I'm curious, as it's stumping me; Why is it that whenever talking about building a motor for higher revving solid roller setups, the nod always seems to go to the 383 over the 396 in that situation??? Is it a stroke thing, or something else (like the 383 being more stable or something)???

Just trying to get cleared up on that, thanks guys.

 

Piston speed is part of it. Something to keep in mind is the minimum CSA that your heads will be at, and the intended rev range of the motor. If you are going with stock LT1 castings, they typically can't support a 383 that wants to peak past 6300rpm, but a 355 can peak around 6500 which is a good number if you are sticking with a stock PCM.

 

I'm going to be using ported Trick Flow 195 CC (ported to ~212CC approx). I'm looking at it being a solid roller revving to slightly over 7K at the track using a F.A.S.T. XFI setup.

Coming from the shop I've spoken with and things I've seen/heard, the general concensus seems to be that a 6" rodded 383 is a better choice over a 5.85" or 6" rodded 396. I'm just trying to get a bit of clarification as to "why."

Thanks!

 

I doubt those cylinder heads will flow the air to continue making power above 7000 rpm on a 396ci engine. I have a friend with a set of trick flow 195's that were absolutely hogged out, port sleeves and epoxy in spots. They flow 300 cfm @.700 on the intake and close to 200 @.700 on the exhaust without a pipe. Cam specs are 254/260 @ .050, he shifts his 383 right around 6500-6800 rpm and runs mid/low 11's in a full size Chevy 1/2 ton Truck.

As far as the 383 vs 396 debate, your heads are better suited for a smaller ci motor. The 396 will give you more headaches than performance. Keep in mind:

Potentially more clearancing required on the block than the 383
Camshaft to connecting rod clearance will likely be non existant, which will require a small base circle camshaft and or connecting rod profiling which = more $$$
Less available off the shelf pistons = more $$$
Less available off the shelf crankshafts = more $$$

If it were as easy as "I have two production engine blocks, a 350 and a 400, I would tell you to build the larger displacement motor almost every time." However, your case is not so simpe, and between the 383 and the 396, you are just asking for headaches. This is coming from someone who has run into these problems before, and currently doesn't have a running car because of them

 

Those numbers seem pretty low for heavily ported 195's especially on a 75cc exhaust port, they flow almost 200 out of the box.

 

I was about to say the same thing.... I've seen 307cfm/245cfm (w/ pipe) @.600 on a set that's 213cc and not hogged out.

Bret

 

Get the 227's and have them worked on to flow 325/240no pipe and ya will have something for a 383. If they can't be made to flow that settle for the 310 they are advertised to flow. They won't flow that on most benches.That is in the 600FWHP range with everything spot on and a real good intake. Remember ya got to deduct at least 10%(sheet metal unless it's a Wilson=$3700.00) off of the head flow when the intake is bolted on and some intakes have 15% or more(LT1\4)

 

Larry I tell ya you gotta send a set of 23° heads to Mr Meaux along with a single plane intake and flow them when you get them back... gonna see that same 4% loss there too! ;-)

Bret

 

Well we all know every flow bench is different, out of the box they flowed 242/16X @.600, turbulent at .700 I want to say. These are the Trick Flow 195's from about 5 years ago now, not sure if we are talking about the same heads? No way those heads would have flown 200 cfm on the exhaust out of the box.

 

Got to much invested in what I got that is a 3% loss.To late to change now. Mine even looks like an EFI intake.You have seen pictures,
That's great on the Victor(if it is). Now all that needs to be done is figure out how to get the torque back down lower so ya don't have to turn it 8,500 to get full advantage of that style intake.It will breathe up there if the heads will. If I go with a different style intake it will be like the one I had for the Ford,sheet metal with two 4 hole air valves with Hilborn nozzles and barrel valve and a belt driven Hilborn pump. On the street too,with pump gas. I can make it so it cranks with the starter without getting out and priming it.But that will probably come with the SB2 set up.

 

Good information guys, keep it coming. AFAIK, I've seen LE put 300/218 out of the TFS heads @ .600, but if I also remember right TFS didn't have LT1 heads 5 years ago, so you may be comparing apples to oranges there (SBC to GenII LT1). That may make for a large difference.

So you guys don't think that the TFS heads, when properly ported, will support a 383 @ 7000-7400ish RPM??? I was kind of hoping to pass on the LLLLOOOOOOONg wait for AFR's/high price of them too, but if the TFS won't work at all........we'll see. Everything I've gotten so far is that the TFS heads would work and do well on a higher RPM increased cubes motor.

 

Got 3% loss with my old LT intake.

Fastbird,
A little over a year ago myself and jimlab put out engines together at about the same time. His was a 396 and mine the 383. His had more cam, mine had less. Mine had better heads and his probably had a better intake. Numbers for the two weren't that far away from each other... north of 650 at the crank. How much power were you looking to make anyways?

Don't get too hung up on "396 or 383", just concentrate on putting a good combination of parts together. Don't buy overkill big $ parts you don't need cause you will need the majority of your dough on the heads, intake, valvetrain and parts that make the car get down the track the quickest. That last part is one that most people will miss. Hence, they go high 10's with 700hp at the rear wheels. The motor is just one variable in the equation.... what a waste.

-Mindgame

 

Mindgame, thanks for the advice. What I'm looking (hoping) to see is north of 600 at the flywheel. I'm not going to scream if it's 575, but I made my goal to be 600 FWHP N/A. Hopefully the right setup of the TFS heads and the right SR cam will get me there.

 

Once you start talking about the 600+hp range NA, I think you need to re-think the use of the LT1 as the starting point. It sure isn't any cheaper, and probably more expensive, then getting to the same place with gen I components and the gen I route is well marked out. Heck, you can pick up the phone and order a 600+hp gen I crate motor just about ready to bolt in. You'd have it by the end of the week and could have it ready to go Monday if you had the tranny, etc. figured out.

OK, a bit of an exxageration but hopefully you see my point. Unless part of the goal is, for some reason, to have 600hp "LT1", why go there? What makes it an "LT1"? Reverse cooling, the Opti, the intake? Most of the 600+hp combos have ditched the Opti and the intake. If the intake is retained, it's barely recognizable as an "LT1" by that point. So, it has reverse cooling, BFD. If that is important, go for it. But as for me, if I wanted a 600+hp NA SBC it's be a gen I, or maybe an LSx.

Rich

 

Well, Rich, I see your point about choosing a different starting platform to begin with. But with most people, I think they go into their projects with the mentality "this is what I have, so this is what I'm gonna use". Whether right or wrong, this is how it appears. Also, some people may just feel that this is an lt1 f-body, it's going to stay an lt1. I personally am going through this dillemma right now: I came inches from ordering new heads, cam, valvetrain, a street twin, a driveshaft, a 9", and all the suspension. The plan was to make a street/STRIP car that would get trailered to the track and cruise the 2 local hot spots (if that's what you call them here, cause it sure ain't H-town ). Trying to wisen up however, I'm at a crossroads becuase I'm debateing on selling my beloved lt1, buying an 01 or 02, tossing in springs and a cam, and making almost the same power. Decisions, decisions. But in the end, what am I going to end up doing? I'll probably just build up the good ole lt1. Why?? Because that's what I got. Whether it's right or wrong, that's just the way I see it happening with 95 percent of people on the board.
Ian