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BOATN70

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Discussion starter · #1 · (Edited)
well, i did get the heads flowed now i need to pick a cam. im waiting to hear from cstraub on this too.

502 gen6
8.75:1 compression
dart intake
holley 850
lifters will depend on cam
crane gold rockers
emi exhaust
gm iron ported heads "188"

Im looking at the crane stuff for a shelf cam but am very interested in seeing if theres a better "custom" cam for my setup. i do understand that a custom should always be better, but id like to hear why and what would be better.

when looking at flow numbers on the BBC heads do you use the long intake runner or short runner to base your decisions?
heres the flow numbers:
LIFT SHORTIN.CFM LONGIN.CFM EX.CFM
.05 40 35.5 38
.1 79.8 71 62.8
.15 112.4 108 94
.2 146.6 144.4 129.2
.25 181.5 179.3 147.1
.3 223.5 219 163.5
.35 250.5 250.5 183.5
.4 264 273 198.8
.45 282 291 215.2
.5 297.7 310.5 225.8
.55 313.5 322.5 239.4
.6 322.5 336 249.1
.65 329.2 345 253.9
.7 336 NA NA


do they look good or bad, seems like the exhaust really looks better to me!!

thanks!
 
#3 · (Edited)
here is my .02

800 to 830 carb
brodex intake
flat tappet Hyd less weight than rollers

Cam
.525 lift int
.550 lift exh
this should give you E/I ratio of 78%

duration @ .050
int 216
exh 224

advertized duration
int 270
exh 280

lobe C/L 112

This puts your HP peak at 5200 RPM s for a 502 CI engine and should net you 596 HP. Air restriction might be the intake. I havent gotten the chance to flow many BBC intakes. Reasoning a 502 needs 290 CFM to reach peak power at 5200. Dont use the cam to push HP up higher in the RPM range use the head work that has been done. The air flow over .55 lift on these heads looks to be flip floping a bit good port becoming bad port .. bad port becoming good port. At .5 lift your over the 290 needed. If you push the envelope further you end up over proping the boat to bring the RPM s down from like 6000 to 5000 realy puts a strain on the engine with little or no benift other than burning up an engine sooner.
 
#4 ·
Cstraub is at PRI - the huge aftermarket parts convention in Indy. He probably won't be back for a bit.
Try him next week.

You have 72% + E/I ratio. This is pretty good.

Turbo - you probably know cams better than I but I'll add my input anyway, more to see how close I come to others guesses too.

I'm thinking quickly with no program the following:

224-226 intake duration at .050
230-232 exh duration at .050
six degree spread on exhaust
Intake lobe centerline 108-110
Exhaust lobe centerline 116-114
To make LSA 112

Best guess on hp at 5200 is 540.
 
Discussion starter · #5 ·
turbo, help me out here...
what do you mean flip/flopping, give me an example please (im learning here!!)

i have the dart single plane intake, is the brodix that much better? as far as the roller set up...i have the stock gm lifters that are said to be good for .570 and ive been told up to 600. if i could use those id be happy (money$$$) i also have the roller rockers, 1.7s, i forgot to mention.

i dont mind running rpm up a little higher than 5200 if needed. that way i can prop for more general use and spin it a little higher for the HP.......does that make sense?

kevin
 
#6 ·
The short intake runner flows more than the long for a period

The long catches up to the short and then flows more than the short

I believe this is what he meant ?

As far as we've seen the Brodix is a little better than the Dart

The Dart is still a good piece. Since you have it , use it.

RPM needs to be considered with the outdrive too. I'd rather things be propped for 5200rpm max for both the engine's and outdrive's sake. In fact, I like 5000 rpm even more.

More rpm really isn't needed for good torque/hp with a 502.
 
Discussion starter · #7 ·
thanks cfm,

i understand what your saying with regards to rpm.

however i have a 4900lb boat that i dont need a fast hole shot and when i run top speed its obviously for only a short period of time. most time is spent cruising, etc. wouldnt it be more efficient to run a smaller prop that can turn the rpm easier (easier on the drive) to 5200 for common use at maybe 90% HP usage, then when i want to run the boat top speed i could turn the motor to 5800 with the same "everyday" prop. i assume it could be setup this way and be easier on the drive and motor and better fuel consumption.

i dont boat on any "big" water, so put the handles down and running WOT isnt common. i would think that would be easier on the drive to turn the smaller prop to 5800 vs 5200 with a bigger prop.

please correct me if im wrong.

thanks
kevin
 
#8 ·
5800 rpm is a lot.

