Turbo331Fox

How's it going guys. Car has a 331 stroker with a T-70 turbo. This is the cam I currently have (http://www.compcams.com/Company/CC/c...csid=1066&sb=0) and the car is falling flat at 5200 RPMS. My tuner (Tony Gonyon) said the cam is definitely the problem and said I should go with an E cam, however I really love the sound of the comp cam in it now. Suggestions?

bluebeastsrt

Get a new tuner. Letter cam??? Really? What heads are you working with? Do they have good valve springs? Is the fuel system up to snuff? Whats your A/F ratio when the car goes flat?

uedlose

That cam is close to mine. Not the same but it is close and my car will pull till I shift or it blows up. I have seen 7000+ rpm a few times. I dont think the cam is your issue. what is your turbine housing? have you done any pressure differential checks? What muffler you running with that turbo? Then all the above questions. How much boost are you seeing?

barnett468

.
what heads do you have?

what conpression?

that cam is sort of big for a 302 imo and not the best unless you have good heads due to the single proifile but it really shouldn't die at 5500 without the turbo and certainly shouldn't die there with it as was mentioned.

Turbo331Fox

AFR 185 heads. Springs are good. First thing we checked was the springs to make sure it wasn't valve float causing the issue. Fuel system is fine. A/F at full boost (10 PSI) is usually in the 11-12 range. The A/F is normal when the car goes flat. It just falls flat. It will still run up the RPMS and make boost it's just loosing power. He said it's because that's a blower cam, and as such the overlap is not designed for a turbo and is causing the turbo to fight itself. My tuner isn't the only person to say that either. 70MM with a .96 hotside. I had a dynomax turbo muffler, but I switched it to a blow through little race bullet. I have a 331 Stroker, so it's not really a 302 anymore. I believe it's 9 to 1 compression.

barnett468

YOU CAN GET A CUSTOM CAM MADE.

uedlose

have you done any pressure differential checks? By this I mean what is the psi. before the turbo at the turbine inlet? what is it at the intake? and what is it at the outlet of the turbine when it goes into the exhaust? You will need to look at them all at the same time. what size is the turbine wheel. How big is your down pipe. if you have back pressure issues it is gone to fall off up top. One way to see if you are having cam issues is pull the upper intake and look at the runners are they black or are they clean. If they are black you are getting exhaust pushing back in to the intake due to to much back pressure or the over lap is to much on the cam. which can be fixed with cam change or you can improve the flow out of the turbine and the exhaust. Which in some cases is better then cutting the cam to fix it. again have you done any pressure differential checks? This will tell you a lot. You can also look to see how much back pressure you are seeing before and after the intercooler that is also some good info to have. Lots of cheap intercoolers can become a restriction. just a few things I have learned over the years messing with this turbo junk. That and my mechanist is a old turbo head helps a lot also. lol By the way what brand turbo are you running?

tinman

Just an idea here.
Ask this 'tuner' just what the difference is between a 'blower' and a 'turbo' cam.
Both of them are supposed to operate with compressed air/fuel moving thru the ports and into the engine.
Myself I would look at the ignition system......