I'm thinking of getting a different cam, since I'm aiming to get 550 cHP at max. 6500 rpm. The cam I'm using at the moment, see below, really pulls strong above 3000 rpm, but does it really match my heads???? The cam was recommended from an engine builder, but it's not really the custom cam I wanted the way I see it. The cam is supposed to make 15 HP more across the board over the 847, even though it's an off shelf cam as I found out!!!!
As I see it, the exhaust lobe has over 12° more duration than the intake and would rather be good for a restricted exhaust system. I was also wondering why he chose a 110° LSA and not 112°-113° like others do.
Please don't tell me to call Comp Cam as I did this already. I also wrote to other cam manufacturers but no reply up to now.
My data is down below.
396 ci LT4
6" H-beam Eagle rods
Cola crank 3.875
SRP Pistons 11.1:1 CR, DCR 8.21:1
AFR 210cc LT4 heads ported by AI flow #'s below
Valves: Int. 2.080 Exh. 1.6
Valve springs: CC Stock car endurance #925 rate 395 lbs. coil bind 1.100
Seat 142 lbs. open 382 lbs.
Comp Cam 236/248 110° .608/578 lift w. 1.6 RR
Crane Lifters #10535
Spark plugs AR 3911 to cold switched to NGK heat range 7
Ported LT4 intake
58mm Holley throttle body
#36 injectors
Meziere water pump
6 sp ZF trani
D44 4.10 gears
Hooker 1 3/4 coated LT headers
No cats, no EGR or air pump
Self made 3" SS exhaust sys., X-pipe, MagnaFlow mufflers

Head flow #'s
Intake Exhaust
0.200 139 107
0.300 190 152
0.400 241 186
0.500 272 204
0.550 278 210
0.600 283 214
0.650 286 216
0.700 289 219
Port volume 205cm³ / 80cm³

Comp Cams 236/248
He/Magnum lobes
Duration at .006 lift 289/315
Lift .608/578 w. 1.6RR
Timing at .050
Int. 8° BTDC 48° ABDC
Exh: 54° BBDC 14° ATDC
Lobe lift: Int.3800 Exh:.3610
Lobe separation 110°
Intake Center Line 110°

 

Have you tried contacting AI?
If they did your heads, I bet they know exactly what cam to put with them.

What didn't you like about the cam? Just not enough power? Disapointing track numbers? Poor street manners?
It should have put down numbers very similar to the 847. A little less TQ down low, a little more HP at the peak.

Did you happen to have that tuned? Something with that much overlap is gonna be a bitch to tune without being on a dyno.
What did quench look like? (deck height and gasket thickness)? How big were the piston dishes?

 

If they really get those kind of flow sheets thats crazy.........


I wish they would return my phone calls!

 

So?

You said you want 550hp....how much do you have now? You are giving us no basis for comparison.

You need more compression.

Stop worrying about the LSA, too many people focus on that one variable.

 

Some of you probably have noticed I live in Germany and I don’t have it as good as you, having engine builders, tuners and dyno’s all over the country. I’ve been building and tuning engines for about 30 years. Since I bought my Vette in 1994 I must and have been doing everything myself. The closest dyno is about 4-5 hr. drive from here and they don’t have the knowledge to tune just have you make a run, that’s all. So I haven’t been on the dyno yet, and the only way I have of checking my HP is my G-Tech (about 525 HP). Tuning the engine on the road I feel is better than on the dyno. I can drive as fast as I can and data log with DataMaster and record AFR as long as I please, make corrections and drive again. BTW, my AFR at WOT is 12.8-13.0

1. I know the CR is somewhat low with just 11.1:1 but I would have to take the heads off to change it. With a DCR 8.2 it’s not so bad but would be better with 8.5. If i change the cam, I would also raise the CR for sure.

2. Quench is .040, Deck height is 0.0, the head gasket is .040, piston dish is 5ccm.

3. Mdaction, don’t know what you mean with “If they really get those kind of flow sheets that’s crazy..” 283@.600 is not very much flow for a LT4 210cc AFR head as I see it, but Phil wanted way to much money at that time to go on to get 300. I will get in touch with Phil and see what he suggests. I know the heads and CR are the weak spots in my combo to get more HP.

4. According to the tuner that sold me the cam, it’s supposed to make more TQ and HP than the 847. The engine pulls from just over 3000 rpm very hard up to 6700 rpm, then I shift. The trouble is really in the tune. James, your right, it’s really a bitch to tune, not so much idle, but there is quite a lot of bucking from 1000-2600 rpm. I’m still using closed loop but think I will try open loop as soon as I put my Vette on the road again. I set the min. and max. BLM Value constants to 120/160 and it runs a lot better, but still with some bucking.

What I’m trying to say is, wouldn’t a 113° LSA be better for the low TQ side and get rid of some of the bucking???
Why did he choose 236/248 with 12° difference; other cam manufacturers use only 6°, like a 242/248 cam??? Don’t have an engine SIM program but the engine should run much stronger for example with a 242/248 113° as it does now. I’ll always have some bucking and a hard time to tune, so why not step up to a bigger cam.

 

You will get rid of the bucking with an open loop tune for sure.
I run a 383 LT4 with an 847 cam in open loop and runs really great.

I just fired a 396 with Trick Flow LE3 with a custom LE3.2 cam and runs incredibly smooth. Open loop tune too.

 

Ricardo, you wouldn't have a DA2 bin file at hand for the 396 engine would you??

Do know the data of the LE3.2 cam??
What HP is the engine making and at what rpm???

 

I use LT1 edit for my tuning. If the file is of any use for you I will gladly email it to you with the appropiate changes ( gear ratio for example).

Still have not been to the DYNO with the 396. I just fired it this week and have only put about 100 miles on it.

PM sent

 

You estimate current HP as 525.

+ Your goal is 550.

+ Your tune is off.

= you need a tune, not a cam.

 

How do you come to this conclusion???
Do have an engine with the same combo as I do, or are you just guessing???

 

Ricardo, as I see it you're using MAF and because mine is a '92 I have MAP and so it won't work I guess. But thanks, most people won't share any info about their tune.

 

http://www.babcox.com/editorial/ar/eb90252.htm


You are way too caught up in "bigger is better" and that is the problem besides tuning though from what you describe tuning is an issue as well.

 

Very interesting but not new, as it comes from someone that really knows what he is talking about. What he doesn’t say is, who can you trust when it comes to cam advice?? Comp Cam, Crane, Bret Bauer, Isky, AI, LE etc. who knows which cam is best. Most of them put all your data in a SIM program and let it tell them which spec’s to use. They won’t tell you the spec’s unless you pay them $25… which will be refunded when you buy the cam.
How are you to know which cam is better. Spending a couple hundred $$ for advice but you still don’t know which one is best for your engine. Buying my own dyno and about 20 different cams isn’t really what intended to do. I was really looking for people with a 396 engine that have about the same combo as I do. The experiences they made with the cam they have installed.
I’m looking forward to Ricardo and what he has to say after the tune with his 396 and the new cam. Hopefully other 396ci drivers will chime in and let us know what they have encountered with their cam/engine.

 

So after reading that you gained no insight into 110LSA vs. 113?????

 

One possible explanation for the larger than "normal", (i.e. your 12 degrees of exhaust duration over intake duration, i.e. 236 vs 248) may be keyed to the intake and exhaust valve lifts (.608" Intake vs .578" Exhaust) that this particular cam has? They may have been trying to compensate for .030" less exhaust lift by adding more exhaust duration. The cam "guru's" play with stuff like this all the time with really no adaquate explanation to end users for their final choices.