ty_ty13

iTrader: (42)

once you narrowed down what CI's you want, what is next-

-meaning... do you pick CR first, or cam, or heads, valve sizes?

i know that you should have in mind what you want out of your new motor but after all the needs/wants are wrote down and thought about what order do you plan your "hardware?"


when i build this motor i want to make sure it is planned and matched perfectly

this is for you JRP

777

iTrader: (21)

I'd start looking at some heads. Then get a cam to match those heads. Then start looking at milling for the right compression ratio. Just my opinion, others may vary. You kind of have to have a general idea before doing anything. This way you don't get some stg 1 5.3 heads and think you are going to make 450rwhp.

Classic

iTrader: (3)

Its really just a big mix of things -- you have to consider everything sort of picked out, then you can adjust from there. Rod length, compression height on your piston, deck, compression ratio, gasket, bore, stroke, heads -- casting, valve size, cam, etc.

Adrenaline_Z

I don't think many are going to disclose their theories on engine building, but
it would be cool to know the thought process of the pros.


I was always taught to think of the goal (ET/MPH), and what chassis was
going to be used.

Race class has limitations on how many gears allowed, tire type/size, fuel choice, etc.

From that information, tire size/gear would also be a huge factor to determine
the engine peak RPM needed.

Then a rough HP calculation was made using race weight to figure how much
motor/head/cam was sufficient.

I never had the chance to apply all of this from A to Z, but I can only imagine
it's a mountain of info to overcome.

Old SStroker

Getting it perfect is a lot of work, but it's almost possible.

Adrenaline_Z made very good points. I'll be more verbose.

0.5. Decide on a realistic budget for the whole vehicle. This comes before first, because if your plan is way over your budget, you won't get it done.

1. Decide what performance you want from the vehicle. If it's a drag car, what et & speed; if it's a road course car or any class car, what are the rules? If it's a street or strip/street car, what kind of driveability, traction, octane, noise, etc. are you concerned with?

2. After 1., decide what torque and hp is going to be needed in what rpm range. There are some decent computer simulations for this. Mostly you will be concerned with accceleration and maybe top speed. IMO (which is never humble), you need to define the size and shape of the engine's torque curve. That and the rpm range will of course determine the hp.

3. Now you can start to design an engine to try to meet the goals you have set. If it's an LS1, you are probably talking from 350 to possibly 427 cubic inches. There are various ways to get the torque/rpm/power you need. I'd look at the best bang for the buck, which might be a close-to-stock displacement. 427 is nice, but really expensive.

4. Here's where good engine simulators and folks who know how to use them can be a big help. IF you put in the correct data, some decent designs result. If you don't, well GIGO appplies. To make torque/hp the engine has to pump air, and to paraphrase Willie Sutton, "That's where the money is.". Sure, you are going to have to build a bottom end to take the rpm and power, but if you build an 800 hp 8500 bottom end for a 600 hp engine that will only need to run 4000-6500, you've way overspent on the bottom end and will probably have to cheap out on the air moving part.

5. There are various ways to get the torque curve you need. Big cubes and relatively low rpm, small and high rpm, or medium cubes and medium rpm. Expert use of a good simulaton can get you pointed in the right direction. Here's where you might want to enlist the help of a pro. He/she will work within your boundaries to come up with a design or three. This service might not be free, but it might be included if you buy either the engine or lots of the parts from the designer.

6. FWIW, cam is probably the very last thing that will be specified.

One last thought:


"Without question, the most common mistake in racing is to buy parts impulsively without having a clear vision of where you want to end up. The result is often a pile of mismatched pieces that will never work together properly." - David Reher

PREDATOR-Z

How could you say that? The cam is THE MOST IMPORTANT part of the motor. Everything else revolves around it.
Once purpose of car is chosen> cubes are chosen>cam is chosen > rest of assembly

lilbuddy1587

iTrader: (1)

Cam is the heart of the motor. The best thing to do is figure out what type of power you want, then how much money do you have to really sink into it for bigger cubes(means bigger cam, better breathing heads, MUCH better exhaust etc.) If you want to stay 346/347 your best bet is to have a custom cam built suited to the needs of your heads.

