Well, its IMO true the head is the limiter.

[turbows6]

I took the car out today and ran it up to ~100 to look for any problems before going to the track. The car was making noticably more power in the cold air. There wasn't any knock, low o2 millivolt was 795 on the recall, and the head lifted.

I had the car towed home because I thought I hurt the motor. I pulled it into the garage and the motor was running clean again, but had a little water in the oil and could hear ticking from compression in the crank case.

I believe it's true. A TTA head will lift before it goes 9's. At least consistently.

 

[rollie]

How much boost were you running?

 

[Jicaju]

Been there done that. Even with the best ARP studs still had same trouble. The heads actually flex. I do think they are capable of 9's but as you stated it will not be consistently or without a lot of additional head gasket replacement. I myself just got tired of changing them.

 

[tta983]

Some call it the weak link, I blew both sides at one time!

 

[turbows6]

Was at 27 or so pounds with a billet 67.

 

[TTA976]

Yes, the only fix is a GN style head.

Joe

 

[bison]

What about changing the combo and build strategy to achieve lower cylinder pressures at TDC? What about reinforcing the head on the intake side? There maybe some sacrifice in drivability but I'm sure at least 100 to 200 hp more could be made with what's there. Getting a good set of rocker arms would be more of a challenge in my opinion


BPE2013@hotmail.com

 

[Nick McCardle]

Suggestions on how to accomplish that goal, bison?

Also, anybody have a suggestion for good rocker arms these days? I know some were made years ago, but not sure if there's any options now...

 

[TTA976]

Steve C. (TTA850) worked with Harland Sharp years ago to complete. I have the 1.6's

Joe

 

[turbows6]

I'd estimate the horsepower level will more or less dictate when the heads lift. Maybe retarding the timing could slightly help, but if the motor loses torque from low timing you have to rev it higher to make the same power. Maybe with a huge camshaft you could turn 7000 and run 9's at 20psi. I don't know...

 

[TTA976]

I'd estimate the horsepower level will more or less dictate when the heads lift. Maybe retarding the timing could slightly help, but if the motor loses torque from low timing you have to rev it higher to make the same power. Maybe with a huge camshaft you could turn 7000 and run 9's at 20psi. I don't know...

The lope overlap creates higher cyclinder pressures.

Exhaust runner being too short is the issue.


Joe

 

[TTA976]

DP is another issue. If we could turn the turbo exhaust side facing the back of the car that would help a lot... Run it straight out without the 90* elbow.

 

[bison]

The DP isn't an issue at all. A good fabricator can easily fab one. More turbine with the correct cam and use nitrous for spool assist. Moving the engjnes peak mass efficiency up the rpm range with a little less mass efficiency will do it. You don't need more boost. You need more rpm. 9's with effective operating range 5800-6300 should be plenty to get 9 sec power with boost in mid to low 20's. Get the converter to flash to 5800 with the correct turbine, CR, cam, cam timing, and a well worked set of heads.


BPE2013@hotmail.com

 

[TTA976]

After 5000 rpm the exhaust runner starts raising its ugly head. Air stacks up in the short exhaust port. If the combustion chambers were bigger it would be okay.


Joe

 

[turbows6]

The exhaust port flows fine, mine flowed 196 cfm on the exhaust. The problem is that the head casting isn't a strong design and the deck flexes. A TTA head is a trapezoid and the GN head is a rectangle. The GN head simply has a lot more material to hold the deck down. Fwiw, im running the biggest hot side I could get and an open 3" downpipe. I don't really think im leaving much on the table regarding exhaust backpressure. The TTA head just won't hack it if you want a reliable 9 sec motor.

 

[TTA976]

Hmmm...thanks. I was unaware it flowed that well.

Bison gave us so great info too.

Little behind on my ability to read posts because of reception right now.

Thanks guys

Joe​

 

[YamikidR1]

Do what I did put on a nice set of TA or champion head and your good. By the way I raced mine last weekend and went 9.6 @ 144.54 on a bad track and shitty air. ya did it on 25-26 lbs forgot my laptop at home and was scared to turn if up as that's the boost I run on the street. It was at beaver spring dragway at Cecil it would have been a 9.3

 

[bison]

The exhaust port flows fine, mine flowed 196 cfm on the exhaust. The problem is that the head casting isn't a strong design and the deck flexes. A TTA head is a trapezoid and the GN head is a rectangle. The GN head simply has a lot more material to hold the deck down. Fwiw, im running the biggest hot side I could get and an open 3" downpipe. I don't really think im leaving much on the table regarding exhaust backpressure. The TTA head just won't hack it if you want a reliable 9 sec motor.

You're not leaving much on the table for backpressure with what you have currently however backpressure isn't the problem. Cylinder pressure is the problem and is the reason you can't get more mass flow through the engine. If the heads flow that much on the exhaust side it will respond like a champ to higher rpm and larger turbines. You need to raise the operating range of the engine while reducing cylinder fill slightly. I was thinking a 75mm turbine in a t4 tang housing minimum. At 6200rpm on a 231ci you should be able to achieve 75lbs/min with boost in the mid 20's even with a reduced CR.


BPE2013@hotmail.com

 

[turbows6]

Are you running aluminum or iron heads? Also, are you running billet caps or a girdle? Im assuming billet center caps and a forged crank will reliable run well down into the 9's

 

[YamikidR1]

Aluminum and a girdle motor. Once the air gets a little better I would love to turn it up and see a low 9