Hi Guys

I'm looking for a little help on were I should be on lift/duration for a 396 I am assembling. This will be a 11:1 c/r, hyd roller engine with GM LT4 heads that flow as follows:

I E

.100 - 62 49

.200 - 135 106

.300 - 190 139

.400 - 229 163

.500 - 255 183

.600 - 279 200

The goals are great TQ and HP with hopefully a little better drivability (cam surge) than I have been experiencing the last 2 years on a LT1 - LT4 hot cam set up.

I read the Lift vs Duration thread by 96z on advanced tech from a month ago and I'm pretty much asking the same question with a slant to the c/r and flows I will be running. Looking to build a very strong daily driver that will see 1 or 2 track days a year.

Also, I'm curious how close you have observed DD2000 results for HP and TQ track to results on the actual engine?

Rich, Brett, would love to here from you guys for sure!

Thanks, msw

 

Automatic or manual transmission (and what type), type of car (ie how much does it weigh), type of exhaust system you plan to run, what rear end ratio?

Glad to offer my $0.02 but with some more info the advice will be a bit less generic!

Rich Krause

 

Hi Rich,

It's a 95Z with stock M6, and I figure it's still pretty much at what ever weight it came at from the factory plus the weight of a KBDD.

The exhaust is the SLP's 1.750 Dia. short tube and Y pipe setup with a B+B catback. The cat. converter may or may not be updated by the time the engine goes in.

The rear end is all stock now but I plan to add a diff cover with the engine. The ratio will not change from stock for the foreseeable future and track days are done on the BFG G-force radials I run on the street.

Thanks, msw

 

You are a good candidate for the following.

CC XE #3190/3192 on a 112lsa and a 108 intake center line
214/224 @ 0.050" .530/.567" (1.5)
intake opens/closes 25/61 BTDC/ABDC
exhaust opens closes 74/22 BBDC/ATDC

Rich Krause

 

Rick,

Curious, how close would DD2000 predict the results of this cam selection?

msw

 

DD is not very accurate at predicting absolute hp. What it's useful for is comparisons. If you want to prove this to yourself, try a combo with a 20:1 CR! It will make a ton of power on DD, but I don't think it would work very well in the "real" world (unless you are running a diesel).

Rich Krause

 

Brook,

It was easily drivable IMO. Just thinking that with the extra cubes it would be nice if the package came with a little less surge. Not required though. msw

 

DD uses much too simplistic emptying and filling models for simulation. I wouldn't trust any numbers you recieve from it.
The cam Rich mentioned is a little mild for my tastes but it would be a very good street cam, not for the horse lover.
I'd prefer something closer to 224/230 112º LCA or even a 230/236 on the XE lobe design. Either cam with good tuning is extremely drivable.

Chuck Riddeck
Progressive Race Engine Development

 

Now how did I know you'd suggest that cam, Rich.

It's Bret's choice, too (at least for a 355), but maybe at 110 LSA.
Most folks don't realize how much area there is under those lift curves.

I get -7 * overlap @ .050 with 112 LSA! Idle vacuum should be very high, as should driveability.

Torque peak 4500-5000 and power peak 5600-6000.

[edit] OOPS! I forgot it was a 396. That pushes peaks down about 400-600 rpm.

Just for grins, I tried a 3192/3196 224/236@ 112LSA; also 4* advanced.

On EA Pro, it showed torque at 4500, power at 6000 and about 30 more hp. Now overlap is +4* @ .050 and about 2-3 in hg less idle vacuum. Still good, though. This was on a 396.
Just about what Mr. HP said.

Ya need to use very good lifters, pushrods, rockers and springs. Keeping south of 6500 would also be good.

 

I'm running the 230/236 XE in my car - it's pretty nice. If drivability is an absolute priority, I'd probably step down to the 224/230 cam, as I find the larger one to be just a wee bit rude at the very low end of the rev range (such as when trying to creep through a parking lot with the clutch completely engaged). I'm also a bit undergeared now that I've got a T56 (I'm only running 3.73s with a 27" tire), so that probably plays a role.

