[Supras] Head Gasket Choice For N/A

[Sean Cavanaugh]

Wow. I'm still trying to get my car to keep running below 500 RPM and yer passing traffic sub 300 :-p
 
I've always liked the low end power the supra naturally has that most modern cars dont. even my friends RX-7s, from an idle start they would have almost no starting power whereas the supra would be almost at speed. i wonder how much of a difference changing the timing of the cam would effect with a supercharger on the engine (little future pet project for mine if i can get it running again......turbo + clutched supercharged 7M-GTE).



> Date: Fri, 2 Mar 2007 12:27:49 -0500> From: wellner.christian at navy.mil> To: supraman88 at verizon.net; supras at supras.com> Subject: Re: [Supras] Head Gasket Choice For N/A> > > Its fairly common knowledge that advancing a cam (intake and> exhaust on one cam) increases bottom end power. So, for my automatic, I> tried advancing only the intake cam and it worked great. It isn't world> beater power, but very noticeable. I can keep up with (or get ahead of)> traffic and never go above 300RPM.> Hope this makes more sense. If not, please let me know what's> confusing (where to start).> > Skip> > -----Original Message-----> From: supraman88 [mailto:supraman88 at verizon.net] > Sent: Friday, March 02, 2007 12:04> To: Christian, Skip; supras at supras.com> Subject: Re: [Supras] Head Gasket Choice For N/A> > 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 12 degrees, then from '75-'77 the exhaust> was> advanced 12 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...> > > > > _______________________________________________> Supras mailing list> Supras at supras.com> http://supras.com/mailman/listinfo/supras_supras.com> > > > > > _______________________________________________> Supras mailing list> Supras at supras.com> http://supras.com/mailman/listinfo/supras_supras.com
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