Well, took the 99 T/A and 80 Z28 (see sig) to the dyno today. Now, the Z28 will keep up, pretty much with my 99 T/A, however, NOT on the dyno. I am no good at tuning carb/timing, and obviously the dyno proved this.

Here were my runs

1) 233/262 (2nd gear)
2) 231/260 (2nd gear)
3) 227/294 (3rd gear)
4) 205/233 (2nd gear)
5) 212/286 (3rd gear)

I had to go down two jet sizes to a 70, when I first got the engine running cause of fouling plugs. It appears to me that the jets are too little though. My A/F wouldn't go below 14:1 at ANY time during the run. I tried letting the screws out, in, everything, and NOTHING. Even with the engine running, you could run the screws all the way in, and it wouldn't change anything??!!! My combo should be hitting 300/300+ EASY, any help?

I would love to find a shop to fine tune it for me, but no one knows my engine like I do, or does an honest job.


HELPPPPPPPPPPPPPPPPPPPPPPPP

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1980 Z28, Chevy 357, bored .040, Dart Pro-1 Aluminum 200cc 2.05/1.6, Holley 750, Performer RPM, Pro-form HEI, 1.5rr aluminum, COMP 274XEH, B&M Holeshot 2400 w/ Quicksilver Shifter, Speed Pro 9:1
1995 Dodge Avenger, 5spd. 2.0L, 32 MPG
1999 T/A A4, LS1, w/ lid 13.7@100

Oh yeah, my stock 99 T/A A4 with a lid pulled 288/309.

Timing set first. Jets / fuel second.

No kidding!
With that setup you should be well into the 300/300 range!

I'm glad that I had the oprotunity to have my setup engine dyno'd.
With some proper tuning, you should be in there.

Not enough info to help you. Let's start with verifying what numbers are what. Which are HP and which are torque. In each run what did you change.

You are way too lean on wide open throttle, A/F should be 12.5:1 or thereabouts. What is the duration at .050 on that cam as well as lift and lobe split? What RPM did you hit peak torque at and peak RPM at?

A few things I do see though are a BIG (although good) head, low compression and what I am going to assume is a pretty small cam.

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70 SS 454 CI Dynoed 684 HP, 702 TQ All Aluminium Fuel Injected Small Block , plus 200 - 500 HP NX nitrous system.

Cam is right a .500 on I/E

The numbers were RWHP/RWTQ

Aside from different gears runs, each time I just tried to get the A/F down into the 13:1 area. I tried moving the timing, but after run 2 put it back to 12* initial, and 32* or so full around 3000. I can't 100% accurately time it, cause light gun was not the best.

I have one cylinder that pings bad enough to hear it, so I adjusted the timing to where it doesn't ping.

[This message has been edited by BamaZ28 (edited December 04, 2004).]

If you are turning your A/F screws all the way in and the Idle of the engine does not change you have a blown Power valve. If you have a Holley that is. When you turn the screws all the way in it should kill the motor.

My understanding is that even if your PV is blown will not affect your idle since it is a different circuit. Nor would you notice a change on the dyno since at WOT it should be open anyway.
Simply cruising around is when you would be pig rich.
I would agree you need bigger jets. I would pull the carb and look at the transistion slot. It might be your exposing it too much and you are running on both the idle and transition circuit? Play with the idle, get it as low as you can and then see if your screws start to work. Screw the screws in all the way first and then back them both out 1 and a half. Then start dropping the idle. Who knows what will happen?

If the power valve is blown it leaks fuel causing a RICH idle.

If the power valve is blown it leaks fuel causing a RICH idle.

How does the power valve make the idle circuit rich? It only affects the main fuel circuit. It will make your idle rich is you are idling on the main circuit, which means the carb is out of adjustment.

I can't 100% accurately time it, cause light gun was not the best.

You need to solve this dilemma - the correct timing is important if you want the power. You need to be sure that your timing mark is correct. Make a mark at 36 degrees BTDC on the balancer so you aren't dependent on a dial-back light. We had a 327 Camaro go from 230 rwhp to 310 with just a timing change. The car was a driver and as far as the guy could tell it was running okay.

You should definitely not be pinging with a 230 degree cam and 9:1 compression. What is the calculated compression? What's the intake lobe centerline as installed?

What kind of carb is it? Vacuum secondary? Are the secondaries opening all the way? We typically pick up 15-20 hp by forcing the secondaries open on a VS carb.

Do you get full throttle opening when you put the gas pedal to the floor? We find this is a very comon problem resulting in some major power loss. We got a 200+ rwhp improvement from one setup, about 60 from another.

Those heads are kinda big for a 350, but not the cause of your problems. They would just move the powerband up some.

I wouldn't even feel safe cruising at 14:1 much less being under full power throttle at 14:1.

Running that lean will make an engine ping under the right circumstances, even with low compression, big cam, and aluminum heads.

First, get a good timing light and shoot for around 36-38. That cam is kinda big for an XE274. I've heard the Proform HEI dizzys have a pretty quick advance so you should be good there.

Second, if you are running a 3310 then either toss it for a double pumper or be prepared to spend similar money on parts to convert it to a secondary metering block, spring set, and quick change spring housing.

If you turn the screws in all the way and the motor still runs then you are running off the cruise circuit. That means your cam needs extra air to idle and you've gone past the idle transfer slot. Drilling 3/32 or 1/8 holes in each of the two butterflys will allow you to close the primaries and run off the idle circuit again. Either that or Holley has a small set screw on the secondary side that allows you to crack them open for extra air. Give that stuff a try! Oh, also like Onovakind said, make SURE you're getting full throttle!!

If your power valve is blown you be about 8 jet sizes richer at idle, If your car is idled up to where the carb is idling on the
primary curcuit instead of the idle circuit the idle screws wont do a whole lot. Is your carb a holley? What List #? Get the jetting right or close then you'll probrably be able to go up to 36-38 degrees total on the timing, the lean jetting probrably contributed to the pre detonation on that cylinder.

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1972 Camaro 350 factory heads 1.94/1.5 street driven full interior
93 octane everything works 7.59
89.54 mph
Never owned a trailer never will!

THE REASON A BLOWN POWER VAVLE WILL RUIN THE IDLE AND MAKE IT RUN RICH.....

When the little rubber diaphragm in the power valve ruptures it allows raw fuel from the float bowl to enter the vacuum chamber on the other side of the power valve. The fuel then dumps directing into the intake manifold below the carb through the internal vacuum port. Drizzling unmetered, liquid fuel into the intake can obviously ruin the idle and will make the carb run rich under all circumstances, but most obviously at idle and light throttle.

What Damon said...
A more detailed explanation describing my "to the point" explanation.

Thanks so much for the lengthy replies!!!

It is a 750 vacuum secondary BRAND NEW Holley. I'll get the model number. I am haveing two O2 bungs welded in so I can diagnose the issues. I found this article

http://www.bob2000.com/carb.htm

Sounds like if I got through all those steps, then my carb should be 100% on the money, and I will get this timing issue solved as well. Once again, thanks and I will posts what was off and how it turned out.

If you don't mind just getting the secondary side "close" instead of "dead on", you can buy the metering plates and tune with those.

I KNOW you've got over 300 hp sittin' there! It's all in the timing and jetting. I think the lean jetting is the reason it's pinging at such low advance. Get the carb more in the ballpark and then bump that timing up.

32 total timing is definately holding you back. I would say going to 36 would make a huge diference. I would definately fix that lean issue 1st, though -