Scott

I made the same choice for the exact same reason. Will you run the engine up to 5700 or will you run at 52-5300. The 731 was a nice improvement over the stock hp500 cam. I think the 741 is too much on that set up.

ctuck0659

If I can run 5400 on the top end, I'll be happy. I don't like breakin' stuff when I'm trying to have fun and when you push too hard, somethings' gonna break. I also don't want to spend thousands more on fuel system upgrades etc. chasing a few more MPH. The law of diminishing returns is alive and well in this game-

jackhammer

Just to mix things up a bit (Isky option)

275*/284* @ .007"open & .010"close (they do it different)
228*/238* @ .050"
.325"/.340" Lobe
.585"/.612" Valve (I used 1.8 ratio)
112* LSA
55.5* Overlap


I bought their full retro-roller kit (Cam, springs, pushrods, roller lifters, retainers, keepers, and button for <$750 shipped.

Put it in a 498CI (.070 over stroked 1/4") with 049 mild pocket ported heads with 2.19/1.88 valves and a Edelbrock RPM dual plane with 2" open spacer and dyno'd at 540+hp running just a touch rich. Idle is still a bit lopey but I can't blame it on the cam yet... I still have some carb idle circuit tweaking to do.

Pat McPherson

Being that this is an EFI engine, the ECU will need to be recalibrated. I suggest that you speak to the guy that will remap your ECU to be sure that there is a proven program.
I suggest Mark at Precision EFI or Tyler Crockett not AZ Speed.
I'm quite sure they will have a program for the Crane 731, 741, Merc 500EFI, as well as their own custom grinds.

ctuck0659

Pat: Do you have a beef w/ AZ Speed? I read nothing but positive comments about them. They do in fact have an ECU remap pgrm. for the 500MPI/ Crane 731 which I plan to have them do (see my original post). Just for yuks, I'll check out Precision and Crockett. Thanks for the input-

mjb

I just went through this with my modified 502 MPI's. If you are not going to modify the fuel system, I would stick with the 731. I would use a 114 LCA. Be careful with too much duration or too small of an LCA in these motors. They use a speed-density type EFI system and depend on a strong, stable vacume signal to the MAP sensor to idle correctly.
Also make sure that you do not have one of the 502 MPI's with the factory defect on the #7 fuel rail feed. You can get by with it with a stock motor but once you start making modifications you need to correct this defect or you may ruin a new engine.

Pat McPherson

My experience with working with AZ Speed on a modified 7.4MPI was not great.
I've gotten great advice and parts from Mark and Tyler. That is where I will go in the future as well.

ctuck0659

MJB: Thanks for the advice. I assume you mean LSA, not LCA. Did you experience a problem with a cam w/ 112 LSA? If so, what cam was it? (duration specs?) What's with the Fuel Rail defect? I've never heard of this- I had to change an injector this spring and the fuel rail is basically a triangular shaped pipe w/ 8 injector holes and an inflow fitting- how could there be a defect in the feed to #7? Mine are 2000 model year if that tells you anything-

mjb

Yes, I meant LSA- lobe separation angle....not lobe centerline.
Have never used a 112 LSA. I just know that reversion is such a problem that I decided not to take any chances and be conservative with a 114. My cam was custom ground by Cam Motion to match the flow #'s of my ported DART heads. I wound up with 228/233- .592/.600- 114/110. The spread between my I & E is only 5* because the E ports on the DART heads flow much better relative to I flow compared to the stock GM heads. My overall duration was a little lower than I expected because my heads flowed so well. I am very happy with this combination. I wound up with about 540 CHP at about 5400 and she idles like a stocker!
I also started with AZM but was unhappy with their poor customer service. I wound up having my ECM's remapped a second time by Tyler. Much better!!
Do a search on this board. There have been many posts about the #7 fuel rail defect. Not sure, but I think they fixed it by 2000. Mine was 1997 and I had the defect.

kennyo

Unless they've change their programming go with someone else. My azm mapping was a nightmare. I'm running the 741 and love it. I'm turning about 5400 rpms.