bcarpman

Thanks SB

Not sure perturbed is the right word, but perhaps. Couple days ago I asked for cam suggestions and got almost no cam advice. Just a bunch of replies from people picking on the rest of my engine component selection. Since then I've been put in contact with several marine cam people, and they all recommended similar specs to the HP500 that I have listed above (different from the Crane cam you listed).

Now I post a question about carbs and get "Your cam sucks" with no explaination or rational, and no discussion of carb sizing at all. I may be new to boat engines (but not car engines), but I'm no newbie to the newsgroups and forums, and generally when I try to give advice, I try to make it useful (as are most people here), just not the first few on this thread.

The reason I asked is that for most street applications, if you're looking for a nice idle and really good driveability, you're probably still going to run a 750 unless you're spinning it, and certainly if you look at the charts on Holley's web site you come to the conclusion the 750 is the way to go, but as you said in your post, the popular opinion around here is 800 or 850. I was looking for examples: What did the old HP500 use? Has anyone run an 850 and have it idle nice and "production like"? Has anyone replaced a 750 with an 850 and really picked up power?

I'll certainly go with the experts opinion, but it's nice to understand why.

Thanks again HP

Griff

The HP500 carb engine uses a Holley 800CFM carb.

The cam SB posted IS the cam for the HP500 carb engine. It was made for Merc by Crane. Crane didn't copy it.

bcarpman

Griff,

Thanks much, that was the answer I was looking for. Also, that is where the cam confusion obviously lies. The cam I am using is from a hyd. roller from the efi version. A completely different cam.

thanks

SB

Do you have the rest of the specs ? If so and you type them please state if seat #'s are at .004 or .006 .

Gracious.

SB

I just re-read that thread: http://www.offshoreonly.com/forums/s...9&page=1&pp=20
and found no one picking on you - we where picking the combo apart to dissect it and figure out if it will really live up to you expectations. Jeesh, if I was one of those you felt being pickd on by, I apologize, but I hope you realize that it was not you being picked on.

Rmbuilder and Cstraub, from that thread, design camshafts. Are they the best ? No, because no one is. Do they have more knowledge than 90% of us or more ? Yes, probably. They don't like to 'just a pick a cam.' If you call them, make sure to have all and everything you can for info, a 1/2 hr of time, and etc,etc because they want to put their best into it.

Anyway - a 800-850 carb is pretty close to madatory on a 500cid engine. Many of the builds I've been a part of, or atleast witness dyno, 'swallow' 700-730 or so cfm at 5500rpm. The depression in the intake is usually a chunk lower than 1" and remember carb's are rated at 1.5", not too mention many carbs don't flow 'wet' what you think - they market - they do.

Many 500cid engine with larger cams, big open plenum intake manifolds, bigger runner heads, and low compression (8.75 to 9:1) idle very nice with superb dock manners.

Like everything, it's all in combination.

Lastly, again, sorry if it looks like we are putting you under the gun. It's quite oppossite - the people trying to help so far are scrutinizing the combo to help you achieve what you are looking for to make you happy.

Hope you understand.

bcarpman

The specs I took down over the phone are:
226/226 @.050 and 545/540 lift LSA114
Not positive I understand your question, but as it says, those durations are at .05 From what I can recall from my cam design days, numbers at .004 or .006 are not very usefull, other than in comparison to the .05 numbers, and only then as a rough estimate of cam ramp design (sorry if I'm missing something, it's been over 15 years since I designed a cam)

As there seems to be such confusion over these cam specs, I'll call again tomorrow and confirm.

PS. Not really worried about being picked on or picked apart. That's part and partial to asking questions on the internet. Just frustrated that of all the obviously very knowledgeable people here (why I joined in the first place), no one seemed interested in actually answering either of my questions.

From the first thread, I did come to the conclusion that although my head choice was sound, they were going to need some port work, and now I'm hooked up with HayJay. I also learned about Tyler Crocket, so now I have somewhere that dynos marine engines once it's assembled. I now have my Carb question answered, which is great.

Like I said in the second post. Sorry if it sounded sarcastic (or pissy, it really wasn't meant that way). I was just searching for some justification to WHY my commponent choice was off.

SB

Cool !

Typing can be a problem because lack of facial/tone/body emotions.

Definatley understood !!!!

Using Hayjay and TylerCrockett puts you in very good hands. Okay, super good hands. Great choices.

Yes, there are not enough data points given to us from the cam manufacturers to figure out everything, so the more we can get, the more we will know about them. I am mentioning seat durations when asking for .004" and .006" They can mean a whole lot, overlap especially and then seeing how fast/quick/agressive the ramps are. Good case in point is that thankfully some manufacturers are stating their .200" lift durations values now.

Got to go wax zee boat - have a good night.

AIR TIME

I just want to chime in for a sec for a carb NICKERSON IS GREAT there building me a 1050 right now. they could set you up. my buddy has a 850 with the auto, choke and the crane 731 cam chevy reg ported heads with a little bowl work C/M headers runs real nice around the docks and with bottom paint hits 76 all day in this 24 super boat. hp is around 550hp. I have a isky cam in mine which is giving me about 650hp and its not bad at the ramp once it warms up. hope this helps a little

bcarpman

Arrgghhh!!

After talking with some more people, I'm now even more confused. Turns out the cam I thought I was settled on is a "regrind" off of the HP500EFI with specs of .548/.547 229/[email protected] 114 LSA, not the original cam like I had been told.

Now I'm being told this will really hold back this motor. I was now recommended a cam w/ .568/.576 224/232 @ .050 112 LSA. I'm a little concerned with reversion at 112 LSA and wonder about cam life with the extra lift at less duration.

Any thoughts? Other suggestions (roller hydraulic)

SB

LSA effects valve opening / closing points which also gives us your overlap and 'where it is.' Without your seat #'s we don't know these points.

This is why I've ben asking for these.

Very critical........especially with boats and wet exhausts.