QUESTION on CAM OPTIONS
06-09-2013, 04:07 PM
#1
Registered
Thread Starter
Join Date: Jun 2013
Location: Chaska MN
Posts: 5
Likes: 0
Received 0 Likes
on
0 Posts
QUESTION on CAM OPTIONS
I have a question on a cam option for my 1992 502 magnum MK4. I had low compression so I did a compression test, and it showed most likely in the valves. I took the heads off and found a lobe on the cam that was starting to round. I am just looking to get my boat back on the water for this year and have a motor I am rebuilding for next year. This is a flat tappet motor, and not going to upgrade to a roller this year as I just want to get out onto the water this year and it's getting late already being June. My question is: What cam can I use? I have been looking at a COMP CAM kit. I can get for around $400.00 and it comes with a timing chain and springs. But there are so many different kinds of lifts and duration, I'd like to get some advice on which one you guys think would work the best for my situation. Thanks in advance for any help and your expertise. Dave
THANK YOU!PS: does anyone know how I can put a picture onto my profile page? I didn't see it anywhere in edit my profile? THANKS
06-13-2013, 08:26 PM
#2
Platinum Member
Platinum Member
If you want a bolt-in flat tappet hydraulic cam for stock exhaust manifolds on a carb 502Mag, then the Crane 454/420 cam is hard to beat.
It will idle fine in a 502 and you'll get another 25 horses out of it with no other changes.
The Crane number is #132561 and sells for about $245 plus shipping from Jegs or Summit.
HOWEVER - there is a Sealed Power equivalent cam that is a VERY close match and is half the price.
The Sealed Power CS-1139R camshaft has a little less overlap, a tiny bit less duration, the same lobe center, and the same lift as the Merc420 cam.
Install it at a 109* Intake Centerline and you'll wake up your 502 Mag and be out less money than any other option out there.
http://www.summitracing.com/parts/sl...9r?seid=srese1 $115.00
You WILL need to replace the valvesprings, since the ones that came in your motor are known to be less than premium quality.
http://www.summitracing.com/search?keyword=vs1581&dds=1 $134.00/set
Your lifters are standard GM hydraulic flat tappet lifters. You'll need new ones with your new cam. You can use any brand or style you want, but you do need to get new ones. And smear break in lube all over them and use Kohler lawn mower oil during break-in. It's a great oil, and has much more ZZDP than ANY automobile or motorcycle oil under $4.50/qt. To get as good of a break in oil, you would have to use $9.50/qt Brad Penn or similar.
And don't ignore that advice. Current oils are NOT suitable for breaking in a flat tappet motor.
There.
That's your answers for the day. As cheap as those options are, you don't need to look any further.
If you choose to go to a roller cam, then there are a million choices to weigh.
Now, with all cams "hotter" than your stock cam, you run the risk of water reversion. The path of your thru-hull exhaust and whether your tips have rubber flappers or not will matter. And chopping the throttle to idle when coming off plane is a bad practice even with your stock cam, so avoid doing that as well.
Again, per my earlier paragraph, install the cam with the ICL at 109*. I'm not positive that the stock keyways are set up for that, so plan on buying an adjustable timing set. The cam will run stronger up top installed at 109, PLUS the exhaust valve closes earlier reducing the chances of reversion even more.
The Merc 420 cam is ground with the advance already in it, and the ICL is 109 installed "straight up" per the marks.
MC
It will idle fine in a 502 and you'll get another 25 horses out of it with no other changes.
The Crane number is #132561 and sells for about $245 plus shipping from Jegs or Summit.
HOWEVER - there is a Sealed Power equivalent cam that is a VERY close match and is half the price.
The Sealed Power CS-1139R camshaft has a little less overlap, a tiny bit less duration, the same lobe center, and the same lift as the Merc420 cam.
Install it at a 109* Intake Centerline and you'll wake up your 502 Mag and be out less money than any other option out there.
http://www.summitracing.com/parts/sl...9r?seid=srese1 $115.00
You WILL need to replace the valvesprings, since the ones that came in your motor are known to be less than premium quality.
http://www.summitracing.com/search?keyword=vs1581&dds=1 $134.00/set
Your lifters are standard GM hydraulic flat tappet lifters. You'll need new ones with your new cam. You can use any brand or style you want, but you do need to get new ones. And smear break in lube all over them and use Kohler lawn mower oil during break-in. It's a great oil, and has much more ZZDP than ANY automobile or motorcycle oil under $4.50/qt. To get as good of a break in oil, you would have to use $9.50/qt Brad Penn or similar.
And don't ignore that advice. Current oils are NOT suitable for breaking in a flat tappet motor.
There.
That's your answers for the day. As cheap as those options are, you don't need to look any further.
If you choose to go to a roller cam, then there are a million choices to weigh.
Now, with all cams "hotter" than your stock cam, you run the risk of water reversion. The path of your thru-hull exhaust and whether your tips have rubber flappers or not will matter. And chopping the throttle to idle when coming off plane is a bad practice even with your stock cam, so avoid doing that as well.
Again, per my earlier paragraph, install the cam with the ICL at 109*. I'm not positive that the stock keyways are set up for that, so plan on buying an adjustable timing set. The cam will run stronger up top installed at 109, PLUS the exhaust valve closes earlier reducing the chances of reversion even more.
The Merc 420 cam is ground with the advance already in it, and the ICL is 109 installed "straight up" per the marks.
MC
