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My GTCS makes 330 horsepower at the rear wheels!

davidathans

Well-known member
Joined
Jul 25, 2004
Messages
703
Location
San Fernando Valley, California
Just got an oil change and made three dyno pulls today.

The results are:
328 RWHP at 6300rpm and
303 FT-lbs Torque at 4400rpm and at 5600rpm the torque is 290 ft-lbs.

If you don't believe me, or you just want to see my beautiful dyno graph, go to page 8 in David Athans gallery.

This is a proud day for me.
 

PB gtcs

Well-known member
Joined
Dec 11, 2003
Messages
161
David, Great pull. Just curious, have you and the engine folks focused on getting the "cheap" horsepower? What we saw with my 428 while sitting on the dyno stand was an increase from around 425 hp to over 450 by getting "cheap" hp. We first started with the timing. Picked up a few hp there. If you have not had your distributor curved, it will help as well. An out of the box dist will not be correct for all cam and carb applications. Then we worked with the jetting on the carb. In fact we found that the new Holly did not open the choke butterfly completely. An adjustment there picked up a few hp/tq on the top end. When we had worked on the timing and carb, we then drained the oil out and put in synthetic. That gained us about 4-5 hp. All "cheap" hp. As well, just curious, did they measure the heat off each header tube. We found 1-2 of my cylinders were runniing lean (too much heat). come to find out, we miss aligned the intake gasket just a little restricting air flow. Soo, some things for you to think about for hp and tq gain that costs time, not new gagets. Have fun.

Brian
 
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davidathans

davidathans

Well-known member
Joined
Jul 25, 2004
Messages
703
Location
San Fernando Valley, California
Hey thanks for the tips!

ya we had Bob Jennings do a dyno tune, where he changed the boosters and jets in the carb, adjusted the fuel/air ratio and looked at the timing curve and set the initial/total timing.

Though he did that, this dyno place had an air/fuel ratio graph that showed me around 14:1...which is a little lean, so i went back to jennings and he gave me bigger jets to try out. As far as oil goes, i changed the oil that day. I used chevron supreme 10W-30 and a fram oil filter. The oil pan is a cannon and is deeper than stock. The oil change takes close to 8 quarts.

My next step to get more power is to use 101 octane and increase the timing a few degrees to see what that does. im also going to try to get the fuel/air ratio around 13:1, the other thing i want to try is open headers on the dyno and see what difference that makes.
 

PB gtcs

Well-known member
Joined
Dec 11, 2003
Messages
161
David, when the guy looks at the beginning and total timing, you might also have him look at when that timing comes in. Diff cams and carbs ask for timing at diff times. That is why I spent 100 bucks to have the dist recurved for my applications on both the CS and the Cobra. As well, when the fellow does the recurve he can look at the dist lobes. On our small block for our CS, a couple of the dist cam lobes were off as much as 6 degrees. In short, if you look down at the timing and lets say you have 13 degrees initial. Two of my cylinders were firing 6 degrees off of that. We went through 3 diff dist b4 we found a good distributor that had less that 2 degree error on the dist cam lobes. It makes a big diff.

If you are runnning a vacume advance, look at when the vacume advances the timing. Two of the Dist we had required a huge amount of vacume to get the timing advanced. We ended up using an old Vacume advance unit for our CS because it required less vacume to advance the timing.

So, three things on the Dist that will give/take HP/Tq. The weight settings that allow the advanced timing to come in at certain RPM. The lobes on the Dist being in sync, and the vacume if you are running a vacume advance.

Oh on the carb. From the factory, Holley is bad about putting a stiff spring in the vacume secondaries. I dont remember how the street avenger does it, but something for you to check. The original spring for our secondary advance in the current carb we have on the CS wud not begin to open the secondaries until we reached between 3 and 3500 rpm. They were not totally open till we got to over 5500. The reason they do that is to keep the car as a 2v for as long as is possible to give better MPG. However, does not do much for your off the line performance. We switched the springs (kits are available) in our 600 and the secondaries now begin to open at about 2k, fully open at 4500.

Diff cams and carb settings require advance in the timing at diff times. As well, needed that fuel for bottom end hp and TQ. Fun to watch on a Dyno.

Brian
 
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