Proper 500HP Carb
 

As with most topics, I seem to get a variety of advice on this one.

I'm building a 490cuin BBC. Hopefully somewhere around 475-500HP. Idle is important.

Just calculating by VE, I come up with 750cfm as the perfect sized carb, but some have told me I should definately step up to an 850.

I'll be using a roller cam from a HP500. What size carb did the old carburated HP500 run?

ANyone run either an 850 or a 750 on a similar motor? What are the tradeoffs at that HP level.

Thanks again

Re: Proper 500HP Carb
 

800 cfm carb

Re: Proper 500HP Carb
 

why use that cam when there are so many better ones!!!!!!!!

Re: Proper 500HP Carb
 

I guess I'll answer that question with another question. How do you define "better"? Higher lift (bad for valvetrain durability)? More overlap (bad for idle, reversion and driveability)? Or do you know something about the lobe profile that I don't know?

Hope that doesn't sound sarcastic, but your question was a little open ended. That cam is obviously capable of making 500HP (all I want), idles like a champ, and reportedly has no reversion problems.

Re: Proper 500HP Carb
 

an hp525 vs an hp500. look at those cam specs.

Re: Proper 500HP Carb
 

That cam will revert. That is the reason that merc switched to a taller Gil riser.

Re: Proper 500HP Carb
 

Merc HP500 Carb
Crane Gen VI#169611 Grind#HR-284-2S-10IG
Adv 284, 292 at .004” Lift with 1.7 .576 / .598
At .050” 222, 230
ICL 105, ECL 115
LSA 110

Part Number: 169611 Grind Number: HR-284-2S-10 IG
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1996 Up CHEVROLET 8 HYD. ROLLER WITH CAST IRON DISTRIBUTOR DRIVE GEAR
Engine Size Configuration
454-502 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 339 @Valve 576 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 352 @Valve 598
Rocker Arm Ratio 1.70

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 33.0 BTDC 71.0 ABDC 284 °
Exhaust 77.0 BBDC 35.0 ATDC 292 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99896
Loads Closed 150 LBS @ 1.900 or 1 29/32
Open 441 LBS @ 1.330
Recommended RPM range with matching components
Minimum RPM 2500
Maximum RPM 6000
Valve Float 6500

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 6.0 BTDC 36.0 ABDC 105 222 °
Exhaust 50.0 BBDC 0.0 BTDC 115 230 °

Remarks:
CRANE 16535-16 LONG TRAVEL HYDRAULIC ROLLER- LIFTERS MUST BE USED WITH GREATER THAN .570 LIFT CAMSHAFTS TO PREVENT ALIGNMENT BAR DISENGAGEMENT.

Re: Proper 500HP Carb
 

Everyone seems to have different specs for that cam, or maybe it's the confusion over early model non-roller, or the confusion over HP500 vs. HP525, but I'm guessing it may also be because it seems like people make "relpacement" cams for the motor and some are quoting those specs. Not sure which, but the one I'm looking at is a Hyd roller with:
226/226 @.050 and 545/540 lift LSA114
Which seems like an excellent compromise from a lift vs. durability standpoint, and from what I've been able to decern, people seem to be very happy with the idle on cams of around 114LSA.

Anyone have any thoughts on the Carb?

Re: Proper 500HP Carb
 

If you go with the 800cfm and a dart single plane intake and run a pcv valve you can mimic the hp500 staggered jetting. That would eliminate a lot of tuning time. I run .060 over 454s with ex hp500 carbs and single plane intakes and really like the combo. The air gap style of the dart is good in a marine application due to keeping the engine cooler in the enclosed engine room.

BT :cool:

Re: Proper 500HP Carb
 

800 mechanical to 850 vac secondary carb should be used on a 500cid engine.
===================

It seems your a little purturbed (sp ?) .

Who's everyone ? Cam companies or just people ?

OSO is a blue motor website - if you know what I mean. A ton of knowledge here. I'd give people more credit. Other than me - I answer a bazillion questions a day all over the place so my head get's 'locked' or 'frozen' a few times each day.


The HP500 (blue carb'd motor )used the HR '721' grind from Crane. Gen V and Gen VI motors. Just different cam cores.

The Bulldog 540cid 500hp motor used a big flat tappet. Also from Crane I believe.
In fact the older 454cid's used a Crane flat tappet.
The 500EFI and 525EFI also used Crane cams, but HR's.

Here's the 500EFI cam.

