hi all

i built a 396...and was on the dyno on saturday...

out came 340chp / 360ctq and im disappointed....

the engine top end consists of AFR 210comp port heads, an single plane EFI and a 224/230 605/622 cam 113LSA

the engine feels not powerless, but also not powerful..

max torque come in at 3850rpm..

i blame the lack of power on the Single plane Intake..

ok, what can do, to solve my problem? there are a few guys here, that yield 400rwhp with this cam and an LTx manifold

personally, i tend to a TPIS bigmouth und fully siamesed runners

i think, this should up power and torque (referring to the article "ten times the torque")

i hope i can keep the cam, i dont want to disassemble the engine, and i also want an acceptable idle...

thank you

 

'NOT a professional engine builder... but looking at your numbers something does seem amiss. That torque peak seems way too low.

First thing: was the cam properly degreed? The single plane should move things (max torque/HP) towards the upper band, so I don't think your limitation is there.

What type of dyno? Was the motor (ECM) tuned?

 

Probably a silly question, but are we talking the 396 Big Block engine or a punched out 350 small block?

I am no hlep on the 350 but on a true big block I was able to get mine to @550 horse on a non-blown carbed unit.

 

hi all!!

the ECM was properly tuned, cam is right up for sure

this is a small block stroker, based on an aftermarket block

i think, its the combination, that doesnt match well

 

You're leaving a lot of info in the table. What does your exhaust combo consist of? What is your static CR? Injector size? Base fuel pressure? Total timing? 1.5 rockers or 1.6? Are the heads ported at all? Any port matching of the intake?

 

ok, sorry, that i dint mention

Exhaust consists of TPIS headers, and flowmaster mufflers, and is 3" diameter

static CR is 10.5, DCR is 8.2 fuel pressure is about 43psi, total timing@WOT is 36°, 1.6 Roller rockers, the heads are AFR 210cc competition port, the intake ports was not matched, but the outlet of the intake was a bit smaller than the inlet of the heads..so this should help with the reversion phenomen....

figure this, i built a 396 with high quality and high dollar parts, and get the power of a stock, oder near stock LT4....

 

the big afr heads and the single plane intake are not matching well to the cam you have, i would suggest you get a more agressive profile.

putting in the tpis big mouth and siamesed runners will choke the motor, that's too much head for the intake.

 

i was told from many indepent people, that the 210heads are fine...sure, they will sacrifice some low end torque, but the displacement should make that up...

what cam would you suggest? i dont want to loose too much idle quality...and also, my ECM is done at 6000rpm

when putting on a bigmouth with siamesed runners, wouldnt that help the numbers?

the bigmouth have an outlet, that exactly matches the inlet of the heads..2.09 x 1.28" so it should be a smooth transition between heads and manifold...

anyways..i cannot throw away the heads...they were not cheap....

 

no suggestions? :-(

 

There is already a mismatch... be very careful at this point on whose
advice you take... science always beats a know it all swager..

here is what I would do:

1. Buy an inexpensive dyno simulation/engine building software program and run your information through it... play with different combo's and look at possible outcomes... allow 10% varience plus or minus.

2. Call AFR... give them the information you have and see what they
suggest.

3. Call Comp Cams or your cam manufacturer and see what they
suggest.

At this point you will have solid advice from 3 different reputable
sources of information... pick the option that best suits your desires
Comp has a simulation program out I believe... or you can choose
a simulation program out of the Summit racing catalog...

Sounds like you have some good pieces that just aren't working
together... get yourself some REAL advice... I'm sure you can solve
this issue and have a nice powerful motor.....good luck!!!

 

Hi Kyle!!

especially the last sentence makes me hoping again...

there is a part mismatch, it seems so...

i have simulated my combo with desktop dyno2000....and the power and torque curves was sooo nice, that gave the Accel single plane a try....


the cam i have, i talked with compcams, and they said that this cam is ok...

i will call Tony at AFR, he has a very good reputation...

thank you

Another thing:

my current cam have 51°overlap, and the idle is rather normal..not total smooth

how much overlap can i have before the idle is rather lopey...?

i know the sound of a CC306, and that would be too much for me..or at least some people in uniform....have 74.5°overlap

 

i also did a 396ci over the winter. i used brodix m2 215 cnc head but im more like 11.5/1 cr. my cam is much large than your and a solid roller, 252/260 @.050 .642 lift with 1.5's on 112 lsa. i have a super victor efi conversion from jeb. my motor on the engine dyno made 572 hp @ 6500 and 530 tq at 4900. should convert to high 400's at the wheels.

who guided you towards the single plane? id say you have a cam that is "small" for even a 350 ci motor. with that cam in a 396 peak hp will fall in the low to mid 5000's for rpm and the tq is about right. id say a superram would suit you best id you looking for mild and lots of tq.

from what i see you bought a heads and an intake that likes 3000-7000 rpms, and a cam that will have a range of 2000-5500. it is very important to match components to make max power and tq. also those heads will like more than 10.5 to perform properly. my head manufacturer said minimum 11.5/1. im at that and im soft until about 3500 rpms.

 

What kind of dyno? An engine dyno or a chassis dyno?
What kind of transmission does the car have? If automatic, what is the stall of the torque converter? Do you have the A/F ratio?

