[slipperywhen wet]

used both but here's the thing. Got the template off one of the sites and drilled one gear at approx 199.5 and the other at the posted 197.5 because i dont think the origionator of the (197.5) post allowed for the extra duration. I cut back the front of the rocker cover to ease access to the pulleys also, and it looks way nicer too. Anyways, while waiting to get a plastic timing disc, i played around with both pulleys and the one at 199.5 was giving better power delivery. When i got the disc and timed all up correctly , the 199.5 was spot on . When i counted back the required number of teeth and marked the pulley, it aligned perfectly with the "drilled" pulley.
So if your not gonna get adjustable pulleys, just follow the directions in that link and you should be fine.

 

[Mx5rc]

cheers!

 

[Lazza]

This is all interesting stuff!

I'm not actually interested in doing this myself as I have my MP62 but just out of interest... You say that it can't be done on a Mk2.5 due to the VVT, could you explain? The VVT is valve timing only, not lift so surely a cam with more lift but the same or similar duration would still be of benefit? Or is it just that the VVT mechanism can't simply be attached to an exhaust cam?

 

[Mr Slow]

The VVT cam as I understand it is completely incompatable with a 'normal' cam.

 

[Lazza]

The VVT cam as I understand it is completely incompatable with a 'normal' cam.

I guess that must be something to do with how the cam gear is mounted to the cam then. I think the VVT mechanism fits in place of a cam gear (which makes sense as it has to advance/retard the cam timing). I'm sure a good engineer could still find a way though

 

[Mr Slow]

The VVT cam as I understand it is completely incompatable with a 'normal' cam.

I guess that must be something to do with how the cam gear is mounted to the cam then. I think the VVT mechanism fits in place of a cam gear (which makes sense as it has to advance/retard the cam timing). I'm sure a good engineer could still find a way though

[/quote]

Probably be cheaper to get a specific VVT cam to be honest. VVT is the cam gear with a solonoid on top of the camcover to control oil flow to the spool valve.

 

[elduce]

I believe the VVT cam lobes are a different shape to non-VVT cam lobes. IRRC the VVT moves the whole camshaft and the different profile of the lobe across it's width is what gives you the differing valve timing.

Using a non-VVT camshaft in a VVT engine is therefore not possible, not only because it won't fit the VVT mechanism, but also because it isn't designed to be moved by the VVT system.

 

[slipperywhen wet]

To MX5rc....... i have just checked the counting teeth method and verified it with the pulley i drilled accurately at 197.5 degrees.

So, forget all the previous , mount the new shortened exhaust cam in place of the intake cam and put the pulley on with the I lining up with the dowel . Count 19 teeth from the mark(indented)above the I on the pulley clockwise and make a new mark. This is your new mark and lines up perfectly with the drilled one. 199.5 suited my engine better but ill wait to get adjustable pulleys and a dyno session before i know the best timing figures.

 

[HMT]

Please keep us posted - i could really use a hint on a good street timing for the cams

 

[slipperywhen wet]

will do but the classic advance the the inlet 2 degs and retard the exh by 2 always works on twin cams but.....every engine is different . I had a spare engine with 2 spare pulleys so drilled one at 197.5 and one at 199.5 and the latter performs better. The accurate way to do it ( hindsight is great) would be to use a dial gauge to find peak lift on the origional inlet cam (allowing for the dwell at peak lift) and attach a pointer to line up with its I MARK notch and then install the shortened exhaust cam, find the peak lift and mark its pulley.

EDIT EDIT EDIT....
dont know why i put 19 teeth on last post, should read 20..........was mixing up the 19 between marks when doing a timing belt change. IT SHOULD HAVE READ...........

To MX5rc....... i have just checked the counting teeth method and verified it with the pulley i drilled accurately at 197.5 degrees.

So, forget all the previous , mount the new shortened exhaust cam in place of the intake cam and put the pulley on with the I lining up with the dowel . Count 20 teeth from the mark(indented)above the I on the pulley clockwise and make a new mark. This is your new mark and lines up perfectly with the drilled one. 199.5 suited my engine better but ill wait to get adjustable pulleys and a dyno session before i know the best timing figures.

 

[Mx5rc]

Brilliant. Thanks for the followup. I will give this a try as soon as i can get hold of a spare cam and new timing belt kit. So we're looking at 5bhp as a conservative figure, going on what i've read.

