Originally Posted by hadleycat (Post 4404111)

I have a very similar build. My motor started as a 502 Mag. Had it rebuilt by Champion Performance last year. Now it is a 509 7 lbs. Boost Procharger with 525 cam. I remember when the builder recommended the cam. In the back of my mind I was thinking why not a custom cam? I went with the Bulders recommendation as he obviously knows a lot more than me about motors. Glad I did.

Originally Posted by bck (Post 4403833)

But surely all customs can't be bad because they are all different. How do you differentiate?

Originally Posted by HaxbySpeed (Post 4403848)

Absolutely.That engine has over 700 hours on it now with a shelf cam. I just recently took apart another one, that was almost an identical build and it had popped the tie bar off one pair, and was about to lose another. I put it back together with a take out 500 efi cam and it's working well. Made a bit more power then the original cam too.

Originally Posted by MILD THUNDER (Post 4403640)

I would also like to add, that my true feeling here, is that this thread, is NOT to bash a business, as has been insinuated so many times on this forum. I think that the issues have been swept under the rug too long, and these posts are there for the average boater spending money, to realize and understand, that there is more going on, and there are some who truly do not wish to see these guys have engine issues.

For those who know ME, on a personal level, know that I am always willing to lend a hand to a fellow do it yourselfer, as I have had the blessing of being coached by some very talented builders and people as well. We are all here to learn something, share something, and at the end of the day, would rather share success stories, than those of failure.

I went to Tim's dyno session, 2 hours away, at my own travel expenses, to offer help if needed, and maybe learn something. Unfortunately, I've been loading up on ibruprofen due to hurting my back, and spent most of the time there sitting on a chair offering zero wrenching help. But, thanks to Ryan Retter of Retter Engine Development, for helping Tim out on his build, mainly to try and get a safe tune, and validate what he has going on there. Not many shop owners going to be staying till 10pm to get things done, taking us to dinner afterwords, and showing us to our hotel, and then meeting us for breakfast first thing in the AM on a saturday, and then back to shop for more dyno work. Once again, I was able to finally meet more oso members in person, enjoy a few laughs, and participate in something productive. That IS, what this site is all about.

Originally Posted by 1MOSES1 (Post 4403871)

I see the morel lifter name getting tossed around on this thread. Just had a set put in our 500's. They seem to be the company of choice by many of the top builders. Not just in the marine world but also the car game.

Originally Posted by Knot 4 Me (Post 4404121)

Damn. Wish I'd known this was going on over in Colfax. I would have brought coffee and scones! :D My engine is sitting over at RED right now waiting to be assembled and dyno'd.

Originally Posted by StraubTech (Post 4404100)

Alex I will add in this type of application one must build a combination that can take 8K#s from 800 rpm to 6000 rpm without the assistance of gear changes. One must build for the widest most usable power within the rpm range and concentrate on torque and not peak HP numbers that in most cases the boat engine will never see.

To do the above one must use cylinder head cross sectional area best suited for maximum performance in the mid range. Large heads make HP, they do not make torque nor due the tend to make wide flat powerbands. The industry if very guilty of marketing "Bigger is Better". This naturally feeds the male ego, but in reality can lead to disappointment in the end.

I think it is key to build for average power.

Originally Posted by MILD THUNDER (Post 4404131)

I have a good amount of time invested in propping and running large offshore style boats.

I do agree that you need torque. However, i will not trade off upper rpm power for low end torque in most cases. What most fail to realize is we prop a boat so that the rpm at wot is where the engine makes peak power. If an engine makes 700hp at 6000rpm, in a particular boat, it might take say a 28p prop to get 6000rpm at full throttle. If the engine makes 600, or 650ft lbs at 3500rpm, the boat isnt going to have a faster top speed. It will accelerate faster, but most guys arent drag racing 35-40ft boats. Also, most of us, arent at full throttle at 3500rpm.

Ive seen way to many engines cammed like they are going in a drag boat or chevelle, that make great low end power, and fall on thier face in the upper rpm range, where things matter when your flogging it across the lake at full throttle trying to creep past your buddy.

My old setups had small roots blowers. Small overdriven roots can make lots of low end torque and response. Engines made as much, if not more torque with the smaller blowers. Switching to larger blowers, woke the engines up above 5000rpm big time. Boat is SIGNIFICANTLY faster . Does it go from 50-80mph as fast as it did with the smaller blowers? I dont know, never timed it, nor do i care about that. Im not drag racing an 11,000 lb boat.

Originally Posted by MILD THUNDER (Post 4403905)

Dyno tests , especially ones that remove a "custom" cam, and install a different cam back to back, tells alot, as far as that area goes. And it has been done quite a few times recently, and the results were not in favor of the "custom" cam.

Then there is the field testing part of things.

Originally Posted by vintage chromoly (Post 4403890)

How much of an advantage is going to a 55mm cam?
Lighter springs and less agressive ramp.
Also, a .904 lifter with a bigger wheel has to provide some benefit over an .842, no?