OMC 2.3L Cam swap to roller cam setup **UPDATED**

[jpwilly]

Like many owners of these rare sterndrive setups I've come to appreciate the info available on the internet. So the purpose of this thread is to hopefully help others with the same issue(s) I have encountered on my boat.

The Ford 2.3L "Pinto" engine marineized by OMC and mated to the "Cobra" sterndrive. My 88 bayliner 1750 has been down on power. I knew when I got the boat it had cam lobe wear. The previous owner said he hadn't gotten around to changing out the cam. So I just installed new rocker arms to get me through the season last year. But now I wanted to fix the boat.

I've found that these motors have the same engine block / heads that were used with the Rangers and Mustangs LX of the time, to name a few. But those vechicles started to be fitted with a roller cam setup and a pre 95 roller cam with 3/8" valve stems will swap directly to these heads. I purchased a good used roller cam, with lifter and roller rockers on ebay for $100 and pulled out the old cam out this evening. So far it only took >2 hrs to tear down and I'm waiting for the parts I purchsed to arrive to install them.

Teardown was simple (follow the manual) :
1. loosen the shift / throttle cable mixer assembly
2. label and disconnect spark plug wires
3. remove valve cover
4. loosen the alternator and remove accessory belt
5. remove the water pump pully
6. remove the timing belt cover
7. loosen the timing belt tension (don't remove the bolts just loosen)
8 remove the timng belt from cam pully .
9. remove the rocker arms...I used a long slotted screwdvriver like a pry bar to pop them out.
10. remove the cam timing belt pully
11. remove the cam retaining plate on back side of cam (two phillips screws)
12. carefully remove the cam as to not damage the camshaft bearings. The camshaft seal will most likely need replacing so just pull the camshaft out and down worry about damaging the seal. I just pryed the seal out with a slotted screwdriver.

Some pictures:

Lobe wear:

Rocker Arm Wear:

Cam removed:

Scrap metal:

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

All the parts arrived yesterday:

Time to get back to work:

So I applied a light coat of moly grease to camshaft bearings and lobes. Next I installed a new camshaft seal and light coat of grease to the rubber seal, slid cam into place and installed the camshaft retaining plate. Then I installed the lifters, compressed valve springs with an adjustable wrench handle (rubber coated) as I installed the roller rockers. Next put the cam gear backing plate on followed by the camshaft gear (put some locktite on the bolt). I turned the camshaft over a few times to be sure all was well, it was and it was very smooth. Still takes a bit of effort due to valve spring tension.

Then the next task was to get the timing set. I ensured TDC with a wood dowel on cyl #1 (the timing belt cover has the TDC on it not the block-rather useless at this stage). Checked the disty rotor was on #1 fire position in relation to the cap (no alignment mark on the block for this either). Fortunately the camshaft had marks to align to. Once all were lined up it took a couple of tries to get the belt on and under tension without the marks moving by a tooth on the belt. But at last success and I tested by (spark plug wires removed) turning the key and hitting the starter. Then checking turning the crank to TDC and checking that all marks were back where they should be.

I then reinstalled the timing belt cover, water pump pulley, and accessory belt, (tensioned buy adjusting the alternator and tightening back down). Finally I reinstalled the valve cover with new gasket, tightened down a few other items that had to be moved out of the way to get the valve cover off, disty cap etc...

While waiting for parts I drained the gear oil and pulled the sterndrive inspected the bellows, etc lubed the u-joints, checked the shifting etc… and reinstalled.
I'm just waiting on an exhaust manifold elbow gasket so I can fire it up and set timing with my timing light.

This wasn't a difficult project and if you have one of these 2.3l's with worn cam gear lobes the Mustang or Ranger pre 95 roller cam with 3/8" valve stems will swap directly to our heads. I have no idea what effects on power this swap will. I'm sure there's some change to the power curve and idle quality. I'll report on this later after I get a chance to run it on the lake.

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

Cam Specs:
Marine flat tappet:
Cam lift is 0.2381 +/- 0.005, 1.64 rocker = .390 valve lift
I don't know the rest of the specs of the Marine cam but I have one at home and could take some measurements with a caliper and figure this out.

(If any Camshaft Mfg would like my old marine cam so they could profile it to fill special orders feel free to PM me.)

Ranger Roller Cam spec's:
Cam Lift (Intake):.216"
Cam Lift (Exhaust):.216"
Valve Lift (Intake):.355"
Valve Lift (Exhaust):.355"
Duration at .050" Lobe Lift (Intake):189 Deg
Duration at .050" Lobe Lift (Exhaust):186 Deg
Valve Lash (Intake):Hydraulic
Valve Lash (Exhaust):Hydraulic

Lobe Center Separation: 112 deg (I like that fact that LS is 112 like most marine cam grinds)
Intake @ 0.050:
- Open: 14.5 deg BTDC
- Centerline: 108 deg
- Closed: 21.5 ABDC
- Duration: 187 deg

Intake @ 0.00 lift:
- Duration: 248 deg
- Lift: 0.390"

Exhaust @ 0.050:
- Open: 30.5 deg BBDC
- Centerline: 116 deg
- Closed: 21.5 ATDC
- Duration: 189 deg

Exhaust @ 0.00 lift:
- Duration: 250 deg
- Lift: 0.390"

I plugged the .050" info from the roller Cam specs above into this Camshaft Calculator and this the output:
The Ranger Roller Cam has an Overlap of 36.00 degrees and has in Intake Duration of 216.00 degrees. The Exhaust Duration is 232.00 degrees. The Inlet Cam has an Installed Centerline of 93.50 degrees ATDC. The exhaust cam has an Installed Centerline of 94.50 degrees BTDC.

