ViciousZ

iTrader: (1)

I took my new 383 setup to be dyno-tuned (with about 700 miles on the motor) and here's the numbers I came up with:
320 RWHP @ 4600 RPM
417 RWTQ @ 3400 RPM

The hp numbers were a bit disappointing, although I realize peak hp numbers are not always indicitave of how fast a car is. Example: I have a buddy with a 383 who runs 11.98 in the 1/4, mainly because he has so much torque and a VERY flat HP curve.

Anyway, the thing that confuses me the most about my numbers is why I made my peak HP so low. I'm wondering if something is choking the motor up high. Here's my setup:

I realize I've got a few parts, such as the TB and exhaust that could use a little upgrading, but could they really be choking the motor that much? With a decent flowing set of heads, ZZ9 cam, and Superram, I'd expect my hp to peak around 5200 or so, not 4600. Ideas or suggestions?

Rustydawg

Wow, that's a mountain of torque. Must be fun to drive.

I would think that an engine like yours has a serious capacity to pump air and the exhaust system isn't big enough for that volume. Perhaps trying a pressure gauge in the exhaust system - maybe where the 02 sensor bung is?

I think a stroker like yours could use 1 3/4 headers and at least a 3 inch mandrel-bent cat-back system with a capable muffler.

I was surprised to see the torque peak under 5000 RPM too, but that's all I can think of - no experience with modding TPI.

89WS-6

Yeah I like your torque numbers. Now it is true that you have a stock throttle body, but I honestly dont think it would make your numbers do that. I am perplexed. If you have money, try putting another thorttle body on. BTW, the run was made with the exhaust attached right? If you want to mess with it, it would be interesting to see what would happen to that hp number and the RPMs with just headers. Btw, one more thing. Stock ignition? Good luck man,

Mark A Shields

Think those 1 5/8 headers are hurting your top end? Maybe some 1 3/4 could help out up top.

And you definately will benefit from a 3'' I pipe.

slayer2000

iTrader: (1)

you said those heads were ported but how much? I have always heard L98 aluminum heads were good but not the best. Also what are the specs for the cam? Are there any tuning issues that still need to be addressed(timing, chip tuning etc.) I don't think the tb is much of an issue but the exhaust might be. Slp's website says they recommend 1 3/4 primaries for 350 and larger engines. What compression ratio are you running? With my trick flows I'm running 10 to1. It sounds like just some minor tuning issues. All in all you've got a pretty stout combo.

89gta383

iTrader: (5)

I dynoed 300 and 380 at about the same rpms on both hp and torque with an older combo.

Mark A Shields

1 5/8 should be good up to about 400hp or so.

I agree though, the aluminum L98s from what I've read aren't the best flowing wise.

Guest

Problem is, the edelbrocks arent 1 5/8" throughout the whole header. I'd bet if you ditch those for something bigger, it'll work alot better.

Matt87GTA

Those of you that keep saying a stock 48mm TB isn't choking that engine are just plain flat out wrong. I have seen it time and time again. People say this and that about what engines make what with just a stock 48mm TB.... And I don't know, they just seem to think that it wouldn't make any more power with a larger - or more importantly better designed TB. There is more to the TB than it's size....... A friend of mine in the MNFBC picked up 11 RWHP on his 385 LT1 going from a 48mm to a TPIS 52mm....

So, get rid of: TB, crappy headers, and that small intermediate pipe and you should see some very attractive gains..... I'm sure the heads aren't exactly setting the world on fire with their flow, but there are plenty of other things to work on before tearing back into the engine itself that will only serve to build more power with a better set of heads later.

Of course..... this is all stuff you already know . :lala:

slayer2000

iTrader: (1)

I know that the ram jet 502 uses the 48mm L98 tb. If it can feed that I don't think it's a bad restiction. I don't mean to say that 52 isn't going to flow more air but in this case I just don't believe it will make that much difference. I still think it's more of an exhaust/tuning issue than anything. If I did my math right( and I may not have, I suck at it ) with a 20% loss of power thru the driveline I'm getting 384 hp at the crank. That's pretty close to the 400hp line for 1 5/8 tubes.

ViciousZ

iTrader: (1)

To answer a few questions here, the compression ratio is 9.9:1, a tad low for an aluminum head, but I'd prefer to be on the safe side. I doubt it's a tuning issue, as it was tuned on the dyno. It wasn't getting any knock, and the A/F ratio was close to 13.4:1. The ignition is mostly stock, just an Accel coil and MSD wires. The heads were ported a little in the valve area, but nothing that I was overly impressed with. Cam specs on the ZZ9 w/ 1.6 rockers is .516/.560 lift 214/226 duration, 112 lsa. The headers are a bit of a concern with the heads. The heads have a raised D-shaped exhaust port, and so the bolt holes are nearly 1/3 from the bottom of the port, rather than being right in the middle. Of course the headers are designed for the usual style iron L98 rectangular ports, so I have a feeling the ports are not lining up at all, and that the exaust gas may be hitting a 'wall' along the top of the port. But right now my financial situation is... ugly, to put it lightly. So I won't be buying anything for quite some time.

