dapiper

I think they cooked my 626 Turbo head to over 500F.

I have a spare set of shims, but still worried about hardness temper of head. Another machine shop "straightened" a head for my old '88 Mazda 626 Turbo which was warped 0.022 after my wife ran it out of coolant. They overheated it or something and the head went dead soft.....would not hold torque....the head bolt washers would sink 0.030" in the head and the bolts would go from 55 to 10 ft-lb and blow the gasket. Had the head tested and it went from Rockwell C60 to B45. Finally had to visit bone yard for another head.

Just determined my P90 destined for stroker build is humped 0.010" (concave up) and machinist wants to heat to 300F and clamp to straighten to avoid removal of 0.010" off both cam and block surfaces. I am doubtful it will straighten and worried about loosing temper and loosening seats. Anyone have experience with this?

Mfrs my abbreviation for manufacture's. Older Arias were even worse with recommended clearance of 0.007". Slap city and shorter ring life. Never had an Arias fail, although evidence of moderate detonation.....frosties (erosion pitting) on head land opposite plug. They had less ring land bellmouthing wear than other brands also.......not cheap at $150 a pop and somewhat heavy, since I spec'd thicker dome, around 3/8" and 1/4" head land.

Thats tight at 0.004" clearance for an Arias forging. I run the 7000 series alloy Arias forgings popular 10 years ago at 0.0055 minimum and at that time they recommended 0.006", since the later forgings can be run tighter. Depends on the application, more clearancefor turbo, high boost. Go by mfrs recommendation, since they know their alloys thermal expansivity. OBTW, recently inquired Arias during my rebuild as to clearance and they refused to say, unless I had invoice number they could not trace exact alloy used. You need to mic them on the skirts just below the pins. They may be 0.030 over forgings for a 3.416 bore which would explain Arias response. They should measure 0.006 less or 3.410" approx.

Forgot to mention, my oil press is 50 psig at 3K RPM with 10W40 synthetic.

Never liked the comp oil pump springs, since they increase press too much; made for large brg clearances and resitrictive oil cooler. I use stock springs on turbo pump.

Once an EFI engine is fuel mapped, any change of intake (larger) that adds mass will affect the charge air temp (heat soak) causing it to run lean. Retarding cam will make run rich, since engine will pull less air.

Check fuses and that 2.3K resistor inline with tach sig.

Bad plug.

Will try to sked dyno next week sson as weather breaks. Now have to retune since running lean due to greater volume air. Yeah, checked all that and amazingly enough it all matched cam card and was reproducible. Lash is 0.006"I/0.008"E cold at valve. Tell thumper to take a chill pill b4 show time or "yer fired"

Flash news. Just degreed my old Racer Brown turbo grind and wow, what a difference. Was installed retarded 7 deg. Used dial indicator and degree wheel. Need cam timing map. Hardest part is fab of base for mag mount; used thermostat housing mtg bolts as pedestal. Installed at 0 deg adv/ret (straight up) according to cam card. AZ adj sprocket read 3 deg adv side, although actually retarded 3 deg. Cam grinder probably wanted customer to install with 3 deg adv built in for low end torque and higher vacuum. OBTW, be advised, my AZ sprocket reversed the adv/ret directions. Adv is to left of center 0 deg mark index line on sprocket. To adv cam, rotate cam CW relative to crank, i.e. in direction of engine rotation, which moves index line on sprocket to left of center on inscribed scale on aluminum hub. Each inscribed line is 2 deg at crank with 5 lines each side of 0, hence can adv/ret up to 10 deg. Performance improvement was amazing. Pulls much better; less lag during acceleration. Grabs revs very quickly now and no traction. More RPM and vacuum at idle.

Great! What's your boost vs RPM? I get 7 psi at 3K with a lug in 5th with this H3 TO4B with 0.69 A/R on 3" exh. No stroker. 0.63 A/R may be too tight for high boost though; may want to measure turbine back press.

You guys must be running kerosene with that little timing. Power fell off above 0.6°/psi retard (27° total at 15 psig) under my stated build specs. Note difference in fuel, cams, quench, head, CR, charge and head temp as well as how you hold your jaw have big influence on your results. Are your pistons dished and how much? What is your piston clearance to head? Spark plug heat range? Can't compare to Supra, since 4 valve and head design requires less advance which allows less time for detonation to develop. Too retarded is hard on exh valves and turbo. OBTW, max power on old analog ECU was 435 RWHP at 21 psi boost on my Dynojet.

Use the 944 turbo valve; has positive seal rubber seat. I have spare somewhere if your strapped.

I ran 18° initial and 36° total on L28 N42 with Arias at 8:1 and MSD 6T and dizzy. Retard 0.5°/psi boost, hence 29.5° total at 15 psig with Sunoco 94 octane and 11:1 AFR. Turbo is Turbonetics H3 with 7 psi at 3K RPM heavily loaded in 5th gear using 0.79 A/R and 3" exh. Cam is 0.475" lift at 110° lobe ctrs and 238°I/248°E duration @ 0.025" Beyond 13-15 psi, use 5 gal TurboBlue in full tank and 0.35°/psi boost retard up to 18 psi. Beyond 15-17 psi, use C110 octane up to 23 psi boost and 0.35°/psi boost. Now using DIS and sequential EFI with 17° initial and 34° total and 0.5°/psi retard. AFR is 11.8:1. Measured inaudible knock using MSD knock alert into data ack (0-5V) at crossover which persists in higher gears. Soon to tune ign on Dyno. Cam timing may be off. Will advise results. Others?

Application is N42 block with P90 head, sorry for confusion.

Looking for 240Z rods, but considering aftermarket forgings, like Pfaudler. What is best trade off on rod length and still have enough room for stout ring pack on the N42 block? Shooting for 8.5:1 CR turbo at 23 psi boost.

Contact Design Products who fabs the NISMO comp pan. He made one for me for $300, excluding cad plating and sent him pan as core. OBTW, anyone solve problem with flimsy stamped flanges on stock pans. They dimple out at the mtg bolts, then prone to leakage. Use the flange spacers to help distribute the bolt load. Don't over torque.

We got 185 RWHP on DynoJet for a stroker with mild cam, headers, 3" exh and triple webers.

A weak oil pump will also cause low oil press, especially if subjected to debris or coolant from blown head gasket or cracked head. My L28 N42 produces 50 psig at 3k RPM with Amsoil 10W40 full synthetic and oil cooler.

Piston dome coatings will not stop detonation and the coating will be worn away by the erosion of repeated detonation. Save your money.