alecsammy

Hello, does anyone one know what the biggest cam lift and duration I can but into a stock 98 502 Mag MPI without changing or modifling any other parts on the engine(ie injectors or reprogramming ecu) Thanks

kennyo

You are going to have to change the springs at a minimum if you go bigger. I'm runninig the crane 741 cam but i put roller rockers ,springs and retainers,pushrods etc.. You could upgrade to the hp500 cam with just a spring change probably. It's all a gamble if you don't upgade everything.
p.s. I have a set of springs and retainers (Crane) i'll sell for $100.

deboatmon

Changing just the cam would probably net you minimum gains if any. Higher lift will also really work over the stock rocker arms and springs. For as much work as it is to change the cam, it seems smart to make HP upgrades while you're at it.

Someone correct me if I'm wrong, but a bigger cam profile could only make more power at higher RPM. Higher RPM and valve lift is where the stock valve train starts to lose reliability. I believe better valves, springs, pushrods, lifters, rocker arms wth new studs are the way to trouble free reliability and any horsepower gains. Why build it any other way ?

Personally, if I didn't have a decent aftermarket exhaust, that's where I'd start my upgrades. Then the valvetrain.

kennyo

What he said.

mjb

The fuel map programed into the stock ECM is designed to work with the stock camshaft. Only very small increases in lift or duration would still work well with the stock ECM....and changes this small would not even be noticable. If your going to change your cam your really need to have your ECM reprogramed. If your going to do this then you really should change the springs and rockers. and the stock lifters are only good for about .550 lift. any more and you need new rockers.

The big concern with cams and these MPI engines is total overlap. This is a speed-density EFI system which needs a strong and steady vacume signal at idle for the engine to idle well. Too much duration or too small of a LCA will cause problems with the MAP signal AND may cause water reversion into the engine.

I just completed this cam change on my 502 MPI's and after talking to many in the know I went with a custom grind cam with 228/233-.600/.600-114/110. It works great! No idle problems, sounds good and no water reversion. In hindsight, I may have been able to go a couple more degrees at .050 with no problems but I am very happy with this cam.

alecsammy

MJB do you have a number where you can be reached mine is 203 913-5450 Thanks.

jeffswav

Start with the exhaust, any other upgrades you do will need it anyway. A bigger cam with stock exhaust will give you problems. Plan on spending at least $2000 on there are several brands that will work fine but I use the EMI. Don gives an OSO discount http://www.tpmarine.com/

mjb

It's best to contact me by email at [email protected]