A snippet from the big block cylinder heads thread

[Michael]

Folks,

 

Somehow this whole high-performance in a big block thread left me with a jarring feeling of uncertainty. The reason that my post on big block heads may appear scatterbrained is that I have been pondering this issue for a very long time, and have long ago lost sight of the original “goals”. I’ve been through Staeffel’s book, and Currao’s, and various books by Vizard; and on the more technical side, C.F. Taylor’s engine “bible” and Lumley’s recent condensed version. But somehow that is of little help in choosing which brand of which component to buy.

 

The trouble is theory vs. practice.

 

Every time that I go to a machine shop, the first words out of the guy’s mouth are (besides the canonical “speed costs money”), “how much does the car weigh and how fast do you want to go?” So I end up making up a number to placate him, and to get the conversation started. In reality, however, I don’t particularly care how fast the car goes down the quarter mile, so long as it pulls hard enough to scare me. This is why I can only think of a tentative performance number. Then as soon as I mention a number, the machinist starts lecturing me on how “one number does not a race car make”, etc. Then the machinist proceeds to tell me that I don’t need a solid-tappet cam, that stock heads are going to be fine if they are sufficiently modified, that I do need forged rods, etc. Oh, and no one fails to mention that the rear end will grenade as soon as I cast a glance at it, that only stuffed-shirt poseurs run an independent rear suspension, etc. You get the picture. I do not believe that most machinists are obtuse technicians or callous crooks (though some certainly are), but I seem to be unable to avoid “a failure to communicate”. Talking about limiting values of Z-factors doesn’t exactly help. Maybe I should just glue my business card to my forehead?

 

I can’t build the engine myself, because I will forget to pre-lube a rod journal or something like that, and a bearing will spin 20 minutes after I start up the engine. That is just a consequence of the way that I go about doing things. Not smart on a $6000 engine. I can’t even remove the valve springs off my stock heads (the C-clamp style of spring removal tool keeps getting bent, before the spring itself compresses!).

 

I have never driven a car that, to my knowledge, was faster than high 13’s. A few years ago I test-drove a then-new Z28 Camaro, and it was far faster than anything else that I had ever driven. For a number of years I had a Mark III turbo Toyota Supra; I thought that it was fast – but it ran 15.9 at the Pomona track (back when I lived in Los Angeles)! I narrowly lost to a rusted-out ’66 Mustang.

 

So to me, at least at this point, 9.9 or 10.9 or 11.9 or 12.9 or whatever – they are all a jumble of fantasy, pie-in-the-sky, castle-in-the-clouds numbers so divorced from reality that I need not even bother calculating the optimum shift points or figuring whether I should use 0.040” quench or 0.035” or if I would be better off with 3.36’s than 3.54’s in my R200, or for that matter, how many tenth’s of a second I would get from painting the block Chevy orange and gluing Moroso and Jegs stickers to the windshield.

 

Doesn’t it then make sense to just put together the engine that I already have? Maybe, but after 4 years of construction, a frame that’s supposed to pass NHRA tech for a 7.50 car (no kidding), and many other endeavors, it seems only fitting to go the bucks-up route on building an engine. Yet where to stop? Where is the point of diminishing return? Sure, a roller cam will free up some hp. Sure, a knife-edges crank with scalloped rod journals will spool up faster. But is it worth the money? A “stock” rebuild on a 454 costs about $900. But wait, shouldn’t I also get the crank balanced? Yeah, of course. $300. And that 9.5 CR calls for forged pistons, right? Add another $400. Then add ARP rod bolts. And that 2-bolt main could benefit from going to studs in the mains, right? Isn’t a high-volume oil pump a good idea too? Sure, of course. Then add the roller cam and the forged rods, and we’re up to the $3K range on the short block – or more. So why not throw in another $1000 and just get the GMPP 502 short-block? Or for that matter the Merlin II block (more aftermarket support for the 2-piece crank seal, right?), maybe with roller needle bearings on the cam. And the Lunati $2000 crank – the one with the scalloped rod journals. Maybe one of those Keith Black aluminum blocks, or a ZL-1? Up and up the ladder we go, up and up the beanstalk.

 

Or just go find some 70’s GM truck with a big block, pull the engine out of that and call it Version 1.0. Wait a minute – been there, done that.

 

So this is why I want to make up a number, like 500 hp – it is a line in the sand. It is not the belief that one design point will turn my life around and turn me into a happy smiling dude, but that somehow a decision has to be made – and short of throwing darts at my Summit catalog, the “knee in the performance/price curve” strikes me as the most logical approach.

 

Opinions?

 

Thanks!

