Great thread!!!

I'm getting ready to do a large blower cam motor over the winter and this is helping a lot!!

 

You got hmmmmmmm....... $25K? I would think that 625hp NA could be done (streetable, i.e. pump gas and a good idle)...... Maybe 550 ft lbs at peak TQ, but with that stupid LT1 intake that will probably not happen. I think that a high 500 HP engine could be done, really good heads to start and then go from there. Hell I might even base the enigne off a Gen I and convert it to reverse cool, better heads and lighter cranks then. It would take me a while to do the design, but I know I have carbed 400 SBC's (with 23 deg heads) that max RPM at 6800, have 570ft lbs and 610 hp and are complete babies....... your wife or GF could drive them. Just tell her not to floor it!

If you want to spin the 396 you could get those HP numbers easy with the right heads, it's all in the heads.

If you have bottom end to hold it then it's a different story. The big problem is the lack of development on LT1's vs. the old SBC, (10 years vs. 40+ of racing development) there is not enough design change between them to worry about playing with them. The LS1 on the other hand is a awesome new design.

Mindgame, Isky does some interesting stuff, I just don't think as far as lobe design goes they are even close to Comp. His stuff is good, I think it was what is in the winner of the latest engine builders contest. (the results will be out soon, but i'm not going to say anything else)

Bret

 

Interesting thread. Just curious, but what is so bad about the LT1 intake? Too restrictive? I do like sstrokerace's thinking though, small cams putting out lots of horsepower.
From my understanding of this thread would I be correct saying that a cam with the most possible lift on a certain amout of duration be ideal? With the dur. determining how the car was used, street or strip. I get the feeling I'm missing something, I just picked up Vizard's book about cams.

 

First off Check page 66 in that book........... Figure 7-2

That cam would be ideal in TQ and HP standpoint, it can be bad in the durability standpoint. If the cam doens't set the valves down gently then BOOM you go breaking parts at some point.

As for the intake......... the runners are too short. That's why the TPI and the LS1 have such long runners, the LT1 flows pretty well. I like single plane intakes, even on street cars, they just have so many advantages. Flow, tuning, wet flow. The LT1 intake just has very short runners giving it very little tuning capabilities for a broad torque curve.

Duration has alot to do with where the car will be run. A street car needs a good idle and part throttle characteristics. Usually when you have alot of Duration you have to spread out the LSA so it gets rid of the overlap and now you probably moved the intake closing point to a bad spot. So then you advance it. Which tells me that the duration is too big.

If you can make big power with small cams then you need REALLY good heads. Then for a street car that's all about velocity!

Bret

 

Hmmm.....that explains alot. I don't suppose anyone has a solution to the runner length problem you mentioned?
I know there is one guy on here with a custom intake but from the pics the runners didn't look much if any longer than the stock ones, as far as I can remember. I think he was spose to make somewhere around 600 hp NA

Edit: Any way to know or make a good guess as to how much lift on a certain amount of duration is too much? Other than trial and error.

 

I am going to go with an LT4 block, heads, and intake. Those are respectable heads and its also a better intake than the LT1. Would it be possible to make those numbers without having to tach over 6500? If not, how high would I have to tach? What cam would you go with for good low end power? All help is appreciated. Thanks,

Brian

 

The Accell SuperRam. That is a solution.

As for the cam. It's physics. Sometimes you can't get more lift because you already have a small base cirlce on the cam (the part that has 0 lift) and the lobe is up to the cam journal size.

The physics involved in lobe design are something that I don't get that far into. The best guy in the country right now is Bill Godbold of Comp Cams. Basically you physically can't get more lift at a certain duration at some points due to the physical dimensions of the valvetrain. i.e. Roller Size, Lifter Diameter, Cam journal size, base circle, side loading on the lifters etc.... all this pretty much tells the tale. The new LS1 Gen III engines have a larger cam journal so it would be easier to get "better" lobes in that engine.

Bret

 

Brian, depends upon the cubes. Well the stroke.........RPM is limited to piston speed, which tells you how strong of parts you need. If you have along stroke you have alot of piston speed. Right now Winston Cup has a bore limit of 4.200" and a cube limit of 358. So therefore they have a stroke limit too. (3.23" is probably what the Dodges and Chevys are running) They pretty much are at the piston speed limit when they are turning 9500RPM! F1 is the same way, they spin 18,000RPM but they have a stroke length that is half that of a winston cup car, therefore they have the same piston speed.

Now you need realy strong piston pins and rods to run that fast.


