What cam profile for a Blower?

daxtojeiro · Post by **daxtojeiro** » Sat Aug 24, 2013 12:51 pm

OK, got the pistons made, they have all been balanced up with the crank, etc and its ready to be built Finally!!

Anyhow, Ive lost this summer now so Im going to get a cam made for the blower and get everything sorted before re-fitting it.

Between all your experiences and use of cams with blowers, what would you suggest I get made? I will be going to Kent Cams as my engine builder has an account with them and they will build what I need.

Its a 5325cc 9.4:1cr 5.5psi of boost.

thanks
Phil

kiwicar · Post by **kiwicar** » Sat Aug 24, 2013 2:21 pm

Hi Phil
assuming you are staying flat tappet I would recommend
215 to 225 duration at .05 on the inlet with at least .45" lift
220 to 230 duration at .05" on the exhaust with about the same lift on the exhaust with a lobe seperation of 112 to 114 degrees
If it is a roller cam go for about 5 degrees less duration both lobes, 2 degrees less LSA and at least .50" lift. more lift the better and preferably a bit more lift on the exhaust lobe.
Best regards
Mike

daxtojeiro · Post by **daxtojeiro** » Sat Aug 24, 2013 7:06 pm

Hi Mike,
thanks for the reply. When you say 215 to 225 and 220-230 what would the difference be between those angles mean or change? I guess what Im asking is how would you decide on the exact angle required?
thanks
Phil

Blown v8 · Post by **Blown v8** » Sun Aug 25, 2013 7:20 am

I had mine made a fair few years ago,mines very much like Mike recommends,I've got more duration on the exhaust,and have 114* lobe centres
Check out my dyno'd print outs in the relevant section.my torque "curve"is a straight line !

kiwicar · Post by **kiwicar** » Sun Aug 25, 2013 4:01 pm

hi Phil
with a normally aspirated 5.3L is engine power curve with a cam with an inlet duration of about 215 degrees the engine should start pulling strongly full throttle around 1400 revs and take 5th about 200 revs with peak torque about 4200 revs ish. 225 degrees this should happen with about 250 to 300 revs later peak power in each case should be about 1000 to 1100 revs later than peak torque. with the blower it will be similar but stretch the rev range a bit and move peak power away from peak torque 3oo revs or so.
Putting in an extra 10 degrees of exhaust timing in should stretch the amount you can over rev after peak power by about 200 to 300 revs or so further and move peak power away from peak torque a 100 to 200 revs you won't get much gain out of the rover engine but a bit and going out to a wider LSA . with the centrifical blower then the "lift" at the top of the power curve will help the engine further, and here the extra exhaust timing will help further.
Basically a 215/ 220 at 112 LSA and the blower should give a pretty mild road engine that has a good kick in the back in the mid range but preferes to be short shifter rather than reved into the boost. 220 / 230 on 114 LSA would pull well from low down but rev for more through the range and up into the boost but give less of a kick in the back at peak torque. 225 /230 112 is still not an overly agressive cam for that big engine on boost, but would kick hard at peak torque but again it would drop off the top of the power band quite quickly.
None of these cams will give you a "cammy" engine especially with EFI and a big motor it really depends how you are going to drive it, if you spend all you time in top and in traffic on motorways then go for the shorter timing and a the narrower LSA, if you like to drive on A an B roads and use the box go for more duration and the wider LSA, maybe even co to a 225 235 114 LSA combination.
If you decide to go roller cam then you could go for a bit mor timing still.
Best regards
Mike

kiwicar · Post by **kiwicar** » Sun Aug 25, 2013 4:13 pm

Hi Phil
nothing with cam timing works indipendently of anything else but in very crude terms, opening the inlet valve earlier tends to make an engine hit peak torque slightly earlier and harder, more overlap makes more torque but moves peak power closer to peak torque. Opening the exhaust valve later then also holding the exhaust valve open later tends to help an engine rev after peak power and softens the power curve, also opening the exhaust valve later tends to help broaden mid range. As you can see from what I have just said though they are not indipendent of each other and over all duration of each lobe is a big consideration.
remember the boost curve on your blower will tend to help broaden the power curve not just make more power.
Best regards
Mike

Wotland · Post by **Wotland** » Mon Aug 26, 2013 12:32 pm

Hi Phil,

In the past, Crane made F-228 38/72/74/36 290° .491 " camshaft for turbo or supercharging.

daxtojeiro · Post by **daxtojeiro** » Mon Aug 26, 2013 8:55 pm

Thanks for the replies. I think I will see if I can go for something in the middle as you say around 220 / 230 on 114 LSA and lift as much lift as I can have, hopefully this will give me the best of both worlds by your descriptions.
thanks again!
Phil

stevieturbo · Post by **stevieturbo** » Mon Aug 26, 2013 10:09 pm

Tried to post last night, but it wouldnt work.

