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  #1 (permalink)  
Old 01-03-2007, 03:43 PM
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New Cam Advice

Hi All
I received $400.00 in gift certificates from our local speed shop.
And was thinking on a new cam the XR280R or the XR274R....
I dont know if this would be a good upgrade or not......Any advice would
be greatly appreciated...

I have a 357 SBC .30 over
Forged pistons
6.0 rods
10:01 comp.
Lunati roller cam and lifters 248 duration @ .050...555 lift
Roller rockers 1.6
Dart 215 pro1 aluminum heads
Demon 750
Airgap intake
Transmission 700R4
MSD ready to run dist and 6AL ignition box
373 rear gears
2800 stall

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  #2 (permalink)  
Old 01-03-2007, 04:11 PM
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not to nitpick but a SBC 357 is a 350 bored .040 over, a SBC 355 is a 350 bored .030 over no offence
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Old 01-03-2007, 04:11 PM
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What is it you don't like about your current combo?
Too much cam for the compression?
Not enough converter and gear for the cam?

What are the advertised specs on the Lunati cam you have?

I would run the XR274R if your sure about your compression.
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Old 01-03-2007, 04:53 PM
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I dont feel that I have enough bottom end torque
I think that the heads might be to much for the combo..
But I am stuck at this point until I get more money to buy some AFR190's
So I am hoping that this new cam will make up some of the lost power that I am looking for....The car only Dyno'd at 300 RWHP.....

The Lunati cam is a single pattern vs the comp cams whitch are dual patterns..I dont know if that will make a difff...I hope so...
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Old 01-03-2007, 04:56 PM
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New Cam Advice

If you are looking for long term longevity you might want to shy away from an off the shelf street series Comp solid roller cam,turns out they arent made from billet steel as I had thought they were, but are made from an austempered ductile iron which has a hardened surface that can wear.If it has an 8 as the last part number this is what it is.I went from an older Crane solid roller to the XR280R Comp grind and was a bit dissapointed,it lost on the bottom end,had a bit more on the top end,but sure didnt feel as good.I`m going to be changing cams next rebuild and I dont think I will be using another Comp Cams product.
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Old 01-03-2007, 04:58 PM
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Thanks Guy...That is good info to know...
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Old 01-03-2007, 07:52 PM
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Quote:
Originally Posted by Guy Hiltz
If you are looking for long term longevity you might want to shy away from an off the shelf street series Comp solid roller cam,turns out they arent made from billet steel as I had thought they were, but are made from an austempered ductile iron which has a hardened surface that can wear.If it has an 8 as the last part number this is what it is.I went from an older Crane solid roller to the XR280R Comp grind and was a bit dissapointed,it lost on the bottom end,had a bit more on the top end,but sure didnt feel as good.I`m going to be changing cams next rebuild and I dont think I will be using another Comp Cams product.
Tell us about the rest of the engine and vehicle combination.
What was the old cam duration vs new? Lobe separation old vs new?
Was the cam the only thing you changed?

I just recently received my CS XR280 R-10 and called Comp with your same concern, they said: "if the open spring pressure at max lift is less than 500lbs, its not a problem". I went with 110 lob sep due to the weight of my truck.

So 65Guera if idle quality is not a concern consider the XR274R (or brand XXXX with similar advertised numbers) ground on a 108 or even a 106 lob sep to help wake it up.

But the best advice is probably right in your own back yard: http://www.joeshermanracing.com/
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Old 01-03-2007, 08:10 PM
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65, dual pattern cams aren't necessarily better than single pattern cams but at the same time they aren't necessarily worse either. I remember reading an article, possibly by David Reher of Reher-Morisson, that said dual pattern cams were originally developed for cylinder heads that tended to have weak exhaust ports. The added lift and duration on the exhaust side helped the engine make better use of the "restricted" exhaust port. In heads with a good Intake to Exhaust ratio the added lift and duration on the exhaust side may make little or no difference at all. Does that make sense? I am sure somebody will correct me if I'm wrong or help expand upon this. I wish I could remember where I read this, if I find the article I'll share it with you.

You can browse these though, there's a lot of good stuff here: http://www.rehermorrison.com/ Go to the "Tech Talk" link and browse the articles. Good info.
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Old 01-03-2007, 10:14 PM
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71C10
Quote:
Tell us about the rest of the engine and vehicle combination.
What was the old cam duration vs new? Lobe separation old vs new?
Was the cam the only thing you changed?

