines runs off of the cams. Changing the cam timing with also alter your ignition timing. You will need to reset that every time in order for any results to be meaningful.

[TurboRA28]

Hey mate, yeah I do plan to do some back to back dyno runs with different cam timing.

Just thought i'd try to get it set as close to factory as I can, then adjust it on the dyno from there. I like it know what its at, before changing it even more.

Plus the engine while has factory cams, has had the head shaved, head line bored, etc, so cam timing will have changed due to that.

With the ignition timing, the autronic does run off a cam angle sensor type arrangement. I'll reset the timing on the autronic after each cam timing change.

But i'm quite sure 130 - 95 is not factory. It would be great to know what the factory timing is, and i'll set it around there.. Most people suggest 110 - 110?

Cheers
Joel

[TurboRA28]

Hey all, I just wanted to confirm i've actually done this right. I used Bill Sherwood's method which was really simple.

So what do I mean by 110-110 and 100-100?
Again, quite simple to do - With the engine at Top Dead Centre (TDC) #1 or #4 cylinder, and what you are looking for is to have the inlet cam lobes for #1 cylinder just starting to open, ie, the cam lobes on #1 cylinder must be pointing towards each other. If you wind the crank over 110° in the forwards direction, then the inlet valves should be fully open. This is checked by means of a dial vernier gauge, which can accurately and repeatably measure valve lifts to less than 0.001".
To check the exhaust timing, simply wind the engine backwards from TDC #1 by 110° (or 100° as the case may be)
If you haven't done cam timing like this before it may seem a tad difficult, but it only takes a few tools, a bit of patience, and some time. Note that it must be done as accurately as possible, because a 'degree or two here or there' just isn't good enough!

But then i've read on a MR2 forum another method, which sounds way more confusing.

This is how I degree my cams
1. Use a pencil, paper and arithmetic for this procedure, to keep track of the results.
2. Fashion a rigid pointer from stiff wire or an old coat hanger and attach it to the engine block. This pointer locates the degrees on the degree wheel.
3. With a degree wheel installed on the crankshaft, rotate the crank to get the no 1- piston at TDC and check to ensure that the valves are fully closed then adjust the pointer to zero (0º TDC) on the degree wheel.
4. Turn the crankshaft opposite the running rotation approximately 15-20 degrees. Install a piston stop on the top of the engine block fastened in place by two head bolts.
5. Continue to turn the engine in the same direction until the piston comes back up and just touches the piston stop. Make a note of the exact number on the degree wheel that the pointer is on.
6. Rotate the engine in the other direction (running rotation) until the piston comes back up and touches the piston stop. Again note the number where the pointer is.
7. Remove the piston stop and rotate the crankshaft to the midpoint of the two marks. At this point the piston is at the true top dead center. Loosen the degree wheel and adjust it so it will read 0º TDC at the pointer. Don't rotate the crankshaft to do this!
8. Now, it's time to locate the lobe centerline relative to TDC. Attach a dial indicator on the top of the engine block. Set the tip to contact the top of the no 1-cylinder inlet valve shim/bucket. Check to make sure that the indicator plunger is parallel to the valve stem. NOTE - any variance in an angle will produce geometric errors in the lift readings.
9. Rotate the engine in the normal direction of rotation until a reading on the dial gauge of 0.040” lift is reached. (Valve will start to open) Mark the dial gauge and make a note of the reading on the degree wheel.
10. Continue to turn the engine in the normal direction past maximum lift. The valve will now return to its close position. Make a note of the degree wheel reading when the indicator reads 0.040" on the return side
11. Now add the larger of the two readings that you noted on the degree wheel to 180 subtract the smaller number and then divide the answer by two. Your answer will indicate the lobe center of the cam. Example: open reading was 4 and close reading was 43. Now add 43 to 180 = 223, subtract 4 =219 divide by 2 = 109.5. Lobe center is 109.5 degrees.
12. Continue to move the cam on the adjustable cam gear and redo steps 10 to 12 until the required lobe center is achieved.
13. Now do the same for the exhaust cam

I much prefer Bills method. Is there anyone who's done this and can comment on each method?

