I just took my car too the dyno last night too make a few runs because it diddnt seem too run any better after i put the stealthram on it, it only put down 271 rwhp and 327 rwt. I ran it on the dyno before i put the stealth ram and the 1.6 roller rockers and before i upgraded too a 3inch y pipe( and cats were hollow) and it put down 303 whp and 334 rwt on the same dyno and airfuel was good. Now heres what i did, i upgraded too the HSR, put 1.6 roller rockers, and 3inch y pipe( 2 weeks after i upgraded too the 3inch i hit a small speed bump and dented the exhaust a lil, can this be why it started running rich?), also decided too delete the pvc valve and the hose that goes from the TB to the valve cover and put breathers on my valve covers( can this cause the car too run richer?). for some reason its only making peak hp at 4000rpm and peak torque at 5200 and right after 5200 it starts flunctuating up and down as its falling off the power band, and the air fuel ratio is down between 11.5 and 12 all the way. Any help or opinions with this issue would be great

 

Try going back to 1.5:1 rockers. Your particular combination of springs and lifters may not be good for the 1.6 ratio.

 

ok ill do that asap and repost the results, is there anything else i can check myself while im working on the rockers?

 

ever hear the saying
"a chains only as strong as its weakest link?"
well after building a couple hundred engines Ive got to ask a few questions,
like what cylinder heads your currently running ? if they are stock your HSR may be capable of flowing a whole lot more air than the heads can,,
what is the engines true compression ratio,
did you degree in the cam?
what is your fuel/air ratio?
can you post clear pictures of the spark plugs?
whats your fuel rail pressure?
whats your ignition advance curve look like?
have you measured the exhaust back pressure?


look, hp is basically the result of efficient use of cylinder pressure and controlling the air flow thru the engine
if your peak power falling at about 4000 it means the engines restricted, the cam timing may not be sufficient, the exhaust might be restrictive, the heads probably are restricting power...if the heads flow 210cfm and the intake flows 270cfm, the combo won,t flow more than 210cfm,.your best hp is usually at about 12.7:1 so ID strongly suggest checking the o2 sensors and injectors

 

I believe our great grumpy god of engines knows his stuff, but let's keep it simple.
Valvespring pressure is multiplied by the rocker arm ratio. Too much pressure on the lifters can "collapse" them, ( not permanently ) and result in effectively shortened duration at the valve, and effectively reduced lift at the valve, both of which are known to hurt upper-rpm performance.
Also, if you have really quick-opening lobes, and if you combine that with increased rocker ratio, that can sometimes result in spring surge. This is known to create dramatic dips in the torque curve, at whatever rpm it happens. With inverted radius lobes, this becomes more of a problem as RPM increases.
So if reverting to 1.5:1 helps your top end, then that indicates you may have one of these problems. If it doesn't help, then you've ruled out these 2 issues. If it does help, then the next step is determining the current open and closed pressures of your current springs.

 

the heads are mild ported 083`s with 2.02 1.60 valves, and the compression is 9.7 to 1, and the cam is degreed. airfuel ratio was at 11.5 to 12.0 on the dyno and the fuel rail pressure is 44lbs. i gotta get the rest of the info asap

 

Well obviously based on the air fuel ratio I'd say it needs retuned with the stealth ram....You cant expect to just bolt on a new intake and not retune it and expect more power.

the fluctuating in the rpms after 5200 sounds like valve float with the new 1.6 rockers. It may not like the 1.6 rockers now. Have the heads been clearanced for that cam? What valvesprings are you running?

 

I might also try a bit less fuel pressure, to get the A:F closer to 12.5:1.

 

if your getting valve float issues its generally because the wrong clearances and spring load rates are used or the springs are well worn,valve control issues are a possibility,that should be verified,changing to a higher 1.6:1 ratio and swaping cams could cause clearance issues with the stock valve train, but ID get the ignition timing curve and fuel air ratio corrected first.
when valve train parts fail, 99% of the time its a symptom of a clearance or lubrication issue.
a great deal has to do with the CLEARANCES and the springs installed height, theres a very good chance the installed valve spring height and spring bind, or retainer to valve guide clearance was not carefully measured
or the rockers bind on the rocker studs at max lift
guys frequently take the springs that came with a cam kit out of the package and install them with the stock retainers and never give it a second thought!,or install a cam with the stock springs, the truth is that in 90% of the cases I see where parts break,they never measured clearances.
when a cam manufacturer suggests a certain valve spring be used he also suggests the installed height and minimal clearances, you can,t install the springs without verifying clearances and installed height,and if they suggest new springs its generally because the stock valve train and components and clearances and springs won,t work
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READ THRU THE LINKS

http://forum.grumpysperformance.com/...php?f=52&t=181

http://forum.grumpysperformance.com/...php?f=52&t=399

http://forum.grumpysperformance.com/...s+spring#p9383

 

OK so it's NOT a LT4 at all, has NOTHING WHATSOEVER to do with LT4 except that it came from the same mfr (GM). Best to leave that whole line of BS out of the equation altogether.

How do you know this? What pistons do you have? What's the deck clearance?

And that matters .... how?

Of more concern is, what cam it is, and what valve springs you have.

With as low as your FP already is, I'd suggest smaller injectors, rather than lower FP; otherwise you'll have the effect of a fire hose being fed by a bathroom faucet (fuel just sort of barely dribbling out), instead of the effect of a pressure washer like you want from injectors (vigorously atomzing spray).

Sounds to me like you have several issues in progress, besides excessive abuse of buzzwords. Those would be valve float first, potential cam mismatch second, and tuning WAY off third. I would start there and work outward.

Being as how you're in California, and the HSR doesn't have a CARB EO # and therefore can't pass inspection and doesn't have EGR ports and therefore the referee won't even approve it and therefore can't be licensed, you may even want to do more re-thinking than that.

 

im running a lt4 hotcam and the spring are good too 550 lift but not sure which exact springs they are. clearances have not been checked but im just gonna put the 1.5`s back on for now. I dont care about smog with the stealth ram or cam because i just swap motors out every two years too pass.