ported irons/GN1 aluminum or go alchohol?

[ijames]

Bobby, so far as I know, the GN1 headed car I was referring to has at least 3 or 5 mph and .3-.5 sec over the other car with alky, both on 93 octane. The nice thing about heads is not having to keep filling that bottle, but it's sure easier to plumb up the alcohol than it is to bolt on heads. Maybe the original poster should do the alcohol now, and then later when he has a better idea of his goals and the rest of the components needed to reach those goals, he can choose a good set of heads.

It's not just cylinder pressure, it's a complex function of pressure, temperature, and the evolution of both as the crank turns that determine hp (lumped together into bmep - brake mean effective pressure).

 

[Razor]

Carl I understand what you are saying, the point was made as a hypothetical. Once you make the power, if the charge air temps are reduced going into the motor, yes you can make way more when intake temps are brought down via more efficient turbo, better heads, and innercooler.

But the cost of heads, cam, and intercooler.. you can pretty much get the same results if not better with alcohol at less than a third of the heads/cam/IC. One may be permanent, the latter easier and more friendly to tune out. And originality if that matters is maintained.

Heads may be a building block, and the post doesnt say what experience level the person has tuning one of thee cars.

I'm biased..I love the stock stuff and how much it can be stretched out.

Julio

 

[talstar]

I would go with the iron heads from champion. I have GN1s on my car now and the valve guides are shot and its using oil. The iron heads don't have any problems. Tom has agreed to fix them when I build another engine. The car runs great with these heads (12.6 with stock turbo, 93 octane, no alky, slicks). The biggest difference is having cool weather and low humidity.

 

[turbosam6]

Originally posted by Razor

Case in point Roy Garcias car went low 10's at over 130 MPH at 21 PSI. See the heads and cam taking action. I bet that car would ping on 93 at 8 PSI.



I'll take that bet. Case in point. My car will make an easy 400 hp on pump gas. I have aluminum heads, ported everything, bigger turbo, fm, etc. Now stock, it took race gas and boost to make 400 hp. Its all about airflow.

Do a search on Geno's username and check out his pump gas numbers.

Basically you're trying to tell me that on the same motor, ported heads vs. stock heads, the ported head motor won't make more power on pump gas? What is the point of ported heads then?

I can tell you personally that my car picked up about 5 or 6 tenths on pump gas when I put the ported irons on.

 

[frankg]

Go with a good set of ported Irons!! Frank

 

[Russ Merritt]

Be a big dawg and get the GN1s.

 

[turbodave231]

Octane requirements are dictated by charge air temps and charge density. Physics comes into play here (Gas law) PV=nRT

where:
P-Pressure
V-Volume
n- number of atoms of gas (air)
R- Gas constant
T-temp


Ported iron or aluminum heads have better flow characteristics and offer less restriction. You effectively lower the pressure needed to move the same volume of air into the combustion chamber (same power level). Lower the pressure=lower the temperature of the intake charge=lower octane requirements ....equation balances.

The same system with a higher boost level (P) will result in more air flow and higher charge temperature (T), Octane requirements will go up and the engine will produce higher brake horsepower.

Alcohol injection does 3 things: lowers charge air temps due to vaporization, richens the mixture (adds fuel), and raises the overall octane of the Air/Fuel charge (100 octane). Easy to understand why alcohol injection helps pump gas users. The downside to alcohol injection is that is also displaces air. The vaporizing liquid expands and displaces oxygen.

Narrow band O2 numbers are a very poor indication of true A/F ratios. The narrow band sensor works best at 14.5:1 A/F and that is not where you run at WOT!!

EGT's used with O2 readings help you get a better indication of A/F ratio. My particular setup will run O2 reading of .812 at 1500 degrees EGT and at 1650 EGT. You can bet the A/F ratios are just a little different!!

 

[peterkin]

hey man, just go alky and ported irons if i were you. i just ran 12.08 in my car with just alky and no head work. i think with ported irons and alky you will be ver surprised at your performance. i know i am.

 

[Bmason]

Grasshopper

Kwai Chang Caine, you've taken the pebble from my hand...it is time for you to go now!

Not bad for pump gas, alky, street radials and stock heads! Let's stick to the plan and see what happens on 11/2.

-Bobby

 

[mgmshar]

Perhaps a different point of view, for the original question...

It depends on what you want to do with your car. If you seriously don't want to get into the 10's some day, then I would recommend that you get the alky kit, and do NOT disturb your stock head gasket seal.

Example: I've taken the approach of keeping the engine stock (never had the heads off, hope I never will). So, I get all of the nice low-end torque, spoolability, and fun of the stock engine. I instead have chosen to optimize everything else. So, I am running a TA-49 with Precision housing, THDP, ATR exhaust, CAS V2, Tin Man Cold Air Kit, and 57's. You get the idea. Car will run 109mph in the quarter in 94-octane trim. My best to date with 100-octane is 116mph, with a few more to go (didn't get to finish my tuning before the rains came). The car spools lightning fast on the street, which is why I did what I did.

Alky with 93-octane and a stock motor can be tuned to at least duplicate 100-octane performance. With the right tuning, that's at least a mid-11 at 116mph (with 93-octane and alky), with the right bolt-on's and traction. And, your odds of blowing a head gasket are much lower. And, your car will retain all of the low-end torque and spooling fun.

If your eventual goal is to run low-11's or better, then maybe you should consider the heads instead of alky. You will definitely have to run good gas to make low-11's, regardless of what heads you use.

I'm a big supporter of maxing out what you have before you spend the big bucks for big-time parts. That's just me. Many others will disagree. I guess it just depends what your goals are.

For what it's worth...

 

[bradofflorida]

I am going with ported stock heads and SMC progressive alchohol. I was going to buy the Champions, but I found on Ebay a set of heads that were fully ported by RHS for $310 with shipping. Apparently they will work, but I knew when I bought them that they are from an 80-81 Monte Carlo Turbo. If they don't work, they go back on Ebay and I will get the Champions(possibly GN-1's but only if I can verify that they will not reduce low end power or move the power peak too far up.) The car is going on the dyno before and after, so I will post the results.

My theory and goals on performance are a little different than lots of people. I want to maximize the performance of engine with the stock turbo, converter, and hopefully the injectors, while keeping zero knock. My car will never see a set of slicks. I want a state of tune that is easy to drive all the time, even if I only drive it one day a week.

I went to the track for the first time with this car last week and ran twice: 13.8 @ 100 and then 13.5 @101. Left at zero boost, cold tires(BFG Gforce 245's), and 15.5 lbs boost. Probably could have gotten a 13.2 with a little practice. This was on 100 octane for saftey, but the car was tuned for 93 octane.

Thanks for the help everyone!!

 

[Razor]

Good luck with your choice tho. I wouldnt touch heads on one of these cars for a street car with goals of 11 seconds or slower. If they are the original GM heads that have never been off the car.

Stock cam and stock head..mid 11's at the same track you ran at. On 93 and alky. Would of been there with ya last time..my tranny is in the hospital in ICU

Come by the BK on US19 at 110th sat nite sometime..lots of TR's there.

Cheers..

Julio

 

[bradofflorida]

What time does the BK thing start? I think I can make it. I have a family thing going on today, but it should be over by late afternoon.

 

[Red Regal T]

Approximately 7 to 9 pm.