[QUOTE=SB;4397357]I thought the later tall risers got rid of the reversion on the HP500 ? They are pretty damn tall.

http://www.cpperformance.com/images/...e/15730_1_.jpg[/QUOTE
Anyone know of a place to have the inners extended on my tails?

Not sure the material but they were the cams that had the black color inbetween the lobes. The gold ones were the good ones.

The ones that were black in color were were breaking. The copper colored ones were not breaking.
Don't know the specifics on the different cores that were being used.

Yep.

Milds add from " compperformance " says it is a billet steel core

so these are the good ones[IMG]20160128_215413(2).jpg[/IMG]

well i have a pict of a steel billet cam but cant seem to post it with the gold between the lobes

Blurry pic
http://static.summitracing.com/globa...rn-1449051.jpg

..

Funny thing is the 5150 is actually a better base material than the 8620. But due to the difference in material requires it to be induction hardened rather than oven baked which is more controlled and yields a better finished product.

[QUOTE=dvalen11;4398021] Call the manufacturer and if they don't offer that service I bet Stainless Marine will.

A custom cam does not guarantee that it will work, or work better then an off the shelf cam. Even if it does will it even increase the boats speed or reliability or just make the owner feel warm and fuzzy inside due to the hype.

There's a LOT of R&D already put into off the shelf cams.

But custom cams are cool just not for everyone.

What I enjoy are these threads helping fellow members look at multiple options!

What are peoples thoughts on the large split duration of many off the shelf cams? Many Crane cams have close to 10 degrees more on the exhaust to help out the poor exhaust flow of stock gm heads, but most aftermarket heads have much better exhaust ports. Does less of a split, say 2 or 3 degrees work better on a good after market head?

In some cases, the custom cams have actually made less power and proven less reliable than a well designed/picked off the shelf cam.

Lot of variables on that i think. I think some of the custom cam guys tend to overshoot that concept. They start looking at exhaust flow numbers, that may be false. Like some heads advertise big flow numbers on the exhaust, but when you take the pipe off , they dont really flow much better than some other comaprable heads.

I think there's some merit in that, with better flowing heads. For instance, my cams were spec'd with less of a split than I was running previously with Merlin heads (now AFR 357 CNC). I also went went from a solid roller to hydraulic. I also had the benefit of running the solid roller with the Merlin heads and also the 357's. When I built the new engines last winter, they were basically the same (a few cubic inches "less") and I picked up a decent amount more power with the new cam and roughly 3 mph increase in my heavy old resin bucket.

What we did was work backwards from the Crane solid cams that I had in my engines and designed a hydralic cam that was similar in duration (converting solid to hydraulic) and maximized the lift profile, splits and LSA to work best with the heads.
https://youtu.be/xzefrv28RE0 https://youtu.be/lEqFPYBB6Vw

Sounds awesome!! Those 357cc heads must really turn on with some rpms.

Thats kind of what I was thinking with the split, but agree with Mild that there is a lot of other things going on. I'm will be running 4 degrees more on the exhaust with dart 308s, but my buddy will be running 10 degrees more (731 cam), but he has 188 heads.

I don't think custom cams should be bought untill YOUR actual heads have been flowed.

Advertised "marketing" numbers shouldn't be used.

You are correct flow numbers are for marketing purposes. When you start bumping elbows with the top cylinder head guys in the country they don't provide flow numbers for cylinder heads. Why? Cause flow numbers don't mean anything and that's not how a proper port is designed.

And yet almost every cam company/ cam designer, wants flow numbers to design your cam.

I have never had any issues ordering cams without flow numbers.

Really ? Ive had marine kinetics ask for flow numbers, jones camshafts ask for flow numbers, bullet ask for flow numbers, and even my controlled induction cam software wants air flow input to design a cam.

Sure, if you are using an off the shelf head where the cam guy has those numbers in his notes, its not needed. A custom ported cylinder head, i havent had a cam company tell me "flow data not needed "

If you call the top cylinder head guy in the country. That has all the Prostock wins over the last 5 years and does all of the cup heads and tell him you want to go race Prostock he will tell you it's $150,000 and you get three sets of heads and 2 intakes. That's all you get. No flow numbers.

When I spoke to Bob about using a set of heads from Curtis Boggs (no flow numbers) he said it was no problem. Soon after that conversation I called Bullet talked to Tim (I always check up on people I deal with). Explained the situation of no flow numbers. Again response was its no problems.

I've ordered cams from other companies and decided on using different heads for the build. Camshaft never changed.