 

You have the makings for a SERIOUS motor. Your cam looks like something I would put in a torquey 350 with 180cc heads. However, I still would question your PROM/tuning. You need to extend your top end to 6,500 RPM, and probably bring in more timing, sooner (as long as you have enough fuel). Your cam has decent lift, but the duration is too mild. Also, your 396 with those healthy heads and that open intake, needs more help filling the cylinders (exhaust scavenging). I would recommend a single pattern cam with duration between 232 and 236 @ .050". I would narrow the LSA to 110, but if you think your emissions laws/testing would forbid this, then no more than a 112 degree LSA. These first two choices would help find a desired lift, somewhere between .595" to .625". Most motorheads with that intake and AFR 210s would be considering a solid roller with even more duration! If you can't, or don't want to, change the cam, then you need to go to a Super Ram intake and try a 1.5 rocker on your EXHAUST valves.
Your output numbers and RPM are telling us you have a very limited power band and a curve that is more like a stock motor. Your combo SHOULD yield slightly more HP than TQ. With the correct tune and an optimized cam it should be more like 500-520 HP and 480-500 TQ at the crank (are your 'chp' and 'ctq' CRANK numbers or CORRECTED rear wheel numbers?).
What are your limitations related to emissions laws? What kinds of tests do you have to pass?

 

hi all!!

it was on a chassis dyno, car is a manual six speed, A/F ratio is fine...

the numbers i have are crank numbers....

i have to pass a sniffer test, but thats not the real problem...;-)

when i install a 236/236 XFI series, how would the idle be?(63°overlap) that would be a bigger concern than the other things..

theres an article in a chevy magazine, where they built a 396 with about 200cc ported AFR heads, a Superram and the same cam i have..and they predicted to be something around 480hp and also 480tq

i will also change the single plane to another intáke, if that will help....i just want a powerful car...

i will look for another thing..maybe the cam is a tooth off....one tooth advanced..i think, thats nearly impossible, but all the signs are there..

im clueless what to do now...

thank you

 

my cam is large and my idle is still fine.. youll be good..

 

hi all...

finally...i installed a Lunati cam , 234/238 .565 after talkign for an half an hour with the Lunati tech..very helpful :-)

the 1.6 rockers will elongate the duration 2 more degrees, so it should be a good cam to go...

the car have a nice lope at idle, and i got a lot of spark knock, the first time i was (carefully) driving....it seems, the vlumetric efficiency have gone way up with this cam now...

im in the progress of tuning in, and i hope i can post good results soon....

let me know what you think...

regards

 

As noted by others, you have mismatched components. You've also left out some important information. Did the dyno guys run the test with a wide band O2 sensor? Your AFR could have been way off. Were your valve springs new and matched to cam specs? Your peak torque rpm seems way low, valve float? With a single plane intake and 210cc "comp port?" runners your looking at a high rpm horsepower motor, not a mid range torquer. What is the motor to be used for, street or track? 113LSA is pretty wide for your intake and heads. 110LSA would be more like it if you want power. Even with the above, there is something wrong with your power and torque numbers, you should have gotten more with peak torque at a higher rpm. On the last motor I built I got 400 HP at 4800 rpm and 500 ft lbs at 4000 rpm out of a 355 that could pass CA smog. Too many unknowns to give you a specific answer.

Larry

 

Steve basically copied my 396" almost to a "t" and it made the EXACT same hp and a little more torque... Mine was 571 hp and 505 tq on a Stuska engine dyno; the torque descrepency I blame on the fact that my heads had larger ports which sacrificed some velocity and therefore some torque.

Like others have said you can talk to 10 different people and get 10 different answers but the fact is an engine is a SYSTEM...And as such the system will never work properly if there are mismatched components within it. Ransome Berry's little LT1 396 that I just did the DFI on made over 380 hp to the wheels with a fairly mild camshaft, ported LT1 castings, a STOCK 48mm t.b., and an unported LT1 manifold... The reason it did this well is that the combination was pretty evenly matched...

I've stated in the past on numerous occasions that the single plane is great for bigger cube motors (over 383) that have heads with a large airflow potential (which your AFR's do have) and a large camshaft... Your lift numbers are nice but your duration is pretty small... As is your compression ratio... I'd like to see a dyno graph of your engine and look at what the curve looks like. The torque is peaking awfully low and I'm almost wondering if you aren't running out of fuel. But to agree with the others your combination is NOT optimized for what you're attempting.
-Jeb

 

Thought I'd throw my two cents in as for something is wrong either in your tune or mechanically as you should be making more power with what you have. Put it on a dyno and get your fuel air between 12.7-13 to 1. (Whatever the car wants) Scan it to see if a knock sensor is pulling out timing and also to make sure your 02's are working like they should be. Are you sure the cam is not installed one tooth off???

Whenever I dyno my personal car and am looking for absolute peak performance it gets scanned, the oil gets changed, new plugs and new 02 sensors installed. It doesn’t go on the dyno unless we are sure everything is perfect to include looking for header leaks, or anything else that could affect performance.

As for the cam, I'm in 100% agreement that your cam is way too small. Regardless………. you should be making more power so don’t think changing your cam is automatically gonna to add 100 rwhp.

I made 445 rwhp using a GTP 236/242 cam on a 114 in a 383 combo with Lloyd Elliot LT1 heads and it drove like stock. In the process of re-camming but my current cam for a 398ci combo is 245/248 .630/.630 lift using 1.65 rockers (Jeb has seen my cam card so he knows the numbers are for real) and it drives very well. So don’t be afraid to run something in the high 230’s to mid 240 due to drivability but to make power the combo is capable of making, you need more duration for sure.