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Cam Specs on a standard 502 GM Marine engine?

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Old 02-13-2012, 11:20 AM
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Default Cam Specs on a standard 502 GM Marine engine?

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
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Old 02-13-2012, 11:45 AM
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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)]
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Old 02-13-2012, 11:49 AM
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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.
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Old 02-13-2012, 12:19 PM
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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.
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Old 02-13-2012, 12:24 PM
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Quote:
Originally Posted by 1BIGJIM View Post
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.?
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Old 02-13-2012, 08:04 PM
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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.
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Old 02-14-2012, 05:46 AM
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Quote:
Originally Posted by 1BIGJIM View Post
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.
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Old 02-14-2012, 06:29 AM
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Originally Posted by A.O. Razor View Post
4$? C'mon. You should try boating around here. 9$ a gal.
I would have to get rid of the first mate.
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Old 02-14-2012, 07:41 AM
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Quote:
Originally Posted by 1BIGJIM View Post
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.
This is the right spec numbers for the new GM base 502 new engine only

Last edited by Rockfish71; 02-14-2012 at 07:45 AM.
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Old 02-14-2012, 11:27 AM
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Thanks All.

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