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What is the safest cam duration to run with injected headers? Large duration or small? WT:)devil
 

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The less cam duration the better, if trying to avoid reversion (water in oil)
 

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I think overlap and lsa have more/as much, to do with it. What cam are you lookin at???
Do a search for cam duration, 71 hallett started a thread with alot of good info, I'd post a link but I'm too stupid.
 

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I think overlap and lsa have more/as much, to do with it. What cam are you lookin at???
Do a search for cam duration, 71 hallett started a thread with alot of good info, I'd post a link but I'm too stupid.
[email protected] .050 intake 240 exhaust 252
lobe lift .3780 .3600
Sep. 113.
Dur. @ .006 .297 .317
Gross valve lift .643 .612
Degree intake lobe to 108
 

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Now there's a funky cam.

Do you have the option of running the headers dry at idle and add water at a higher rpm ?

Can you give us engine specs along with header specs (primary ID, length, collector ID and length)
 

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You are obviously concerned about water reversion since this is the second thread you started on this subject. 1st is located here:
http://www.performanceboats.com//showthread.php?p=479712#post479712

There, you mentioned using exhaust manifolds.

I have questions about this cam since you are so concerned about reversion #1, and #2 it just doesn't add up any which way I put a scenario to it:

1) What where the particulars and concerns when you bought / had this made ?

2) What was the reasoning behind grinding the cam with the specs it has ?I still have not seen nor been answered on the rest of this engine's build. I've just seen exhaust and cam info.

I am not the only asking as to why the cam is the way it is ?

[email protected] .050 intake 240 exhaust 252
lobe lift .3780 .3600
Sep. 113.
Dur. @ .006 .297 .317
Gross valve lift .643 .612
Degree intake lobe to 108

I don't believe you are going to get away with this cam with headers that inject the water right under the port. How old id this cam? Seems like a lot of ad (.006")duration for only 252 @ .050
Some of the things that raise my eyebrow:

-Why the 113°LSA ? To cut down on overlap ? Still, the overlap is huge for what the cam is vs what it could be with same .050" .
-This cam has 81° of overlap at .006" seat. That's big folks - and remember it has 113 LSA (ie:wide) and 240°/252° at .050.
-The intensity is very large at 65°.
-The i/e split is 20° at seat.
- 317° at .006" to only raise the valve .612" with a 1.7 rocker.
 

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steelcomp was here
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You are obviously concerned about water reversion since this is the second thread you started on this subject. 1st is located here:
http://www.performanceboats.com//showthread.php?p=479712#post479712

There, you mentioned using exhaust manifolds.

I have questions about this cam since you are so concerned about reversion #1, and #2 it just doesn't add up any which way I put a scenario to it:

1) What where the particulars and concerns when you bought / had this made ?

2) What was the reasoning behind grinding the cam with the specs it has ?I still have not seen nor been answered on the rest of this engine's build. I've just seen exhaust and cam info.

I am not the only asking as to why the cam is the way it is ?



Some of the things that raise my eyebrow:

-Why the 113°LSA ? To cut down on overlap ? Still, the overlap is huge for what the cam is vs what it could be with same .050" .
-This cam has 81° of overlap at .006" seat. That's big folks - and remember it has 113 LSA (ie:wide) and 240°/252° at .050.
-The intensity is very large at 65°.
-The i/e split is 20° at seat.
- 317° at .006" to only raise the valve .612" with a 1.7 rocker.
You're obviously in the wrong business. You should be designing cams.
Or reading people's fortunes.
 

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I could be wrong, but the last time I saw numbers like that were on a old school GM hipo "offroad" cam. Really lazy lifter intensity and wide LSA. Some of those old GM cams had some insane adv. numbers that made the cam look way "bigger" than it really was. .006 lifter rise isn't enough to take up the lash, and they would seem to stay there for 10* to 12* before lifting anymore. Exactly the reason I pay no attention to adv numbers or even .050 for that matter. Tell me what its doing between .050 and .200,and .300 etc. Bet if you cam doctor that thing it's not what it appears to be.



