Hey guys

As I put the bottom end of the stroker (383) together, I wonder if I need to get a bigger cam.

heads flow:

.100 64.2 47.8
.200 132.8 92.3
.300 188.6 134.5
.400 237.7 160.0
.500 267.1 179.1
.550 277.8 186.9
.600 279.0 191.7

Might be a little better cause they just got a new valve job. Compression is a static of a high 10.

I am going to be running juice on this motor later on after i get more money, and let the rings set and expand a bit. A max of 200 shot probably and that will only be occassionally. probably mainly use a 175 in a dual stage most of the time.

Right now, I have a 230/236/112 .544/.555 on 1.6s. Im thinking i could get some more exhaust duration with the 230/242. Im not sure if i want to increase intake duration. I would really like the power to peak around 6300 or 6500.

I honestly dont have the money for a custom cam so off the shelf please!

Thanks guys

 

Assuming emissions is no real concern, I'd probably take a chance with:

Comp Cams xtreme energy, 242/248 .540/.562 112

That cam would give you a ton of power with your heads and still be very streetable. According to my simulator, peak power would come in at just over 6000 rpms.

 

The cam you speced is probably a good choice for you considering where you want that rpm peak. I wouldn't go with more than 236, but your 230 will work fine.
The 112 lsa is ideal for a daily driver that will see occasional nitrous use. 10* more exhaust duration (230/240 for example) would also be about ideal, as would a bit better flowing exhaust port.

Bret will likely prefer a smaller cam where as I'd rather turn more revs. Then again, I draw a finer line between street and strip with the majority of my experience being at the strip.
If you have a really well ported high-velocity head, then the smaller cams can make good power and turn more revs. If not, then based on my experience, a larger cam is needed to make the power. Honestly, you should be able to make ~525 hp with that cam in a well built engine. I know most guys down't get that but that is where the power should be with good heads.

-Mindgame

 

mindgame what do you reccommend i go with? and how much power do you think i will be able to make in this stroker? 450? 475?

 

Hard to say for sure, but in my mind, 236/244 with ~.560 lift and 112* ls would be about ideal.
According to some people, that's too aggressive but I have to wonder how many of those people have run a cam like that in a 383.
Well tuned, it'll be a very tame daily driver cam that shouldn't be too hard on valvesprings. If you can find a grind in that range specifically ground for nitrous use (the intake/exhaust closing and opening points will be a little different) then that's what I'd spend my money on.

On hp, it's a tough call. I hate to always say this but it is in the heads more than anything else. I have seen a change from a ported head that flowed 270 cfm at .600 to a head of almost the same flow make a 20 hp difference! It's not just about the numbers... it's about consistency in port area, velocity and lots of other things that are not so easy to see. That's why I don't recommend guys porting their own heads. The guys who really know this stuff are well worth the money.

-Mindgame

 

how will the 230/236/112 perform in the stroker? peak rpm?

lloyd elliott did the port work.

 

Should be very drivable and from what I've seen, I'm thinking 6300 rpm for a peak.
Again, it depends on the port volume of the heads but it's likely gonna be in that range ±200.

-Mindgame

 

I'll be trying the next size up in my 383 shortly - 236/248 (.556/.600 with 1.6 rockers). Should make peak power appox 6300-6500. I'll be running a little more juice than you, and I plan on running it a little more often, so I went with 114lsa. (gonna try to pass emmisions with DFI tuning as well) I'm also taking my stall up from 3200 to 4000.

You running a standard or auto? If it's an auto, you might want to look at stall size before picking your cam.

 

its a 6spd car.

mindgame if i get porrt volume, can you give me a better estimate of power and power band?

also, how does changing exhaust duration effect the powerband? like increasing intake duration moves power up.

 

Late exhaust valve closing increases the overlap period. So, you sometimes see a little loss of low speed torque with a later exhaust valve closing. Why? Because at low speeds, the exhaust velocity may be too slow and some exhaust may revert back into the cylinder.
With higher engine speeds, the exhaust velocity is high enough that no reversion occurs and later valve closing aids in expelling exhaust gasses at high rpm.
All theoretical because alot of that would depend on how efficient the exhaust port and exhaust system in general are. It's a matter of pressure differences from one place to the other..... the intake port vs the cylinder vs the exhaust port. If there is less pressure in the cylinder than in the exhaust, the exhaust flows into the cylinder... then there's inertia.

For a nitrous motor, you definitely want more exhaust duration even at the expense of a little bit of torque loss (if there is any at all). Easy enough to check if you're running 1.6's all the way round.... run a 1.5 on the exhaust. If you pick up a bit of low-mid range torque, the chances are you have a bit of reverse flow going on. Hence alot of gus run 1.5's on the exhaust. I wouldn't worry about it with a nitrous engine though.

On the port volume, I can make a guess but that is about it. Much of the port velocity thing is dictated by the smallest cross section area of the port. But knowing the flow numbers and the port volume can give you an idea of how high a velocity the heads are.

-Mindgame

 

runner volume is about 195.

how much of a gain do you think i would see going with a slightly bigger cam? and which cam? not sure if the 236/244 would be right for me.... seems to high of a revver. maybe the 230/242? keep the intake the same but more exhaust for the juice?

 

I'd keep the intake/exhaust at a difference of about 8-10*, but no more. On that 236 cam, knowing now that you plan to run a bit more nitrous, I might opt for a 113-114 lsa. If you had a really good free flowing exhaust... duals, x-pipe etc., I might stay with a 112.

Like I said before, 230/240 is a good call. I wouldn't care to give up more torque with much more exhaust duration. You're gonna be wanting off-nitrous performance from this engine. So I'd keep that in mind.

My estimate (6300 rpm) was assuming a head in the 195 cc range.

-Mindgame

 

Im actually thinking of switching to duals once i get some new shocks/springs as ground clearance is horrible right now.

how much midrange tq do you think i would be giving up going from the 230/236 to teh 230/242?

any ideas on power output with that 195cc?