-Michael

[labrat]

That's about the general concensus between me and my buddy (who also has a hybridZ)... How fast is fast? Do I care about big (or little) numbers, or how the car feels? I saw the movies of darius in his Z, and thought mine would be like that with just a stock 350 thrown in it... Not quite! I don't want to have the fastest car around, i just want a car that feels fast to me. The $20 on the dashboard is probably one of the most important tests my car will ever go through. Numbers mean little to me, it's the huge grin when i bawl third that really counts. Just a stock 350 didn't cut it, so i'm redoing my entire conversion. At least I get to use the same motor mounts:) Going for a new motor, tranny, everything. I'm just balancing income vs. time vs. how bad i want to drive the car. I have loads of respect for those of you who are taking years to convert your rides and restore them at the same time and doing a job that is worthy of a magazine, but i'm trying to be realistic, and actually get my beast out of the garage while i'm still young enough to enjoy it. So how fast is fast? Fast is what my car will be after my next paycheck... eternally.

 

Bill

[pparaska]

It takes the same amount (almost) of time to build a 400hp BB as a 600hp BB.

 

With cubes (454) you can have 400hp easily.

500hp for a bit more money and work.

600hp will probably start getting more expensive for parts and require more prep.

 

I was conversing with Mike Kelly over many mixed drinks at the hotel in CA lately over what constitutes "enough" motor.

 

Well, for me, it has to be Normally Aspirated. Just the way I like my street cars.

 

But the most important thing I want out of the car is what Mike Kelly had in his first V8Z rendition: It was scary fast.

 

You see, I've done the performance buildup thing before, and one thing's for sure - you always want more power - until your afraid to apply the gas pedal for fear of your life or license.

 

My next motor will be bigger, and more powerful, no doubt. I built small, and that was a mistake.

 

I'll be driving my Z in days or a week, but I'm sure of one thing: If DD2000 is right, and I have 380 hp at the crank, I'll get used to it at some point (a month, 6 months, a year) and then I'll want more.

 

To me enough is when it's still streetable, but scary fast! The beauty of the early Z is it's light enough to have both (right Scotty?! )

 

Anything less is a stepping stone!

 

Build it for high 10s and don't look back!

 

(You're money is so easy for me to spend )

[Guest JAMIE T]

Fast. It's a relative term. I've had fast cars and I've had FAST cars. Sure my Z28 is fast, compared to my stockish 240Z. But it is not fast compared to a Big Thumper turbo'd Pro 5.0 Mustang. My supercharged Mustang(dyno'd 500hp at wheels(but still weighed 3000lbs) was fast too, as was my '70 442 Olds. My HybridZ will be the fastest, most powerful car I have ever owned. When you(WE)decide what fast enough is, that will be the point when you have decided that you aren't going to spend anymore money making the car go forward. The engine for my HybridZ made 500hp at the wheels on the motor. It does that becuase that is what I decided is enough for me. The same engine is equipped with a NOS ProShot Fogger, and a plate NOS system, because that is what I decided is enough for me. So If I ever get the balls to push the limits of the rear, trans, chassis, it's just a squeeze of the "trigger" away. I want my car to excell in every aspect of automotive performance. 1/4 mile, road race, skid pad, braking, what ever Anyone wants to challange me at, bottom line is I have decided that I want to Stomp them. I want the local street racers to me!!!

 

What ever you decide to build, fortify the bottom end with the best parts YOU can afford. Whether it's a stock steel crank, Eagle steel crank or a Sonny Bryant billet steel stroker crank, build it strong from the beginning. You will be thankful. If you engine is a 2 bolt main, then opt for Splayed maincaps. Same goes for the connecting rods, get the best ones you can afford. You may have already decided that your car is a race only car or a street/strip car. Give attention to the compression, and use a forged piston. By building the bottom end strong from the beginning, you can run your stock heads(ported?) now, and later upgrade to a set of alum. race heads. One thing you will know for sure is that your bottom end is bullet proof and if you decide to make more power, you short block can take it.

[Kevin Shasteen]

Michael,

 

What can I say? Reading your post I found myself chuckling (because I-er-uh "WE" have all been there) and at other times truely "Feeling Your Pain" We have all been there & some of us are going thru what you're going thru at this very minute.

 

I only suggest to people to read & educate themselves because I always prefer to learn from someone else's mistakes...this brings up my next point.

 

You may not like this: BUT IN YOUR SEARCH FOR 'HP' YOU WILL MAKE MISTAKES. It doesnt mean your any less of a shade tree knuckle bustin rod building grease monkey than the rest of us...it just means you're human. Experience doesnt come from ala(sp?) or divine intervention..it comes from hands on attempts at chasing, grasping at a particular goal...and sometimes-you actually achieve and exceed your goal. But we all make mistakes---its the mistakes that an individual makes that allows that person "To Be Knowledgeable" on any given issue.

 

Make a decision; just be sure its an educated decision...but make that decison nontheless & then dont second guess yourself-go w/it & HAVE FUN! If you try to think about too much you're gonn drive yourself crazy.