Old SStroker

Interesting concept.

If I understand you correctly, you would chose the heads, intake, etc. based upon the valve events you chose first, right?

That's sorta like starting with your favorite LSA, and specing the duration, lift, agressiveness and intake centerline around the LSA regardless of what the engine likes. Yeah, I've seen that tried also.

Would it not be more effective to match the airflow to the displacement and rpm range, choose an intake manifold to match the flow and rpm band, then determine what valve events your airpump needs to get the torque/power desired in that rpm band? More than a few engine designers/builders practice this approach.

Generally great heads and a fair cam will do better than lousy heads with a great cam. Mother Nature (aka: airflow thru the system) is in charge, not the camshaft. While the cam is vitally important, it needs to provide the airpump (engine) with what the airpump requires, not the other way around.

Ben R

http://www.hardcore50.com/Articles/E...ilding_101.htm

Read it. Learn it. Use it.

If you're serious about going fast your best bet is to leave the engine building to somebody with experience. Tell them your budget and what you want and let them work their magic.

Ben R

It honestly doesn't take much computer simulation for this. Anybody with any experience on a dyno can give you some very close estimations as to where certain combinations will make peak torque. Then, if you know how much HP you want/need to make, you can determine about how many RPM you'll need to turn to achieve your goal.

This stuff is really quite simple...

Ben R

Wrong. The cylinder heads are the most important parts to an engine. The camshaft compliments the cylinder heads. That's why a good set of heads can cost tens of thousands of dollars and a custom cam still only cost a few hundred.

Old SStroker

Thanks for the link. I haven 't seen it previously. Really!

While Erik and I don't always see eye-to-eye, I like this write up...especially these parts:

"The FIRST thing I ask people is what kind of realistic budget do you have?"

"Last would come the camshaft..."

PREDATOR-Z

Well because you are talking about ranges. I'm talking about a specific, well thought off, calculated and designed system for a specific application.

No pissing match as to how to and who's best way, just a different angle of approach for (I repeat, a specific application)

I'm not talking "off the shelf" parts, but custom tailored motor with the heart of it all, the CAM. A range of operation, alternatives will still exist, but it will be much narrower.
At least, this is the way I go about it and I've been happily rewarded by doing so.
(The best is only the best at the moment of victory, as there is already research on how to defeat them next time.) One of my own quotes. LOL

DrkPhx

iTrader: (15)

Predator - I would suggest you contact FMS, Rapid Motorsports, ED Curtis or anyone who grinds custom cams and and ask them to spec a cam before the engine is built. The will ask you to provide the following information first;
*size of engine
*Intake type (MAF, Lid LS6/LSX, TB?)
* HP goal
* intent of car (full drag, street or both?)
* raceweight of car
* transmission type (if A4 what stall TC, shift extension, STR)
* rear end gears
* planned static compression
* Head brand; combustion chamber size, milled or not and flow numbers
* Chassis modifications
* rear tire size and type (for drag racing)

I know this for fact because when I called them to spec the cam for my LS2 402 this is what they all requested. Fortunately I had all of this information (and more) typed in a Word document ready to send out. Some even have their own forms to fill out.

To answer the thread starter's question, I would agree with SStroker and Adrenaline77. You need to really think it out before hand and establish a goal, budget and determine if it's in your means to complete the project. Realistically your budget will affect the outcome more than anything. My project came in slightly under budget, but has taken much longer to complete due to a supplier back order and extenuating circumstances.

SStrokerAce

iTrader: (2)

When is a engine build not "specific"?

I build motors that are custom tailored, from the block, heads, intake etc.... and the last part that gets ordered for every one of the motors is the camshaft... it's what brings all those wonderfull parts together.

Anyways.....

