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 Post Posted: Sun Oct 24, 2010 12:37 pm 
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I am going to change my camsahft this winter. I am also going to take a different direction with it. What do ya think about lower duration/ higher lift on a tight centerline in a BBC? I am thinking of something in the 270@050 range with over .800 lift on a 108.


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 Post Posted: Mon Nov 08, 2010 6:51 am 
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Wow a lot of veiws but no one has a comment to make? I am looking at say 275@50in and 290@50ex with 830in/810ex on a 106 for my bbc. I would like to make around to 900hp


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 Post Posted: Mon Nov 08, 2010 7:14 am 
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Engine specs??

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 Post Posted: Mon Nov 08, 2010 9:12 am 
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Okay I was tring to get a disscussion on cams going but okay. Here is my combo now, it is a 4.560x4.00 522 with 345AFR`s and a 1050 in a 3000lb Camaro. It currently has a roller in it with 285/288 and 765/731 on a 110 installed at 108. Like I send earlier I am changing cams and was thinking of taking a different approach then the norm.


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 Post Posted: Mon Nov 08, 2010 7:53 pm 
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I haven't dealt with BBC's much, but with any engine the head flow and cam specs are very closely related. If you have a head with weak low & mid lift flow the engine will like more duration than if it has really good flow low-mid lift. Getting the head to feed the cylinder at just the right rate will make the most power. Too much flow or too much lift too early and the velocity will be down at the end of the stroke when the piston reverses direction and not enough flow and the cylinder isn't full enough either. It's all a balancing act.

Chamber shape plays a part in it and how much cross-flow there is. Most BBC engines like you describe run cams similar to what you already run. Cams will move the rpm range around but won't normally make big differences in HP IMO.

Rick


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 Post Posted: Mon Nov 08, 2010 10:03 pm 
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Bigger isn't always better. I like how the 108 LSA camshaft performs in my 468 BBC.

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 Post Posted: Tue Nov 09, 2010 12:04 am 
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It would be hard to have a general cam shaft discussion, they are too application specific.

I saw 900 HP wanted, but what about rpm?

One of the most important factors for any engine is the minimum rpm it will need to make power at.
For a drag car that's starting line rpm.
If an automatic car, stall speed will be a very important factor in cam selection.

If a cam change is made in a car that nets 15 more HP, but the car will be 1.8 seconds into the pass before any of that power is seen, but it lost 5 HP at stall speed, will the et be lower?

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 Post Posted: Tue Nov 09, 2010 6:19 am 
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Sorry but I dont think its that hard to have a disscussion. I`am talking about most racing bbc`c with 13.1 and up compression and good aluminum heads that run 5500 to 6000 convertors and 456 or so gearing. All the cam recommendations usually are in the 288/300@50 range on a 112/114 cl. I am interested in what will happen with less duration and a tighter center line. Wont that make better low end power and help the car excellerate quicker?


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 Post Posted: Tue Nov 09, 2010 6:29 am 
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Steve, This was the cam I put in the new 540 that I just got done with and IMO I think it's a little on the big side as far as the duration...
283/295 @ 50 with 801/792 lift...

I was thinking about getting something in the 280s/low 290s with about the same lift on the same 112.

Now it made 945hp and on it's one and only pass to date it did
go 5.29 at 134 in the 1/8 so can it go faster I think so but we
will see................Next year ;-)

But then again it's supposed to be in the 60's for this weekend so
I may just go one more time =;

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Last edited by Beretta on Wed Nov 10, 2010 6:32 am, edited 1 time in total.

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 Post Posted: Tue Nov 09, 2010 7:52 am 
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Barry,

In another post you listed your Cam duration as 283/295 @ .050, which is correct?

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 Post Posted: Tue Nov 09, 2010 8:27 am 
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Slowpoke wrote:
Barry,

In another post you listed your Cam duration as 283/295 @ .050, which is correct?




Oops May be a typo :-s ..Have to check when I get home!! At the old folks home all day........ :- ..Working ](*,)

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 Post Posted: Thu Nov 11, 2010 7:20 pm 
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I am looking at 272@50in and 306@50ex with 830in/810ex on a 106 for my bbc. It is a 4.560x4.00 522 with 345AFR`s and a 1050 in a 3000lb Camaro. It has a 4.56 gear and glide with a 6000 8in and gets shifted at 7400.


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 Post Posted: Thu Nov 11, 2010 8:02 pm 
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Strange Ranger wrote:
I am looking at 272@50in and 306@50ex with 830in/810ex on a 106 for my bbc. It is a 4.560x4.00 522 with 345AFR`s and a 1050 in a 3000lb Camaro. It has a 4.56 gear and glide with a 6000 8in and gets shifted at 7400.


Maybe it would help the discussion if you said what you intended to gain or cause by changing to this cam. More power? Change in RPM?

That will have a BUNCH of overlap (77º @ .050) Your old cam has 66º overlap. Why such a big spread between intake & exhaust durations (34º O:) ) ? Is there a problem with the exhaust port size, valve size or header size you are trying to correct? Nothing like making a CHANGE to see an effect.

40coupe is using a 108lsa in his very strong performing 468ci, but a 522 is another matter. I think the bigger engines need more duration and wider lsa. I'd be more conservative and go high 270's (in) and low 290's(ex) and a minimum 108lsa. But that is just my "opinion".

Rick


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 Post Posted: Thu Nov 11, 2010 8:22 pm 
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What kinda power are you making now, and what does it run?

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 Post Posted: Thu Nov 11, 2010 9:27 pm 
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I am interested in more hp and torque and making my car accelarate faster. I believe that the tighter lsa and lower int duration will do that. Not sure of the affect of the large split but i beleive the 106 would work good even a 108, there dosent seem to be much difference between the two.

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