Just did a LT4 hotcam swap with 1.6's and a set of S/R Torquer heads. The car is running awful. No power at all. At the track today my best was a 16.4 when last year I went 14.3 on the stock cam and heads. What could be wrong?? She's also running pig rich, I burned three times as much gas going out as I did last year. I have a few ideas on what the problem could be, what do you guys think??

 

could be a lot of things. First I'd check the codes. Tell us if you get any. If your car is a speed density car, it shouldn't be its an 88, but if it is there is no way that swap you made will run good at all without some chip tuning.

Interesting problem I had that might help you. I swapped my rockers with roller rockers on my vette heads, and they didn't fit right, even though i got the valve covers on. The rockers would not let the valves seat against the heads on 5 of my cylinders so i had major compression loss, resulting im a loss of power, and wicked ****ty running.

All that because i trusted my dad to buy roller rockers, i even specifically told him they needed to be for centerbolt valve covers, o well, he's taught me everything i know so i forgive him.

 

Thanks gta, I'll look into that as a possibility. Anyone else??

 

First, recheck your ignition timing.

Second, ensure that the computer is at least trying to correct the fuel consumption. If you do not have a scanner, take out your handy-dandy digital voltmeter and go the ECM connector at terminal E14 with the positive probe. Then, Go to a good ground with the negative terminal. Fire up the engine and watch to see if the voltage is bouncing around from .1V (lean) to about .900 (rich). Or if it's staying above .450 for the majority of the time (indicating a rich condition). If it is stuck at any particular voltage, your O2 sensor is bad.

Though, without a scanner, you won't be able to tell if you're getting into closed loop operation.

Also, I've heard that even for MAF cars, there's a limit to how much you can alter the engine from stock and get away with it. Going from a stock 202°/206° cam to an LT4 218°/228° cam is a pretty big jump. The timing curve is going to be very different between the two. You may need to have a chip burned.

 

Anybody else??

 

so are you guys saying SD is more flexible than MAF when it comes to mods?

 

ACtually, the exact opposite is true. Since the MAF cars measure the airflow directly, they're able to compensate a little better. The MAP cars simply measure manifold pressure and make an "educated" pre-programmed guess as to how much air is being inhaled by the engine. This is why significant modifications can wreak havoc on engine operation (espcially when playing around with camshaft profiles). It's been my experience that increases in duration that top 7° or 8° more than stock on the intake side start pushing the calibration to the limits for MAP cars.

 

ok its just the way this thread was going thats what it sounded like. thanx for clearing it up.

 

the spark cal wouldnt be the huge killer here it would be the idle that went from 30-35kpa to basically 60kpa with the hotcam(im running the same thing in a SD setup)... Your car is prolly getting so much fuel it doenst need below 3k now that your gonna end up washing the cyl walls down unless u address the tuning issue asap....

"If" everything is assembled correctly and mechanically/electrically good, your only way out is pay someone to tune it or learn prom burning yourself........

Its not that bad i do it now, wish i started sooner and side note, just learn how to do it unless u want to pay for a waste of $$$$ from fill in the blank....or work with them by sending your chip back twice a week and have no car for 3 days at a time
LAter
Jeremy

 

So basically the only way out is to bet a proper tune done. I will check a few things mechanically and electrically first and then I will get a custom burn done. Thanks for all the help guys.