Question about GMPP 502ho crate engine.
 

Looking at the GMPP 502ho crate engine it appears to be built very similar to a boat engine if not almost exactly. There's an old guy here in town that purchased one new to put in a nova. Drove it about 200 miles over the last two years and decided he wanted to to Efi. Pulled the engine as is going the LSx route. I can pick the engine up for $3500 carb to pan. 850 demon carb msd hei dist and msd 6al.

Is this a good engine for a 25 outlaw as it is? Cam ok? I will post some pictures of the specs. If you want to google "gmpp 502ho crate engine" it will pop right up.

http://i19.photobucket.com/albums/b1...pswhmzmqbw.png

http://i19.photobucket.com/albums/b1...psp5i8ulmn.png

http://i19.photobucket.com/albums/b1...psl8ff4dwb.png

I bought a brand new one in 2002 for my then 253 Checkmate, it was a great improvement, and a great engine, ran it 7 summers w/ no problems at all, it had very good power and performance for your size boat, sounds like a good deal.

$3500 for a basically new complete 502ho?
Id be at his door picking that bad boy up...

Wow ! Great deal ! You have it already don't you ? LOL.

Just make sure you have the correct bypass valve installed in the oil filter pad, so you don't bypass your filter and cooler and cook you bearings. Do a search on the subject on this forum - lots of info.

A friend had a pair of them in his boat, ran flawlessly for years and still running. Years back, I bought a pair of 454HO crate motors for my 33 Fountain. Zero issues. -As above check the oil bypass valve (or just block it) in the filter pad so the oil does not by-pass the cooler.

my buddy always recommends replacing the push rods. with a beafier one, however it is more precautionary.

i would think that it needs marine distributor marine carb and some type of aftermarket exhaust stock exhaust wont work with that cam will it?

230* exhaust duration with a 112* LSA might be borderline with stock Merc manifolds, but I recall kidnova running the more aggressive ZZ502 cam with stock exhaust and I think it lived. I'm sure if I tried it with my luck the damned thing would suck water like a straw. :crazy:

yea i do not recommend running stock exhaust with any engine :) and would use some sort of aftermarket ignition msd, crane etc.

His boat had riser blocks...thus why I think it didn't.

It's all about the gravity. ;)

496HO manifolds and tubular risers workout?

I am curious as to the cam and would it fall off too early after looking at the graphs....

Maybe a single plane intake would help out?

It shouldn't fall off too early, however, if you want more power you'll have to break out a wad more cash.

Cam, lifters (for higher lift) , Roller Rockers, ValveSprings, Pushrods.............

How about the freeze plugs ?? Are they brass or SS ?? If not one of the 2 might want to change them.. Head gaskets will prob be ok. Run the exhaust valves a little on the loose side.. And yes might want to use a marine style carb with the looped vent..


John jr

And when you think that wad of cash is big enough, grab some more. ;) Wish I had come across a deal like this when my 454 bit the dust a couple years ago. Would have saved me a LOT of money. Should run similarly to a 502 Mag. Depending on your intentions for the boat, might make a nice package. If you are worried about reversion, look for a used Mag cam in the Swap Shop. Should be pretty much a bolt-in swap.

Freeze plugs are brass. I bought the engine.

What carb would y'all recommend?

Stick with the gmpp dual plane intake?

Do a search on in this section for ZZ502 modifications to marine use and/or Kidnova username search. He and I both have done the ZZ502 motor. And to your question on the intake, NO. Throw that crap in the scrap bin. Single plane--4150 based intake of your brand choice. I found the HP950 Holley worked very good. Before you guys all say that it is too big, it is NOT. That carb is really a high velocity 750-800 carb.

Changed out the oil filter bypasses as mentioned.

I'll look at single planes today. Dart? Victor jr? Something else? I'm only looking to run up to 5-5200 rpms

Spacer?

Thanks for the help so far.

I like the edelbrock rpm air gaps myself. I had a 540 ci with a tunnel ram single dominator (wasn't my choice) and ran until i could not stand how much fuel it used. I put ann rpm air gap and a 950 and there was a 100rpm difference at wide open throttle

On the intake subject, remember one of the most popular motors around (Merc HP500 carb) used the single plane, 4150 base Dart manifold. That would be my choice given your motor situation. Other notables:
1) ditch the stamped rockers and go with some nice roller rockers.
2) because of #1, you must now go to a marine style valve covers.
3) staying with the valvetrain, ditch the .058 wall push rods and replace with some .080 replacements.
4) replace the intake and exhaust valve springs with at a minimum the next step up in springs available for your specific requirements.
5) Lastly, go talk to Bob Madera aka rmbuilder about a new cam for your motor.

6) Break out the checkbook from that account that the wife doesn't know about. ;)

RE #2 - you can keep the stock covers if you double up your gaskets or go with one of the extra thick sets. The Scorpion marine endurance rockers work well with the stock covers when you do this.