Merc 500EFI
Gen VI #169621 Grind#HR-292-2S-14 IG
292,298 at .004” Lift with 1.7 rocker .598” , .610”
230, 236 at .050”
ICL 109 , ECL 119
LSA 114


Part Number: 169621 Grind Number: HR-292-2S-14 IG
Engine Identification:
Start Yr. End Yr. Make Cyl Description
1996 Up CHEVROLET 8 HYD. ROLLER WITH CAST IRON DISTRIBUTOR DRIVE GEAR
Engine Size Configuration
454-502 C.I. V

Valve Setting: Intake .000 Exhaust .000 HOT

Lift: Intake @Cam 352 @Valve 598 All Lifts are based
on zero lash and theoretical rocker arm ratios.
Exhaust @ Cam 359 @Valve 610
Rocker Arm Ratio 1.70

Cam Timing: TAPPET @.004
Lift: Opens Closes ADV Duration
Intake 33.0 BTDC 79.0 ABDC 292.0 °
Exhaust 84.0 BBDC 34.0 ATDC 298.0 °

Spring Requirements: Triple Dual Outer Inner
Part Number 99896
Loads Closed 150 LBS @ 1.900 or 1 29/32
Open 454 LBS @ 1.310
Recommended RPM range with matching components
Minimum RPM 3000
Maximum RPM 6500
Valve Float 6800

Cam Timing: TAPPET @.050
Lift: Opens Closes Max Lift Duration
Intake 6.0 BTDC 44.0 ABDC 109 230.0 °
Exhaust 57.0 BBDC (1.0) BTDC 119 236.0 °

Remarks:
CRANE 16535-16 LONG TRAVEL HYDRAULIC ROLLER- LIFTERS MUST BE USED WITH GREATER THAN .570 LIFT CAMSHAFTS TO PREVENT ALIGNMENT BAR DISENGAGEMENT.

Re: Proper 500HP Carb
 

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

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

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

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

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 :D

Re: Proper 500HP Carb
 

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)

Re: Proper 500HP Carb
 

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.

Re: Proper 500HP Carb
 

The newest cam will be fine and you should have no problems with reversion. You could even go bigger. I definately would.

My cam is a Crane 168731. Its .587/.610, 226/236, 112 lob sep and its in 454. Idles at 700rpms in gear and no problems with reversion. I would not go any smaller than this for 490ci.

Re: Proper 500HP Carb
 

when we went through my 500hps we used 850 cfm marine demons I am prsently at 565hp

Re: Proper 500HP Carb
 

I tried getting those numbers for the first cam and they didn't have them. I forgot to ask for the second cam. I'll ask when I talk to them again. Sorry

Re: Proper 500HP Carb
 

Here's a good comparison of 3 Mercruiser hydraulic roller cams. One is for low hp 454's, next is for Magnum 454/502 motors, and third is for the 502 HP500 (carb) . Take a good look at the .004" , .006" seat #'s , .050" #'s, lift, etc,etc

If we just went by .050" #'s we'd probably make incorrect assumptions about all the rest of each cams spec's.

Also, since most manufacturers don't come out and tell you what the seat °was taken at (.004", .006" or what have you) imagine if you where told cam #1 had 280°,299° advertised duration and cam #2 had 288°, 288° seat duration. We'd be screwed !!! This is why all of us, when comparing cams, we need to know where the seat ° durations are taken at. Impossible to compare two cams without EXACT info.

Merc Std BB Roller
.004” 280,299
.006” 266*/284*
.050” 204*/209*
.200” 113*/114*
Lift .480”/. 483”
ICL 115.5*
ECL 120.5
LSA 118*

………………
Merc Mag Roller
.004” 300*/ 300*
.006” 288*/288*
.050” 225*/225*
.200” 125*/125*
Lift .483”/. 483”
ICL 109*
LSA 115.5*

……………………..
Merc HP500 Carb
Crane Gen VI#169611 Grind#HR-284-2S-10IG
Adv 284, 292 at .004” Lift with 1.7 .576 / .598
At .050” 222, 230
ICL 105, ECL 115
LSA 110

Re: Proper 500HP Carb
 

Ok, so maybe I'm back to this (168731) or
Merc 500EFI
Gen VI #169621 Grind#HR-292-2S-14 IG
292,298 at .004” Lift with 1.7 rocker .598” , .610”
230, 236 at .050”
ICL 109 , ECL 119
LSA 114

It appears to be similar except for a little more intake and lobe separation. Since I wouldn't mind sacrificing a little top end for more assurance of a better idle and no reversion, maybe this is my best bet. Of course that's where I started in the first place. With the HP500EFI cam, just not the specs I thought that cam had.

thanks again everyone

Re: Proper 500HP Carb
 

Similar - Let's look closer.

