Changing just the CAM pulleys / installing adj cam gears

[gslender]

Hi,

Just bought a set of adjustable camshaft pulleys and intend on installing them but don't need to replace the timing belt as it has been done fairly recently... so looking for any tips on the easiest/safest method to replace the intake and exhaust pulley only.

Any tips or process that someone has followed that you'd recommend?

G

[NitroDann]

This is the easiest way for a beginner.

Remove intake crossover pipe

Remove leads

Remove cam cover

Remove top belt cover

Use a spanner and hammer to crack cam gear bolts -Dont skip do this NOW-

Take your 19mm socket and rotate the crank clockwise and time the engine up -NOW-

Use whiteout, draw a clear line across the belt and cam gear once on each camgear, draw it straight across where a cambelt tooth goes into a cam gear valley.

Take your new cam gears and hold them against your old ones. Make sure you align the exhaust camgear with exhaust camgear, dont mix them up, they are different.
Hold them in the same timed up orientation as the ones on the engine.
Mark the exact same valley on the camgears.

Use zipties to firmly hold the belt to the intake camgear, tie only where they touch each other, do not add extra tension.

Remove the exhaust cam gear bolt.

Gently wriggle the cam gear free holding vertical tension so the belt stays taught and stays locked into the cam gear.

Carefully slide the new camgear in as you slide the old one out, lining up your whiteout mark.

HOLD TENSION NONSTOP. This will keep the crank and intake gear timed up.

Fit that camgear back. If the cam has turned have a shifter ready, under the cam cover the cams have a hexagon cast into them so you can turn them with a shifter.

Tighen cam bolt finger tight.

Repeat for intake, EDIT: if your a noob, ziptie the exhaust cambelt on now.

Tighten cam bolts with hammer and spanner.

Turn engine clockwise twice with 19mm crank bolt.

If its timed right (and it bloody should be!) reassemble.

Dann

[noobee]

I just changed cams without changeing anything else a few weeks ago(I only wanted to change one thing at a time).I used a couple of small steel wedges from work first to press belt back onto tensioner pulleys (tight but not crushing tight) so it would not move on crank pulley.actually ended up doing it 3 times due to new inlet cam needing a little bit of fixup machining.had to put stock inlet cam back in for a while so I could keep driving.I did have photos on my phone for a little writeup,but have since lost my phone.I am actually doing pulleys and belt myself ,starting later after lunch.I took wedges back to work but my be able to dodgy something up later and get a photo to show you what I mean.
Mick
I see Dann has done some decent instructions while I am (slowly) writing this.I used cable ties to hold pulley to belt and also marker paint just in case.the wedges were so I didnt have to keep tension on pulleys.It took me about an hour each cam each time and several cups of tea.

[NitroDann]

Off topic, Mick hows the car go?

10% extra on stock ecu?

Lumpy idle? When can I come for a lap?

Dann

[gslender]

I used a couple of small steel wedges from work first to press belt back onto tensioner pulleys (tight but not crushing tight) so it would not move on crank pulley.

That's a good trick - I think I follow with what you mean. You are suggesting to apply lateral force on the idler/tensioner pulleys so that the belt cannot move and fall off the lower crank pulley?! is that correct?

If you have a photo, yeah that would be great.

G

[noobee]

sorry,have not got any real photos,they were all on my lost phone.here's a dodgy simulation using big stanley screwdriver,not sure if you would get these in with covers still on.the wedges I used were spare parts for one of our small lathes at work so I had to take em back!(unusual for me,lol.but I want that lathe fixed) they were almost the same width as belt and just right length to fit in without taking covers off.I cold hook them back out easily because they had small 6mm adjuster bolts in back end.

IMG0061.jpg

other side wedged on spring tensioner tongue(not a good photo,sorry)

IMG0071.jpg

Mick

[noobee]

Off topic, Mick hows the car go?

10% extra on stock ecu?

Lumpy idle? When can I come for a lap?

Dann

car went better even with just exhaust cam changed.idle is a little lumpy with both,not much.
you'll get to drive it in a couple of weeks when I bring you these.(7 weeks to rego,and hole in muffler not getting any quieter)

IMG0101.jpg

I know it looks like a random assortment of mufflers etc (cause it is)but only $142 so far!
currently car looks like this.Putting those adjustable pulleys on and new belts/waterpump/seals.
got this far this afternoon

IMG0091.jpg

note aircon delete and added redness!
havent bought new crank bolt yet,and need a new cas o ring too.order these from Bradstreet?
If I have it together by next sunday arvo will get to sugarloaf.
Mick

[gslender]

I dialed in some 2 deg retard on my intake and 2 deg advance on the exhaust and got 14psi boost out of my SC M45 with a 15% reduction pulley. That is nearly 3psi up from where I started and it only cost me $300 in adj cam gears. Idles fine, and behaviour is essentially the same - except now it kicks a lot harder than before and I kinda feel it wants to rev more than before... hard to say, as with the extra boost, perhaps that is what I'm feeling... anyway, easy upgrade and worth doing for anyone who has FI their car with std cams.

[NitroDann]

Edit: Ive had a couple beers so maybe im not thinking straight.

