Anyone running a big cam, can you post your BAR & MAP readings or Vacuum readings at idle. I'm trying to chase down why my readings at idle are wierd and my service light comes on, but when I start drive the light goes off. Check DataMaster and it gives me 33,

Bar: 30.4
Map: 24.7

Cam Spec:
- Duration
242-I
252-E

- Lift
525-I
540-E

- Lobe Separation
112

Someone said I have a vacuum leak, but I've checked everything using both methods, propane & carb cleaner all around the intake and vacuum lines, but nothing.

Thanks,

Jody J.

 

ttt

Anybody???

 

Look at this:

http://members.aol.com/InjuneerZz/ScanMast.htm

It says in here that MAP readings for a radical cam should be about 18.

 

Your data is sort of confusing..... "DataMaster .... gives me 33"... is that the reading, or is that what DataMaster says your MAP should be?

And, the link above is to my website, but the 18"Hg MAP is not a "one size fits all" number.

Stock cam in a 350 you would see about 10" MAP = ~35kPa.

My 230/242 114LSA in a 381ci engine MAP runs about 15.5"Hg. That's a pretty mild cam for a 381 and the 114LSA reduces the overlap, which is what kills vacuum.

The 245/252 112LSA is a BIG cam. What's it in? Didn't see a displacement anywhere. In a 350.... really big. I have no idea what the MAP should be, but 24.7 at idle sounds too high, and will definitely trigger the trouble code. There's a guy who posts on the Project TransAM BB LT1 Tech forum, TripnTaz... and he has a huge cam in a 383 and has had numbers similar to your if I recall.

Have you checked the valve adjustment?

 

Thanks for you replies guys.

Fred, sorry I didn't clarify properly. The 33 I mentioned is in regards to DTC33 (Low vacuum, High MAP)

BTW, this cam was spec. out/installed by my engine builder without talking with me. I knew I was changing the cam, but I didn't know it was that big of cam (long story).

This went in a 355ci with forged internals built for spray and a TH400 and P&P heads. Car drives great around town and and on the freeway and at WOT shifting at 7k RPM feels great :^)

Do you have a link to the Project TransAm BB?

I haven't readjusted the roller rockers since I got the car up and running two weeks ago, but I did adjust them to 1/2 pass zero lash before dropping the motor in.


Thanks again,

Jody J.

 

Project TransAM Bulletin Board

Look for posts/search for "TriPinTaZ" in LT1/LT4 Tech.

 

Thanks!