 

What I've done lately...in preparedness for my next project (maybe never) which is hopefully gonna be my Z; I've read as much as I can on what makes an engine tick & then I've catorgorized certain levels of performace, like so:

 

1) Mild Street Car

2) Moderate Street/Mild Strip Car

3) Heavy Street/Moderate Strip Car

4) Non-Streetable/Heavy Strip Car

 

All performance articles, I read, I will make a mental note of where that engine build up/car's performance lands & by realizing that, I can further classify the parts they used in building that engine or car that performed the way it did.

 

If I were you I would concentrate on:

 

1) Displacement: What would you like your final Displacement on your Big Block to be? If you know the displacement but are'nt sure of the bore or stroke req. to get there then play w/these formulas:

 

a) Stroke = Displacement/(.7854 x Bore^2 x # of cyl's)

Bore = Displacement^.5/(.7854 x Stroke x # of cyl's

 

2) Compression: Have you chosen a Static Compression (remember this is a street car-that may be raced or vic-versa): use this mulit-formula for playing around w/static compression:

 

[you need to know the displacement per cylinder & then convert that displacement for once cylinder to cc's, this will also allow you to home in on what cylinder head you may/may not need:

 

a) Displ.Per Cyl= Total Displacement/#of cyl's

cc's Disp.of one cyl = [a] x 16.387

c) Comb.Chamber Req'd = cc's Disp.of one cyl/Requred Static Comp-1

*NOTE: the answer to this will tell us what our final Combustion Chamber cc's will need to be to run on whatever Static Compression you're requiring

 

...,Now lets put the above to action: Lets say you intend on using the 454 in its factory displacment & want 9.5:1 Static Compression-using the above three steps we'll work it like this:

 

a) 454/8 =56.75 This rep's disp.for one cyl.

56.75 x 16.387 = 929.96cc's This rep's once cyl.displ in cc's

c) 929.96cc's/9.5-1 or 929.96cc/8.5 = 109.40cc's

 

So what we just learned is: if you want to run a 454 w/9.5 Static Comp. you're gonna need a Comb.Chamber of 109.40cc's (remember-this number also reflects your piston's crevis cc's, dish/dome cc's which will add/take away from the cyl.head's actual comb.chamber cc's. So when you're looking into pistons & cylinder heads: be sure & work the dish/dome cc's w/the cc's of the cylinder head whose sum should match your equation: for our example we would want the sum to match 109.40cc's...simply work the math.

 

The next step in determing what cyl.head are required will be the airflow characteristics in relationship to the cam you're choosing. Read the airflow numbers of the cyl.head at .100" increments up to .600" valve lift: then choose a cam whose lift reflects the max airflow you want at that lift. (keep this in mind & make note of it on paper)....remember-we're only building a paper engine at this point...no money required.

 

Now-the hard part: you gotta either learn how to determine Dynamic Compression-or you're gonna just have to take someone's word for it. You need to find a cam & determine at what point of piston travel in the cyl. the Intake Valve Closes. At this point-you will use the Compression Formula to determine your dynamic comp.

 

The only difference is you wont be using the entire displacement of one cylinder, instead, you'll be using the remaining volume of that cylinder after the Intake Valve has closed: such as...,

 

Final Comb.Chamb.Req'd = Cyl.Vol.Remaining after IVC + Cyl.Head's Comb.Chamber/Cyl.Vol.Remaining after IVC

 

...this will tell you if your engine will be able to run on pump gas or req. racing gas.

 

This last point is why I liked Ed Staffel's book; particularly PAGE 110 (the engine graph for a .030 454) and PAGE 112 which are its instructions on determining Dynamic Comp, Pump Gas or Race Gas. Remember tho-when using the graph...only the stroke, con.rod & Piston Comp.Height matter as the bore doesnt come into play till later. The graph will only tell you piston location not volume of the cyl. You'll determine volume of the cylinder once you've chosen a displacement for your engine...read the suggestions in his book & read his chapter on cyl.heads. IMO, he did an excellant job of discussing Big Block Cyl.Heads.

 

After all that; you basically need to choose a cam whose LDA, Duration will match your requirements of 1) Mild Street 2) Moderate Street/Mild Strip 3) Heavy Street/Moderate Strip or 4) Dedicated Strip Car....the intake manifold & carb choices will be relatively easy as the guess work has basically been take out of the equation for you & I.

 

Determine these issues first & foremost & the actual building of the steering, suspension & driveline can come later.

 

The most important thing to remember: Always have fun-make an educated decision & dont second guess yourself....becaus we all make mistakes.

 

Kevin,

(Yea,Still an Inliner)

[Guest Anonymous]

If I had the money, I would research Grump's posts and probably select a special Good Wrench motor or one similar with a big warranty to insure reliability but gee, my old silver Zee with the 2800 going to the post office in Fall Creek goes faster around the corners than I can steer. I love to see that front end raise up about a foot when I hit 100 mph before the next curve in the road. Nothing quite like passing another car and find them far out of sight before you can check the progress in the rear view mirror. My 350 conversion in the Tomahawk will probably put me in cardiac arrest or ecstasy but I enjoy the dream! and the HUNT!