How much hp/tq would you all estimate that a streetable (LT1) 383 could/should produce?

This would include such things as ported LT4 heads, ~11:1 CR, roller rockers, and a streetable cam. (right now I have a 222 duration cam that I like the feel of, and would probably like to not go too much larger than that, and also would have LT headers and Borla exhaust.

The reason I'm asking is I expect I'll be rebuilding mine with a year or so, and am wondering if it's worth all the extra money to go with a stroker.

Right now my LT1 dynos at 385 RWHP(with ported LT1 heads). and is no slouch, but I'd like to pick up another 75-100hp naturally aspirated

Edit: To add more to this, my LT1 heads are an early porting from TEA, and I hear that they are likely able to even get another 20 hp or so just from an improved porting program with those. So hopefully I'm not way off base thinking I can get 75-100 hp by stroking and moving to ported LT4 heads.

Thanks!

 

Damn! What kind of dyno were you on? If your 350 is putting out 385 hp at the wheels with only head work done, I wouldn't change anything. You can see where I'm at with my 383 in my sig. And I was quite pleased with my results.

 

i think he meant 285 rwhp.

 

An LT1 with a good cam and a set of TEA heads with a good exhaust and ported intake can make 360-370RWHP no problem.

I am in the middle of a 383 build but I went with AFR 195 more performance ported LT4 heads and matched intake with a CC 306 small base circle cam and 10.7:1 comp and am hoping to be near 425 RWHP. I doubt you will see the 480's without a almost unstreetable cam with just a stroker and ported LT4 heads. There is a set of AFR 220's in the for sale section that could be the foundation to a big HP motor but probably not the most streetable motor in the world.

 

Look at this months Drive Mag. Smeding Performance.310,360,440 Hp. Looks like the cost on the motors are reasonable. Don't know anything about the company though.

 

385 is correct. It has had the heads done, cam, 1.6 roller rockers, 11.25 CR, headers, ported intake, borla and alot of tuning.

Thanks all for the info, I wonder how much the high CR is helping me out.
It's a great motor, very smooth with a nice power band.

I'll check quasars sig and look into the Smeding Performance motors.

 

I don't know how much more hp you'll make, maybe 50 more or so, but I can garentee you'll gain a ton of torque down low and in the midrange.

 

I hate to be the burden of bad new, But I highly doubt your making 385rwhp with the mods you have. Not saying that you did not get those numbers off a dyno. I just don't believe they accurately represent your true hp numbers.

And to a further degree you will not see another 100 rwhp without some power adders or a new platform.

If your talking fwhp, then I would say your ok.

Again this is another classic "Dyno Mystery hp hour". Again not saying you don't have the paper to back it.

But lets put some things into perspective here. And please refer to these figures when you see HP numbers off a dyno on this board.

Lets make a few assumptions: 1. Typcial C4 weights ~3300 lbs 2. 20% drivetrain loss

Based on some of the HP calculator I use, which nearly hit the numbers dead on from my experiences in real world applications here are some numbers:

Jims-85vet ~3300lbs 121MPH trap speed = 397rwhp (476FWHP) mind you this is a solid roller cam, and 11.5comp, and probably one of the fastest 383 vettes in the country. So its crankin out some serious power.

My 406/AFR/SR/242 Solid Roller (same as Jims 85vet) - 3350#s 123MPH Trap times = 417rwhp (500FWHP) Again, one of the quicker setups in the 406 CI motor arena.

My 434/having probably the best 23* heads on the market/custom intake..you know the rest:

130MPH trap speeds, 434CI motor, 3450# car = 492rwhp (590FWHP)

You see where I am coming from. I could go on and on about how some of these numbers I see posted on these boards do not make 1 bit of sense. I recently passed on the opportunity to join a local group of guys at our airport to dyno their cars.

Some of the numbers were totally absurd they were putting out. Like here are a few. 585rwhp from a 400 inch motor. 520rwhp with 720ft-lbs (520CI HEMI).

I beat both these guys the following week at the track by .5sec and .3sec respectively. And it wasn't traction issues either, cause in both cases throughout the day, one of the guys redlighted on me and they were ahead of me for about 1/8 mile, till I blew past them on the topend like they were standing still. Meaning 1 thing, my car was making alot more power throughout the run to catch them and pull ahead on the topend.