As for the Block/Heads/Intake. First as long as you have a good block it doesn't matter if it was a LT1 or a LT4. The LT4 intake is better so I would stick with that. The LT4 heads are the same as the Impalla SS iron heads and the truck Vortec heads. So go with an aftermarket head, like AFR. I can't stress how important REALLY GOOD cylinder heads are.

So You could spin a LT1 based engine up to 7500rpm if you wanted. It would be a fun design to do, but it could be done. Would it be cheap, no. But it would have mucho power.

First what's the budget for parts, machine work etc..... then you can find out how much power you are going to make. It's hard to say that $=HP but 95% of the time it's true.

Bret

 

Hey Bret, dont give us bad news about the LT4 heads, this thread was just about to go where I needed. I'm a DIY'er and I have plans to buy LT4 heads cause there's so much debate and hocus pocus about porting. At least this way I get all brand new parts, fresh machine work, and some reliable improvement over my LT1 heads. I might venture into some clean-up of any casting flash and possibly tear-drop the valve guide area to reduce turbulance there. So with your average LT4 head whats a good cam pofile? I thought it was interesting about a 224/236 duration mentioned earlier.

 

Torque is a double edged sword... good when you can get it to the ground, bad when you can't. Too much of a good thing like Pamela Anderson's bosom.
Besides, my LT1 , like many people here, runs through a 6 speed tranny and I don't think it ever drops more than a grand between hard shifts. For that reason alone, I think the short runner LT intake is right at home.
Now, if I should decide to go with a slip-and-slide-powerglide... I'll take that Super Ram jobbie.

-Mindgame

 

What size cam are you running in these? Sounds like something I want

I plan on getting the absolute best forged internals. Also, I thought that the LT4 heads are better than the LT1's (higher runners). Nostang 96z had his ported by GTP and these were his numbers:

Lift Intake Exhaust
.200 152.4 117.1
.300 216.6 157.7
.400 253.1 198.3
.450 269.8 213.7
.500 285.0 222.7
.550 295.9 226.9
.600 301.5 229.4
.650 302.7 n/a

301/229 @.600 is pretty respectable. Plus I'm getting the heads for free, so... Also, don't you think that a 4-bolt main (LT4) would be better than the 2-bolt main (LT1)?

In this case, money is no object. Well, it is, but I'm willing to spend what I have to to make a bulletproof motor that will last. That's why I don't want to have to tach it too high. Midas well do it right the first time, heh? Let me know what you think Later,

Brian

 

Depends on who's flow numbers those are as to whether or not theyre respectable . Theyll tell you their stage2 lt1 flows between 275 and 285... well for whaaaaatever reason, they all flow 255-265 on benches of ppl who've no reason to lie... and guess what.. their power output is generally in line with heads that do that, and not the 20cfm higher they claim. Some also tend to use different models/brands of flowbenches to give results that SHOULD be standardized, but arent, and compared to the accepted standard are inordinately high (useless/fake/donetodecieve/whatever).

*shrug*

If you wanna go fast.. dump all your $ into topend parts. Most guys dont want the added expense of aftermarket engine management, so you're going to be limited to 7krpm.

As far as what mindgame mentioned.. thats a good point. People are dumb.. they want "torque torque torque"... well theyre not really asking for torque, theyre asking for lowend torque, as opposed to highend torque. Yeah.. you want alot of area under the curve, but unless you want to tow with your car, HP is what you want.. mid-highrpm torque. Make hp, gear to take advantage of it, and spank the **** out of everyone else who smokes the tires & runs out of breath up top when it's finally hooking up

Of course.. that's a generalization.... so many different ways to go fast, but IMO, that's the best one. I get a dozen emails from people wanting us to build them a 900hp engine... I ask em what they have now, and theyre stock with boltons, havent ever driven anything over 250rwhp, but are telling me 400-450rwhp "isnt enough." If you want to build a money is no object motor, that's fine.. but you have to be realistic! If you really DO want to play racecardriver, you're gonna be dropping ALOT of cash on chassis/suspension/drivetrain/fuelsystem/enginemanagement/safety/brakes/etc., as a killer powerplant is only part of the equation to going fast.

 

The 4-bolt is better than the 2-bolt only if it's left alone. A splayed 4-bolt conversion on the 2-bolt block is better than the Vette block.

 

I realize that, and that's exactly what I plan on doing. I was also thinking about sending my heads out to you. You seem like you might be on to something But will you be able to get me the power I'm looking for? Thanks for the reply. Any more?

Brian

 

LOL, well i wasnt really specifically talkin about you, i just wonder sometimes about some of these emails I get .

and.. eeaar... power isnt a problem, you'll either be going fast, or dead in no time