Check this beauty out! Head Gaskets

[bcn30141]

Well as my story goes ...all was well until quarter way into fourth gear...then all there was is a huge cloud of smoke. I was in the ball park of 28 lbs of boost

[bcn30141]

Tear Down

[bcn30141]

Considering roller can since I've gone this far...

[trashmechlv]

What fuel were you running, 91 and alky for 28lb boost?

[bcn30141]

I was using 93 and alky set on 8....I had a conservative tune by use of my Gen2...kept around 24 degree on timing, had about 785 all the way through third and zero knock except between shifts...it was the first time I really ran it hard into fourth-

[Steve Wood]

You sure did a number on them.  I would never try to run that hard in fourth gear as it puts a heckuva load on the engine and is an invitation to break something.  Running that much timing on top of that much boost just made it more of a bomb waiting to go off.

[bcn30141]

I'm learning something new every time I drive this car it seems Steve....just a a while back I didn't even know what the function of a knock sensor was or even the meaning of those numbers jumping around all over the place on my scanmaster...t he last hot rod I had was a 650hp 2003 supercharged cobra modded out and it had no problem spraying 100 shot of nitrous in 5 th gear at 170 mph. I would think the car could handle a little  fourth gear but it didn't. I am looking for a descent roller kit to match my 2800 stall, 1.94 1.50 ported iron heads, CPT 61 DBB turbo....any suggestions on what lift and duration I can get away with? I can say one thing ...I have learned a lot! Thanks!

[Steve Wood]

I would stick with something in the 206 to 208 deg range at 0.050".  Whatever lift comes with a cam in that range.  It will be close to 0.500"

These cars respond more to boost than the cam-at least on the average street car.  Extending the rpm range a bit with a cam may gain more than that gained from duration or lift because it makes it easier to keep the car in third which accelerates better than fourth.  Even a stock cam with decent valve springs should normally run better in third thru the lights than it will making another shift to fourth.   Obviously one wants to make sure the car is shifting around 5200 or so out of first and second.  Some shift considerably lower and that makes it hard to reach the line in third.

Not only does fourth increase the load building more heat, but, when you combine that with the drag coefficient of a concrete block, it really has to work hard to accelerate past 100 mph.  I suspect a TTA with equivalent drivetrain will et a couple of tenths faster than a Regal just on aerodynamics.

If I were running one hard in fourth gear, I would probably run about 18 degs of timing because boost seems to make more power than timing and reducing the timing keeps combustion chamber temps from flaring as badly.  I am using "boost" in a generic sense when I really mean how many air molecules (density) are crammed into the cylinder.  In any case, I would not be looking for prolonged running in fourth.  These are not top end machines.

Another factor is that it is easy to blow a hg without actual detonation-particularly if one is running stock head bolts.  The head lifts a bit because the bolts stretch and the gasket is not clamped well.  This is more prevalent when running shims because there is no cushion in the gasket to maintain the seal.  It happens with conventional gaskets as well and studs are worth it on a car that is going to be pushed to the limits.

[bcn30141]

I am seriously considering taking out then engine to stud the heads, heck it already has studded rod and main caps, eagle crank in all,...I wonder how those straight six turbo supras handle there crazy boost at high top ends like they do....is it totally bennificial to install an rjc plenum plate or upsize the MAF, everything is under pressure in boost....I can see the benefits with a NA engine or putting on a 4 inch intake kit on a turbo car.  I hope one day I can run with you big boys , hehe

[Steve Wood]

First, there is no need to pull the engine to install studs.  ARP has allen headed studs that can be installed thru the heads.


And the Supra was around 2 liters with very small pistons and low reciprocating weight on the rotating  assembly.   Given the small displacement, they had to be twisted high to get any power.  Put an overhead cam system designed for high rpm on top and they were designed for the task.

The Buick was not designed for high rpm but was modified with extremely heavy pistons for low rpm, turbo'd operation.  Buick created an Indy engine with lower displacement to meet the rules as well as some nascar versions.  These engines used a beefed up assembly/block and were twisted around 8000 rpm with some success.  Billy Anderson built an engine one year that was around 200 cubic inches that screamed at top rpm but it was still large compared to a 120 cubic inch Supra.

Totally apples and oranges

[phil_long]

I hope one day I can run with you!!  That's an experience to be had but you seem to have it under control.  I bet that Cobra was a heckuva lot of fun to drive!!!

[bcn30141]

Steve I applaud you car knowledge .....  I heard it was a pain on the passenger side to set the head in place on studs with the block still in the car....I'm also thinking I could have some gasket material in my pan. Plus I won't get a back ake when I go about torquing the heads down with it on a stand lol hehe....


Phil here are some pics of my Cobra...it pulls very strong...

[bcn30141]

Oh Nevermind Steve ....I see what your saying...put the heads on and run the studs in and tighten down all the nuts....gotcha

[bcn30141]

First, there is no need to pull the engine to install studs.  ARP has allen headed studs that can be installed thru the heads.


And the Supra was around 2 liters with very small pistons and low reciprocating weight on the rotating  assembly.   Given the small displacement, they had to be twisted high to get any power.  Put an overhead cam system designed for high rpm on top and they were designed for the task.

The Buick was not designed for high rpm but was modified with extremely heavy pistons for low rpm, turbo'd operation.  Buick created an Indy engine with lower displacement to meet the rules as well as some nascar versions.  These engines used a beefed up assembly/block and were twisted around 8000 rpm with some success.  Billy Anderson built an engine one year that was around 200 cubic inches that screamed at top rpm but it was still large compared to a 120 cubic inch Supra.

Totally apples and oranges

The Supra I m referring too is the early mid 1990's 3.0 TT that tuners single turbo out, but I suppose they work just the same as your explanation of the other....I think a lot of it has to do with the DHOC....

[Steve Wood]

yes, it is easier to pull the rpm out of a valvetrain that is designed to be stable at high rpm...and if you compare the weight of a a piston/rod from that engine to the weight of one from a buick, it becomes obvious why the assembly stays together at high rpm