lps&vettes

At the risk of opening a can of worms, I'd like some feedback on this topic. My 383 put down 367 HP to the rear through a TH400, 2000 converter and 3:36 gears on 225/70R15 street radials, and frankly, is somewhat disappointing. I'll be returning from Afghanistan in a couple months and will be starting a 427 build. My goal is more torque for driving on the street. I'll probably take the car to the strip once to see what it does, but beyond that, it's a daily driver, weather permitting. I've been told: large heads with a small cam will help achieve more street torque; small, high velocity heads with a small cam will also do the trick; large cam with small heads will not work well at all; large heads with large cam will also not achieve my street oriented goal. AFR's Tony Mamo suggested that the comp ported 195 eliminators and a small cam will work well for this. Since I've never tried this combination before with this particular goal in mind, I'd like to hear from anyone who has gone this route. Nary a part has been purchased, so the canvas is blank, so to speak. That's one reason I've used the vague term of "small" and "large" WRT the cam and heads. Whatever combination I decide to put together, I'll be keeping the 3:36 gears.
On another note, I remember reading in this forum about flow numbers of the factory 70-72 LT-1 intake compared to the newer manifolds offered today, so I thought I'd toss this nugget out there. When the RPM Air Gap 1st came out, I bought one and had it flowed against the LT-1 manifold and the old chevy manifold was exactly three CFM less. I don't remember the exact numbers, but the difference of only three shocked me, and I never forgot it.
Anyway, any insight or feedback on the cam/heads for the pending build would be great.
Thanks
Todd

gkull

I owned several versions of solid roller 383's. Like you 383 wasn't enough so I moved up to 427. I also had an automatic tranny.

At some point small gains in power start to cost $$$$ for just minor amounts. So I started looking at alternative ways to gain "power" Weight loss & power parasites are what you need to look into.

The TH400 is sucking your 383 dry. The pump and TC are a major power loss compared to a manual tranny. Your 367 RWHP will probably jump to 400 ish with a manual tranny.

My views of small heads and cams............ Lot's of stupid sheep in the world and very few leaders

You need the biggest free flowing exhaust. Like 3 inch true duals with some kind of X or H pipe.

I just wanted to add. Chevy put a small head and cam in a real late 60's C-3. It was a POS called a 390 hp 427. At the all Corvette drag races 20 years ago I had nearly a one second ET over the mighty 427 with my 355 ci small block. Even the next higher hp tri-power 425 hp was a dog when equiped with a auto tranny

Gordonm

I'll agree with Gkull on this.

The 400 is sucking a lot of power from your motor. A daily driver? With 3.36 gears and 225 size tires you can't hold the power you are making why make more. You need t ofigure out what yo uwant. Do you want bragging rights and be able to say you have gobs of power. It is going to cost $$$ to make power.

My 385 combo made 409 RWHP with a set of older AFr 190 heads and a large solid flat tappet cam. I would not want to drive this as a daily driver. It can be driven and has been driven all over but the big cam makes it a little much for DD duties. I have added fuel injection since which has helped and just bought a new custom grind solid roller to make it a little more driver friendly. Now all this costs $$$ so don't expect a low dollar figure. If a 427 SB is wha tyou want with loads of torque it can be done but will be $$$. You will roast the 225 tires to pieces. I cannot hook up with mine on 275 tires.

lps&vettes

As the car sits right now, I have no problems whatsoever keeping it on the road. I feel the 383 isn't delivering what I expected, and I'm sure the 400 is causing a significant power loss. I'll chalk it up to a failed experiment, not building a large cube engine to start with and move forward. I know exactly what I want, I'm just trying to figure out the best way to get it. I want more useable, streetable power/torque, below 5500 for 95 percent of the time. Without question, the 400 will be replaced at some point, but for now, (at least, when I get back) I'm going to build the 427 SBC that I've been wanting to. But, as I haven't tried this before, I was looking for feedback on the big head/small cam idea.

63mako

I would spend my $ on a TKO 500 if your motor runs good now. You only feel the power and torque you put to the ground. Proper gearing and the ability to select that gearing makes a huge difference in this perception. Ask both of the above posters about this.

gkull

Well I have a 434 ci 4.155 bore 4 inch stroke the 4.185 over bore makes it 440 ci.

Smarter people use the 4.155 X 4.125 and end up with 447 ci. Which will whoopass on any little 427 with everything else being the same. Foot pounds of TQ is a direct function of CI


I have rear 335/35/17 tires and I'm still kind of traction limited and I have to be careful about not using WOT in lower gears. That is the fallacy of the small head and cam idea. The 195cc head might work because it is near 300 CFM, but it would take a solid roller cam of over 242 intake and over .600 lift to make it breath. A restricted motor is restricted it doesn't make more average TQ over the whole operating range

Sho'nuff

a good set of Nitto tires might make you rethink the 383 with a TKO or well built 700r4. IMO. I had a 71 Datsun 240Z with 400hp 355. Regular street tires made it feel like it was just making noise from all the wheel spin. I put on some BFG Gforce drag radials and then it felt like it was a 454. Went from hi 12's to 11.50s

tshort

I hate to spoil your party but I also think better tires and something like a TKO would be your better starting point. Your 383 is currently making at or above 440hp at the crank. Not exactly a monster but no slouch either. If you put in a little monster small block, sure, you can get much more tq and hp but you're going to be very limited when you can use it with those tires. And if a manual tranny is in your future then you might try that first and you could very well be pleasantly surprised what 'new-found' power you have with a more efficient transmission. If you still want to focus on the engine now, cool. There's some terrific guys here that can help you out with lots of experience doing exactly what your goal is.

MotorHead

gkull knows what he is talking about, I ain't even entering this one

I do wonder one thing though, if there would be anyone on the planet that drove my Vette or his and say our motors needed smaller heads and cams

billla

I'd look at getting this power level to the road before looking at making MORE power that you also can't get to the road

By comparison, that's around what a C5 Z06 puts to the pavement, although a C3 is 200-400# heavier...and I wouldn't consider that performance "somewhat disappointing" at all.

As for the small head idea - no one would advocate this for a max-performance build

lps&vettes

I'll be the 1st to admit that I may have my priorities slightly askew. I'm not locked into anything yet, so I'll look into a TKO with a steep 1st gear and keep the 3:36. I don't particularly care how I get the results, I would just like the end product to push me back into the seat more. I noticed Keistler has some new, more economical kits available for about half the price of their perfect fit kits. In all honesty, I'll do both; I have the disease just as much as anyone else here, but if I can get more tangible results from a trans swap, I'm all about it. Same for tires, exhaust, etc, although wheelspin now is decidedly not a problem.

ZZ71S

http://forums.hybridz.org/showthread.php?t=100261

Something to look at

7T1vette

The THM-400 is sucking somewhere between 50-70 hp from your powerplant. Of course, it is also multiplying torque at lower RPM's via the torque converter. All in all, going to a manual (5-speed) tranny and a 3.70 or 3.90 rear gear will get you a gob more torque at the rear wheels. Then you will be asking what tires you need to "get a grip"....