All this talk of cams and blowers....yet no mention of exactly what type of blower you have, which will affect power delivery, expected rpm range etc etc.

One thing that is certain, mild cams always work well.

Although if you're a PD style blower, you might want to select a cam more biased towards top end performance, as this is where the blower will be at it's worst.
At the low end, things the blower will take up any slack so to speak. Although at only 5psi, even a mild n/a camshaft will work very well, as the engine could almost be considered n/a with just a little extra shove.

If it's a centrifugal, you might choose a cam biased towards low-mid range, and the blower will take care of things at the top end..

bigaldart · Post by **bigaldart** » Mon Aug 26, 2013 10:16 pm

There is scope for more experimentation but I have to say the Real Steel blower cam just flat out works. If you are using the car on the street it would be a good choice. Lift is not too extreme, the timing follows Mikes suggestions in particular the wide lobe centres. Although we run methanol I can't forsee any issues running pump gas with this cam. Ours is close to 500 bhp on a 3.9 short block, running no more than 14 lbs of boost and probably nearer 12 psi.

Alan

bigaldart · Post by **bigaldart** » Mon Aug 26, 2013 10:21 pm

There is scope for more experimentation but I have to say the Real Steel blower cam just flat out works. If you are using the car on the street it would be a good choice. Lift is not too extreme, the timing follows Mikes suggestions in particular the wide lobe centres. Although we run methanol I can't forsee any issues running pump gas with this cam. Ours is close to 500 bhp on a 3.9 short block, running no more than 14 lbs of boost and probably nearer 12 psi.

Alan

daxtojeiro · Post by **daxtojeiro** » Tue Aug 27, 2013 6:07 am

I've rang Real Steel a few times now and they are no longer able to get that cam made. No idea why. So my only option is to get one made, but I guess there could already be something out there for NA applications which would fit the bill.

Its a centrifugal blower,
thanks
Phil

stevieturbo · Post by **stevieturbo** » Tue Aug 27, 2013 7:52 am

If you're only going to make a max of 5.5psi at max rpm, then I would say that a milder cam aimed at low-mid range might be better.

That said, I guess it depends what sort of rpm range you actually want to be using. You might want it more biased towards high rpm usage because of the blower.

But it really wont be far off a n/a profile as most of the time it wont be making much boost at all if 5.5 psi is the maximum

Only aim for lots of lift with aggressive ramps if your valvetrain can handle that, otherwise it could end up preventing you using higher revs.

bigaldart · Post by **bigaldart** » Tue Aug 27, 2013 6:13 pm

V8 Tuner is still advertising the blower cam. Duplicating the profile with maybe a little more lift and duration should be easy enough. My feeling is the lobe centre angle is the important factor in making power. With the available dual valve springs they last well for us with the blower cam, but wore out quickly with the racier cams we have run in the past.

Alan

mgbv8 · Post by **mgbv8** » Thu Aug 29, 2013 7:18 pm

I'm currently running a Crower 50303 cam. It gives a really good idle. The engine is smooth at low rpm with no boost while driving it around. No lumpy feel at all to be honest. She ticks over at quite low rpm after a burnout and sounds lumpy, but it doesnt feel lumpy, even with solid engine mounts now fitted.

It runs hard with 13psi of boost and absolutely flies with 13psi + a 150 shot of nitrous on my engine

Theres a link here to the cam specs if it helps:

http://www.crower.com/index.php/camshaf ... 2-fdp.html

It doesnt make a heap of sense to me though. It just runs nice !!

And here she is using this cam:
You can hear she is ticking over around 800rpm after the burnout. It sounds like its going to stop, but it doesnt?

http://www.youtube.com/watch?v=oJSx-ccg ... GyG4tfRrjw