Question about GMPP 502ho crate engine.
06-29-2014 | 12:31 PM
#41
Thread Starter
Registered
Joined: Mar 2011
Posts: 167
Likes: 0
From: Beaumont TX
I did a similar upgrade to my 260 Baja a few years ago. Went from the stock Gen 5 454 to a Gen 5 502 Mag. I used a Performer RPM manifold, a Holley 9022, a DUI distributor with 24* advance and 12" x3" oil cooler with a separate 5" x 2" PS cooler. Used the stock cast iron exhaust. The jetting I ended up with after much trial and error was 87p, 98s. The stock jetting in the 9022 was 72p, 87s. WAY too lean. You should be good with the dual plane that comes with engine. I would swap the water pump for amarine unit with a stainless steel impeller. My only concern would be the cam. Would want enough LSA to not get reversion with stock exhaust. I could not be happier with my swap. I have over 200 hours on it now. Really woke up the boat with a 24 pitch Bravo 1.
What he stated about the spacer on a dual plane is correct. I support that with dyno experience. SBX if your set on using a dual plane, best one to use (as previously posted by others) is the Edlebrock Air Gap 4150 based manifold.
Take a good look at the HP950 Holley. It has a 750 throttle plate. This is really a 850 hi velocity---sorta. Again, I had dyno time on the carb too. Don't be confused with the CFM numbers or model numbers issued by Holley. Many times they do not make sense as to the true carb in the box.
Take a good look at the HP950 Holley. It has a 750 throttle plate. This is really a 850 hi velocity---sorta. Again, I had dyno time on the carb too. Don't be confused with the CFM numbers or model numbers issued by Holley. Many times they do not make sense as to the true carb in the box.
Im not SET on using a dual plane, but I also dont plan to run the engine up high probably mostly around 3-4000 RPM
I will look into that HP carb
Thanks for all the help.
06-29-2014 | 09:40 PM
#42
Registered
Joined: Feb 2011
Posts: 2,640
Likes: 4
IMO, a Holley 800 marine carb from an HP500 would work well on this setup. They can usually be found in the Swap Shop for less than $300. Plenty of people are running them on OSO, so it should be easy to find someone with a baseline to get you started.
For the record, I am running one on my 489 with AFR heads and hydraulic roller, Lightning headers, etc. Yes, I could have probably made more power with a bigger carb, but it made 585 HP on the dyno, which is more than enough for my old tub. Point I'm making is that it should run fine for your application. Good luck with it, and let me know if either of those manifolds I have might help you.
For the record, I am running one on my 489 with AFR heads and hydraulic roller, Lightning headers, etc. Yes, I could have probably made more power with a bigger carb, but it made 585 HP on the dyno, which is more than enough for my old tub. Point I'm making is that it should run fine for your application. Good luck with it, and let me know if either of those manifolds I have might help you.
07-03-2014 | 10:42 PM
#48
Gold Member
Joined: Jan 2002
Posts: 702
Likes: 26
From: Southern, IL.
You need a dist. and carb. approved for marine use, get a mechanical advance unit, set timing at 35 degree total advance, I would jet at 74 frt./86 rear to try it see how it runs, it may be a little rich.
07-03-2014 | 11:26 PM
#49
Banned
Joined: Jun 2013
Posts: 1,014
Likes: 0
From: AZ
This: http://m.summitracing.com/parts/dui-m12611bk