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i dont know if this is the cam that chris ground for colbys motor or not:)bulbbut if it is im sure there is a reason;)

as far as water they make cut-off switches that with a flip of a switch no more water:Dif you are using injected headers.

i have one so does all of my peeps i run with,moroso makes them and they are 100 bucks wire it up flip a toggle bamm!!!!!water, no water.:)hand

i always cut my water off anything below 2500 rpm not that hard to remember when it comes to the money you have in a mill.good luck colby and may next season be better for ya!!!!:D
 

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Thanks for your factual input Steel. I'm sure you'd take your comments well if directed towards you. Guess it's only okay for you to dish it out though. An FYI here: I am 100% curious about why/how/etc these specs where used.
==================================
Anyhow,
Here are some further facts/specs with this cam. Anyone, Please feel free to discuss them.

seat at.006"
IVO 40.5° BTDC IVC 76.5° ABDC
EVO 96.5° BBDC EVC 40.5° ATDC
81° overlap (40.5° BTDC, 40.5° ATDC)

at .050"
IVO 12° BTDC IVC 48° ABDC
EVO 64° BBDC EVC 8° ATDC


Intake_: 297 at .006", 240 at .050", 160 at .200" ___lobe lift .378" (.643" valve)
Exhaust: 317 at .006", 252 at .050", 165 at .200"___lobe lift .360" (.612" valve)

In intensity: 57
EX intensity: 65

OEM cams are usualy around 65-75 Intensity
Aftmkt usually 50°-55° or so.

Comp's off the shelf Extreme Energy Marine cams have 54° intensity.
One Extreme Energy (XE) has 44°. Others 50°. Gosh, the old 268H high energy cam has 50°.
====================================================

This is part of what begs me to ask these questions. Why would I want a lobe with 65° intensity when I can get one's with less and are proven to be stable?

Edited: Made a typo. Why would we want to start the blowdown of the exhaust at 96.5 BBDC (83.5 ATDC) ? End of Edit.

I think these are very fair questions and I would like someone to explain them to me. I am not asking for derogatory comments, especially without some good info or questions presented. Lets discuss this and see what comes about it.

====================================================

GN7 - I believe those GM cams seat where measured at .0015" and thus why the seat #'s look so dang big.

The cam above is measured at todays normal .006" . Crane does do it at .004"
Imagine the seat # if measured at crane's spec and then compare to a Crane ? That 317 would be around 327 or more? at .004".

=====================================================

Let's not forget what reverts water. It is actually spent exhaust gases that are reverting back into the combustion chamber that is carrying the water back. The more exhaust gases being pulled back into the combustion chamber the less available room for fresh air/fuel. Call it an EGR valve. Might as well.
 

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steelcomp was here
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How does anyone know anything about this cam without knowing anything about the heads?
CFM...what are you getting at here? You're "criticizing" the cam (as you do every chance you get with Chris' grinds) but you're not saying what the negative effect might be with this cam, or how it could be better. I'm not going to pretend to understand why Chris does what he does, but suffice to say, whatever it is, it's successful. This build, from what I understand, is no exception.
What would you do differently, and what would you expect to improve over what this grind shows? Have you seen the dyno sheets? Have you seen the power curve?
IMO your motives are transparent, and I don't think you really care about the cam, except to discredit Chris.
There's your facts.
 

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It was not known to me this is one of Chris's grinds. That is one fact you gave me. Thank you.

Anything that looks odd to me is worth investigating. I start investigating and putting in info along with questions and then you come out swinging a sledgehammer.

I look at good info and bad info the same as that it will make myself and others futher ourselves.

If something stinks, so be it, learn from it and use that to move forward. If something really shines, so be it, learn from it and use that to move forward.

That how everyone moves forward.

If you post information publicly and it kills you to have someone study it and critique it, then don't post it. These forums are here to further ourselves, not to beat our chests. This thread is a perfect example - I do not know why this cam would be one of the better choices to use and thus why I have stated my not understanding this.

I have asked for more motor info, use info, what was discussed as fas as wants/needs/expectations/pasrts that it's stuck with using/etc,etc,etc, and I've gotten no info. I have had you come down on me though thinking that I knew it was Chris's design and bashing me for supposedly bashing him.

Jeez, why don't we just pat everyone on the back for anything little they do or don't do and don't ask questions - don't add opinions - don't add facts - and etc,etc.

Just so you know, forums are actually called discussion boards. So, true to the name, why can't we discuss this?

Stop making things into an emotional mess and discuss this as to why are are all actually here for. To discuss and learn from our discussuions.

Let me know the info I've been asking and add some input on what you think about the cam.

Believe it or not, when you are calm and collected and add info, I read it and think about it in a very serious nature. I'm here to learn new things and to help when I can. Foremost is learning.

=================================

Sorry for the sidetrack everyone. I really don't try to get in this mess.
 

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I only brought it up because I don't believe that cam is going to be wet header friendly. Perhaps with the right offshore type manifolds, but not an injected header. Cam appears at first glance to be very easy on the valve train.
Offshore manifolds won't be better. It (manifolds) would have to be completely dry and either have water exit well outside the exhaust tip or the collectors/tubes be at an extremely large rate of fall with the water at the very end.

Much lesser (seat. .050", etc) cams have reverted in offshore systems.
 
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