Suggestions please...600hp sbc buildup

[lowflyr]

I know this Ed,

I agree that everything stated by Troy about driveability needs to be stated. It does clarify what is being talked about.

I simply responded with what I am willing to deal with and clarify for him my goal with this build. This resulted in a personal attack for no reason other than a miscommunication. It appears he thought I had slammed him. I did not. But I am unwilling to let someone insult me the way he did in his next post and get away with it.

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Since I can see no downside to using a rev kit, I will be installing one on this build. Better safe than sorry. Thanks Joe and Wolfplace for your input on this.

Wolfplace,
What oil do you use with these clearances? I am going to be running the engine no higher than 7300rpm.

Thanks,
-Brad.

[stevek]

I must be missing out on all the fun because I run aftermarket EFI and simply don't have any of the driveability issues, as subjective as they may be, as stated in this thread.

Brad, have you considered aftermarket EFI?

Ok - release the hounds.

Cheers,
Steve K

[lowflyr]

LOL thanks Steve,

I had considered it. I would like to avoid the added expense at this point, but I may end up there anyway.

Cheers,
-Brad.

[Troy Patterson]

Brad,

I apologize for sounding as though I were being condescending or slamming you.

I'll try to say this without sounding derogatory in any way, and I apoloigize in advance if I don't quite succeed. The thing is, after being around it all for so long, when a person characterizes or states things in certain ways, in ways that I have heard many many times before, it's pretty easy to come to the conclusion - assume, perhaps the wrong conclusion, that this is just the same ol' thing as before...

Knowledge always stops where Ego starts. It's good to be open to new information - always.

And this is an exceptional Forum for the level of maturity and knowledge present.

With regard to low end and so forth, referring back several posts, you need to care about low end. You can reduce low end (to make it easier to get off the line) by building your engine accordingly, or run a poor carburetor and or tune for the application to soften low end that way, (of course there are other methods, but with regard to the prior discussion of carbs). But let's think about this for a moment. If one carburetor makes 50 lbs more tq at launch rpm than another, and you run the carb that lets you get off the line (because it makes 50 lbs less tq), how are you accomplishing that? What's being affected to reduce engine efficiency?

You are destroying combustion efficiency by way of messing with the a/f mixture - ratio. When it comes down to it, you are either making it too lean, or you are making it too rich (sometimes both intermittently) - either way, your engine and performance pays a price. Additionally, I have found, this poor low to mid range fuel management also affects top end performance, as well as sets up undesireable conditions within the combustion chamber the engine may not recover from during that pass in the 1/4 mile, or that lap, or may never recover from during a given event session.

The carb that makes the extra 50 lbs tq, can only do so by giving the engine something it wants and needs. The carb that doesn't make the extra power deprives it - at a cost, perhaps at the loss of your engine, perhaps not restarting in the pits, perhaps on a Sunday afternoon drive when you're the guy on the side of the highway - or your customer is.

Troy Patterson TMPCarbs.net TMP Carbs

[Ed-vancedEngines]

If you have to de-tune to be able to launch, do it with a switcable retard, so you can switch back after you get going.

A/F is whatever that particular engine wants and it will tell you if you can pick up the clues even without an A/F Meter. Most A/F Meters are slow in response in processing the signals coming from the sensors. Even the fastest ones taht we call Real Time, aren't. The quicker the sampling rate it will be closer though.

When you do get this completed, at the track do not tune for ET or 60'. Tune for best mph before even being concerned about the other stuff.

Ed

[lowflyr]

Thanks Troy,

I am not specifically intending to use poor carburetion to get the car rolling. I know a weak bottom end will be caused by way of having an engine that is not yet up on cam. As you were getting at in your post with regards to driveability, the engine will be weak because of combination--- the engine running out of its efficient range. This weak bottom end will allow the street tires to have a better chance to get the car rolling before the bigger torque comes in.

I know the weakness is due to fuel distribution, atomization, reversion and the low efficiency due to operating out of the combinations power band, etc.. And I know that good carb/manifold selection and tuning will help with the first two.

