I am in the process of a repower on a Donzi 22. I went with the 502 crate (marine) from 1800runsnew.

I called and asked them what the cam specs are and their response was that G.M. keeps those specs close to their chest and that they did not know the specs. ...sounds like B.S. to me but that is as far as I got.

Does anyone know what the cam specs should be? ...standard 502. I am trying to order a distributor from DUI and they ask for the cam specs so they can set the advance up properly.

Thanks,
Jay

ENGINE MODEL

454 MAGNUM

502 MAGNUM

8.2L


Lobe Lift + .020 (0.051)

Exhaust

.342 (8.687)

Intake

.342 (8.687)


Duration at .050 In. (1.27 mm)

Cam Lift

Exhaust

227°

Intake

211°

Journal Diameter

1.94282-1.9492 (49.485-49.509)

Journal Out Of Round

.001 (0.025) Maximum

Camshaft Runout

.002 (0.051) Maximum

Timing Chain Deflection

3.375 (9.5) from taut position [total .75 (19)]

Found that @ Perfprotech.com

Do a little looking on yahoo or google. It is not hard info to find. No secret. It would be mercruiser info not gm you would be looking for.

GEN 6 Billet Roller Cam

Mercruiser 454 502 Mag Roller
Merc# 431-850478 / GM#12551622
.004 300*/ 300*
.006 288*/288*
.050” 225*/225*
.200” 125*/125*
Lift .483”/. 483”
ICL 109*
LSA 115.5*

I also purchased two brand new engines from 1800runsnew
Took them apart to put in RMBUILDER cams, and did some headwork.
Best of everything, no problems whats so ever.

What kind of gains did you see with the Bob cam? Did you do anything else? Different springs, lifters, valves, rocker ratio ect.?

Yes, I had to change the springs to match the cams.
As always, great idle, they pull to 5,000rpms no problem.
The other reason I wanted new cams, was to get a fuel pump lobe.

If I had to do it all over again, I would have saved the money for $4.00 a gallon gas.

4$? C'mon. You should try boating around here. 9$ a gal.

I would have to get rid of the first mate.

This is the right spec numbers for the new GM base 502 new engine only

Thanks All.

My plan is to run it for a season and then consider going for a cam change too.