Adjustable CAM Gears, Who uses them, do and donts

IJ.

Grumpy Old Man
Mar 30, 2005
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I come from a land down under
j_magers said:
Good to see a discussion on here that is going to help tune our cars, instead of the damn "which Spark Plugs to buy" threads. I fricking hate them albiet Iam new to the 7M myself, I have worked some engines in my day and dont need help buying spark plugs.
Jay: Ditto!

I'm a bit old school so have had to learn a hell of a lot during the Supra build as I ran it stock for 6 years without an issue!

On my last performance motor I made my own billet steel cams and had a local grinder grind them to my specs and played around with lobe centres, MUCH easier moving an adjustment on a pully than swaping out cams!

Way back in the late 80's I worked on a race team as a fabricator with 2 litre turbo cosworth motors and helped the engine builder dial in the cams (He was from our old team and had been building V8's for years but DOHC was new to him)

We picked up 100hp dropped egts and gained some fuel milage so a good result all round (and won the next race our first 1st place)
 

quicksilver

New Member
Apr 16, 2005
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owensville mo
Maybe someone can varify this. I herd somewhere that you can safely retard the intake came 3 degrees to just take some of the overlap out. I've been running it this way for a while but I don't have any before or after dyno sheets to prove if this helps.
 

bowsercake

New Member
Aug 24, 2005
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Irvine, Ca
There is no best setting, you need to dyno tune your car and see what works, even comparing stock cars to other stock cars you will get differences.

If I were you I'd leave the stock cams alone, they work well enough for most people.

But anyways, i'm going to link a short writeup from the old SOGI list:
http://www.supras.com/pipermail/supras_supras.com/2004-August/005731.html

>Here is a little bit more I have found out, over time, concerning the
>HKS cams that were, at one time, available: Intake: 218 duration @
>0.050"/256 rated duration and 0.3208" lift; Exhaust: 218 duration
>@ 0.050"/256 rated duration and 0.3188" lift. Intake (0.050" point)
>is set 3 deg after TDC; Exhaust (0.050" point) is 9 deg before TDC.
>Thus, valve overlap is very, very minimal.
>
>7M-GTE TurboA cams: 272 (Total Duration), 0.350" (8.9mm) lift.
>Special valve springs (TurboA valve springs) were required to resist
>valve float at high rpm.
>
>Having said this, it is best to place that race cam'd engine on a dyno
>and adjust the cams, fuel, ignition (if you have a stand alone) to
>optimize the engine for the performance you desire (e..g., low end,
>mid-range, high end - since you can't have all three). Basically, this
>is my take for dyno setting longer duration/higher lift cams:
>
>Advance Both Intake and Exhaust Cam: Increases bottom-end
>power, closes the exhaust valve earlier and opens the intake
>sooner to move the entire overlap period earlier where it scavenges
>the cylinder better at low rpm.
>
>Retard Both Intake and Exhaust Cam: Increases top-end while
>decreasing bottom end, moves the overlap period later in the cycle
>where it is more effective for scavenging the cylinders at high rpm.
>
>Advance Intake Only: Increases overlap and starts overlap earlier.
>This helps bottom end and mid-range without greatly effecting top-
>end power. Works best on heads that have not been
>"tuned/ported." This is why I recommend to begin tuning with
>advancement of the intake cam.
>
>Retard Intake Cam Only: This starts overlap later and, therefore,
>reduces overlap. This helps top-end at the expense of lower mid-
>range. Most street engines do not like this, and idle suffers.
>Works well on ported engines and undersquare engines (the stock
>MarkIII Turbo is nearly square - the stock MarkIV is square).
>
>Advance Exhaust Cam Only: Reduces overlap and increases
>blowdown by opening the exhaust valve sooner. This will, most
>likely, shorten the power stroke. Usually helps top-end power at
>expense of lower mid-range. Most street engines do not like this,
>but it will help to smooth idle.
>
>Retard Exhaust Cam Only: Increases overlap and helps bottom
>mid-range. Works best on stock heads with poor flow. Usually,
>liked by engines that have long stroke and short rods; because this
>is not us (MarkIII or MarkIV), we gain little by retarding the exhaust
>cam. This will, most likely, create a lope to the idle. However,
>since retarding the exhaust cam does show gain on most engines,
>this is the next thing to try after advancing the intake cam.
>
>Before getting on the dyno, learn all you can about Duration, Lobe
>Separation, Overlap, Bore-To-Stroke Ratio affects, and Ignition
>Timing.
>
>Bottomline, high-lift, long duration cams have better power at high
>engine speeds but poor idle and poor emissions at low engine rpms.
>Thus, for most, the compromise is somewhere in the middle, based
>on what we have done to the engine. This is why most cam grinders
>off their wares as "mild", "street/track" and "race". Take a look at
>the duration and lift specs for Crower's 2JZ cams at:
>http://www.crower.com/cat/import/toyota/camshafts.shtml

>Arlene Lanman
>88T automatic
 

supradavenz

LOL HIES!
Apr 1, 2006
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AUCKLAND, New Zealand
Nope, and that write up has some good info on it cheers bowsercake, yeah i kinda figured there wouldnt be a "best" i guess some ppl want power in different area's but just towards the stock cams i thought there would be a way of moving the power around a bit to suit as my power peak at the momment is at 5,300rpm but im still getting good low down torque.

Just wanted some info as to what advancement and/or retarding timing does in combinations and thats exactly what you've given me thanks.

I'll try each out and see what my power curve does.
 

bowsercake

New Member
Aug 24, 2005
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Irvine, Ca
I don't think that its explained there but, rotating the cam gears (in DOHC) changes the lobe separation angle. LSA is related to overlap, so, the less LSA you have, the more overlap you are going to have because the lobes are closer together. This will hurt you a little at low rpm but it will help with scavenging at higher rpm, moving your powerband up.