hello, i would like some input on cam selection, comp cams and cam motion suggested these profiles, here is the spec on the setup

SBC 355
8:5-1 COMPRESSION
BRODIX TRACK 1 HEADS FULLY PORTED 310/240 CFMS
2.10 1.60 VALVES
HOGANS INTAKE MANIFOLD
FAST FUEL INJECTION
TURBONETICS T100 TURBO 1.00 EXHAUST A/R, 1-3/4" PRIMARY , 2-1/2" CROSSOVER, 5" DOWNPIPE
AIR TO WATER IC
POWERGLIDE TRANSMISSION 5000 STALL CONVERTOR N/L
4:30 GEARS for now
33X10.5 M/T SLICKS
FULL CAGE CAR , RACE ONLY CONFIG, 3070LBS
going to run about 20-25 psi when fully tuned,looking to make 1500hp

here are the specs
comp cams: cammotion:

292/302 adv duration dont know adv duration
259/266 dur at .050 255/251 dur at .050
.645/.630 lift with 1.5 rockers .643/.642 lift with 1.5 rockers
lobe separation 114 lobe separation 114
centerline 110 centerline 110

thanks for the help

 

Without a flow sheet on the heads it hard to determine what lift would work nice on each side. The exhaust flows very well. When trying to make 1500hp with a 1.0 A/R you migh have some pretty decent pressure ratios. This may cause a little reversion, this leads me to pick the cam motion cam, being a reverse split it will help keep you away from this. Also it may help with spoolong caracteristics.

I should note that it could be debated for days as to which is better on a turbo set up. Single pattern, traditional split, or reverse split. Depends on many things like header design and exhaust housing, and hp to be made. In you case I would choose the cam motion grind though.

 

I would also pick the Cam Motion cam.They really know what they're doing on the turbo stuff.

 

thanks guys, i too agree the cam motion is the choice

robert

 

Robert

What is it in?

What block are you running?

thanks
Robert

 

hey rob, its a dart block , brc crank, h beam rods, je pistons, brodix track 1 heads,

robert

 

Pure race application.... both cams sound too small.

 

hey Don, do you think they need more duration or more lift or both,
thanks for your input

robert

 

A RACE engine is going to have to push some limits. Typically that means that the RPM limit is basically around 5500 ft/min piston speed. If you wanted to play it safe stay under 5000 ft/min. Now with that being said you are looking to run an engine with that much stroke in the 7500-9000 range. Remember a typical turbo converter slip somewhere around 10% on the big end. There are better converters but a typical Neal Chance or similar turbo RACE converter that will allow you to spool a large turbo with that short of a stroke is going to not be super efficient up top. You have all good parts so the RPM is a non issue. In my opinion a cam in the 250's @ .050" is too small. Your compression ration also isn't very conducive to a larger cam, most likely the reason the Cam Motion didn't spec something larger. If it were my engine the compression ratio would be approx 10:1 with a cam somewhere around 275 @ .050 with .800 or more lift depending on rocker ratio. You need the added compression ratio to make the larger cam work, no compression and a big cam is a disaster. So don't opt for a larger cam without the compression it doesn't work. There is a reason the single turbo outlaw guys are running 11:1 because the cams are in the 290's @ .050 and some are approaching an inch of lift. You can easily make 1500 HP with either of the two cams you have spec'd, however, you would be leaving a tremendous amount on the table.

3.48 stroke
7500 =4350 ft/min
8500 =4930 ft/min
9500 =5510 ft/min

 

go the smaller cam, with help mid range torque with less exhaust. Also will not come in like a 2 stroke power band and blow tyres off.
You got heaps of intake runner size, use the boost/ CFM to make the power.Also get them to grind some advance into the intake centre line, boost like crazy...
ash

 

thans ASh for the reply, i went with the cam motion one,
robert

 

ha Don Bailey would a cam that is comp cam rollor 301 311 adv 265 275 @.050 with .654 .660 with 1.6 rockers 106 lobe centerline work with a combo like his with 10.1 comp...

 

:agree:

 

Where are you going with the advance? that will give the engine more bottom end, come off the line harder but it will also not deal with boost as well... I usuaally like retarding turbo cams a little bit to better take advantage of the available boost

 

For what it is worth, I was lucky enough to spend some time on the phone with Ken Duttweiler a couple of years ago and he said about 90% of the time, people go too big on turbo cams. He mentioned to me that he built a big block twin turbo setup (approx 540 ci) that made over 2500hp with a cam that was under 240 degrees duration at 0.050 on both int & exhaust. Granted that was probably with a serious set of heads, but the principle stands nonetheless.

That being the case, I always suggest starting conservative with the cam and getting everything else dialed in before moving up to a bigger stick.

Chris S.
Midwest Turbo & Performance

 

Yes that is true, but work out how long a car is in each part of the track, spends more time in the first 1/3 than the 2/3's in the deep end. Get the car moveing quicker.... e.t will come down.
Made 1014 hp and 960 ft/lbs with 355 ci and 24 psi t3/t4 hybrids..
mid 250 intake @ .050, mid 240 exhaust @ .050, 107 intake centre line 121 exhaust centre line, 114 lob sep.
Rpm only to 6800. 960 ft/lbs from 4000 - 5200 rpm.........

 

makes me feel better about my 213/219 at 112LSA

 

2 step, trans brake and all sorts of other stuff can be rigged to get around that problem. Coming off the line at 4k and 15psi boost can be fun'¦

is that a solid roller?

Am I reading that right, 7* advance ground into the cam???

How about more details about the car/engine/drivetrain?

What did it run like this? (not doubting you, just sounds like you took a bit of a different approach successfully and I'm trying to see what I can learn here, especially since I'm odering a cam for my next project in the next few days)

 

I would agree, but I would also suggest that a lot of us have quite a bit to gain with getting some more lift, and it's very difficult to get lift numbers that match the rest of your combination and duration numbers that fit also, when we're talking about turbo setups.

For example, my heads keep getting better past .700' lift, the spring package is more the sufficient to go to .650', but I'm already looking at cam lobes that are on the big side of what I want to get .544' lift with a roller cam (I'm looking at comp HR XE lobes because at least I can keep the advertised duration down even with some pretty big .050' durations). and that's an SBC with 1.6 rockers'¦ it's difficult to even find more then 1.65 rockers for them and that would only buy me .561' lift'¦ still not that much.

 

if i remember right a pontiac rocker is a 1.7 ratio i cant remember what motor but i do now that some racers used them on sb chevys ..