[bonuts]

I'm relatively new to building engines, I've built plenty of small power small blocks, but really never ventured into making a big power mill. I will be building a new engine for my new circle track car this winter and I'm gonna need help.

The plan for now is to run a set of Dart Iron Eagle heads (might change) they are a 49cc chamber head 215 runners. I need help understanding the numbers. Now what is the difference in runners? You know 180-215 or any number they run. I would assume it would be how well they flow?

Second, to run a small chamber head like this is there a limit to what pistons you can run? I've never built anything with-out just running a flat-top piston, so I've never dealt with anything larger. There is no limit in the class (for compression anyways) this car will run in, but I would also like something that will be somewhat reliable (like run the 10 events we plan on running with-out a major melt down). I know the majority of guys in this class run 13:1 engines or really close anyways. I understand with running this engine it will run high RPM, 6800-7000 on the majority of tracks. I will need to run screw in studs, guide plates, but is are stud girdles necessary?

If stud girdles are necessary, what all do they entail? Does any machine work need to be done to run them?

I know there might be some stupid questions, but I need to know, and you guys are some of the most knowledgable guys around. So who better to ask? I also probably won't end up putting the engine together, but I will need to be the guy buying the parts.....


bonuts

 

[1BAD80]

http://www.hotrod.com/howto/51578/index.html

 

[bonuts]

Great link, but really it explained nothing I wanted to know. As I said, I have built numerous engines before just no real high HP engines. None of the specific questions were answered, but it gave a few good tips.


bonuts

 

[killerformula]

bigger the port, more flow, but slower velocity. 215's are pretty big for a 400 and absolutely GIANT for a 350. Of course it depends what cam you're using too, bigger cam can use the bigger ports, because you're trying to flow more air anyway.

The problem with using too little port is you get a motor that falls on its face and never reaches its potential. Too big a port and you have a lazy motor that stumbles off the line due to lackluster intake velocity.

WHat's your motor, I'll tell you what you need.

K

 

[bonuts]

It will be a .030 over 350. Keep in mind that this is for my circle track car. Operating RPM between 3500RPM and 6800RPM. So low rev performance doesn't matter.

I have not chosen a cam as of yet. Not knowing exactly what heads I will be running or a idea of what compression either. Hoping for close to 13:1


bonuts

 

[4 Jaw Chuck]

Lets see if we can actually answer some of those questions shall we?

First off the "185 or 215" number you refer to is the size of the port in cc's or cubic centimeters. For the RPM range your thinking of running I might lean toward the 215's but seeing as this is a race car that will come apart regularly you might want to buy the small port head to start, porting can gain you the added volume if you need it later.

Second I would stick to a flat top piston and zero deck the block, that way combustion chamber volume can be adjusted using gasket thickness or milling the face of the head to get what you want. You do the math I'm too lazy.

Third, stud girdles require only a special set of nuts that typically come with the girdle set. The question of if "do I need girdles" is answered by your limited requirements of durability, 10 races shouldn't stress your studs beyond their limits unless you plan on running higher than 7500 rpm or running very high spring pressures/high lift. My opinion is to stick with the screw-in studs and spend the money elsewhere. Nuff said, don't blame me if you break a stud because you valve float it...that is the major cause of stud breakage.

Last I recommend you stick to a major manufacturers "circle track" cam to start, leave the experimentation to the front runners and those with a thick wallet. Driving ability is more important than a few HP anyway.

You may want to run a lower compression ratio than 13:1 if you have to run pump fuel (usually specified in the rule book), those guys who are telling you they run 13:1 either have lots of money/ run a huge cam thats bleeds off a lot of cylinder pressure/ or are cheating and mixing fuel. The engine will detonate at 13:1 (with pump gas) and leave you with a pile of junk if everything isn't perfectly balanced, don't find out the hard way...add compression as you gain experience with your setup and the requirements of the rules. I would recommend 12:1 as a max to start, and even then you better have your ducks in a row.

If you got the bucks and want more power, concentrate on getting some rpm out of your combo. A SBC can run in excess of 8000 rpm if everything is right and you did your homework on the bottom end, add a little gear and you can be outpulling the big boys out of the corners where it counts. Most successful circle track racers I have known have utilized their experience with engine building to run more rpm (and gear) than the other guy and simply outgun them out of the corners. Building an 8000 rpm SBC is not easy using junkyard parts but it can be done, just be aware that at the end of the season (if you can get it to live) the guts will be junk and will be overstressed...toss them before they bite you next season.

