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| cam question http://mudmotortalk.com/mmt_v2/viewtopic.php?f=3&t=14598 |
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| Author: | cb5331 [ Wed Dec 15, 2010 3:36 pm ] |
| Post subject: | cam question |
We have a 32 briggs pd. The motor has heads decked .055, roller rockers, springs, rods, exhaust, and a 36 carb. Recently the case gasket started a slow leak (nearly 300 hours and I believe the first time), so we had plans on replacing it after the season and putting in the arp studs. We talked about putting a cam in it, and a deal came up that I couldn't pass up, so we bought it. It's a 493f. I was talking to someone the other day who suggested that the cam was a bad idea in the 32. It was someone whose opinion I definetely trust when it comes to these things, so we have pretty much already decided it will be going back up for sale soon. Wasn't able to get much more out of em than the fact that it was a short stroke motor built for torque. I was hoping to get a little more elaborate response as to why it would be a bad idea. Not second guessing, just would like to understand it a little better. Why would the short stroke motor not benefit from a performance cam? Thanks! |
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| Author: | JD [ Wed Dec 15, 2010 6:07 pm ] |
| Post subject: | Re: cam question |
cam and rollers not a good idea ,mine lasted 2 hours with the evt and i have about 50 on the bps. too much duration if you have any real lift in the cam. JD |
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| Author: | cb5331 [ Wed Dec 15, 2010 7:16 pm ] |
| Post subject: | Re: cam question |
What exactly happened to your motor, and what cam were you running? I've seen a bunch of problems with the cheetah. The 493 is pretty mild. Just about every piece of literature, every forum, and every performance shop I've spoken to says the rr's pay for themselves when paired with the cam. I am still learning and appreciate the input, but I'm curious if what you think caused the problem is really what happened. |
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| Author: | craig [ Wed Dec 15, 2010 7:24 pm ] |
| Post subject: | Re: cam question |
The rollers or a waste of money dude....you will NOT notice any performance increases using them! |
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| Author: | cb5331 [ Wed Dec 15, 2010 7:26 pm ] |
| Post subject: | Re: cam question |
Yeah, I know they aren't worth the money. The heads came with them. It was cheaper to get everything already put together than to just have the heads decked and get the ss valves. And we got to keep our stock heads. Any input on the cam? |
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| Author: | jbert22 [ Wed Dec 15, 2010 7:29 pm ] |
| Post subject: | Re: cam question |
So peformance cams are a bad idea? |
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| Author: | cb5331 [ Wed Dec 15, 2010 7:42 pm ] |
| Post subject: | Re: cam question |
| Author: | jbert22 [ Wed Dec 15, 2010 9:46 pm ] |
| Post subject: | Re: cam question |
I'm just wonderin if addin a cam shortens the life of the motor. |
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| Author: | cb5331 [ Wed Dec 15, 2010 9:53 pm ] |
| Post subject: | Re: cam question |
Anything you do to modify the way the manufacture intended it can shorten the life of the motor. But stock cams and other parts fail too, even on bone stock motors... If you have someone do the work that know's what they are doing, they can get you a lot of relatively reliable power. The stage 1 motors seem to be lasting a loooong time and making some killer power with the right recipe 
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| Author: | craig [ Wed Dec 15, 2010 10:06 pm ] |
| Post subject: | Re: cam question |
| Author: | caddobrook [ Wed Dec 15, 2010 10:23 pm ] |
| Post subject: | Re: cam question |
I still don't see an answer to the question that he asked in the thread.... And I am curious myself.. Is adding a cam to a 32/31 a good idea and if not, can someone (that knows what he is talking about) give us non-mechanics an idea or thought as to why not? I hear that someone knowledgeable said it is not a good idea and so the question why not? not arguing with that answer just want to understand the mechanics of it if not... It is how we learn.... Carry on.... |
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| Author: | drake1 [ Thu Dec 16, 2010 7:07 am ] |
| Post subject: | Re: cam question |
That cam will make a differnence in that 32HP. That is a different cam grind then what JD had. You will be fine with that cam in your 32. I run that same cam grind in my Gennie right now. |
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| Author: | JD [ Fri Dec 17, 2010 7:11 am ] |
| Post subject: | Re: cam question |
The problem with the briggs big block is that it is a split case and the cam is supported only on the ends. Roller rockers add more ratio and leverage againts the cam, add more lift with a performance cam you have even more stress, then you need to add more spring pressure for higher rpm adding even more stress. Welding up cast cams and regrinding is part science and part voodo . If it comes out too hard it can be brittle , too soft the the lobes go flat. The cam seems to be the weak link in that more of them fail than rods or case's from what I see here. My cam failed at 2 hours one in the drive way one on the water. If you add a cam check for spring bind . Same heavy ass load "with a cam 27 mph" "with out 20 mph" on a 20x60 and a hard blind pleny of wind resistance) Hoyt at Gtr has a good set up for makeing power and haveing good engine life. JD They make power but at a cost of engine life. |
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| Author: | cb5331 [ Fri Dec 17, 2010 6:31 pm ] |
| Post subject: | Re: cam question |
I want to say the 493 cam is not welded up. I think the lift is the same, and they are doing something else to create a little more duration. I still wasn't saying I was using it either. Actually I was kinda saying that I did not plan on using it, I just didn't really understand why. Anyone else got any input on why a short stroke motor would have an issue with a performance cam? I know some others with the 31's and 32's using them with good luck, and a few more with the genny which is a short stroke motor also. |
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| Author: | deadbird8 [ Sun Dec 19, 2010 9:57 am ] |
| Post subject: | Re: cam question |
| Author: | cb5331 [ Sun Dec 19, 2010 7:24 pm ] |
| Post subject: | Re: cam question |
What two cams are those db8? The one we got looks more like the one on the left...Sharper peaks. The one for my kohler looks more like the one on the right...More rounded. I'm assuming the rounder edge would be more duration, no? |
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| Author: | deadbird8 [ Sun Dec 19, 2010 7:57 pm ] |
| Post subject: | Re: cam question |
left Stock Briggs 35, right is BPS cam for 45mag Rounded is longer duration. |
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| Author: | cb5331 [ Mon Dec 20, 2010 3:49 pm ] |
| Post subject: | Re: cam question |
Weird, wonder if the one we got is stock... I just went and looked at it again and it is def sharp like the one on the left. Don't see how very much duration could have been added at all. Anyone else got a pic of the 493 for comparison? |
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