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[GMR-PERFORMANCE]

The pro charger is the issue. The way it is designed will build boost in the 3500+ range on avg.  Cam will not effect it much as where ti builds the power . You can try to spin the blower faster with a smaller pulley and lower the Peak RPM but again , this is not a cam thing and they do the very same thing on cars as well.. They do not have that massive brick low end power.

Now go ride a Aerocharger bike and you will see it makes peak boost by 2500 so the tq curve is instant,

Two different methods to build power. Myself like the latter big end rush..

[BigLew]

That part I think I understand pretty good. But the 640 has so much overlap its bleeding off a lot of boost on the top end. S&S says the 585 or 625 would be a better choice. If I go with another type of cam then I will need to deal with the compression releases. Not sure what all is involved with that.

BigLew

[GMR-PERFORMANCE]

It may help a bit but its not going to be a 1500+ RPM shift.   It is a centrifugal super charger.so by design it has to spool up to make boost.

A smaller cam will not make power sooner just less power. 

The cam is not bleeding boost off on the top end. The over lap would lower both static and dynamic compression off boost. However when you go to a smaller cam the boost comp ratio will also rise.. SO there are some times that you have to run a a new pulley to build less boost.


But this is simple look at a stock 103 with stock cams 8 PSI  and the tq curve looks the same just less in numbers.

Post your sheet

[BigLew]

Maybe I'm using the wrong terms. But the 640 is a horrible cam for a blower engine. Just pushes a lot of the boost out the pipe. With the current pulley the gauge says we are making 13 lbs of boost but its not usable. Got a lot of good tuners close, T-man, Kendall Johnson, and a guy at a Harley store that does a lot of the NASCAR boys bikes and they are all in agreement, this cam has got to go. Just trying to find the best fit.

BigLew

[GMR-PERFORMANCE]

Lets see the sheet as I am not understanding not usable. What is late?? 3000 3500 5500 ?? . We do tune a fair amount  of these pro charger bikes as PC sends them to us for tuning.

What is the entire build specs??

[BigLew]

Well the built 110 to 124 came apart (Crank walked out). So I bought a crate 124 HC from S&S. We put the new wider pulley and belt that one of the guys here devolved. Much better tension point will look at another pull after the new clutch goes in. The cam guys are telling me to much overlap/duration. I guess the cam profile allows the exhaust valve to stay open to long? The blower is making plenty of boost but we are loosing it with the cam. There is no way I would try to run 13 lbs if the engine would use it. Last graph 3800-4000 came on pretty hard and we shut it down at 6,000, its running out of fuel and i really don't want to turn it any more.

Mike

[HILLSIDECYCLE.COM]

Part of the problem is the belt not staying tight/stretch on those.
NAPA has a good one.
Scott

[BigLew]

With the new wider belt and pulley thats really not a problem anymore.

BigLew

[HILLSIDECYCLE.COM]

Maybe so, but it was a LARGE issue, and much discussion was had with them in regards.
Sounds like they listened.
Scott

[BigLew]

Actually I was told that a guy here started the pulley project and I believe Walt now has it at ATI

Biglew

[HILLSIDECYCLE.COM]

Certainly needed attending to.

[GMR-PERFORMANCE]

Well That pull you see there was making 15 PSI and as you can see even at the graph I will show you, and at the limited RPM we did pull it was not slipping. The engine was tuned beyond that and made even more power. However over driving the S/C can lead to issues. And yes open A/C for drag racing use only or larger filter with custom built parts will yield more. And that cam is larger has way more duration than the 640 .. Look up the specs on the RX267 SE cam

 Yes they have had to make some changes however it can be adjusted and not slip and not have a bearing failure on the pulley as well. 

But again when you install them, build them and tune them you get to know what to look for and a few simple things that can be done to improve the performance of the kit .


The S/C is not very picky when it comes to lift more so duration.  The 640 Pops the ex valve open very soon.. But again I have run bigger cams and made great low end power. However a MVA head stock will outflow the S&S head , chamber config etc all play a apart in that.


But try the 585 should be helpful .. BTW what EX??

Here is some boost info as well
Here is some basic info on a crate engine 124 HC with 13 psi and 1500 feet above sea level

640 cam

Your dynamic compression ratio is 8.86 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 181.36 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 13 PSI is 16.70 :1.

So if you run a cam with a early close point like the 635

19.5°    43.5°    58.5°    37.5°    243°    276°    .635"    .635"    102°    100.5°    .115"    .175"


Your dynamic compression ratio is 9.66 :1 corrected for cam timing, altitude, and rod length. Your dynamic cranking pressure, corrected for cam timing, rod length and altitude is 202.56 PSI. Your dynamic boost compression ratio, reflecting static c.r., cam timing, altitude, and 13 PSI is 18.20 :1.

all based on 13 PSI of boost..

Good luck.

[BigLew]

Wow that is really a lot of info, thanks for sharing. So in your opinion what would be my best cam solution? The other engine we built had a T-man 662-2 and it made a lot of power up around 5-6k. Seems like a top end engine. would trade the hp for some tq. Ride about 50% 2 up. Would Head work really be worth the money. I know we talked about the 585 and the 625 do you have another suggestion?

BigLew

[HILLSIDECYCLE.COM]

Some shops have disintegrated customers Pro-Charged engines while up on the dyno.....

[BigLew]

I could see that happening!

BigLew