With this in mind, it is difficult to run an engine out of it's powerband much of the time and will undoubtedly result in chamber deposits, fouling. I hope to avoid major deposits with occasional blasts through the rpm range though. The whole street/strip idea is filled with compromises. If the tires are getting mutilated when just trying to pull away because the engine either wants to stall or pull hard (like an on off switch response at part throttle, low rpms), then a little more accelerator pump shot can help somewhat. But you are absolutely right about reducing efficiency/running too rich and the engine must recover from this. Ideally this setup will run well enough at 2000rpm that throttle control will be predictable enough to let me keep traction without having to backpedal. If another carb can give me 50 ft-lbs more torque on launch, then it is obviously the better choice, supposing that this carb is not going to kill my top end to accomplish it.

I guess what I really am looking for is if someone has experience with a similar combination, primarily cam, intake and carb combo. I'd just like to know what I can expect. If there is a carb recommendation that would help, great. There is alot of support so far in favor of an 850. If it is felt that I cannot accomplish this with a carb at all, then I guess fuel injection will be my next option. I know I can tune a fuel injection sytem to run this setup well, and I will go buy an electromotive TEC3 system if I have to. I would just prefer to avoid that expense.

-Brad.

[lowflyr]

Agreed Ed,

Tuning for mph is what needs to be done, launching is second priority. I will try throttle manipulation first, but a switchable retard would be a good choice if I cannot succeed with the throttle. Here to hoping the trans makes it to the track at least once before it's cooked.

[Troy Patterson]

One of the main issues with poor a/f and combustion is the tendency to cause hot spots, then detonation. Detonation may not be audible, and may not show up on plugs as you may think, assuming you were even looking for it.

With varying degrees of poor a/f ratio, atomization, fuel distribution, adequate % of atomized fuel vs. liquid flowing into the cylinder, etc., etc., there can be both rich pockets and lean pockets within the combustion chamber space, simultaneously. The area which ends up with a lean spot once, will likely end up with a lean spot over and over again. Depending on conditions, it may burn there, and may run localized temperatures up, and we're not even talking about an overall lean condition.

Now with a lean condition, there will be hot spots. Once a hot spot is created, how long does it take to cool off once the a/f ratio is optimal? How long does it take for the a/f ratio to become optimal? Does it ever become optimal before the end of the run?

To add some additional complexity to this, when a hot spot is created and (low level) detonatin begins and affects combustion efficiency by upsetting flame propagation, combustion efficiency falls off to some degree (how much?), then the exhaust valve opens and you have less combustion pressure to release, this changes the rate and strength of the exhaust pulse affecting resonant tuning of the exhaust system (at a given rpm) outside or differing from design (intended) parameters as well as the effectiveness of inertial scavenging.

The exhaust system isn't working to aide cylinder filing as you intended and tuned for - perhaps under more ideal conditions, so the carburetor sees less signal strength - drawing less fuel and effectively leaning the a/f mixture delivered to the cylinder. You already had a hot spot due to momentary leanness, now you've allowed the engine to lean further - all everything I just explained gets worse and the engine has only turned another 20 or 30 reveloutions. The engine has only climbed a few hundred rpm - you've (no one in particular) got another 2000 rpm before you shift or let off the throttle.

The fact you've relied on a cam with excessively tight lobe centers to maximize the benefits of inertial and resonant tuning exaggerates the whole dilema because it relies more heavily and is more sensitive to what's happening in the exhaust system.

What helps to reduce or even eliminate these undesireable conditions is a great carburetor tuned properly. Fuel injection - as stevek provocatively jabbed - just kidding - requires tuning, whereas a carburetor may be deemed good enough out of the box - whether it is or not. The fact that it is accepted fuel injectin needs some tuning to function, and carbs may not is without examing the facts an advantage credited to fuel injection, often unfairly.

Ed's right, the best way to pull out power is a retard box, and a/f meters aren't all that effective and may give a readying for lean, for example both for a lean condition and for a rich condition causing poor combustion / scavenging etc., as I have explained - it's happened to me. They are too slow. Data acquisition systems will likely record the data at a faster rate than you meter (be it lights or whatever) can register and read them, never mind your eyeballs seeing and your brain registering them while your driving and applying throttle.

I found meters to be distracting (requiring me to take my eyes off where I was speeding) and required significant understanding of what's going on in the engine and with a/f ratio in the first place to properly interpret and apply, and data acquisition systems to slow with regard to downloading / reviewing, interpreting, etc., after the fact as I had already developed my own methods any way. If I had more money at the beginning, I probably would have purchased a data acquisition systems and become dependent on it, or not.