On #6, hell no. Only the valve covers really pose spending some real money. All others are very affordable. If he checked around, many have those parts (good used) for sale. Especially some engine/motor shops.
Good info on the Scorpion rockers and the gaskets. Learned something today. Thanks.

SBX, clear out your inbox.

Cleared pm box

Here's the old engine

http://i19.photobucket.com/albums/b1...pse9fa6d21.jpg

New engine as purchased

http://i19.photobucket.com/albums/b1...psrqm3adjm.jpg

A few parts from the new and the old engine

http://i19.photobucket.com/albums/b1...psnvsebdwf.jpg

And start of assembly
http://i19.photobucket.com/albums/b1...psmn6owxgn.jpg

http://i19.photobucket.com/albums/b1...psppvvbjny.jpg

I do think I am going to pull the intake though and swap to a rpm air gap or small single plane. I've been reading and reading and there's so many opinions. Some say air gap with a 1" hvh super sucker spacer.

Honestly, unless you go with a larger cam I doubt if you will see that much difference between the Air Gap and a Dart-style single plane. The plenum design on the Air Gap works pretty well all the way up to around 5000 RPM. Above 4700 or so RPM's, the single planes start to make more power, but below that, the AG excels. However, either would be an improvement over the stock one, which is 1960's technology. I have both if you are interested.

Air gap with a spacer or no?

Send me a pm with the price shipped to 77662 please budman

I have square port heads.

SBX, it really depends on the application. I tried a 2-inch super sucker on my 489, and it didn't really help, but there are others who are seeing a solid 10-20 HP increase with them. SB might be able to help with this. I think they probably help out more on the dual plane applications in general.

I'll send a PM with price and shipping estimate this evening. Have to tie some things up at work before Miller time.

So you are ditching the MPI?

Yeah the mpi is gone.

The entire setup from intake to oilpan is for sale it was running when pulled but getting water into 4/6 not sure how really. Planning to take the engine to the machine shop for tear down and inspection. Then either putting back as long block and selling or parting out. Not sure.

I wanted a little more hp and going carb was the easiest quickest and most cost effective route.

Yes hvh spacer and an air gap is what I am using

If your carb is on the small side for your motor, use an open spacer on the dual plane. Shhhhh, speed secret.

If you have plenty of carb, then a spacer won't do much on a good dual plane.

What is this going to have for a carburetor ?

850 demon or 9022 800 holley

Own the demon already but it's been sitting a little over a year.

Yep, it lived just fine. Like SB said, I had the 3 inch riser blocks on my stock Merc exhaust, which likely helped prevent water sucking. I ran the ZZ502 hard for 4-5 seasons and it ran like a Swiss watch... flawless. I know zip about the 502HO but if it's built to the same standards as the ZZ502, and if it hasn't been opened up and fk'd with, I'm pretty sure all you'd need to do to get on the water is change the bypass valve in the remote oil filter pad, step up to a bigger oil cooler, get a decent exhaust system, bolt on a marine carb that's the correct cfm for the CI, and go boating.

I need a good carb. Thinking the Holley 9022 800cfm would be perfect

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.

I also changed the oil bypass valve to the 30 pounder from a 6.2L diesel. And I used the 1" carb spacer that was on the 454. Good luck.

I ran mine w/ the stock exhaust and ignition, one inch spacer w/Holley 9022 Carb, did not change anything else, it topped out at 5100 rpm, it ran perfect and dependable, I did not want a hot rod engine, I wanted dependability on a low budget ,

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.

502 HO Technical Information

Horsepower ..................... 450 @ 5250 RPM
Torque .......................... 550 Ft. Lbs. @ 3500 RPM
Max. Recommended RPM ..... 5500
Compression Ratio ............. 8.75:1
Block ............................ 10237292 Cast iron - Four bolt maincaps
Crankshaft ...................... 10183723 Forged steel
Connecting Rods ............... 10198922 Forged steel -Shot peened, 7/16" bolts
Pistons .......................... 12533507 Forged Aluminum
Piston Rings .................... 12524293
Camshaft ........................ 24502611 Hydraulic rollerLift: .510" I, .540" E.Duration @ .050" 211o I, 230o E.
Timing Chain ................... 3891519 Single roller
Cylinder Heads ................. 14096801 Cast Iron118cc Combustion chambers
Intake Valves ................... 14097045 2.19"
Exhaust Valves .................. 14097049 1.88"
Valve Springs ................... 14097002
Rocker Arms .................... 12523976 1.7:1
Intake Manifold ................. 3933163 Aluminum with Holley flange
Torsional Damper .............. 10216339 8"
Flexplate ........................ 10185034 14"
Valve Lash ...................... Net lash
Spark Plugs ..................... MR43T Gap .045#10 Rapid Fire Gap .045
Fuel ............................. 92 Octane
Ignition Timing .................. 36° @ 3600 rpm With vacuum advancedisconnected

NOOO Use an HP Holley carb. Before you keyboard captains sound off, "now hear this". Send the carb off to a carb shop. For lunch money they will install the correct marine vent tubes. Bam, you now have an HP marine carb.