Hp500.....731.....500EFI
#19611...#168731...#169621

Note: figures below include cams ground or installed 5°advanced

IVO...33BTDC....33BTDC.....33BTDC
IVC...71ABDC....75ABDC.....79ABDC
EVO...77BBDC....82 BBDC....84BBDC
EVC...35ATDC....36ATDC....34ATDC

68°......69°.....67° overlap measured from .004"

105°....107°....109° intake centerline
115°....117°....119° exhaust centerline

284°.....288°....292° intake seat duration at .004"
292°.....298°....298° exhaust seat duration at .004"

222°.....226° ...230° intake duration at .050"
230°.....236° ...236° exhaust duration at .050"

Re: Proper 500HP Carb
 

In case one hasn't logged in I edited info to include the 731 as was being compared. Sorry. So please log in to see the 3 cams side by side with each other. Kind of interesting anyway when looking at them this way.

Re: Proper 500HP Carb
 

Bc, Talk to Tyler about Quickfuel Carbs. They know how to build them. They engine test each one. They will be cheaper than a stock Holley or Demon. Mine on my previous boat felt like fuel injection. Tyler can order one set up perfect for your app.

Re: Proper 500HP Carb
 

Thanks for the direct comparison! My educated guess would still be that the 731 and 500EFI would be pretty similar. They're pretty close except for intake duration (+4 deg) and overlap (+2 deg)

Actual power output would probably depend on the In/Exh flow balance of the heads, but the 500EFI would probably also idle a tad better and make a little more torque down low. The 731 might pull it at the top end if the heads were intake dominant.

Then again that might just be mental M@$terbation given that who really knows what a cam will do in an engine.

Re: Proper 500HP Carb
 

Thanks, I'll do that. Up until know I had settled on a 850 Barry Grant, but I'm still open to suggestions, especially if Tyler feels more comfortable tuning them.

Re: Proper 500HP Carb
 

If anyone has a lead on anyone who has a "takeout" 500EFI cam, please let me know. I'm not in a hurry, and it wouldn't hurt to save a few $$$ over a new Crane cam.

thanks

Re: Proper 500HP Carb
 

I'd like to put a small 'plug' in here for carbs.

I've been using the BG 'Sea Demons' (both mechanical sec and vac secondary) for the past few years and absolutely love them. 4 corner idle - glass sight bowls - very little tuning needed if any - built like a 'brick schithouse' - and OSO member Rumrunner is head tech over at BG so he is right here and very reachable if you have any questions.

The 850 has been wonderful on 502's and the 650 on small blocks. Both from very mild to pretty stout engines. Wonderful stuff.

Just my experience which is limited in comparison to many others here.

Re: Proper 500HP Carb
 

mech or vacuum secondaries, which do you favor?

Re: Proper 500HP Carb
 

Very good question, I really like both of them. The vac secondary carbs have a 2 second (as I call it) quick change secondary spring pod. Awesome btw.

For applications at 1hp per cid or over, I really prefer the mechanical secondary carbs. WOT means WOT. :D

However, driver / owner has a lot to do with what I pick. The DP's will dilute oil a lot quicker and need a strict oil change schedule. Also, a driver that is 'on/off the gas happy' he/she is less likely a candidate for mech sec's. All those accelerator pumps shots go somewhere other than back to the tank. :D

A properly sized DP will out run a properly sized vac sec. 98% or more of the time.

Re: Proper 500HP Carb
 

BTW: I'll never forget the first Sea Demon I tested. I pulled the bowls to try different jetting and seeing that it had non-stick gaskets put me to my knee's thanking the carb god's !!!

I absolutely dispise taking most Holley's apart for the first time because of the gaskets breaking and being stuck to everything.

Just another plug. Huge in my book !!!

Note about non-stick gaskets: I still advise to have a back up set just in case, especially if doing it on the water on a week-end. :D

Re: Proper 500HP Carb
 

I know, I try and pull them apart before they ever see gas, what would it cost Holley to use the good gaskets?

:eek: :drink:

Re: Proper 500HP Carb
 

Or atleast chapstick to coat their gaskets ? LOL.

Re: Proper 500HP Carb
 

Chapstick, thats a new one to me, I was told to use Pam spray cooking oil amongst other things. Worked well enough. :D