5200 rpm is a lot to but a good compromise between engine + drive reliability.

A prop that loads the engine to 5200 rpm will let you get out of the hole easy, especially with that size boat, without having to use a lot of throttle.

You have good cids - use them.

Remember, more cam duration brings the rpm power band up. More cam duration = more chance for reversion.

It's a fine balancing act and one that will make you pull your hair out when making a cam selection. and thus the importance of effecient cylinder heads - they will let you use a smaller cam to make the same power (with a wider power band) than a poor cylinder head that needs more cam to give the air time to get into the combustion chamber.

So = cams are more than power band in a boat:

1) Reversion
2) Engine longevity - ie: rpm
3) Drive longevity - ie: low end torque - too much can kill
4) Drive longevity - ie: high rpm - too much can kill
5) Engine power in the range wanted

So, with these I really believe - and thus my build up - that good cylinder heads will give you what you want. You are not forced to 'cam up' for real good power levels.
 
#10 ·
It's true.

Hydraulics lose control pretty quickly. Not uncommon for a regular hydraulic roller to lose control over 5400 rpm.

You seen AFR's claim of making 80hp or so with their Rev Control kit? Called the Hydra-Rev I think? It's a set up that places springs over the hydraulic roller lifter (surrounds the pushrod) and just under the shelf of the head. The hp is from letting the engine climb to more rpm's where, eithout it the power falls of abruptly because of the lifters losing control.

This places spring pressure on the body to keep it on the cam. You can only run so much spring pressure before you sart to collapse the hydraulic plunger.

A small block can run more R's because it uses less spring pressure because of lighter valves. It still happens though, typically closer to 6k.

It's true - it happens without notice.

The Morel lifter you here Cstraub and RMbuilder (where's he go?) talk about all the time extends the rpms before this happens.
 
#11 ·
Baja - hear is their blurb. I copied it from their website www.afr.com and pasted it below:

Hydra-Rev
Hydra-Rev Can Add More Than 100 Horsepower On The Top End!
With today’s valve train components and the steep acceleration rates on hydraulic roller cams, it isn’t possible to properly control the valves and valve train by simply increasing valve spring pressure. This usually results in collapsed lifters. AFR has created a solution! The Hydra-Rev applies additional spring pressure to the lifter body, not the plunger. This vastly improves valvetrain stability which results in more power at higher RPM without any loss in low end torque. In testing (see the dyno charts below) Hydra-Rev increased power at 6500 RPM with Comp Cams’ CS280HR10 by more than 100 horsepower!



In addition, Hydra-Rev eliminates the danger and the potential damage to components that valve float can cause. The easy to install Hydra-Rev Kits come complete with all the components you need and requires no additional machining or modifications when installed on stock or aftermarket cylinder heads. Hydra-Rev is available now for Chevrolet V8 small block and V6 engines except the cast iron LT1 Impala and Vortec truck heads, Pro Action Iron Lightning or Dart Iron Eagle. If heads are already installed on the engine, a spring installation tool will be required.



--------------------------------------------------------------------------------



These tests were conducted in AFR’s digitally controlled dyno facility using a 350 cid Small Block Chevy equipped with AFR 195cc aluminum street heads, Edelbrock RPM Performer #7101, 600 cfm Holley carburetor, 10 to 1 compression ratio, and the camshafts shown in the title of each test.
 
Discussion starter · #12 ·
ok, im with you cfm.

thanks

does anyone know of a "shelf" cam that fits my needs....
or, as i suspected, should i just get a custom grind. i would like to use my silent choice set up and it sounds as if the cam i need may be a good candidate.

with the specs that turbo and cfm recommend, hows the idle quality....ie.....hows it gonna sound???

kevin
 
#13 ·
We can get you a custom cam for not much more than an off the shelf -

can we wait for Cstraub to come back?

Idle quality - like a baby's azz.

Mine idles down to 450-500 rpm smooth as butter.

Reason it's smooth - overlap and LSA. Kept to a minimum because of not wanting reversion.

Your silent choice makes reversion even more threatining since water is introduced into the pipes even earlier.
 