It's just my opinion but you want to know flow numbers in selecting the right cam. Advertised numbers don't always tell the story either because a lot of those numbers are listed at max lift, like 700 or more. Back that down to 650 or so and now we're looking at numbers that might make more sense. Some heads don't flow well with a certain amount of valve lift and if you don't match the lobe profile to what the heads like then you're leaving power on the table. It's not a be-all-end-all but it's definitely important when choosing the right cam to go along with your heads. If you don't know exactly you can still guestimate and pick a decent cam but I don't think I would rely on that. Again, just my opinion.

I spin them up to 6K rpm.

With the Merlin heads the boat ran about 87mph. Several years later I bolted the 357's on and didn't change anything, literally bolted them on and I picked up 300-400 rpm and the boat ran 92.3 mph with the solid cams. Then several years later I with the new engines and the hydrualic cam I picked up another 1-200 rpm and the boat runs 95.4mph GPS.

[ATTACH=CONFIG]550245[/ATTACH]

Back in the day when Chet was still alive he made us some bh2 cams on a 114* they were a straight profile 240 @050 and 640 1.7 they made great numbers on 540ci and under engines with a nice idle, I still have a few of them left I think we did a run of 100 back then sold most in packages I really liked them.

So basically, you are saying that a 502 with gm iron heads, will be ideal with the same cam, as a set of cnc ported afr heads ? Why? Because their intake port volume is the same ?Or maybe even a big chief head ? So a 502 with a 325cc head, irregardless of brand, will utilize the same cam? What data is the cam designer using to design the cam if he has no idea what the heads flow?

i`d say those top guys are protecting their numbers that`s why they don`t give em out, kinda like cam guys won`t give you all the specs either.
Designing a cam without head flow numbers is equivalent to a mail order tune.

On a side note, why does Bullet cams have the cam recommendation page? What a waste of time filling out all that info and receive no response.
Jones got back to me within 24hr. I don`t agree one bit with the cam choice but at least he got back to me:duel:

Hmmm so does that mean after you get the head you can't flow them.

EngineLabs: How important is it for an engine builder to own or have access to a flowbench, and why?

Curtis Boggs: Personally, when I’m involved in an engine build I want to have the most data possible. For an engine builder it really depends on the level he/she wants to work on in the cylinder head program. There’s a ton of good data for an engine builder with a flowbench. Once there’s a fair amount of data collected over several builds, it becomes easier to identify trends. A good cylinder head supplier would take some the pressure off of the typical engine builder to log flow numbers. However if the builder uses several different sources for heads it could help with data and identify trends if they did it themselves. It’s important to flow heads from different sources on the same bench with the same technique. Typically when one of my customers, or any engine builder, buys a flowbench, they learn some things very quickly. First, it doesn’t take the huge flow numbers people think to make power or win on Sunday, and a peak flow number isn’t the most important number. There’s a tremendous amount of data for an engine builder. I wouldn’t build anything without one.

EL: Anything else you can say about flowbenches or airflow in general, beyond what has already been published in Engine Labs?

Boggs: Well, only that I have a reputation for saying that flow numbers don’t matter, and that couldn’t be farther from my intention. Flow numbers are very important—we are working on air pumps basically. However, the other things in a cylinder head like I mentioned earlier are as, if not more, important also. The biggest flow number doesn’t always win.

EngineLabs: How important is it for an engine builder to own or have access to a flowbench, and why?

Curtis Boggs: Personally, when I’m involved in an engine build I want to have the most data possible. For an engine builder it really depends on the level he/she wants to work on in the cylinder head program. There’s a ton of good data for an engine builder with a flowbench. Once there’s a fair amount of data collected over several builds, it becomes easier to identify trends. A good cylinder head supplier would take some the pressure off of the typical engine builder to log flow numbers. However if the builder uses several different sources for heads it could help with data and identify trends if they did it themselves. It’s important to flow heads from different sources on the same bench with the same technique. Typically when one of my customers, or any engine builder, buys a flowbench, they learn some things very quickly. First, it doesn’t take the huge flow numbers people think to make power or win on Sunday, and a peak flow number isn’t the most important number. There’s a tremendous amount of data for an engine builder. I wouldn’t build anything without one.

Good info from Curtis Boggs about flow benches and airflow

http://www.dragzine.com/tech-stories...w-flowbenches/

I'm surprised to hear that. My experience has been difference. Hopefully that's just a one-off experience you had.

Below is from a SBC I built a few years ago.[ATTACH=CONFIG]550248[/ATTACH]

I'll try to answer that a little better, based on some research i have done on this topic, for my own reasons.

One reason a longer ex duration may be chosen, is yes, to help out a weak exhaust port, or poor scavenging exhaust.

Another reason, may be to increase upper rpm power.