There are a number of gents here on the forum that can offer you some real life experience, I suggest you seek them out by PM and get some honest advice from those that have been there and done that.

After all, I could be some 15 year old kid telling you what to do...right!

 

[bonuts]

The fuel is no problem Chuck, we can run AV Gas, C12, if we want to complete, pump gas would be a waste of time.

As for cam selection, I use a guy out of Vancouver on all my previous engines for my circle track cars. Give him what I'm using for parts, what weight the car is, operating RPM, etc. And he'll grind up a cam. I have never had problems before, and my cars always seem to pull with the big money guys.

None of the parts will be junk yard parts, I have never cheaped out before, why start now.

As for the Flat top idea, I've tossed that around as well. I will be spending somewhere near 5-6k on mine as machine work and some of the parts are sponsored to me (love freebies), all my buddies who run Late Models in the North West are running with guys who spend a minimum of 25k on their flat top compression engines. Keep in mind these guys run the SB2.

Also with lifting the RPM's as high as you say on the little tracks we run around here (small 3/8's, and 1/4) not happening, don't need to make speed that way $$$$$. The guys who run these tracks now have been running some as high as 72k but no higher. I won't spend morethan I need to.


bonuts

 

[killerformula]

Its hard to recommend a head without knowing the specifics about the heads. Arbitrarily saying "215 sounds good" is a little shady if you ask me. Call the head manufacture to be sure. THe dart 215's state 383 or 400 to 7000 RPM, which sounds like a bit much for a 350 topping out in the 6500 -7k range. Call them and make sure its what you need. These variables also depend on your cam choice.

As far as slugs are concerned, open chamber heads always influence more flow. I think if you're sure you're set on a high compression engine, why not help yourself out by running a small dome? Sure, if you're going to swap things around on the engine, use a flat-top, but a consistently high-compression ratio engine is what dome pistons were made for. DOn't be afraid to use them if its going to make life easier! I would avoid messing with gasket thickness if you can avoid it, and if you spend a grand on heads, I would avoid milling them for compression too. This is a race motor, there's no reason to worry about "driveability."

Call up your parts men and make them do their job. You're spending the big bucks here.

I can tell you from personal experience that I run my 388 to about 6k on the top side, and the 200cc's pull plenty hard for me.

K

 

[engineczar]

Need to know more on the track rules and about the track in general. Is it a 2 barrel carb class or 4 barrel. Car weight. Gear rules. How big is the track, does it have long straightaway's or is it a bullring. (etc) sometimes big power off the turns doesn't work if the track is notoriously slick or has long straights.

 

[1BAD80]

Here is GM site with crate motors. You can see what the specs and the parts are, and the different cams & HP levels.

http://www.gmpartsdepot.com/store/category.asp?SID=8&SID=8&Category_ID=7

 

[4 Jaw Chuck]

Sorry Bonuts, I thought this might be for a claimer class. I'll try to be a little less "shady".

 

[johnsongrass1]

215cc port heads will be just fine turning 7200 with about a 5.73 gear or 7500 with a 6.00 gear.

Alky: Port's need to be 230.

Two barrell class: Compression is the only way to make power on restricted two barrels. Aim for at least 14:1. VP Clear or Purple is a better fuel than AV gas or cam2. 500 Carb or 350? Alky is worth a little midrange but expensive at 4.75 gallon if you buy it in bulk. Dart iron eagles are designed to be a stock type replace head and they have a low plug location so don't run over a .100 dome to get compression. Deck the block to get it. Or angle mill the heads.

Stud girdle's aren't needed but you need at least to pin the stock studs. Screw in studs are the best option if allowed.

You'll need to make around 550 horsepower. Assuming the car weighs around 26-2800.

PM for specific recomendations at your track.

 

[4 Jaw Chuck]

Speaking of people in the know...:thumbup:

Thanks Johnsongrass1.

 

[2wld4u]

bigger the port, more flow, but slower velocity. 215's are pretty big for a 400 and absolutely GIANT for a 350. Of course it depends what cam you're using too, bigger cam can use the bigger ports, because you're trying to flow more air anyway.

The problem with using too little port is you get a motor that falls on its face and never reaches its potential. Too big a port and you have a lazy motor that stumbles off the line due to lackluster intake velocity.

WHat's your motor, I'll tell you what you need.

