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Discussion Starter · #1 ·
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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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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Discussion Starter · #4 ·
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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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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Guy Hiltz said:
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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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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Discussion Starter · #9 ·
71C10
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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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. :sweat:
 

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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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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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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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65Guera said:
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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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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It seems to me that your heads and cam are matched OK right now. Your cam could be bigger, but I dont think it is out of the ballpark. The compression is a little low for the current cam you have though, so I think the fact that you did not go any bigger on the cam is a good thing. Being that your heads are as large as they are, I dont know that going with a smaller cam would gain you the low end power you are looking for. I think you would be better off buying a 3500 converter to get the stall speed more into the powerband when you hit the gas. When you sell the cam and heads, you could also sell the converter with them.

Adam
 

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454C10 said:
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.


As to your split duration comment. It depends on if the intake is less, or the exhaust is more than the comparison cam. He is considering splitting to a shorter intake, thereby reducing the overlap minimally.

My poor choice of wording.
I should have said

"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.

..... If you were to use more cam the dynamic compression and the overall combination would be worse. You compression likes a 224-230* cam. Crutching the combination with a minimumly smaller cam would be disappointing in my opinion. Not much will help the slow port velocity of those large heads that like 7000 rpm on a 355 cube.

Luckily you have a dual plane intake which crutches the cam overlap. If you had a single plane intake it would be rough idle and be horrible to drive. YOu would drop 4" idle vacuum. You probably also have very large headers.

The heads and cam might be matched to each other, but not matched to the intake and cubic inches as the heads/cam implies a race car.

I would go for a maximum chassis dyno tune-up to see what you can get from what you already have, and then carefully consider changes. In my opinion your combination is ill chosen.

I would look to cam timing, ignition curve, and fuel mixture as already suggested by this forum crew.

Trouble is, chassis dyno time will eat your money and might net you minimal gains.
 

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Guy Hiltz said:
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.

Just curious here. Not being a smart-a..s. :welcome:

If you chose a ductile iron cam OR if you chose a grind that did not perform as you hoped, is either a fault of CompCams..?????

All engines are combinations and some parts work together better than others. Often minimal spec changes are quite noticable.

Did you try altering the lifter clearances to see if the cam is too big or too small for your combination? Did you alter cam timing to adjust for variations in combination? Often cam changes need fuel mixture and timing tweaking.
 

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Discussion Starter · #19 ·
Thanks all for you comments and advice.......
I will take your advice and not go with a bigger cam but instead continue to save my money for some AFR 190's....I took some ill advice from the guy at the speed shop he talked me into the Dart pro1 215's as soon as I drove the car I new I had made a mistake...The are nice heads but as you guys said not enough cubes.....I will save them for another build.

Also i did call that guy Joe Sherman...He would not give me the time of day unless i was going to buy a engine from him..He was real jerk...
 

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65Guera said:
Thanks all for you comments and advice.......
I will take your advice and not go with a bigger cam but instead continue to save my money for some AFR 190's....I took some ill advice from the guy at the speed shop he talked me into the Dart pro1 215's as soon as I drove the car I new I had made a mistake...The are nice heads but as you guys said not enough cubes.....I will save them for another build.

Also i did call that guy Joe Sherman...He would not give me the time of day unless i was going to buy a engine from him..He was real jerk...

Interesting. Every time I have talked to Joe he has been the nicest person and wanted to visit about our hot rodding experience beyond my technical inquiry. I have never done $ 1 worth of business with him.

Maybe somebody was kicking his cat.
 
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