I have an 1985 Camaro with headers and a mild cam (.454 lift and 216 duration). I had the car tuned, checked fuel pressure, checked vacuum lines and it still seems to flat out around 3,000rpm. It runs really strong up to that point and then just dies off.

My mechanic said that it could be because the cam is using too much vacuum and that's what's causing the problem. I also need to test the mass flow air sensor.

Could this be the issue? I thought my cam had a mild enough lift and duration to work perfectly fine in my TPI 305. It's SUM-1065 I believe if you want to look it up on summitracing.com

Any help would be greatly appreciated!

 

How was it tuned?

 

He just timed it. I'm not exactly sure what advanced he set it but I'm assuming he set it to near stock timing.

 

You will need a new chip tune to properly handle those mods. thats a decent amount of duration for a 305, and being a 85 ECM, its gonna be easier to tune if you upgrade to the 86-89 style and tune with those systems.

Its likely cutting out due to lack of fuel but its hard to say without air fuel reading and looking at plugs. It could be ignition related as well, but you are not going to beable to run well just by setting timing. Thats not tuning.

 

i can almost certainly guess it's knock retard...

 

What would cause knock retard and how can I deal with fixing it? Just adjusting the timing @ the distributor?

 

I had a chip custom burnt from harris performance. I told him my cam specs and everything, so I would assume he programmed it correctly.

 

any noise will cause the knock sensor to retard timing, search for disable knock sensor, there is a resistor you install, i've never done it, but my car felt like i hit a brick wall at 3k when i did the tpi swap, found it was knock, i replaced the knock sensor.

what grade gas are you using?

 

Could the knock sensor really decrease your power that much? I can't even turn over the tires and when it was bone stock I was still able to do pretty good burn outs.

I'm using 89 grade gas. The Super/Ultimate grade...should I maybe switch to 91 or 93?

 

you could try 93, when i was driving my car i think it was taking out 11-14 degrees of timing, literally it was like the motor made no power beyond that.

 

I heard you can put a 3.5k ohms resistor on one of the wires of the knock sensor to "bypass it"

 

Just unplug it. You can on maf cars with out setting a code or turning on the CEL . SD cars you cannot.

It almost sounds like your cam timming is a tooth off.
Had a guy that put a cam in a few years ago with that prob. Car ran ok but power was waaaay off.

 

I thought I made sure it was perfect, but who knows...it's my first cam install ever so I'm sure I did screw it up and off by a tooth. Does that mean I'll have to take off all the accessories, belts, pulleys and everything off again?

 

prolly. you could do it with a small degree wheel and one valvecover off. do a quick seach to see how to do it

 

Yeah, I'm coming to conclusion that I didn't time the cam properly...I disconnected the Knock Sensor and it still ran like crap.

I'll look into timing the cam through the valve cover. Thanks for the suggestion. To lay it to rest, my cam wasn't too big was it? .454 intake/exhaust with 218 duration @.50 or whatever it is. It also has a 110 LSA (I heard that MAF engines are fine with 110, it's the speed density engines that dont like the 110 LSA's)

Thanks for the help again

 

Cam is decent grind for a 305 but capable of running fine when tuned properly. Mail order tunes are so-so, its hard to get it right the first time. Need to really dyno tune or street tune it to see whats going on.

 

By tuning, what do I need to "tune" to get my engine running properly? Because I'm completely lost for ideas of what could be the issue.