Troy Patterson TMPCarbs.net TMP Carbs

[stevek]

Out of the box, I've had every engine run on first go without any major dramas. A good start, so to speak, but what has been even more impressive is driving around on a base tune for 15 minutes whilst data-logging and then hitting the 'tune' button. The difference is night and day. You end up with the AFR as you wanted it in every part of the fuel map that you logged. Anything outside of those areas is either not used or the required values can be inferred mathematically.

With respect to timing retard, our timing maps are switchable. We can build the retard in the base timing map or have the driver flip a switch and use a specifically prepped map with the desired retardation. We can also switch to another fuel map prepped to deal with the retarded timing.

If it is any consolation I'm strictly carb when it comes to Propane - and I'm not talking Landi or Impco carbs, I'm talking performance gas carbs from Gas Research. The concept of 'jetting' propane is out the window and infinitely more difficult to deal with than gasoline. Performance propane injection is just not quite there yet, but I AM working on it!

Cheers,
Steve K

[Wolfplace]

Wolfplace,
What oil do you use with these clearances? I am going to be running the engine no higher than 7300rpm.

Thanks,
-Brad.

=
15/40, 20/50, 10/30, depends on what it is for.

I honestly have had no issues in most small blocks at .002 & have run tighter with small journals to 8000+

Thing is, a little extra clearance will rarely hurt you, not enough will.
If you are happy with the way your stuff looks at .003 I see no good reason to change it based on my preferences

[lowflyr]

Thanks Troy,

Interesting discussion. Check out my earlier post in the advanced engines forum regarding running lean and burning up. Its incredible how similar that was to what you are saying here. I guess great minds think alike LOL. I find what you were saying very thought provoking about the effects of scavenging and detonation, as well as the signal to the carb being affected, and exhaust tuning. Regarding hot spotting, I am in complete agreement. Hot spotting is very troublesome, and it concerns me greatly. This is one reason I prefer aluminum heads so much. Hot spots are quickly (well, relative to cast iron or steel) dissipated to the coolant. The higher heat transfer of the aluminum reduces efficiency, the extra compression that you can run offsets this, but the benefit of the reduced hot spotting is still there. I know you know all this, just typing for the sake of typing I guess.

With the cam I plan to use, I fear I will be steadily hunting to improve something that may already be all that it can be. This is why I have been asking what I can expect for driveability, or rather stating what I expect and wondering if it is attainable. I really do not want to spend months of trying things to make it run better, wondering what the engine wants. That is to say, if my end goal is simply not attainable with a carb.

Troy you are obviously well versed and I trust your opinion, so do you think I am going to be able to reach my goals with a carb?


Steve K,
What fuel injection system do you run? I have experience with the electromotive tec3, but no other systems yet. What would be my expected cost for the complete system to go on my non-computer engine?


Wolfplace,
I figure I will tighten up a little on the clearances this time. And meet halfway with what you run. Baby steps here, I am running the large journal crank of course, I don't want to hit that 'oops too tight' spot. LOL Thanks again.

[stevek]

Brad, believe it or not I run a plain old MegaSquirt v2.2. It cost me a $140 and a couple of hours soldering because I chose to do it myself. I could have opted for a completely assemble unit for a little more but I liked the idea of building it myself. Laugh if you will, but this unit has a list of configurable options that is incredibly long and in some cases can make things worse - a kid in a candy shop never knows what to choose. Traction control is in there, nitrous, boost, electronically controlled transmissions, switchable fuel and spark tables, WB / NB O2, knock sensing and retard, alpha-n, speed density, hybrid alpha-n, staged injection (small injectors for low down in the rpm range, then big fat ones when you come on boost etc), shift light, there are a load of options. For $140 I've gotten a HECK of a lot out of it.

For hardware, I suggest you look at what comes 'out of the box' on an EFI SBC, fuel rails manifold etc. Injectors - you'll have to size yourself at 600hp, Narrow Band O2 is cheap and works but Wide Band is way better and costs a little more. Throttle body, I'm sure you'll find one without spending all your cash. I don't know a whole lot about Chevrolet motors so I'm sorry I cant be more help there, but the principle remains the same: look around; do your homework; cut through the marketing hype; find what you can use from already existing systems, adapt if necessary or go the full hog and buy lotsa shiny bling bling stuff when you need to. Don't be scared by it though - EFI is *not* a black art.

[Eric68]

Been away for a few days and am just catching up.

