Offshoreonly.com

Offshoreonly.com (https://www.offshoreonly.com/forums/)
-   General Q & A (https://www.offshoreonly.com/forums/general-q-20/)
-   -   Mercruiser 502 MPI 1995 Running issues (https://www.offshoreonly.com/forums/general-q/361389-mercruiser-502-mpi-1995-running-issues.html)

217andy 06-24-2019 09:32 AM

Yeah, I know, I checked it and it's at 165-170 on all of them

mike tkach 06-24-2019 10:03 AM

according to comp cams the duration at .050 lift is 243/248.that won,t work with stock exhaust,the water is no doubt reversion.plugs don,t fire very good when they get water on them.also lsa is 112,not 114 according to the info i found on line.

217andy 06-24-2019 10:57 AM

Man I really appreciate all the work you guys are putting into this for me. I have the engine back out now, but before I put it all down, should I contact Comp cam and find out? Or is there someone else you would recommend?

SB 06-24-2019 11:25 AM


Originally Posted by mike tkach (Post 4693434)
according to comp cams the duration at .050 lift is 243/248.that won,t work with stock exhaust,the water is no doubt reversion.plugs don,t fire very good when they get water on them.also lsa is 112,not 114 according to the info i found on line.

Double check what I found, since is different:
Lobe Catalog: http://www.compcams.com/Technical/Ca...terCatalog.pdf
Lobe #3110
Duration at .006" - 284
Duration at .050" - 224
Duration at .200" - 144
Lobe Lift - .350"

Lobe #3112
Duration at .006" - 290
Duration at .050" - 230
Duration at .200" - 143
Lobe Lift - .340"

217andy 06-24-2019 12:57 PM

I just talked with Comp cam, it's a custom grind and not listed online. They told me there should be absolutely no problem with the cam. They are thinking my valves aren't adjusted correctly, so that's where I'm going next.

articfriends 06-24-2019 02:07 PM


Originally Posted by 217andy (Post 4693426)
Thanks, that was my understanding as well.

I've dynoed with them where they belong, swapped to opposite injectors and all 1 batch down one side and all one batch down other side. Hp, tq, idle-exactly the same. Now, what helps a tiny bit IF your tuning is to fire them every motor revolution vs every four stroke revolution. That evens out cyl to cyl afrs and tiny bit more tq. 500 efi is this way from factory. You have to account for deadband or "latency" in your pwm tables as it will go lean if you dont,Smitty

217andy 06-24-2019 02:23 PM

I'll take your word for it, lol. A lot of that info went way over my head. So the bottom line for this application is that it really doesn't make much difference?
Also, just curious what a dyno looks like that could hold this thing when it's running right.

SB 06-24-2019 02:24 PM


Originally Posted by 217andy (Post 4693499)
Also, just curious what a dyno looks like that could hold this thing when it's running right.

Huh ?


All times are GMT -5. The time now is 04:25 PM.


Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.