As it sounds like the car is used in the twisties, I'd probably err towards a smaller cam. While it's great having the power up top with a larger cam, a smaller cam will be more forgiving when something goes wrong and you find yourself in too high of a gear. For hacks like myself, a broad powerband is more important than peak power.

 

OldSStroker posted:

"On EA Pro, it showed torque at 4500, power at 6000 and about 30 more hp. Now overlap is +4* @ .050 and about 2-3 in hg less idle vacuum. Still good, though. This was on a 396. Just about what Mr. HP said.

Ya need to use very good lifters, pushrods, rockers and springs. Keeping south of 6500 would also be good."

I was also thinking about the same lobes on a 110lsa, might be a better choice. As far as #3192/3196, I wonder about the drivability with a 110 or 112lsa, since that seems to be a priority. It would sure make more hp, but I am familiar with these lobes with a wide LSA. In that use, the drivability is quite good, but with a "narrow" LSA, I wonder....

In terms of springs and lifters, would you guys take a look at the new thread I started on exactly that question? I'd like some opinions.

Rich Krause

 

Eric,
Using that cam in the heavier Impala probably plays a good part in it too. I ran the same cam in a 66 Nova, (388 cid) w/4.10 gears and a 5 speed Doug Nash tranny... it was a very nice daily driver combination. My girlfriend at the time would even drive it. But I agree, for more torque in a little heavier car I'd probably opt more towards the 224/230 cam too.

-Mindgame

 

For a 396...........

At least the 3192/3196 @ 112 if you want it to act nice. It's not a cheap cam to run considering the parts that go with it. With that much lobe thou split that far apart that is about the minimum cam I would go with on a 396, maybe even up to a 3194/3196 still on the 112-114 LSA to give it the low speed traits you want. This all depends thou, I would want much more head than that. It it was me I would shoot for a 233-240cc port with 300cfm flow at .500 and max @ 330cfm flow. The problem is that is $ when you are talking about a LT1. It's basically a 215RR AFR or a well ported 227 LT4 AFR. Those cost stupid money for what they are.

Bret

 

Well, I have real world experience with the CC305 on a 112 LSA with my 396. My car has a manual with 3.73. It is VERY easy to drive and will only surge a little bit under about 1,200 or so RPM. I'm thinking I can adjust the timing some to get rid of it, but I've been lazy. Adding cats to my Mufflex y-pipe has actually improved the situation too.

I like Rich's suggestion, good lift numbers...but it sounds a bit too docile and may peak too soon. I'm very picky about drivability and the cam I have works quite well. It would be interesting to try that Ruch's cam on a 110 LSA though...

It's interesting that the HOT cam is claimed as not being very drivable. I'm assuming it's because it has gentle ramps which creates more overlap then an XE grind cam.

-Alex

 

I wouldn't put anything less than a Comp XE 236/248 in a 396.

I have a 224/236-113+5 in my 350 and my buddy has a 230/236. Both cams have a very reasonable idle (850) and vacuum (11hg). These would be too small for the 396 in my opinion.

The Comp XE series are quite nice since they concentrate on midrange torque. Mine starts tapering off at 6000. You do need some decent springs, though, due to rapid lobe acceleration. This gives a nice area under the curve.

My springs have 140 seat, 350 open pressure.

With this cam, stock iron heads with some pocket porting, stock valves, and 3800 stall, my 4400lb car with the 350 LT1 has run 107s, and this is with a non-lockup converter with around 8% slip at the top.

My previous cam, the Comp 304, gave my car a best of 101.6mph with the 2400 stall lockup converter with <1% slip. (Bone stock was 90mph, 1300 stall)

On the juice, MPH went from 114 to 119.

I would guess that in a 396, a jump from the Comp 305 to the XE 236/248 would make similar gains, 5+mph (in a 4400lb car, more in a lighter car).