I just recently received my CS XR280 R-10 and called Comp with your same concern, they said: "if the open spring pressure at max lift is less than 500lbs, its not a problem". I went with 110 lob sep due to the weight of my truck.

So 65Guera if idle quality is not a concern consider the XR274R (or brand XXXX with similar advertised numbers) ground on a 108 or even a 106 lob sep to help wake it up.

But the best advice is probably right in your own back yard: http://www.joeshermanracing.com/
Yesterday 11:58 PM
I checked out the Link....This guys is right down the street from me...I am going to call him tomorrow and I hope he can help me decide what to do...
As far as what I have...its a
1965 El Camino
I have a 357 SBC .40 over
Forged pistons
6.0 rods
10:01 comp.
Lunati roller cam and lifters Part#50157 248 duration @ .050...555 lift 110 LOB
Roller rockers 1.6
Dart 215 pro1 aluminum heads
Demon 750
Airgap intake
Transmission 700R4
MSD ready to run dist and 6AL ignition box
373 rear gears
2800 stall

The idle quality i have with the current cam is good...
its smooth not to rough..I have enough vacuum for brakes...
and it goes like a bat out H.ll down the freeway...But out and about on the street kinda feels like it needs more power....When I had this thing chassis Dyno'd it only output 300RWHP..I was hoping that it would be in the 400 - 450 range.....
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Old 01-04-2007, 05:21 AM
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I was hoping Guy would give us his old vs new info as well...

I like to go higher than the "bare" minimum advertised compression, stall and gear recommendations. http://www.holley.com/50157.asp

Maybe you should consider more converter (since your below the minimum recommended) until your ready to build a new motor?

Take your car down to Joe, you'll find him "very" straight forward and honest with his opinions.

Let us know what he says.
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Old 01-04-2007, 07:09 AM
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Only 300 on the dyno means your engine isn't making the power it should or the dyno is wrong. Have you ran any timed 1/4 miles?

You combo should be making about 350 rwhp even with the mismatch of parts. So, maybe you should find out where the problem is before installing new parts. What is your total timing? Did you measure air/fuel ratio on the dyno? Checked cylinder pressure?

Yes, the cam and heads are too big for your combo. Get a smaller cam and head cc or add more cr, more gear, and more stall. A smaller cam would help but as you know already, those heads are killing low speed torque.

Typically heads that flow well don't need split durations or narrow lobe centers to aid in cylinder filling. However, narrower lobe centers will allow the intake valve to close earlier which will make more dynamic compression ratio and help low speed torque. Have you tried advancing the cam 4 more degrees?
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Old 01-05-2007, 03:18 AM
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New Cam Advice

71C10 wanted to see the differences between my old cam and my new one so I found the old cam card.The cam that was in my car when I bought it was a Crane solid roller part # 138021,valve lift was .567 for intake & exhaust,duration @ .050 was 234 intake and 244 exhaust.The new Comp solid roller is part # 11-771-8,valve lift is .646 intake & .653 exhaust, duration @ .050 is 242 intake and 248 exhaust.For what its worth,the old Crane cam lasted for over 15 years,and if I had of known that the squealing noise that I thought was the alternator was actually a lifter,I could have put new lifters in and probably still be running that cam.
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Old 01-05-2007, 05:09 PM
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Another advantage on dual patterns is slightly smoother at the same durations,and more vacuum.But other than that there isnt much it does for performance.Sometimes single patterns will still make power past that of the dual patterns.
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Old 01-07-2007, 02:21 PM
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Quote:
Originally Posted by 65Guera
Hi All
I received $400.00 in gift certificates from our local speed shop.
And was thinking on a new cam the XR280R or the XR274R....
I dont know if this would be a good upgrade or not......Any advice would
be greatly appreciated...

I have a 357 SBC .30 over
Forged pistons
6.0 rods
10:01 comp.
Lunati roller cam and lifters 248 duration @ .050...555 lift
Roller rockers 1.6
Dart 215 pro1 aluminum heads
Demon 750
Airgap intake
Transmission 700R4
MSD ready to run dist and 6AL ignition box
373 rear gears
2800 stall

I think it would be a waste of money to change. You already have an outrageously large set of heads and cam for your cubes/compression and more cam might really hurt the mid range due to duration and dynamic compression loss.
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Old 01-08-2007, 07:47 AM
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I think you got that back-wards. A split duration cam typically makes an engine run rougher due to more overlap.

For example a 270/270 degree cam ground on 110 lobe separation will have 50 degrees of overlap. A 270/280 cam cam ground or 110 lobe separation will have 55 degrees of overlap.
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