[Brian5475E]

Do you think it is posible to have our factory cam gears machined to be adjustable, has anyone lookied into this. I checked the search and didn't see anything. If someone could get this done,maybe we could do a group thing.

 

[Supra Bob]

Umm.. I really think that would entail ALOT of work.. and cost would be similar of buying the 2JZ cam gears and having those machined to fit... tho thats only a guess... I could be very wrong.

 

[RaptorRacing]

This isn't really answering your questions...but the Jun cam gears are basically stock cam gears made into adjustables.

 

[SilverMk2]

Cheaper to just buy the JZ ones and have them machined. You can buy them fairly cheap used.

 

[dogstar]

i thought 7mgte cam gears were avaliable and fit well, if thats the case, why not use them?

 

[RaptorRacing]

The 7m cam gears won't fit the 5/6m...but the 2j ones will. Plenty of selection for those:

Fidanza
HKS
Unorthodox Racing
AEM
Jun

 

[dogstar]

ah, thanks, i knew thered be some silly reason :?

 

[SilverMk2]

The 7m cam gears won't fit the 5/6m...but the 2j ones will. Plenty of selection for those:

Fidanza
HKS
Unorthodox Racing
AEM
Jun

They don't fit directly. You need to bore out the ID another mm to fit. I had to do this on my HKS cam gears. You could even machine the 7M gears to fit. You also need to convert the early 5Ms to the later round tooth belt to use the cam gears. Stupid thing on Toyotas part is that the 5M/6M, 7M, & 1JZ/2JZ cam pulleys all have the same outer belt pulley part. Just each one has a different bore diameter. Kinda stupid on their part to redesign it for each engine.

 

[RaptorRacing]

I know...that was mentioned earlier...so i didn't see the need in repeating it.

 

[Dave A.]

What about drilling out the dowel pin hole in the stock cam sprockets and inserting a eccentric bushing to advance or retard the cams. I used to do this on small and big block chevy V8's with roller timing chain sets to dial in a camshaft that was slightly out of spec.. The eccentric bushings came in a kit that included bushings with various different offsets to allow you to dial in a set amount of advance or retard by simply swapping the bushing. I think the kit was made by Mr. Gasket at the time. Ahh, here you go, "Infinitely Adjustable Timing", Summit Racing catalog item #s CLO-9-3100A and CLO-9-3110A. Cloyes Hex-A- Just timing system. This works on the very same principal as what I described above but uses an eccentric bushing that has a socket head on top of it for an allen wrench. This wouldn't be quite as easy to tinker with as a set of aftermarket adjustable cam sprockets, but would be a whole lot more secure in that there would be no risk of the sprocket adjustment slipping. 8)

 

[Dave A.]

A whole lot cheaper than aftermarket sprockets! Modify the dowel pin holes to form a U-shaped slot, insert the adjustable bushings, dial in the cams, secure the bushings and sprocket bolts, and away you go.

 

[Dave A.]

Hmmmm....this way you could have adjustable cam sprockets and no one would even know unless they took a close look at the stock sprockets. Dern! Maybe this should've been kept as my own secret mod.! LOL!!!

 

[WadeT]

What about drilling out the dowel pin hole in the stock cam sprockets and inserting a eccentric bushing to advance or retard the cams.8)

Exactly what i was thinking Dave!

The main reason I'd want to switch to after market ACGs is that they are much lighter than stock. Reducing the rotating mass off the head will help in throttle response and slightly higher revs. 5/6m cam gears are very heavy compaired to those on the 7m.

I was about to turn and drill the cam gears (for my 6m and 7ms) in a lathe at work but it looked like too much setup time and too many interrupted cuts.

 

[williamb82]

its been done dave. look at the pics here.

http://www.villagephotos.com/pubbrowse.asp?selected=467869

defiant_7m posted the link on this thread.

http://supraforums.com/forum/showth...d9730&threadid=152922&perpage=25&pagenumber=2

william

 

[Dave A.]

This is just a shot in the dark, but I'm thinking that perhaps the stock 5M, 6M cam sprockets are beefier and heavier since the valves on the 5M and 6M are physically larger with heavier duty springs than the lighter weight 7M valvetrain parts. More turning effort may be needed to rotate the 5M, 6M valvetrain than on the 7M and thus the need for stronger sprockets. The weight of the sprockets themselves is going to have less effect on rotational torque required to spin the valvetrain than the load placed on the crankshaft by the heavier valve springs on the 5M and 6M. The heavier sprockets could actually be to an advantage in that the rotational inertia will be greater with heavier sprockets, which in turn can serve as a damper to help reduce pulsations and harmonics that are present in the rotating valvetrain. Less overall stress would be placed on the timing belt, the timing belt drive sprocket on the crank, and the cam sprockets themselves due to the inherent dampening effect of the heavier stock sprockets. Maybe someone could check and see how much rotational force is needed to rotate the valvetrain on the 5M, 6M, and 7M engines? All you need to do is use a torque wrench on one of the cam bolts with the timing belt removed and see how much torque it takes to compress the the valve springs on each engine.


Dave A. (preparing to put on my flamesuit) :burn:

 

[Emohawk]

"...rotational torque..."

All torque is rotational.
(HA! I flamed you good! LOL! (j/k))

What's this about 2JZ cam gears? Aren't those VVT-i componets? Or am I thinking of something else?

 

[RaptorRacing]

You are right...to a certain point...vvti was on the later 2j's for the is300 and mk4. The earlier 2j's came didn't have vvti and cam gears fit on the 5/6m with little work.

 

[WadeT]

Heavy cam gears might help in rotational torque or inertia while cruising at a steady speed but these engines need power in the higher rpm range. With exception of the crank pulley/harmonic balancer it is always good to emiminate unsprung weight and rotational mass.

I think the MK2 cam gears are crude and heavy as a by-product of economics or production costs rather than by design.

 

[AJ]

This was from the Mk2 list for machining Cam gears

Redline Crank & Cam in Albany, Oregon
541-967-4187