ME Leigh

I bet its your heads, the valves are to small for optimum horsepower, and the heads are small port lower flow designs. If you got heads with 2.08" intake and 1.6" exhaust valves, you would make about the same torque but lots more horsepower also. You could get pro lightnings at www.enginekits.com

IROCZZ3

I don't think your heads are hurting you as much as everyone says. L98 heads, when properly reworked, flow really well. Lingenfelter uses them on his 383 packages and is able to coax amazing power with these heads. I don't know how good your head porter is, and without any flow numbers it's hard to say if they really are holding you back.

I agree the Edelbrock headers are probably holding you back. If you get rid of them, Hooker long tubes have been proven to add substantial gains over shorties. Good luck

EDIT: I see you're in CA, so long tubes may not be an option, smog-wise.

Kingtal0n

Going from 219/229 @ .050 to 244/254 @ .050 moved our horsepower number up from 380 @ 4700 RPMS to 430 @ 6200 Rpms. that was number one. of course our low-speed throttle response/driveability/fuel economy/torque took a nose-dive...
but it illustrates my point. having the highest horsepower number doesnt make the car the funnest thing to drive. keeping the engine rpms below 6K can also help it live much longer.

Acceld Z

The sole reason that the 502 ram jet has a 48mm throttle body is that it was already in GM inventory. The belief that the 502 wouldn't pick up power with a larger TB is flawed. The amount of air that engine would move would be astounding.

ViciousZ, now that you're done(for now) your build up, drive it and enjoy it. Those numbers will get you into the 12's easy.

MikeH

iTrader: (10)

Like you said you could upgrade the exhuast some. I picked up some more pull in the 5000+ rpm range. swapping from Edelbrock headers to SLPs 1 3/4 header. I also added a better flowing system from there back. I Think its the long runners of the TPI intake thats hurting your topened. Even though you have a SuperRam plenum and runners. Its still a torque based design, your horsepower and torque peaks are similar to others with the SuperRam that ive seen.

What base intake are you using? I ported my Accel base and runners out to about 1 3/4" Seemed to help the topend. I havent had the car back to the dyno to see if there was anything gained for sure though. Ive had problems with mine from the start, just found out recently that when I drilled the steam holes in the heads. Two were a little off and caused some water to leak in the cylinders.

flashincamaro

I have to agree with some those heads are for sure slowing you on hp, but for sure give you good torque. I have a zz4 with the same heads the small valves give you torque but kill you on high rpm hp thats why chevy sells the zz430 with fast burn heads not the same L98 heads Also ya the headers and exhaust hurt too but your exhaust can only flow what the heads flow and the heads can only flow what the throttle body lets it so I can't say anyone is wrong but for sure when you get $$ the heads will help you the most for hp gain from what I see ??? I hear ya on the money too bro I saw a set up on http://www.sdpc2000.com/cart.asp?act...=1579&pid=9010 this should scream in my 70' camaro

zippy

i'd be looking into other are's. yeah, the headers are a bit small, but not that small. exhaust isn't fantastic, but it is usable. i'd look into getting a bigger throttle body as a start. i assume this is in your camaro so your not dealing with a restricting m.a.f. sensor. do you have the air box gutted is another question. during your dyno run, did you have any detonation, was it rich, lean, etc as programming may not have been perfect either or a lack of fuel could have caused it. the numbers aren't bad though, but your right it seems like 4600 is a bit low to peak.

camarojoe

Like others have said, a good set of heads like Dart or AFR with bigger valves =20rwhp and a set of Hooker longtubes=15+rwhp. You could be running mid to low 12's 1/4 times now and with those two upgrades, you could be high 11's. I think your numbers are pretty darn good considering your setup.

colonboy14

iTrader: (7)

Sorry, I know this is a little off topic, but while we are on the subject of dynos, about how much does it cost to get your car dyno'd?

BillZ28

Around here is $80-150 for a pull on the dyno.

385LT1

I agree 100% and would like too add...

Get a 58mm TB, Ditch those dinky headers, there killing ya...

1 3/4" Airborne coated Long tubes, 3" y pipe , 3" cat back, good muffler

You may want to highly consider upgrading your fuel system also... ie: injectors and pump , what do you have in there now?

Here is an exampel (fuel system)

I have a 385cid LT1 with a small Holley 119 ltr / hr in tank pump / all stock fuel lines

SVO 30 # / hr injectors

with 52 psi of rail pressure the car is still running a touch lean 13.8-1 I want too see 12.5-1 Air fuel

So the plan is to upgrade my fuel system

rezinn

The headers are probably what is hurting you the most. Gaining 11rwhp from a large throttle body isn't something you're going to notice as much as changing to decent headers. I'd only upgrade the tb if you find a used one for cheap, since they're way too expensive new for such a small gain(in my opinion, at least). After you've got your exhaust and whatever else you need, run it on the dyno again and you can see how well your fuel system is handling things.

Matt87GTA

And these are??????????

385LT1

www.AirbornCoatings.com

_________________________________

Long tubes are 1-3/4" primary tubes. They are available either in plain black painted, or ceramic coated.

PN: 66-2210 Hooker Super Competition long tube headers, 1982-1992 265-400 $399.99

www.ThunderRacing.com

Matt87GTA

Ahhhh.... IC. I thought maybe they were another brand of headers. Thanks.