Discussion starter · #14 ·
well, i suppose a good idle will make a sleeper out of it thats for sure!! and.................my wife will be happy!!

is cstraub workin the show or is he just shoppin it??
i assume hes workin...i am anxious to hear his results!!
so what are you runnin that idles so good? what cam, and did you get you test set up done yet??
kevin
 
#15 ·
Boatn80, if we knew all about CFM's motor details, the 'other' thread on here about his motor would DIE!!!

CFM won't let us know the complete details, YET.

So watch the other thread!!

All of us who have HP500's or similar are waiting with baited breath as to what he is doing.

I do know that I saw Canfield heads in one picture from that thread...
Take care,
Kent
 
Discussion starter · #16 ·
that threads gettin old, off track, not even about his setup.........im wish hed get it going on here!!!

just kiddin CMF, keep us posted!!!!

i spoke with cstraub, hes pumped on CMFs ideas, cant wait!!!

im still waiting for more cam suggestions!!!

kevin
 
#17 ·
Boatn70 -

Cstraub works for B&B and Stef's. Yes, he's workin' the show.

Stef's is out of New Jersey , so the reasons why I think Cstraub is so important is because 1) he know's his stuff, and 2) he has a southern draw which is more appropriate for the hardcore circle track guys.

Is a New Jersey accent or a Tennessee accent more akin to this industry? Answer: A Tennessee accent is more suitable :winker: :winker:

I keep reading about CMF - who's that guy and what's he doing?
 
#18 ·
BOATN70 said:
turbo, help me out here...
what do you mean flip/flopping, give me an example please (im learning here!!)

i have the dart single plane intake, is the brodix that much better? as far as the roller set up...i have the stock gm lifters that are said to be good for .570 and ive been told up to 600. if i could use those id be happy (money$$$) i also have the roller rockers, 1.7s, i forgot to mention.

i dont mind running rpm up a little higher than 5200 if needed. that way i can prop for more general use and spin it a little higher for the HP.......does that make sense?

kevin
Click to expand...
By all means use what you already have I know what you mean by $$$$. What I mean by flip flopping is the air is becoming turbulent and unstable air flow might do something like jump up and down the sound of the air running through the head changes pitch and volume while holding or attempting to steady 28 in. On a flow bench such as mine I have a air flow gage that is approx 6' long and can easily see it start to fluctuate before I can hear it. At this point the the air is unstable and it is useless to attempt using lift points after that point. An analogy might be like driving a car that surges at certain speeds.

Actually you can prop for more general use most of the time by not loading the engine and drive over propping shortens the life of the engine and drive if your just racing its different. Plus or minus 200RPM from 5200 makes little difference If you already have the Dart intake have the guy flow it on your cylinder head with that info my choices might change a bit. Another option would be to port the intake if its to restrictive.
 
#19 ·
cfm said:
Cstraub is at PRI - the huge aftermarket parts convention in Indy. He probably won't be back for a bit.
Try him next week.

You have 72% + E/I ratio. This is pretty good.

Turbo - you probably know cams better than I but I'll add my input anyway, more to see how close I come to others guesses too.

I'm thinking quickly with no program the following:

224-226 intake duration at .050
230-232 exh duration at .050
six degree spread on exhaust
Intake lobe centerline 108-110
Exhaust lobe centerline 116-114
To make LSA 112



Best guess on hp at 5200 is 540.
Click to expand...
Your lobe C/L's sound good

My guess on the duration @ .05 is somethig like a 5 HP gain at top end but with a loss of 20 to 40 HP at lower end figures. Not worth it to me. Probably couldnt run more prop but engine would loose drivability economy a lot of midrange. Re work of the seat and bowl s of the ports for a bit more low end flow would be a bigger help.
Of course a lot of people just want that choppy idle.
I always like the comment after beating some guy "Ive never been beaten by such a quiet vehicle before".



Te shop owner left last night for Indy if I had known I would have went used to live there.
 
#20 ·
Just for snicks here is some fully ported data from a set of 14011076 BBC heads we did...

LIFT_____INT_____EXH
.700_____361_____236
.600_____335_____228
.500_____304_____206
.400_____274_____182
.300_____227_____151
.200_____155_____119
.100_____ 78_____ 75

Haven't any idea as to the application of this head but flow is comparable to out of the box Canfields with 2.25/1.92 valves but not sure which Canfield model.
 
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