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advancing/retarding cam

9K views 29 replies 12 participants last post by  Pilch 
#1 ·
Just been playing around with my dyno program before I freshen my 351. Basically its 10.5:1 CR, ported iron 2v's with 4v valves, Crane F238 etc etc.

It seemed to make pretty good power and torque according to the program, 435 hp @ 6000 and 399ftlb @5000.

When I retarded the cam 10degrees, it jumped to 465 hp @6250 and 415 ftlb @ 5000. Not that I would retard it that far tho.

I'm not sure how accurate these dyno programs are, so Iwas wondering if anyone has actually tried retarding or advancing the cam timing with a similar combination and what the results were.
 
#5 ·
TruBlu351 said:
Now, for about 800 bucks your could turn that graph into this!....and drop the mufflers!

No guesses how :hehe:

$800 would suggest a nitrous system, probably a high flowing setup.

As for your "mufflers" on being close, for a good quality race engine, large tubes w/mufflers seems to be right while with a "normal" hotted up engine, small tubes w/mufflers seems to be right...even on a real engine dyno without mufflers (except for the large diesel stack type with 5" pipe going into it!).

I suppose that the more recent version is more accurate and/or has more features?


:davis:
 
#8 ·
TruBlu351 said:
No fantasy. Just a GUIDE on what combos may work better that others.....saving $ and time.

I didn't think most racing teams use them on their R&D.
Actually, it is a very powerful tool that is useful in R&D. Don't pay any attention to croc. It doesn't have to be exact to be useful in demonstrating a trend. As a computer simulation tool, it is very close...considering its limitations.

On my BBF 520" engine, it predicted 670 HP and the dyno showed 667. That is too close to call, IMO.


:davis:
 
#11 ·
smally351 said:
When I retarded the cam 10degrees, it jumped to 465 hp @6250 and 415 ftlb @ 5000. Not that I would retard it that far tho.
Out of interest, how far can a cam be realistically retarded? And how far would that shift generally move the power band?

I remember seeing a general rule of for every 1degree, it shifts the power band XXXrpm (but have forgotten it).
 
#12 ·
Plenty of people in the real world have retarded and advance cams. It's common knowlege. Most don't do it for power though. They retard it to change the power band to ****rpm or visa versa. Most would end up advancing theres as this makes everything happen earlier.
 
#13 ·
Pilch said:
Out of interest, how far can a cam be realistically retarded? And how far would that shift generally move the power band?

I remember seeing a general rule of for every 1degree, it shifts the power band XXXrpm (but have forgotten it).
One of the cam manufacturers I used (Yank) said that "if you retarded or advanced the cam by 2 - 4 degrees it should only make a minute difference. If it makes a big difference you've got the wrong cam."

In my own small field of experimentation with racing (no dyno work) we could generate better throttle response and a harder launch by advancing 2 - 4 degrees but no quicker or slower times. I never tried retarding; it was always about the launch and first half of track.
 
#14 ·
trublu351 said:
I didn't think most racing teams use them on their R&D.
davis said:
Actually, it is a very powerful tool that is useful in R&D. Don't pay any attention to croc. It doesn't have to be exact to be useful in demonstrating a trend. As a computer simulation tool, it is very close...considering its limitations.

:davis:
I'm hearing you! I was playing with a sarcastic subtle double negative for the stirrer! :hy:
 
#16 ·
smally351 said:
Just been playing around with my dyno program before I freshen my 351. Basically its 10.5:1 CR, ported iron 2v's with 4v valves, Crane F238 etc etc.

It seemed to make pretty good power and torque according to the program, 435 hp @ 6000 and 399ftlb @5000.

When I retarded the cam 10degrees, it jumped to 465 hp @6250 and 415 ftlb @ 5000. Not that I would retard it that far tho.

I'm not sure how accurate these dyno programs are, so Iwas wondering if anyone has actually tried retarding or advancing the cam timing with a similar combination and what the results were.
Most aftermarket camshafts that we would buy off-the-shelf have a number of degrees of advance "ground into" them. This promotes a lower-RPM torque benefit at the risk of losing some higher end HP. It also narrows the powerband somewhat--based on the exact cam profile and the engine.

In the case of a 351C, even with the rather large 2V ports (we think of them as small compared to the 4V ports, but compared to all other small blocks, a 2V has BIG ports!), we find by using a camshaft that starts "lower down" that we still have enough flow capacity to run well at the higher end.