What you have done would have made a peakier power band... Dam, I cant think... But you should try to get a lower guage reading not higher.

Dann

[gslender]

Edit: Ive had a couple beers so maybe im not thinking straight.

What you have done would have made a peakier power band... Dam, I cant think... But you should try to get a lower guage reading not higher.

Dann

I've removed the overlap which would naturally be present in the standard 1.6 cam profiles and timing. The overlap would be allowing boost pressure to escape out of the exhaust side and reduce the overall intake compression volume (and fuel). This approach is commonly done and most turbo cams have less overlap and I've just done the same thing. The increase in boost is an indicator that the charger pressure is being maximised and before it would be similar to having a small boost leak due to a bad silicone fitting etc.

Obviously exhaust and combustion chamber headflow is still the same and I've done little (if anything) to improve that.

G

[gslender]

Obviously exhaust and combustion chamber headflow is still the same and I've done little (if anything) to improve that.

G

Actually, to be technically correct, by advancing the exhaust cam, I've increased the exhaust valve temperature slightly as it now opens sooner and earlier meaning the combustion process is slightly hotter and leaving earlier... so long term the life of the valves might be reduced. 2 deg is not much, but reducing overlap by 4 deg without impacting either exhaust or intake timing too much is certainly the goal. Better would be to buy a new cam, but at nearly $1000 for a new grind and potentially new cam lifter buckets I felt this was the easiest way (and besides I'd still want adj cam gears if I put in a new profile cam).

G

[NitroDann]

PM wozzah about cam prices.

As in the other thread, turbo cams just have less overlap for the same torque band, its not that less overlap is better for power, its just what is needed for an identical torque curve shape, as dictated by physics.

Dann

[gslender]

Dann,

I've made my point about why I think it does improve things. You and wozza both give no explanation as to why it doesn't, suffice saying check it on a dyno.

Boosted air is lost on overlap. That is a fact. Every manufacture does it when releasing a turbo version of their engine. That is a fact.

I'm keen to have you clearly explain why no change to overlap doesn't result in lost air and fuel and overall a negative effect compared to what I've done which reduces this loss.

G

[gslender]

Actually my point is that if you take our mx5 engines and turbo or sc them, you really should reduce overlap. The existing cam profiles were designed to suit high revving naturally aspirated engines that need and benefit from scavenging that overlap provides. When you change to forced induction, my view (and this seems to be what manufactures and cam shops do too) is dial in less overlap.

I agree there are lots of reasons why you should look at cams on a dyno, but the simplest and logical reason to simply reduce overlap is #1 that less is now needed, and #2 there is a chance cylinder filling pressure is lost along with fuel.

I've done this and can report two clear side effects. More boost pressure and more backside HP.

I agree a dyno would be more definitive with results, but alas I've yet to pickup my SuperCheap dyno kit!

I'd encourage folks to give it a try. 2 deg on adj cam wheels is easy to quickly dial in, go for a drive and judge for yourself.

G

[NitroDann]

Boost is ONLY a measure of restriction.

If we agree on that then you should understand why seeing more on the gauge doesn't help.

Ok, so we agree that bigger duration moves torque to a higher higher rpm, and bigger overlap concentrates that power up high, and bigger lift increases torque across the whole range.

If boosted cars really worked how you are thinking then EVERY SINGLE ONE would have absolutely zero overlap.

Your way of thinking about this assumes that the engine opens the exhaust valve and magically 100.00% of the exhaust leaves the engine, and the cylinder just instantly fills with an atmosphere plus some boost.
It doesnt work like that, its much more dynamic.
A good set of extractors pulls a vacuum on the exhaust valve, and the intake stroke pulls a vacuum, and the atmosphere on the other side of the intake valve has atmospheric pressure or higher. Its the total pressure differential that makes the air move from one place to the other. All boost does is increases the pressure differential, and makes the process happen faster, and more efficiently (ie: it increases VE).

See what im saying?

The engine ALREADY gets 14psi of atmospheric pressure, all 5psi of boost does is increase it to 19psi.

So you havnt added anything amazing that wasnt already there, just changed a factor of pressure differential.

THEREFORE principals dont change whatsoever, but increased VE does mean the cams will work better at higher RPM, just like a port job (which increases VE) increases power up top, and if you want to counter that change in TORQUE CURVE SHAPE, reducing overlap is the easiest way to do it.

Cam manufacturers lower overlap on turbo cams ONLY because they have a few grinds of cams, lets say a stage 1, 2 and 3 (for the record I hate this term). They have a torque curve and drivability in mind, and on a turbo car if you are trying to get a 'stage 2' worth of late 'laggy' powerband with that cammy kick, but NOT a stage 3 worth of super high end snap on out of nowhere power, you would need to reduce overlap on the stage 2 turbo cam.

In the same way as this manufacturers know what will sell, and the cams in an engine are designed to suit the chassis, just as big commodores are built to have mid range grunt, and NA6's dont make power till 4500rpm, because those are the attributes that suit the car, and the potential customer, so to keep these attributes in a turbo model, guess what?

Reduced overlap.

Dann