On the carb deal. Keep in mind that Demon rates their carbs differently than Holley. So an 800 or 850 Demon will flow different than a 850 Holley. (in my experience the Demon acts much bigger than a Holley of the "same" size). My point is that it is difficult to compare the two.

Also, I need to point out that I was using annular booster Demon carbs (an 800 and an 850 -- not an 825 -- that was a typo). It is possible that my particular combo for some reason does not like annular boosters (My 750 Speed Demon has down leg boosters).

On the solid roller cam deal. Running one on the street for lots of miles does require some compromises IMO and some careful planning. I have run Hot Rods Drag Week 2 years in a row with my solid roller setup and had ZERO problems with the valvetrain. Here is how:

I am running an XE lobe. LikeMr Sherman said they are probably down a little on power compared to more agressive grinds. However, these lobes will hold up on the street if setup correctly. Use a 2 piece core as previously suggested (billet cam, with a cast gear) this eliminates distributor gear wear issues and problems associated with soft (cast) cores.

The rev kit is a must. They do work well and keep the lifter in contact with the lobe and reduce skidding and bouncing.

Finally, spring pressure -- you need enough to control everything, but not an excessive amount. Too much spring pressure is hard on rocker arms and lifters, the problem is determining how much is too much. I can tell you that 185-200 seat and 480 open is enough to control the valvetrain on my setup (Comp XE286R lobes)

[Troy Patterson]

Yes.

I mentioned EFI requires tuning to make run. This is not an inherent advantage of EFI. Carbs out of the box will likely perform acceptably, although far from optimally.

Because you must go through a tuning sequence with fuel injection, but don't have to with a "box stock" carburetor (in most cases) the injection set up will likely out perform the "box stock" carb - falsely making it appear injection is superior.

As those familiar with fuel injection on high performance / racing engines knows, it is an entirely different animal on an engine making 600 hp than it is on an engine making 350 hp.

Fuel injection is mearly a means of metering and delivering an a/f mixture to the engine, hopefully the right one, right? A carburetor is also, right? So, lets level the playing field, let's assume your carburetor is state of the art, or that it optimizes your engines potential, and you have a fuel injection system that does the same.

What you are left with is the manner by which you meter the fuel. As I pointed out in the "Carbs / EFI" thread is that the carburetor's metering of the metering signal is a dynamic process, and the monitoring of engine parameters is not. I'll put it this way, a carburetor is like you having [Blank Post] with your wife, and the fuel injection system is like your buddy having [Blank Post] with your wife, it's once removed from the actual dynamics of experience, or in this case the working fluid (air flow, compression & expansion waves, and more).

Now, most people have not had the opportunity to spend a bunch of money on an awesome carb, let alone drive one. Most opinions and attitudes about carburetors are based upon the perspective of over 50 years of collective experience of hot rodders and racers with mostly "box stock" undeveloped carburetors not tuned real well. Now, fuel injection hasn't had this advantage, or disadvantage depending on how you look at it. The magazines still plug these "box stock" or "near stock" (in my opinion) carbs as though this represents the state of the art in carburetor development.

Tuning a carburetor is not an evil as some seem to want to characterize it. Tuning does not indicate inferiority on the part of the carburetor. Tuning becomes easier if the carburetor is more developed. Unfortunately, my own R&D program had come to a scretching halt a few years back when California's Bureau of Auto Repair tried to extort over $10K worth of work from me. They said they had discretion. I chose to fight and ended up in a set up car crash and death threats. (Right, I got a little off track didn't I?) Otherwise, I may have by now significantly simplyfied carburetor tuning and increased carb performance much further still.

What I have offered only represents what I was willing to share / loose to my competitors, and not all that I had developed or was developing.

The proponents of fuel injection generally over-simplify there use. If you want 600 hp and you don't want to have to build a 640 hp engine to get it, then I'd go with a carb. The better the carb and tune, the better the driveability. The engine combination is still the single biggest factor in driveability and tuning. The better the package, generally, the easier it is to tune. A benefit of carbs being around so long is that it isn't a big deal to ballpark them, then you can tune as you like. That doesn't mean there won't be something unusual about your engine even if you are using common parts.

Troy Patterson TMPCarbs.net TMP Carbs

[stevek]

Troy,

You sell carbs.
I don't sell EFI. I just use it.

Sorry Brad, I was really hoping to add something useful to the thread. Are you any closer to a resolution?

Cheers,
Steve K