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1,150+ rwhp club
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Discussion Starter · #1 ·
Messing around with AEM new vs old logs and tuning my newly installed hks 280 cams (Thanks 417motorsports!)

Specs:
The car is a GT42-70 non dbb
6 speed
AEM
Stock long block
crower springs w/ Ti retainers
HKS 280s


Scenario:
93 octane. 3rd gear pulls. 17lbs of boost. Only changes to tune post cam install was air/fuel tweeks to get it in line.

Stock Cams
5328 - 17lbs (full boost for pump)
4250 - 8.25lbs

280 Cams
5465- 17lbs (full boost for pump)
4250 - 3.21lbs
4350 - 4.61lbs

Observations: I had to add ALOT more fuel in the big end (5500 rpm up)compared to the stock cams. Boost comes on later, but spools faster. See 4250 rpm comparisons. I added the 4350 rpm to show that it the 280s were more then just 100 rpm behind.

Summary: On pump gas/low boost, 280 cams cost me ~100rpm of full boost spool. 280s make my turbo spool later in the rpm band, but come on stronger. The slope of the engine load curve is much greater compared to stock cams.


Hope that helps.

PS - I know some of you will ask about idle. At 14:1 and 21 degrees of timing, it idles smooth with a healthy lope that makes guys who like V8's w/big cams smile.
 

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Super Moderator
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James,

Good info, bud. Thanks for taking the time. Although I have 272s, I LOVE the way our cars sound at idle with those 280s. Looking forward to your race gas data as well. Thanks again.

Ken.
 

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I would now love to see your car with 280's and have a set of those Crane cams ( the ones from SP)thrown into the mix.


Staats
 

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I am in the market for new cams. I have the 76 version of the gt42. The lag doesn't seem that bad on the 70 version with a big turbine section.

Thanks for taking the time to do the comparisson. A video of the car at idle would be nice also. Someone lend James a videocam.
 

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1,150+ rwhp club
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Discussion Starter · #6 ·
SteelCitySupra said:
:scratch: So what was the power difference?


Not sure. Have not been to the track or dyno yet. The cams increased the ramp rate of the turbo. Or in other words, it made it more of a on/off switch.

I can feel a seat of my pants difference. Also I know they flow more air on top simply due to the massive amounts of fuel I had to add on the big end (5000rpm plus).
 

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Boost Junkie
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I would think you would need a stroker or a larger turbo to really take advantage of cams that large. Thanks for the data and looking forward to dyno results.

Steve K.
 

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Are the cams really that big? I am no expert but looking at the post from Larry from SP it sounds like the 280's are more hype than anything else. I am looking to get a set of Crane cams and Larry told me that he has seen 40-50hp increase over the 272's and has not seed a diff between the 272's and 280's.


Staats
 

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1400rwhp/8 Sec Club
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JamesN1830 said:
Not sure. Have not been to the track or dyno yet. The cams increased the ramp rate of the turbo. Or in other words, it made it more of a on/off switch.

I can feel a seat of my pants difference. Also I know they flow more air on top simply due to the massive amounts of fuel I had to add on the big end (5000rpm plus).

ohh, i thought you dynoed it.. but instaed you are looking at AEM logs. Gotcha
 

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320hp
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Jstaats said:
Are the cams really that big? I am no expert but looking at the post from Larry from SP it sounds like the 280's are more hype than anything else. I am looking to get a set of Crane cams and Larry told me that he has seen 40-50hp increase over the 272's and has not seed a diff between the 272's and 280's.


Staats

James,

Thanks for the comparison, Sure dyno data is good. but nice to see really how far off spool up is. I bet the 272's would of yeilded the same spool up so nice to see they are right inline together.

But now regarding the crane cams i have heard they spool up real late and are lazy. One guy swapped them out for 272's and said it spooled up over 500rpm faster.

When it comes down to it, ill just swap out cams and see what works best.
 

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Jstaats said:
Are the cams really that big? I am no expert but looking at the post from Larry from SP it sounds like the 280's are more hype than anything else. I am looking to get a set of Crane cams and Larry told me that he has seen 40-50hp increase over the 272's and has not seed a diff between the 272's and 280's.


Staats

The cams have much more duration than the 272's but no more additional lift. The power comes from the additional lift. The longer duration just moves the powerband further up.
 
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