I chose a wide LSA camshaft for my 4V Cleveland "Q-Code" engine. Basically, I was moving the RPM where peak torque occurs up in the RPM band, while broadening the entire band somewhat from the 2800-6000 RPM range. This camshaft was/is a 112* LSA, or, fairly wide as most Cleveland cams go where 110* is "normal" and 108-106 is most common in the F-2x6 varieties.

My "strategy" was to give up the lower end of idle-2800 RPM altogether and focus on the RPM range where the 4V head starts working well, which is at a reasonable minimum of 2500 RPM and higher, IMO. Then, the idea was to use a converter that would allow the vehicle to stay in the RPM band as much as possible and a final drive ratio that would be condusive to moving the mass early on. While I didn't exactly meet all of my objectives (the chassis chosen was much heavier than initially planned for the engine and the gear ratio is probably 5-tenths too high) the final result is "not too bad."

http://www.webcamshafts.com/cam_glossary.html

...is a good summary of camshaft terms and the effects advancing/retarding, using wider or narrower LSAs, etc., have on an engine.


:davis:
 
#17 ·
crochunter said:
I dont have to prove anything. My numbers show it. Wheres yours.
For a guy with an avatar spewing twin streams of nitrous, I'd say that your "numbers" are power-added based, if anything. How about my numbers croc? 7.96 at 184 nothing added? Anybody who has to go back to their "numbers" to prove their "worth" around here is wasting everyone's time. The point is, that there will always be a quicker car out there somewhere. A good number is nothing to brag about. It is a personal accomplishment. I don't think that I'd ever want to compete with Joe Amato's numbers...I just don't think that I'd feel comfortable going well over 300 MPH in a slingshot. I think that I'll work up to 200 MPH first...and maybe never see 240 in my lifetime. But what do you care about how fast or slow I run? I certainly couldn't care less if you ran a 6.40 or a 16.40. They're your numbers, not mine...and, frankly I don't give a damn about your numbers. I don't even really care all that much about mine. They're just a reflection of the amount of effort I've put into going faster/quicker and say very little about me as a person.

What are we seeing here about you as a person? You seem to be the first one to take a swing at someone else and for what benefit? Tells us about your skill in determining the value of commercial software in R&D engine design? What qualifies you to have anything more than an opinion? You've voiced your opinion. While for some segment of the population your opinion holds some amount of water, there are THE REST OF US HERE who think that you should give it a rest and come back when you can contribute in an effective way that doesn't just bring negativity to every thread you post.

Yes, there are wankers who will race their "desktop dyno" against someone elses. Hell, the stupid Engine Masters Challenge had that as part of their contest earlier this year! Racing my software against yours? Okay, whatever floats your boat. I don't think that any of the "voices" that I "hear" regularly here are the kind to use DD2K to inflate their egos. Sure, we all know that it is not perfect, DOH! Wake-up already Croc-inator. Consider the possibilities beyond your own shallow experiences and if you can't say something nice, STFU.

Using DD2K is a good and useful tool for SIMULATING the effects of camshaft modifications/changes in an engine. For that reason, it is a perfectly acceptable use of the TOOL, especially as it applies to this thread. No program is worth JACK without good data input. Maybe your experiences do not include data input? Hard for me to say from what I've seen coming from you in recent times. How about redirecting yourself toward the positive?

I couldn't find you in the "Members Timeslips." Maybe you're not "all dat?"


:davis:
 
#19 ·
crochunter said:
I dont have to prove anything. My numbers show it. Wheres yours.
Anyone can type numbers, here we go: 9.56, see, here's some more: 7.68.
Since when has a persons worth been measured in 1/4 mile times?
While i don't claim to know allot about clevelands where ever possible i try to contribute in a meaningful and constructive manner, and try to provide feedback from personal experience, you however rarely have anything useful to contribute at all, your reputation preceeds you, you could run a 4.99@301mph for all i care and you'd still have no credibility here, you're a bit like an annoying little brother who's trying to hang out with his older borthers friends and act cool...
Please go away and take a good look at yourself.
If you dont want people to pick on you then learn to contribute in a helpful constructive way with something meaningful..
 
#20 ·
Is this 4Vman for real. I have only been at these forums for a short time but it seems everything that crochunter guy has to say he has a answer for. He might be a **** but you seem like you always have to make a smart *** remark too. Wouldnt it be better to just ignore. Or are you just as bad.