K

port size really doesnt matter (except in extreme cases..lol) it's all in the shape..Thats what makes power, not the runner size itself...

 

[killerformula]

I agree somewhat. Its difficult to make a blanket statement like "shape is what creates power" when nearly all smallblock chevy intake ports are the same shape! I would say that the size does have a direct relationship to flow rate, as it does, even more, to intake velocity.

K

 

[2wld4u]

I agree somewhat. Its difficult to make a blanket statement like "shape is what creates power" when nearly all smallblock chevy intake ports are the same shape! I would say that the size does have a direct relationship to flow rate, as it does, even more, to intake velocity.

K

yeah, ok, I see what your saying, but that relates little to making HP

2wld4u

 

[killerformula]

intake velocity relates little to making hp?

K

 

[2wld4u]

intake velocity relates little to making hp?

K

lol, thats right.... thats why say a 180cc head can support so much HP... would you say a 180cc head has more potential than say a 200cc head? or a 200cc head and a 215cc head?



run the buggest cc head you can, if need be alter its internal shape for maximum performace, on or off the street..


Thats why I can run a 230cc runner on a 383 and make peak power @ 6500 545hp to be exact and thats with a small solid roller, 240 Duration @.050

570+ is waiting to be unleashed, right now its so sneaky I cant hardly bring myself to drop in the "big cam"...lol

2wld4u

 

[killerformula]

lol, thats right.... thats why say a 180cc head can support so much HP... would you say a 180cc head has more potential than say a 200cc head? or a 200cc head and a 215cc head?



run the biggest cc head you can, if need be alter its internal shape for maximum performance, on or off the street..


Thats why I can run a 230cc runner on a 383 and make peak power @ 6500 545hp to be exact and thats with a small solid roller, 240 Duration @.050

570+ is waiting to be unleashed, right now its so sneaky I cant hardly bring myself to drop in the "big cam"...lol

2wld4u

Well to each his own, but I pretty much disagree with everything you just said. I DO think its important to carefully consider your choices when building a motor. You basically just said "put the biggest runner you can on your motor." Your motor's build sets teh demands for the intake runner size. Sure, you may make a few more ponies with bigger heads, and probably that would be true to a point, but peak horsepower means NOTHING. How a motor builds power and the topography of its torque and HP curve is the king on the street. You may find its very hard to lose a matched 450 horse motor on the street with a 550 horse motor that's very peaky. Horsepower building from the bottom up is done by runners that are "big enough" not "as big as you can get them."

K

 

[2wld4u]

well, yeah and thats what lead me to my build, 2500 and up it absolutely Pulls and thats my point, I didnt loose anything I would have gained by a smaller runner head, but I did port these heads, 220CC PTL's to a 230cc runner to attain the results I have, not to just go bigger but to gain where I needed it..

and alot of what your overlooking is the rest of the heads, chamber design for instance plays a major role in performance, and you simply cannot go by runner size and determine your performance level...

Thats my whole point of this matter, people are so caught up in runner size they overlook other aspects in engine building..

Look at the Vortech heads and say the old 462 casting, the Votechs are way better, not because of smaller valves but because of the internal shape, and yes, thus comes velocity, but look at where the heads flatten out, now imagine a head just like the vortechs but keeps on climbing to .700 lift, a larger runner can have as much velocity as a smaller one, or even more so, obviously you wouldnt want a 250CC head on a 283, not because the head is to big but because the larger runner will supply more air than a 283 can injest..

a street driver 400SBC may get away with 180cc heads, great tourque and maybe mileage, where they would be disapointed is when and if they decide to hop it up, adding more cam, bigger intake etc.. would absolutely kill the performace after a certain extent..


most people con'ed into buying these small heads wouldnt pick up more than maybe 10-15hp if that over a good set of factory castings, hardly worth the 750+$$$$$ remove the clutch fan and run a electric fan will get you close to that, you need more cam and better induction all around, and if a 180cc head can feed a 400 all the air it needs then so be it, but I likely doubt it..


another example and I just found out that the 215cc PTL's (I thought) pn the 355 in dads 72 chevelle in fact had 230cc cast Iron PTL's untouched, 9:1, 355 (whitch was supposed to be well over that) pulled the wheels @ 2800 RPM, on the footbrake, stock suspension, you live and learn, and I have learned alot, ,mostly from mistakes, so yes indeed to each his own, I have two seperate engines here to back up my statements, and pics too, I put some up for ya...lol

2wld4u