Hey all I am gathering info and parts for my next project. I'm going for a 383 or 396 with 400hp of juice looking at peak power at 7500 and shifting around 8k, about 750hp(flywheel) or as close as I can get.

The question that keeps killing me is the intake/heads situation.

It seems the general conseious is that the LT1 or LT4 modified intake will give up power and a single plane is needed.

I have dug through all the old dyno graphs but it seems there is still a great debate on this.

So looking at the options I can either convert an Super Vic type intake for LT1 use or convert a set of heads SBC heads to Lt1 and use a SBC Super Vic injection intake. Is this correct? Is there a benefit to either situation? I want to keep the reverse cooling aspect of the Lt1.

For heads I am thinking either AFR 277 Eliminators when the come out or AFR215RR. Which set up would be the least hassle and give me the best power. I am on a budget so the big $3k intake idea really doesn't blow my skirt up.

 

Sorry cam specs might help as well

PART #: 08-000-9
SERIAL #: B 6598

GRIND #: CS 4874S / 4875S SR112.0
SPC INSTR 1: SMALL BASE CIRCLE W/ CAST GEAR

VALVE ADJUSTMENT - INT: 0.16", EXH: 0.16"
GROSS VALVE LIFT - INT: 0.571", EXH: 0.577"
DURATION @ 0.015 TAPPET LIFT - INT: 280, EXH: 286

VALVE TIMING @ 0.050" - INT OPEN: 13° BTDC, INT CLOSE: 49° ABDC
VALVE TIMING @ 0.050" - EXH OPEN: 60° BBDC, EXH CLOSE: 8° ATDC

THESE SPECS ARE FOR CAM INSTALLED @ 108.0 INTAKE CENTER LINE

DURATION @ 0.050" - INT: 242°, EXH: 248°
LOBE LIFT - INT: 0.3810", EXH: 0.3850"
LOB SEPARATION: 112.0°


Springs - PN 26094-16
174 lbs. @ 1.9" installed height
441 lbs. @ 1.3"
Coil bind: 1.165"
Rate: 445 lbs./in.

1.500" Ti Super Lock retainers - PN 732-16
11/32" Super Locks - PN 611-16
1.500" spring shim kit - PN 4757

I also have the Crower Superlight off set lifters for use with the big AFR heads.

All of this came from Jimlab if you are familiar.

 

You're going about this the wrong way.

First of all, a 23 degree headed-LT1 is going to have alot of problems making 750 horsepower on motor... in other words, it isn't going to happen with the setup you're talking about. I think that one of the members here made 750 horsepower on a SB2.2 converted to fit the LT1, but that's more of a novelty to "see how it would work".

Secondly, a 242/248 cam in a 383/396 isn't going to peak nearly that high.

Thirdly, what are you going to use to control a 400 shot?

There's alot of holes in your plans. Hopefully there's not that many in your block.

 

I haven't collected much yet as far as part so all opinions are welcome, if this package won't get it done what will?? The 750hp isn't a must have just a ball park, I'd be happy with 650 on motor.

I have no holes yet, so help me fill them before they appear. I really just want a 396/383 with A big set of AFR's mixed with a whole lotta nitrous.

Just playing with the Desktop Guesser it says Torque peak 570ft/lb@4800rpm Hp peak 630hp@7000 which I would be happy with for such a small cam. Is this guess even close? I used the flow numbers from the AFR 227 off there website.

I'll swap to the 215RR flow numbers and see what then.

 

Depending on what heads you used, that cam would probably peak somewhere near 6400-6500 rpm +/- a couple and should shift around 6700-6800 rpm.

Honestly, I haven't followed the LT1 stuff enough to know what the newest thing out there is, but throwing a bunch of parts/money at it isn't going to cut it. A guy I know spent serious $$$$ building a forged 383 LT1, 25x/26x solid roller, AFR 220s, converted single plane intake manifold, and turned 480/420 on the dyno. That's somewhere around a heads/cam 346ci LS1 territory. (the new Trickflow 215cc heads have been making right at or under 500 rwhp with a heads/cam setup on the stock bottom-end.) I would be SERIOUSLY PISSSED OFF if my car performed that poorly after throwing a ton of money at it.

Anyway, obviously the LT1 stuff isn't 13.5 degree valve angle heads like the LS1 Trickflow stuff is, but you need to find someone to completely go over an entire project with you. Combination is key.

I'd suggest either calling Phil at Advanced Induction or Allan at Futral Motorsports (Walker, LA) to help you out. Since you're from Alabama, Futral would probably be a sure-fire bet.

 

That's not bad to get a ballpark figure, but AFR's flow numbers are a little bit "optimistic" if you get my drift. I'd do the 215RRs before I did any of their other LT1 stuff.

 

Hehe not in Alabam anymore I'm in Germany now, and the car is in Wa. I'll give them dudes a call and see.

Sorry I still have a lowly LT1, maybe some day I will get a LS1 like all the cool guys.

 

Solid roller is going to make more peak HP for sure.

I have NO experience on solid roller engines in the LT1 range, except for the fact that the harder you run it, the more valve adjustments you will need to make. Which means, you will need to consider frequent valve cover swaps. This can be a pain if a process isn't worked out, as the passenger cover can be a PITA.