Should I assume I have 600+rwhp and 800ft-lbs ??? When I am lucky if this setup as good as it is, is maybe at best breaking the 600fwhp range.

I don't think I am going to think that since I know the limitation of HP and how hard it is to make 600+ hp on a SBC. Yeah it can me done and yeah there are some serious setups making alot more. But they also have some serious $$$$ in them, to the tune of 50k+.

I guess the point of this post, is not to call anyone out. But rather put a little perspective on the subject. At the airport, I told the one dyno runner above with the hemi, I am lucky if my car is making 600 fwhp(this is after running and beating him about 4 times), he stated that thing has to be making well over 700hp to pull on me like that. I just replied, maybe it is. And the sad thing is that he truely thinks it is, cause his car made that sorta power on that specific dyno. If I put mine on that dyno, maybe the rwhp would have been 580+rwhp. But I would automatically told the dyno operator his machine is FUBAR and definately would not have assumed it correct.

At the end of the day, a dyno is a machine for measuring gains and losses, it should be used accordingly. And even with the recent dynos shared with me by some buddies, I would not even put much stock in them for that.

Corky, now would be a good time to share you and Jims dyno session results with the group.

 

Thanks for the reply ski_down_it. I could imagine it being off somewhat for a number of reason, but I doubt it's off by any significant amount.
I didn't build this engine, a very close friend of mine did, as this used to be his car, but I did get the dyno sheet when I bought it from him. I have to give him credit for being one of the most knowledgable engine guys I've ever met, and his belief in the dyno numbers being/sounding credible make me pretty confident that like I said, if they're off, it's not by much. He had dyno'ed the engine at each major mod, and I think the hp increments were realistic with the changes done.

 

Take it to the track. Weight the car, and run it through the 1/4 mile. Report back the MPH and weight - that will tell the true story.

If your anything short of 120MPH, then you aren't makin what you think. The numbers are very accurate and don't lie.

There are several 406CI motors on here with some very good equipment in addition to one 396, nephew to the other guy, that runs these sorta MPHs or less, depending on track conditions. If your 350 hits the 120 MPH range, you either have 1 of 3 things.

1. A VERY light car
2. A 383 or 396 that is running damn good.


Near 400rwhp is easy to accomplish via a dyno, its MUCH MUCH harder to make the track numbers (MPH) jive with the HP numbers. We see it time and time again.

Again I anm not ripping on you personally. I am just trying save you the grief that will come when you don't come close to the numbers you were predicting with your buildup. If your 350 truely runs the 120MPH trap speed, I would not touch that thing for ANYTHING. If you do, you will probably run slower with the bigger motor.

 

I have to agree with Jesse's replies. Well put

BTW, is 119.6 MPH close enought to running damn good in the 1/4 ?

 

Its all in the chip

No I want to make it very clear that my posts were no intended to make F1Fan out to be a liar of his HP. It would not surprise me the least to see him post a dyno run of his 350 making that sorta power. What I wanted to point out, is the FACT that these numbers are universally meaningless.

I am on other boards, which guys running times that boggle the mind. NEVER do you hear of them talking dyno numbers. Seldom do you even hear a HP claim estimate.

I guess its because we race/drive our/their cars, and not dyno run them.

Dyno numbers have an allur about them, and to MANY these numbers are what people understand, in and out of the car scene, so I guess to have stout dyno numbers make one feel good. Face it, 90% of the people out there would not know if a 1.35 60' time was good or not. Nor would many of them be able to make sense of a 4000# car, hitting 120 MPH in the 1/4 vs a 1000# car doing 140MPH.

Hope I did not offend. Just trying to put a common sense spin on the discussion.

 

Never heard of a head/cam. a 222 duration @.05 made 385rwhp on a 350ci LT1/4 for that matter. As someone has say, that number may look good but is not as accurate. One way to test that is to get your car to the track for 1/4 mile blast. It does not matter what the et. But if your car can trap 119+mile in the 1/4 run than I believe it. The highest head/cam setup for LT1 can net you about 370rwhp. unless you got a very big *** cam, (306 cam)


Bruce