[Supras] Head Gasket Choice For N/A

[supraman88]

Now, you want to put this in terms an idiot like me can understand?  ;)

I used to be an Engineering Technician, but that was Electronics!  I can
usually figure out mechanical things, but this dissertation you wrote
did a 747 Syndrome on me!




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...
>>     
>
>
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