I have a buddy with AFR heads (the 205s I believe), on a 396 with a mono-blade TB. He made 460 RWHP/TQ naturally aspirated. Pretty crazy numbers if you ask me. That is the MOST I have ever seen an LT1 396 make. This was with an LT4 intake as well, which have skyrocketed in price since GM discontinued them.

I've also seen 355s with long tubes, cat connected through cutout make 375RWHP with ported heads and a 110 cam pass emissions.

If you want 750 FWHP WITHOUT the nitrous, then man alive... I do not believe its going to happen. LT1s simply do not have the technology in the heads to make those numbers happen.

 

Yeah I'm cool with that, it was really just a number I threw out there.

But what I am trying to figure out is what is the best course of action to get close to there?? SBC heads converted or LT1 heads with a converted single plane? Or a Modified LT1/LT4 manifold?? I can't afford the sheet metal stuff unless I get one used for a steal.

Thanks for the input guys, I know reality will settle in the closer I get to the final package.

 

I agree. I think your going about this wrong. First you probably wont get the 750hp out of an n/a LTx motor. Even with the best of the 23* heads out there it will be tough and probably fall short. Yes the intake will probably be restrictive for a set up like that also. You would probably have to convert to a different intake setup for that kind of power.

If you have to convert to a carb style intake then I have to ask whats the point of building an LTx motor? You will get more power for less money in that HP range with an older SBC.

I was down this road when I was planning my motor. To conver to a single plane you can expect to shell out a solid $1500 and it probably wont fit under your stock hood. For that kind of coin you can have a sheet metal intake fabbed up for not much more. This would be your better option if you must have an LTx motor.

If you can settle for a bit less HP you can go with an LTx intake setup and still make good HP (600-650 range). The LT4 intakes are expensive but you can still pick one up for under $500 if you shop around. Thats only an additional $200-250 more than what they used to sell for before GM discontinued them. Not too bad if you ask me. Thats what I did because I want an LTx motor.

Also I hae to agree with the cam being too small. I just put a cam motion SR in my 355 LT4. (263/270 @ .050, .686/.674 lift,) I went with TFS heads ported by TEA's newest cnc program(220cc's)317cfm w/ 2.08/1.60 valves at .700 lift. Forged bottom end and domed pistons. Shaft mount rockers and a ported LT4 intake. I am only expecting to hit the 600 mark if I get the tuning right.

Your looing at less than I have and you probably will come up short even in a 383/396.

 

If you thinking about sbc head then just build a sbc... if you convert all this over you end up with great heads and great intake on a great bottom end that wont turn over 7000 on a stock PCM. next thing you know your looking at aftermarket management systems... might as well just build an sbc and put an aftermarket system on in right away.

 

Thanks for the info, I have seen the converted intakes going for rather cheap latley so maybe I can get one that way. The cam is easy enough to change if it doesn't do what I like

The 750 was just a number to shoot for initally, its looking more like 650hp will be reasonable to achive and within my budget means.

I wanna keep the Lt1 for the reverse cooling as this will be driven on the street as well and will help keep the octane requirements down a little. Plus I just wanna

As far as the intake thing, the LT4 ported and maybe with some pleanum volume added would suffice for my budget/serious stroker? What about the differences when on the spray? I have seen tests where switching to a larger carb when on the same shot of juice yielded some extra ponies due to the VE increasing.

 

I already have DFI

 

A converted Super Vic will fit under a stock hood with the right elbow, I disagree with "If you are going to convert gen1 heads to work on the LT1 you may as well build a gen1 because it will make more power" DOn't know how they came up with that. The LT1 is superior to a gen 1, it has reverse flow cooling, you can run more static and dynamic compression and make more power. If you convert gen 1 heads you dont have to convert the super vic, it bolts right on. All you have to do is get it converted to efi. Intakeelbows.com does it VERY reasonably. And does and excellent job, builds killer elbows also.

That cam aint gonna get it done, you need to decide on how many inches you want to build, decide on what heads/intake setup you need to feed it, then have a cam ground. To make anywhere CLOSE to that power a super vic or sheetmetal is in order. To make north of 600 you need a Super vic or a VERY well worked over LT4 intake.


David

 

If you say it will fit I have no proof that it wont. I have researched it and have found that it wont by people here on the boards.

Converting you have to weld in inj bungs, fuel rail mounts, buy new fuel rails, a new regulator, lines, elbow, new TB, TPS sensor, ect... and possibly a new hood. I just found that in order to do it right you have to spend quite a bit.

BTW, I agree that the LT1 is superior to the gen 1. I said "at that power level" (ie: 750FWHP+)its worth it to just stay with a sbc. Less headaches IMO. an LT1 tends to get more expensive with higher hp because of the intake, PCM, and ignition limitations. They can get expensive to make them work rather reliably. This is not to say the LT1 cant do it, but if you have to convert sbc heads to get to that level you tend to inherit a few of the LTx engines problems that you dont need to. Just my 2 cents...

if you already have DFI then your already in good shape. It might be worth it to convert an intake setup to support 750 hp. But that cam probably wont