Yeah the first things you need for a engine buildup are a set goal, some idea of budget and then a plan.... If a customer doesn't have this it's more akin to a monkey humping a football than a quality enging build up.... The other thing that I see is people wanting to mirco manage a engine buildup. If you have a engine assembler doing your motor that is a good idea, if you are giving your money to a engine builder then after goals and budget have been set, you let him come up with a plan and excute it.

Bret

Adrenaline_Z

I'd much rather tune a camshaft than tune heads, exhaust, intake, etc. to
match the cam specs.

Just my approach.

The camshaft doesn't determine the amount of air flow. It would be difficult
(in my eyes) to spec a camshaft to need, 1200 CFM @ 8500 RPM @ 28"/H2O...( < or something like that )

PREDATOR-Z

That is exactly what I said. And that is exactly what I do. But I wouldn't build a motor and then decide what cam to put in.
take a look around.
LS1 motor has been around since 97 (production), How many cam profiles have been designed since then??
Every week, there is a new grind and everyone says "look at the latest BEST cam!!", but you need to change this, and that, and these etc.....

Choose the cam you want (design it if you have the knowledge), then build a motor for it. You'll have the best setup for THAT particular cam and you will have maximized THIS combo.

Anyways guys, we can go round and round as to who's right and who's wrong, but that is not the point I want to make. MY point is, that there is more than one way to look at things and more than one way to build a motor.
Your preference is up to you.
Just because X, Y, and Z do it F-way, that doesn't mean that MY way doesn't work.

SStrokerAce

iTrader: (2)

I think I'm going to agree with the guy who has pictures of a degree wheel, checking P to V, crankshaft endplay and what looks like a closed chamber BBC head in his sig here lol.....

Z if you wanna go on living in "Preditor-Z land" than do that.... The rest of the world will do it the right way. I almost think you like to see your name in writing sometimes with these posts about your fantasyland... Not to pick on you here but I do say "my lord" a lot when I read your posts.

In fact do me a favor, go fill out EDC's camshaft form WITHOUT any info on the heads, no flow numbers, no port volumes, valve sizes and of course no idea of static compression ratio because without the heads you don't know that. See what he e-mails you back and says.... It's close to impossible to pick out a cam without any knowledge on the heads and that's just one part of this. I know what I would say, but I would guess postitive re-enforcement of these same principals MIGHT get the point across.

Yes you can pick out a T-Rex or a F13 cam and then get a good set of heads and do well, but be warned that you might be close but not OPTIMIZED. There are so many things that come into play in a good camshaft design and the fact that there is a new "cam of the week" only goes to show the lack of knowledge the avereage consumer has on camshaft design. It's not black magic like some guys want you to think, it just is a very big variable in a motor that is so completely dependant on other specs and parts that it's scary and way to much for most people to gather all together and make sense of it, that's why even though it seems like it on the net not everyone is a actual cam/valvetrain designer.

Bret

PREDATOR-Z

If you read my previous posts just on this thread, you'll find that I did no attack you, calling you names, or fantasy midget or anything else.
I keep MY mind open unlike you.
You only read what you want, because you are only inside your box. Your way is always the only way.
Must make you feel good, I take it.
Anyways, I know one thing, I would never come to you for building my motor. Because from what I gather, It is certainly not your lack of knowledge, (you have plenty knowledge), it is the way you always like to impose your opinions as the final ones without trying to listen, understand and being a teacher of knowledge, instead of an imposer of knowledge.
I'm sorry (actually I pity), characters like yours, that always have to put down people, because you have achieved a certain degree of education in a certain subject.
God bless you, at least he understands.

Ben R

And there you have if folks. Spec the cam, then build the motor around the cam.

'Everything I learned about my car I learned on LS1Tech.com'

This is why I think that 'LS1 People', as a group, are the biggest bunch of idiots ever. This is far worse that the Ford people arguing the Pro's and Con's of a 331 vs. a 347. LMAO!