 

[slipperywhen wet]

Brilliant. Thanks for the followup. I will give this a try as soon as i can get hold of a spare cam and new timing belt kit. So we're looking at 5bhp as a conservative figure, going on what i've read.

I would say 10 at least. The yanky cams from one of the write ups have less lift than the jdm ones.

 

[elduce]

For anyone wishing to try this on a Mk 2, I have an adjustable cam gear (with timing sensor pegs) plus a 4W exhaust cam sitting in my shed that I would be willing to let go for what they cost me.

I was going to try it on my 10AE, but it turns out my car has the more aggressive 5A "Mazdaspeed" inlet cam as standard.

 

[Freaky Roadster]

Planning on doing this mod on my 1.8 Ltr '95.
What are the Ebay vernier cams like ? Reasonably well machined for the price ?? I think from Avoneers "Head Skim" thread, the bolts are just ally so will need changing.
The only other option I've found are either import some or Kent Cams (about ?220).

From the little info I've gleaned on t'net about n/a tuning and cams, adjusting the degrees on the cams can move the power band and also things like overlap.

 

[PF.]

will do but the classic advance the the inlet 2 degs and retard the exh by 2 always works on twin cams but.....every engine is different . I had a spare engine with 2 spare pulleys so drilled one at 197.5 and one at 199.5 and the latter performs better. The accurate way to do it ( hindsight is great) would be to use a dial gauge to find peak lift on the origional inlet cam (allowing for the dwell at peak lift) and attach a pointer to line up with its I MARK notch and then install the shortened exhaust cam, find the peak lift and mark its pulley.

EDIT EDIT EDIT....
dont know why i put 19 teeth on last post, should read 20..........was mixing up the 19 between marks when doing a timing belt change. IT SHOULD HAVE READ...........

To MX5rc....... i have just checked the counting teeth method and verified it with the pulley i drilled accurately at 197.5 degrees.

So, forget all the previous , mount the new shortened exhaust cam in place of the intake cam and put the pulley on with the I lining up with the dowel . Count 20 teeth from the mark(indented)above the I on the pulley clockwise and make a new mark. This is your new mark and lines up perfectly with the drilled one. 199.5 suited my engine better but ill wait to get adjustable pulleys and a dyno session before i know the best timing figures.

Let me know please if I have understood this the right way:

If I don't want to drill the pulley at 197.5deg, I have to set the timing at 20 teeth clockwise from the I. Am I right?

 

[slipperywhen wet]

yeah, count 20 teeth clockwise and make another mark . This will be your new I mark.

 

[PF.]

And what would be the teeth for 199.5deg like you have? What differences you experience between 197.5 and 199.5 drilling?

It doesn't cause timing issues, right?

 

[slipperywhen wet]

it just seems to work better for me but i just used the 197.5 as a guide. When i checked the timing with a clock gauge, it was retarded and hence the second fitting with new pulley drilled at 199.5 which happens to line up perfectly with the pulley rotated anti clockwise, 20 teeth.

 

[PF.]

I'm very sorry for the dumb question (again), but, you mean setting the new mark at 20 teeth counter clockwise?

So 20 teeth clockwise "=" 197.5 deg pulley drilling, and 20 teeth anti clockwise "=" 199.5 deg drilling?

I've got an mk2, does it make any difference?

 

[elduce]

I'm very sorry for the dumb question (again), but, you mean setting the new mark at 20 teeth counter clockwise?

So 20 teeth clockwise "=" 197.5 deg pulley drilling, and 20 teeth anti clockwise "=" 199.5 deg drilling?

I've got an mk2, does it make any difference?

It makes a huge difference - the Mk 2 has the cam angle sensor picking up the cam angle from the cam pulley. If you slip the belt around 20 teeth on the oem pulley to get you your new cam timing, it will bugger up your CAS readings and I would imagine you'd get at least a Check Engine Light and at worst the ECU won't be able to run the engine.

I have a vernier cam pulley that allows you to maintain the CAS pegs on the pulley in the correct location for the CAS sensor to function properly, regardless of what degree the cam is actually orientated at.

I also have the right exchaust cam to do the Exhintake mod on a Mk 2.

If you're interested, I would be willing to sell them both for ?95 collected or plus delivery.