Advantages to a smaller split, or single pattern, is typically, more low RPM torque is produced. Everyone tends to overlook the fact, that what happens at 2500RPM, is vastly different, to whats happening at 6000RPM, or 7000rpm.

Everything is a time constraint. Its like an engine with a very late closing intake valve (more duration per say). At low rpm, it doesnt do well. There is simply too great of a loss of cyl pressure, due to the valve closing so late. However, when the engine is turning high rpm, the late intake valve closing, comes to life!! Why? because the time for filling, or should I say leakage, is reduced.

The exhaust functions on same concepts. You simply cannot have maximum efficient cylinder blowdown, at 2000rpm, and at 6500rpm, without changing something. At 6000rpm, you need more duration to evacuate the cylinder, than you do at 2000rpm. Besides valve timing, the efficiency of the port itself, and exhaust scavenging, overlap, can have an effect on what dicates the most efficient exhaust blowdown event.

It all boils down to what you want out of the engine, what RPM you are turning, and so on. I think its all about balancing the combo together. Would your engine maybe make a little more power with a larger split at 6000rpm, maybe. Would it make a little more torque down low, with less split? Maybe.

I know you have a 454 build going. Lets say for example, you stuck in a 1985 GM truck 454. its got a small high velocity oval port head, a very early closing intake valve, and very mild valve lift. You dyno that engine, and it makes 420ft lbs of torque, at 1800rpm. Thats actually an impressive torque number for such a slow engine speed. That entire engine, was designed, to tow a trailer, and it works great for that. How would it run in the boat, compared to your 454 with 308 iron eagles, fairly late closing intake valve, and higher lift? It would be a turd compared to it. Unless of course, you planned on pulling a wakeboarder around at 1800RPM all day.

My point is, that truck engines combo , was great for its intended use. Outside of that, it sucks. And your combo, would probably suck at lugging a trailer up a mountain at 1800rpm.. In order for GM to get that truck engine to do what it did, they knew that design, would net big low rpm torque, and chitty high rpm power. Your boat engine, you chose parts that will trade off some low rpm power, for much more upper rpm power. Camshafts operate on the same priniciple being that everything is a compromise, especially when dealing with an old school big block engine design with fixed cam timing.

As far as your split, if your rpm/flow outruns the cam/head combo , than you may see a power loss in the upper rpm, vs a longer split. If it isn't , than you gain nothing, and probably lose some power. Unless you're ready to start swapping cams on the dyno, it would be very hard to say what would be better.

I also think this is why the exhaust system needs to be considered when designing a cam for the combo. A set of short runner marine manfolds, might require an entirely different exhaust lobe, than a ideally spec'd header for the combo. One might say, "Well, I swapped out my GIL manifolds for a true header, and didnt see much power gain", well, maybe they would have, if the cam was redesigned with the exhaust as a consideration.

Same goes for cylinder head mods. IF, you had the absolute perfect cam for your combo, and went in and worked on the heads, changing the low lift airflow characteristics of the cylinder head, that cam is no longer "perfect". While you may see some gains from the head work, in a perfect world, making changes to the camshaft to work with that, would net even greater gains. How someone could "cam" an engine, without cylinder head flow data, is a new one to me.

1 million percent I agree on this.

Burns my azz when this get's no consideration until engine issues arise and then it get's blamed. This should be dealt with off the bat. My trust would be a cam co, person, etc that asks and understands this.

maybe they should have optimized the cam design for this.:D,,just poking fun at all of you for the 10-20hp you'll never feel in a boat.

https://www.youtube.com/watch?v=azPKIjxmmdU

I agree. Bob M wanted my AFR'S flow numbers and wanted to know about my exhaust system when designing my last cam. It turned out everything I wanted and more.

I don't known if this is a stupid question but I was thinking of going to a 525 cam in my 500efi's looking for a little more out of them. Would this work

Side note I just did top ends on them so was going to waste until they need to be done again and replace them completely with the aluminum ones. Maybe lol

Dammit, I wasted my time and money with 5" Stainless marine exhaust. I could have just got some 454 log manifolds for 1/3 of the price and lost no horsepower. :(:(

Not what I was saying.

Quote from MT
"Everything is a time constraint. Its like an engine with a very late closing intake valve (more duration per say). At low rpm, it doesnt do well. There is simply too great of a loss of cyl pressure, due to the valve closing so late. However, when the engine is turning high rpm, the late intake valve closing, comes to life!! Why? because the time for filling, or should I say leakage, is reduced."

Is it time for someone to develop an adjustable cam timing solenoid powered system for our ever popular BBC marine builds? This would lessen the need to compromise so much when choosing camshafts around specific parameters.

I also agree that its very important, and that's the exact mistake Bob made while working with my initial build.