[edit] from the Sherrif :ymca: TruBlu351. No swearing please. You are right though, "ignore" is the better option. :hy:
 
#22 ·
351AFD said:
Is this 4Vman for real. I have only been at these forums for a short time but it seems everything that crochunter guy has to say he has a answer for. He might be a dick but you seem like you always have to make a smart ass remark too. Wouldnt it be better to just ignore. Or are you just as bad.
He's not as bad as everyone makes out but he also doesn't have an answer for everything. Most but not everything. Ignore seems to work for most.
 
#23 ·
351AFD said:
Is this 4Vman for real. I have only been at these forums for a short time but it seems everything that crochunter guy has to say he has a answer for. He might be a dick but you seem like you always have to make a smart ass remark too. Wouldnt it be better to just ignore. Or are you just as bad.
Ive said all im going to say.. now lets get back to talking Clevelands shall we?! :hy:
 
#25 ·
crochunter said:
Yes but your numbers are done in a lightweight dragster.
Yeah...so? I guess that I missed your point. I don't "hide" behind my numbers either. I don't have a problem telling everyone every detail about my combination, including my race weight. In fact, I don't have a problem telling everyone that I'm not even a "real" racer, but that I just like to go out and have fun going fast. To me, it is play time. I dink around with my electronics (of my own design, not something out of a box ordered from somewhere) and I learn this or that about the machine, about the tune, about the weather and how it all relates to performance. I think that if you took the time to carefully consider the accomplishment of going into the (albeit high) sevens with a 393 N/A, that you would spew forth a lot less "nitrous" from your nostrils in haste. It isn't quite the same as falling out of bed or running a 12 in a "big" car.

If you're not quite getting the picture, perhaps a contrast is in order?

http://www.corral.net/forums/showpost.php?p=5452813&postcount=2

...a guy named Dave C on the Corral.net forum says that he's running:

225" Undercover Dragster
alky injected 557 BBF
4.88 @ 143.5 1/8 mile, 1.09 60'

...per his signature.

My longer (more length means more chassis weight) 256" dragster running 164 CID *less* is running *quicker* at:

1.070 60' 4.743 @ 146.82 in the 1/8th and it is SET UP for the quarter mile.

His car must weigh a bunch! I wouldn't know how much, but it certainly isn't a lightweight by any stretch of the imagination. Of course, his engine is 142% the size of my engine, but he's not exactly running 142% quicker than me.

If I was to put my spare 393 in my F100 (assuming that I could hook up in it) I'd expect somewhere in the low 11s in a +4000# ride.

Those are respectible numbers regardless of any bickering or personality conflicts. But, as 4V Man illustrates, we're not about the numbers we run in the quarter mile. A guy with a totally cherry straight 6 early Falcon wagon is just as cool as the guy running a flat 6.0 in a 815" '50 Ford Custom...okay, so maybe the "kind of cool" is different, but it isn't any less cool.

I ought to remove my numbers. I've been working on a new car in addition to the F100...and the old numbers are meaningless these days anyway since I changed to an engine making some 804 HP at 7400 RPM in the old RED. I sold one of the 393 strokers and have two left to sell, the original and a spare.

If I thought that it would be helpful, I'd reply to your PM that basically tells me that you are a man because you're out in the open about what bothers you. Funny method, PMing to say that you're open...oh well, I don't really care...or to use WH's expression, I don't give a rat's red ring...I love that one, BTW.

Anyway, before this gets completely out of hand and forever boring and repetitive, it is all about you, isn't it? You need some metric to base yourself against the rest of us, right? If nitrous helps you get there, great. Enjoy yourself. Some of us prefer the N/A approach because we can get there without the kicker. Me, I just like things that are simple and easy to work on. Once you start messing around with nitrous, you have to retard the timing and the next thing you know, you're wasting your time thinking about it and not out playing and having fun with it.

Good luck in your future endeavors. You've been a real pal.


:davis:
 
#26 ·
xbgs351 said:
Which is far smarter than lugging a family sedan around.
...and in some ways, not as much fun! Have you ever tried to parallel park a 256 RED? It takes a GOLF COURSE to just turn around <grin>

Besides, you definitely CAN NOT make out in the back seat of a RED the way you can in the family sedan...<snicker>

Just remember: Everything has a purpose, no matter how distorted its owner is!


:davis:
 
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