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

I buttoned up the ranger roller cam install last night. It fired right up and then I set the timing. Here's a video of it idling in the driveway on muffs. I still need to adjust the idle speed on the carbs but I like to do that in the water. Water Test comming soon hopefully this weekend.

 

[wcasey5]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

excellent writeup! The power on the water will be interesting. Let us know. It sounds good!

 

[Kainon]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

GREAT Post !!! Great Info!!! Good Luck!!

 

[Scott Danforth]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

good write up.

if you find that the reduced lift of the ranger cam isnt cutting it, contact Elgin Cams and have them grind you one.

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

After searching and finally finding some more info in my OMC Manual here's what is says about the cam lobe lift and rocker arm ratio on page 3-20 of the 1986 - 1998 OMC Sterndrive Manual:
Lobe Lift 0.2381" +- 0.005" metric is:6.05mm +- 0.1mm
and
Rocker arm ratio 1.64:1

I measured the marine cam with my calipers to check for myself. But the battery was dead so I used the backup numbers on the slide. I measured the cam the diameter; 30mm and 36mm from top of lobe giving approx. 6mm of lobe lift or .2362". If the battery was working I'm sure this would have matched up with the spec in the manual more closely. Now that we have those specs we can run the numbers and that’s .390" valve lift. The SAME theoretical valve lift as the roller cam!

So here's my theory: There is NO difference between the marine / automotive flat tappet cam AND there is no difference between Marine / Auto flat tappet or the Ranger Roller cams with respect to valve lift since it’s .390" on all three. Who knows how the valve overlap and duration numbers all play out but I'm guessing not much of difference there either.

Another theory. When Ford figured out that the slider cam lobes were wearing flat they didn't feel they needed to start over and instead they engineered the roller cam to meet or simply replace the slider cam, i.e. lift is the same, and most likely there is little difference in other cam performance specs.

Furthermore, Ford or OMC didn't change the CAM specs for a few pesky boats ( I mean the marine the version ). The only major issue to deal with would have been reversion and maybe they didn't find any problems and left it alone?

Thanks for the feedback everyone! I'll report back after our trip to the lake.

UPDATE: We had the boat out at Lake Pleasant AZ today. We arrived 8am and stayed untill 12 noon, ramps were busy! The engine ran great. Much smoother than before. First thing I noticed is the lack of valvetrain nose and engine happily ran 4000-45000rpm 3/4 throttle no sweat with max RPM today 5200 trimmed up. The low end power was also back. We had trouble planing before if there was too much weight aft. Not this time it took about 4 seconds to plane even with wife a kid and gear in the very back. I'm running a 13 3/4" x 15" prop. We had a fun day boating and very happy to report the cam swap was a big success at this time cannot say I discovered any drawbacks!;

 

[skidooseadoo83]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

Nice write up, good info. Bookmarked.

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

UPDATE second outing:

Runs well! My father-in-law and I with my three kids, full fuel, and gear went out to Lake Pleasant again. I set timing advance on the lake (he floored it and I turned disty counter-clockwise to advance timing. Once the engine hit full rpm I advanced some more no pinging but no RPM gain so I back down to max advance required for best RPM, I run 91 octane).

Swinging an OMC 13 3/4" X15P we hit 5600+-RPM and 33-34mph indicated on GPS. Swapped over to my 13 1/4 x 17P OMC prop and we hit 35-36mph at 5200+-rpm with slower time to plane and overall just felt "mushy". The 15" prop feels like it bites the water any small throttle input and the boat reacts immediately.

I don't know what the compression is on this motor and I'm guessing that it's on average for a 24 year old boat. I think new the boat came with a 14"x19P" OMC prop that was capable of running in the the same RPM range.

 

[Ivan DeSlayer]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

UPDATE second outing:
Swinging an OMC 13 3/4" X15P we hit 5600+-RPM and 33-34mph indicated on GPS. Swapped over to my 13 1/4 x 17P OMC prop and we hit 35-36mph at 5200+-rpm with slower time to plane and overall just felt "mushy". The 15" prop feels like it bites the water any small throttle input and the boat reacts immediately.

I don't know what the compression is on this motor and I'm guessing that it's on average for a 24 year old boat. I think new the boat came with a 14"x19P" OMC prop that was capable of running in the the same RPM range.

Thanks for this info I've been all over the web today looking for prop info since the boat I got came with a mystery prop and the original 14" x 21P. Which will get on plane but you need to weigh 50lbs. and half a 700 acre lake to get there.
Next season will be freshy fresh time for the motor but for now just a prop change will do.

 

[jpwilly]

Re: OMC 2.3L Cam swap to roller cam setup

Re: OMC 2.3L Cam swap to roller cam setup

Thanks for this info I've been all over the web today looking for prop info since the boat I got came with a mystery prop and the original 14" x 21P. Which will get on plane but you need to weigh 50lbs. and half a 700 acre lake to get there.
Next season will be freshy fresh time for the motor but for now just a prop change will do.

How did the new prop treat you?

My family and I went out again yesterday and the boat is running good. The new roller cam is smooth and the motor is happy at all RPM's. I ran it wide open for for a few min when we first got out, there was no chop the kids loved going fast without bouncing accross the lake. I find myself settling in at 3200-3500rpm for most of our cruising is much easier on everything.