Asmodeus

So, he was watching it PULL 26 degrees of timing? Like, he had it on a scanner, and it was baseline 28 degrees and pulled all the way back to 2 degrees?

briannutter

Here's a test you can do quickly and easily. Drill a small hole right in the header collector and tap it for for a zerk fitting or small brake line. use a hose clamp to keep it on. Run a rubber hose to a 0-15psi pressure guage. if using a zerk, the rubber will melt after a few runs, but it's long enough to get a reading. A small 6" section of brake line will hold up a bit longer. Run the car up to 6000rpm or so under wot and load. See what kind of pressure you see at high r's. My True Dual 3" with straight-through type mufflers and Random Tech cats registered about .8psi average. That's considered Very good for a full exhaust. The guage fluctuates a bit, but you'll get an idea. My factory stock c4 '94 corvette had 3.5 lbs of backpressure...2.7 lbs of which it turned out to be in the stock rear mufflers when I ran pressure taps all the way through the system for testing purposes...before the cats, before the resonater, before the muffler...etc. To be honest...reducing the backpressure 2.7 lbs didn't add much more power with a stock cam at that point because of small overlap. 2.7 w/ a cam w/ more overlap would probably add considerably more power, but I didn't do that test.

When finished testing, plug the hole w/ a pipe plug. It will probably strip out easy, but I didn't find it made more noise either way.

mailman2000

iTrader: (1)

have you had it dynoed somewhere else just to see if the dyno reads low?

joshp14

iTrader: (5)

I'm not sure what the timing is set at when it was mail order tuned. I didnt have it on the dyno to tune, just to get numbers.

Brian, I am a Tech at GM so I do have a back pressure tester for testing plugged cats. I can run a back pressure test for everyone that was asking, but I HIGHLY doubt thats the problems simply because I KNOW first hand what a car feels like when the cats are plugged. I may just take the cats out and put the straight pipes in to get rid of any problems with the cats at all.

Also, I have not had it dynoed anywhere else. Funds are tight as I have a wedding in 4 months...I dont think the fiance would understand this...

"Sorry hun, couldnt get a cake cuz I had to have the car tuned."

briannutter

Excellent deal Josh, Yeah Plugged cats would make about 200whp , but I'm looking forward to seeing if they are a restriction. Please PM me when you've had a chance to test it at wot...just curious to see the number.

Irocss85

iTrader: (1)

while you have it apart working on the intake/inj.s and such, Id def. take the time to pull the timing cover off and check the cam. spend a little time though and do a full cam degree on it though, dont just trust the dot to dot method. the tchain could be off due to manufacturing tolerances, you could have a crank with the key cut at the inc. position by a few deg.s, but thats one test that will give you definate results when your done. and at the vary least, you can check one more thing off the list and move on.
you didnt hit the track with that car all summer? bummer. I have heard of cars though that dont dyno high at all, but run very fast times. not sure why that is, but just check out the drag racing forum for proof of that.
good luck man.