[Supras] Was: Head Gasket Choice For N/A Now: cam timing

[Christian, Skip]

Jim,

	I thought they were trading off emissions & economy.  But, my
gas mileage only went down about .5-1 mpg.  Emissions went up seven
times but was still only about 1/5th of the allowable test limits.  I do
not know how much gain there will be with a CAT installed.  Before you
change the cam timing, be sure to check your valve clearances.  I
couldn't set eight with my intakes set at .004 - expect there was too
much duration.

Skip

-----Original Message-----
From: Jim Wooden [mailto:jwooden at carolina.rr.com] 
Sent: Friday, March 02, 2007 18:28
To: Christian, Skip; Supras at supras.com
Subject: RE: [Supras] Was: Head Gasket Choice For N/A Now: cam timing 

Skip:

Skip:

Thanks, it's ok, I'm an engineer too  ;-)

I remember the "5th Cycle" Isky racing cams they were pushing in the
'70s

So you ended up with 8 advance on intake and "stock"  (zero) on exh.  ?

I have Manual tranny NA I will probably play with this at next timing
belt change.

I thought I had the data somewhere on how many degrees of adv/retard
moving the pin in the std. gears gives but can't find it now.

If +4  and -4  gives better power everywhere I wonder what the Toyota
engineers were trading-off to get in exchange for the narrower powerband
of the "stock" overlap?

Jim



At 11:18 AM 3/2/2007, Christian, Skip wrote:
>Jim,
>
>         I have adjustable sprockets.  Alfa Romeo used the same engine 
>w/ same cams from 1972 until 1995. All Alfa cam specs are common 
>knowledge (no silly secrets).  As emissions rules got tighter, '72-'74 
>cars had intake cam retarded 14 degrees, then from '75-'77 the exhaust 
>was advanced 14 degrees.  Cat was added in '78 and cam timing was 
>restored to pre-emissions settings.  However, exhaust restriction kept 
>power down.  In the Alfas, when overlap was reduced, bottom end power 
>went down.  Longer durations disappeared in 1969 - possible as a result

>of the mechanical fuel injection.
>         So, for the Supra, I started by advancing the intake cam 2 
>degrees and retarding the exhaust 2 degrees.  Drove & check power &
>response.   Bottom line is if cams are set at intake advanced 4 degrees
>and exhaust retarded 4 degrees whole power band is improved.  Since my 
>car is an automatic, I set all eight in the intake to produce the best 
>bottom end power.  Only problem is power now runs out at around 5200 
>RPM and the blasted automatic cannot be re-programmed to shift when I 
>want it to under full throttle :-)  Anyway, (when the car was running) 
>if the throttle is punched (about 1/4 throttle) at 2000-2500  RPM, the 
>nose comes up.  Just what an N/A automatic needed.  FYI - I tried 6 
>retarded for the exhaust and 2 advanced for the intake and the engine 
>power was still increasing when it hit the 6500 RPM redline.  The magic

>number seems to be eight degrees (if the valve clearances are within 
>spec).  If I went higher than eight, power dropped off due to a flow
restriction.
>For all this, car had no CAT, HKS sport exhaust, K&N open filter, and
3"
>intake pipe (in place of the plastic noise canceller).
>         Car always got 20-22 MPG before adjustments.  After, its
20-21.
>Not much change.  Also, easily passed emissions (with CAT installed :-)
>         If you but the adjustable sprockets, try to find the ones with

>the degree markings (if the government still allows them).  Finally, if

>I remember correctly, each tooth slot on the cam sprockets corresponds 
>to eight cam degrees (but please check this first).  All the above is 
>in CAM degrees.
>         I tried to keep this short, but, sorry, I'm an engineer.......
>
>Have Fun, Skip
>
>
>-----Original Message-----
>From: Jim Wooden [mailto:Jim at WoodenU.com]
>Sent: Friday, March 02, 2007 10:52
>To: Supras at supras.com; Christian, Skip
>Subject: Re: [Supras] Head Gasket Choice For N/A
>
>Skip:
>
>If you have a second, tell me about that increased overlap on the cam?
>;-)
>Did you use custom gears on the cams or move the dowel pins?
>
>I have MkIII 86.5 NA and am due for a new timing belt soon....
>
>Along with the increase in performance, did you notice any dramatic 
>decline in gas mileage?
>
>Thanks,
>Jim
>Original owner 86.5 MkIII NA
>
>
>
>
> >Bob,
> >
> >         Thanks. I've done the head gasket once already.  Stuck on a 
> >stock gasket, torqued to 54/58 (?) ft-lbs (from TSRM).  Lasted two 
> >weeks & I started hearing the tell tale bubbles in the heater.  I 
> >figured the engine was trash, so I got out the torque wrench and 
> >torqued all of them to 85 ft-lbs.  FYI - Block deck is trashed from 
> >acid damage.  After the
> >85 ft-lbs, as long as the car was COMPLETELY warmed up before 
> >touching the accelerator pedal, the car used NO coolant no matter how

> >hard it was driven.  But, touch the gas before and gurgling from the
heater.
> >Gasket would seal with head expansion at 85 ft-lbs !
> >         Unfortunately, I used a "Gates" timing belt....... Because I

> >was in a hurry...  It shredded itself at 82K miles and I ended up 
> >with bent valves.  Intakes were set at .0004 because dealer had no 
> >shims and
>
> >cam timing was changed to increase overlap (big power difference - 
> >more
>
> >than all the aftermarket parts combined & still passed emissions).
> >         So, here I am.  Planning to buy a "rebuilt head" & install.
> >Maybe, I just don't learn :-)
> >
> >Thanks, Skip
> >
> >P.S.  Wonder if those 85 ft-lbs stock bolts are going to come off.  
> >My
> >'88 had one of the Allen heads crack...