Thanks
Joel

[Joshstix]

I haven't tried bills method but I have a couple of issues with it.

1. Turning the engine backwards then measuring the timing doesn't sit well with me because the timing belt will be getting pulled against the tensioner and not necessarily turn the cams the same amount as the crank
2. The cams are at or very close to maximum lift for quite some time making it extremely difficult to look at the dial guaege and say yep that's maximum lift

I used a method that assumes the cam lobe is symmetrical for the 40 degrees or so around maximum lift.

1. Find TDC
2. Adjust the degree wheel to be 0 degrees
3. Turn the engine over to 20 degrees before where you want maximum lift
4. measure actual lift
5. turn the engine over to 20 degrees past where you want maximum lift
6. measure actual lift
7. The two measured lift numbers should be the same if maximum lift is at the required location. If the lift on the first measurement is more than the second the cam is advanced and vice versa
8. Adjust the cam in the direction indicated by the difference in lift in the previous tests
9. Once you have the lift 20 degrees before and 20 degrees after the required maximum lift point the same you have the lobe centre set right, this can be tested by measuring closer to the required maximum lift location

Yeah it takes a while but it works really well and doesn't need heaps of maths, which is handy at 3AM when you're trying to get that engine running for the event the next day

[TurboRA28]

Hey Josh, thanks for that info mate. When you say the cam lobe is symmetrical for the 40 degrees or so, are you meaning on the tip of the lobe that is pushing the valve down, or on the back of the raised lobe section?

Sorry probably dumb question.

I was using the dial indicator on the buckets, and had a hell of a time trying to get it down in there and keeping it anywhere close to a right angle against the bucket. Maybe my dial gauge is just the wrong style.

[Celica RA45]

joel do you have notches in your cams like the 2tg have .also machining head and lineboring the head wont really change much at all

[TurboRA28]

Howdy, yeah I do actually. They are not lining up either, both the cams on the notches seem to be retarded.

Almost, but not quite a whole tooth out. If I moved both gears 1 tooth, the notches would be slightly advanced I suspect (haven't actually tried).

[Celica RA45]

what you will have to do is set up the exhaust 1st until you get the exhaust back to where its got to be in the std posi then you go to the inlet ,ps you might have to do this a few times till you get this right the verniers will help but they only have about 8%any way
pss the tensioner will have to be in the vice a few times and this is all done at TDC

[Joshstix]

Yep I am talking about the nose of the cam being symmetrical for the 40 degrees of highest lift.

The trick with the dial guage is to externd the probe. Generally the probe is hollow and capped offf, if you remove the cap you can insert a thin rod in the probe to make it longer and a lot easier to get it perpendicular to the bucket. Apparently TIG welding rod is good to use for this.

The other thing is that the absolute lift numbers are not important in the method I describe above, they are just a comparative measurement between befoer and after the lobe centre. This means the need for the guage to be perpendicular to the bucket is not as important.

[TurboRA28]

I'm thinking I might first get the cams as close to those notches as I can. Then try this method of measuring them.

Do you reckon this will help bring down where it's making max power in the rev range?

[Celica RA45]

if you can get it close to the std posi maybe ,but you have changed the inlet track and that will change when torque and hp come in the rev range

[Joshstix]

what you will have to do is set up the exhaust 1st until you get the exhaust back to where its got to be in the std posi then you go to the inlet ,ps you might have to do this a few times till you get this right the verniers will help but they only have about 8%any way
pss the tensioner will have to be in the vice a few times and this is all done at TDC

This is one of the reasons why I bought the lovely vernier gears made by Enginelogics



They have 20 degrees of adjustment in each direction. Luckily when I slapped it together I was a bit more accurate than that and only have about 4-6 degrees of adjustment made with the gears.